AU2601199A - Breath sampling bag and gas measuring apparatus - Google Patents

Description

_1

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): OTSUKA PHARMACEUTICAL CO., LTD.

Invention Title: BREATH SAMPLING BAG AND GAS MEASURING APPARATUS r a The following statement is a full description of this invention, including the best method of performing it known to me/us: 1A

DESCRIPTION

BREATH SAMPLING BAG AND GAS MEASURING

APPARATUS

Technical Field The present invention relates to methods and apparatuses for spectrometrically measuring the concentration of an isotopic gas on the basis of a difference in the light absorption characteristics of the isotope.

Background Art Isotopic analyses are useful for diagnosis of a disease in a medical application, in which metabolic functions of a living body can be determined by measuring a change in the concentration or concentration ratio of an isotope after administration of a drug containing the isotope. In the other fields, the isotopic analyses are used for studies of the photosynthesis and metabolism of plants, and for ecological tracing in a geochemical application.

It is generally known that gastric ulcer and gastritis are caused by bacteria called helicobacter pylori (HP) as well as by a stress, if the HP is present in the stomach of a patient, an antibiotic or the like should be administered to the patient for bacteria removal treatment. Therefore, it is indispensable to check if the patient has the HP. The HP has -2a strong urease activity for decomposing urea into carbon dioxide and ammonia.

Carbon has isotopes having mass numbers of 12, 13 and 14, among which 13 C having a mass number of 13 is easy to handle because of its non-radioactivity and stability.

If the concentration of 13 C2 (a final metabolic 2 (a final metabolic product) or the concentration ratio of 13C t 12

C

2 to CO 2 in breath of a patient is successfully measured after urea labeled with the S isotope is administered to the patient, th resence of 10 the HP can be confirmed.

SHowever, the concentration ratio of 13

C

2 to 12 naturally occurring carbon dioxide is 00 1:100. Therefore, it is difficult to determine the concentration ratio in the breath of the patient with high accuracy.

There have been known methods for determining the concentration ratio of 13 to 12 2 by means of infrared ^2 C02 by means of infrared spectroscopy (see JPB 61(1986)-4229 and JPB 61(9864 22 2 In the method disclosed in JPB 61(1986)-42220, two cells respectively having a long path and a short path are provided the path lengths of which are adjusted such that the light absorption by 13

CO

2 in one cell is equal to the light absorption by 12

CO

2 in the other cell. Light beams transmitted through the two cells are lead to spectrometric means, in which the light intensities are measured at wavelengths each Providing the maximum sensitivity. In -3accordance with this method, the light absorption ratio can be adjusted to for the concentration ratio of 132 to e concentration ratio of 13 in naturally occurring carbon dioxide. If the c 2 t o o ratio is changed, the light absorptin ratio also changes by the amount of a change in the concentration ratio. Thus, the change in the concentration ratio can be determined by measuring a change in the light absorption ratio.

However, the method for determining the concentration ratio according to the aforesai e cocentration S a t t aforesaid document suffers from the following drawbacks.

Calibration curves for determining the concentrations of 1 should be prepared by using gaseous samples each having a known 12CO2 concentration. mp l s e a c h h a v To prepare the calibration curve for the 12 2concentration, th 12 C2 15 concentration the

C

2 absorbances are measured for different Cfor different C concentrations. The 122 concentrations and the 1202 2 concentrations and S 2 absorbances are lotted as abscissa and ordinate respectively, and the calibration i determine by the i c u r v e s d e t e r m i n e d b t method of least squares.

The calibration curve for the 13 2 cocentration is Prepared in the 2 concentration is prepared in the same manner as described above.

For determination o e For eterminatio of concentrations by means of infrared spectroscopy, the preparation of the calibration curves is based on an assumption that the relation between the concentration and the absorb e conom t te bertee ance conforms to the Lambert-Beer Law. However, the Lambert-Beer Law itself is an approximate expression. The actual relation between the concentration and the absorbance does not always conform to the Lambert-Beer Law. Therefore, all the plotted data do noterfectly fit to the calibration curve.

Fig. 1 is a graphical representation in which concentration ratios of 13C to 1 2 2

C

O 2 are Plotted with respect to 12 C0 2 concentrations, the 12 C0 2 concentrations and the 13 2 concentrations and S the 13C02 concentrations having been determined by using calibration curves prepared on the basis of measurements of basis of measurements of the absorbances of gaseous samples having the same concentration ratio (13CO 2 concentration/12C2 concentration v c2oncentration 1.077%) but different 122 concentrations As shown in Fig. 1, the concentration ratios determined for different 12C2 concentrations deviate from the actual concentration ratio (1.077 and form an undulatory curve when plotted.

Although the cause of the deviation has not been S elucidated yet, the deviation supposedly results from changes in the spectroscopic characteristics such as reflectance refractive index and stray light in dependence on the 12C concentration and from the error e error chaacteristics of the least square method employed for the preparation of the calibration curves.

If the concentration of a component gas is determined without correction f the characteristics associated with the deviation, a critical error may result.

A variety of experiments have revealed that, where the infrared spectrometry is employed to measure th netrt of 13 C0 2 or the concentration ratio of 132 to12 (hereinafter referred to as "13 concentraion measurement results differ from the actual 1302 or 13 C02 concentration ratio depending on the concentration of oxygen containedin idpndinon concentration of oxygen contained in a gaseous sample.

Srepresentation in which 13CO Fig. 2 is a graphical representation in which 1302 diluted with oxygen and nitrogen and having the same 13 co concentration but different oy 2 contents, but varies depending on the oxygen concentration. Se 13 2 concentration ratios h ng been determined by measurin ratioosamples contai ning 13C diluted withoxygen and nitrogen and having the same 13in ignorane of t 2 actit ioratios tar e norma ed on te basiffers ofro an actual value.

Fg. 3 is a ga 2 concentration reation i trting the As shown in Fig. 2, the 132 concentration ratio is not constant but varies dependi on the oxyen concentration.ot If the 13C g o n t h e o x y e n ccentrtion.

f the co 2 concentration or the 13C oncentton ratio2 concentration of a gaseous sample containing oxygen is measured in ignorance of this fact, it is obvious that a measurement differs from an actual values o u h Fig. 3 is a graphical representatin illustrating the

I_

result of measurement in which gaseous samples having different 1 3

CO

2 concentration ratios and containing no xygen were measured. In Fig. 3, the actual 13CO2 concentration ratios and the measured 132 oncentra ratios are Pltted CO2 concentration ratios a as abscissa and ordinate, respectively. The 13C concentration ratios are normalized on the basis of the minimum 13C02 concentration ratio.

Fig. 4 is a graphical representation illustrating the result of measurement in which gaseous samples having different 13CO2 concentration ratios and containing various concetratio ofS S concentration of oxygen (up to 90%) were measured. In Fig. 4, the actual 130 t2e concentration ratios and the measured 13 concentration ratios C02 S concentration ratios are lotted as abscissa and ordinate, S respectively. The 13 respectively. The C02 concentration ratios are normalized on the basis of the minimum 13C02 concentration ratio.

A comparison between the results shown in Figs. 3 and 4 indicates that the relationship between the actual 13 C0 concentration ratio and the measured 13CO ncentration ratio in 2 concentration ratio in Fig. 3 is about 1:1 (or th in Fig. 3 is about 1:1 (or the scope of the fitting curve in Fig. 3 is about 1) while the relationship between the actual 1302 concentration ratio and the measured 13C02 concentration ratio in Fig. 4 is about 1:0.3 (or the scope of the linear fitting curve in Fig. 4 is about 0.3).

Thus, the measurement of the 13C02 concentration or the 13 conenraion ratio is influenced by the concentration CO2 concentration ratio is influenced b th xs~~ nfunebyte concentration -7of oxygen contained in a gaseou sample, the cause f hich a gaseous sample the has not been elucidated yet.

If the concentration oroncentration ratio of a component gasis determinedithout performing a oo f a consideration of the oxygen oncentration t is redction in y g e n concentration it that a critical error may result.

Since the concentration of CO 2 particularly, the concentration of 13 CO 2 a t i l r y the cn raon o2 is extremely low, highly ensitive n esee s e n si t i v i t measurement is When ofe is increasednt reuirthe sensitivity of measurement .iameasured lighti 0 is increased, a measured light intensity is ponsive to changes r e s p o n s v e t o changes in parameters of the measurement system, the light intensity of a light ource, the temperature of a sample gas, the temperature of a cell to which the gas is introduced, t tsenstivtas is introduced, the sensitivity of a photodetector and the like. Thus, the 15 measured value may have an error caused by factors not related to the sample gas.

o solve this problem, lve this p le the measurement is started after the meaurent system is stabilized in a timeconsuming manner. Thisa rime-consuming manner. This reduces the operation efficiency and makes i impossible to meet a user demand to measure a large amount of samples in a short time.

For measurement of one breath sample t a p l e t h e C O 2 absorbance is measured and the 12 o is determined on the basis of a calibration crve for 12 a 13 abrbane i meaured and the 1 ration curve fntrati 2 c m 2 a b s o b e is easured and the 13CO c 2 2 concentration is calculated on the basis of a calibration curve for 13 CO as well. The measurement of another breath sample is carried out in the same manner.

If the

CO

2 concentrations of the aforesaid two breath samples are at substantially the same level, the ranges of the calibration curves for 12 02 and 13C2 to be sed for the concentration determination can be limited. Thus, the measurement accuracy can be increased by using limited ranges of the calibration curves.

10 In a conventional infrared spectrometric method as described above, a bag containing a gaseous sample is connected to a predetermined pipe of a spectrometric apparatus, and the gaseous sample is introduced into a cell through the pipe by manually compressing the bag.

However, even small turbulence may drastically reduce the measurement accuracy because the absorbance of 13 C0 2 present in a trace amount is measured in the isotopic gas analysis.

The gaseous sample cannot be passed through the cell at a constant flow rate by the manual compression of the bag. This generates a nonuniform flow of the gaseous sample in the cell and causes the gaseous sample to have a local temperature change and an incidental concentration change, thereby .fltuating a light detection signal.

The flow rate of the gaseous sample may be controlled to be constant by using a pump and a flow meter in combination.

~CI~

-9- However, the accuracy of the flow control cannot be ensured, because the volume of the bag containing the gaseous sample is small and the flow rate is low. Alternatively, an apparatus called mass flow meter for electronic flow control may be employed as flow control means. This improves the accuracy of the flow rate control, but results in a complicated apparatus and an increased cost.

In the method disclosed in JPB 61(1986)-42220, the length of the cell is reduced and, therefore, a cellabsent space is 10 filled with air. The air space hinders highly accurate measurement. If the lengths of paths between the light source and the cell and between the cell and the photoreceptor are .increased, highly accurate measurement may be hindered.

More specifically, since the absorbance of 132 present in a trace amount is measured in the isotopic gas measurement, even a small external disturbance reduces the measurement accuracy. A few percentage of 12C02 and a trace amount of C02 are present in the aforesaid air space and spaces between the light source and the cell and between the cell and the photoreceptor. A 13C02 spectrum partially overlaps a 12CO2 spectrum and, if a filter is used, the band-pass width thereof influences the measurement Ther.fore the presence of 1 2 =ue, the presence of 12CO2 indirectly influences the measurement of the 13C0 absorbance, and the trace amount of 13C02 directly influences the measurement of the 13C02 absorbance.

1 To eliminate the influence of CO 2 present in a light path, an apparatus (see JPB 3(1991)-3121 8 has been proposed in which a light source, a sample cell, a reference cell, a interference filter, a detection element and like elements are accommodated in a sealed case which is connected to a column filled with a CO2 absorbent through a tube and a circulation pump for circulating air within the sealed case and the column to remove C0 2 from the air in the sealed case.

The apparatus disclosed in this document can remove C0 2 10 which may adversely affect the measurement, but equires the S column filled with the CO 2 absorbent, the tube and a large sealed case for accommodating the respective elements, resulting in a large-scale construction. In addition, the fabrication of the apparatus requires a laborious process such 15 as for sealing the large case.

Further, a nonuniform flow of the air within the sealed Scase causes a local temperature change and an incidental concentration change, thereby causing a light detection signal to be fluctuated.

In the infrared spectroscopic measurement, breath is sampled in breath sampling bags before and after a diagnostic drug is administered to a living body, and the breath samples the breath sampling bags are respectively measured for determination of the 13C02 concentration or the concentration ratio.

-11- The measurement of such breath samples is typically performed in a Professional manner in a measurement organization, which manipulates a large amount of samples in a short time. Therefore, breath samples obtained before and after the drug administration are often mistakenly manipulated.

More specifically, breath samples obtained from one patient before and after the drug administration are mistaken Sfor those obtained from another patient, or a breath sample 0 o b t a i n e d b e f o r e t d i s Sobtained re the drug administration is mistaken for that S obtained after the drug administration.

Such mistakes lead to erroneous measurement results and, therefore, should be assuredly prevented.

Further, if a breath sample includes a gas remaining in the oral cavity of a patient, the measurement accuracy is reduced. To reduce a measurement error, breath from the lung of the patient should be sampled Still further, since moisture in a breath sample adversely affects the optical measurement, the moisture should be removed from the breath sample. Furthermore, a consideration should be given to the breath sampling bag to Prevent the breath sample from escaping from the bag.

Disclosure of Invention It is an object of the present invention to provide a -12method for spectrometrically measuring an isotopic gas, which is employed to precisely determine the ncentration or concentration ratio ofa component gas in a gaseous test sample containing a plurality of componentgases by ay of spectrometry when the gaseous test sample is introduced into a cell.troduced into a It is another object of the present invention to provide a method for spectrometricallyn o n t o p r o v hh iymeasuring an isotopic gas, which is employed to precisely determine the 10 a component gas in a at con"centration of 0 a component gas in a gaseous test sample containing a p: lurality of component gases by way of spectrometry by using a limited range of a calibration curve when the gaseous test sample is introduced into a cell.

It is further another object of the resent invention to 15 -provide a method for n v e n t i o n t o 15 provide a method for spectrometrically measuring an isotopic gas, which is employed to precisely determine the concentration or concentration ratio of 13 co 2 contained in a gaseous test sample by 0 2 c o n t a n e d i n a gaseous test sample by way of spectrometry in consideration of the concentration of xygen when the gaseous test sample into a cell.

It is still another object of the present invention to provide a method for spectrometrically w -cn is employed to precisely determine the concentration or concentration ratio of a component gas in a gaseous test sample containing a plurality of component gases -13by way of spectrometry in such a manner that time-related influences on a measurement system can be minimized when the gaseous test sample is introduced into a cell.

It is yet another object of the present invention to provide an apparatus for spectrometrically measuring an isotopic gas, which has a simple construction and is capable of introducing a gaseous test sample containing a lurality of component gases at a constant flow rate fo r spectromet y of ise a constant flow rae eo r e f o r spectrometry It is still another object of the present invention to 10 provide a breath sampling bag, which is given a consideration to assuredly prevent to assuredly prevent a breath sample from being mistakenly S.manipulated.

It is yet another object of the present invention to provide a breath sampling bag, which prevents the sampling of air present in the oral cavity of a patient but allows the sampling of breath from the lung of the patient.

It is still another object of the present invention to provide a breath sampling bag, which is capable of removing moisture from breath blown therein.

It is yet another object of the present invention to provide a breath sampling bag, which has a construction to prevent a breath sample from being escaped therefrom.

To achieve the aforesaid objects the present invention provides a method for spectrometricall measuring an isotopic gas, which is described in claim 1.

-14- In comparison with the prior-art method, the aforesaid method includes an additional step (the third step) of correcting the concentration ratio of a component gas in a gaseous test sample on the basis of the concentration of the component gas by using a correction curve prepared by measuring gaseous samples respectively containing the component gas in known concentrations or known concentration ratios. The correction of the concentration ratio eliminates the conventionally experienced drawback that the measured concentration ratios of the component gas which should basically be the same vary depending on the concentration of the component gas, thereby improving the measurement accuracy of the concentration ratio of the component gas.

Another method for spectrometrically measuring an •1 isotopic gas in accordance with the present invention is described in claim 4.

In this method, the concentration of a component gas is tentatively determined with the use of a calibration curve which is prepared on the basis of data obtained by measuring gaseous samples containing the component gas in known S concentrations within a predetermined range (the second step).

However, all the data do not perfectly fit to the calibration curve on which the tentatively determined concentration of the component gas is based, as described in "Background Art".

For this reason, another calibration curve is prepared by using some of the data within a limited range around the concentration of the component gas determined in the second step. It is confirmed that Part of the calibration curve prepared on the basis of the data in the narrower range strictly conforms to the ,range 5 strictly conforms to the Lambert-Beer Law. Therefore, the concentration of the component gas is determined on the basis of the absorbance thereof by using the calibration curve thus prepared (the third step).

Since the accuracy of the calibration curve is improved over the prior art method, the obtained concentration of the component gas is more accurate. Thus, the measurement accuracy of the concentration of the component gas increased.

Further another method for spectrometricall measuring an 15 isotopic gas in accordance with the present invention is described in claim 6 or 7.

In comparison with the prior art method, the aforesaid method includes an additional step (the third step) of correcting the concentration or concentration ratio of a component gas in a gaseous test sample on the basis of a measured oxygen concentration of the gaseous test sample by using a correction curve prepared by measuring gaseous samples respectively containing oxygen in known concentrations.

The correction eliminates the newly encountere drawac that the measured concentration of the component gas which 'concentrations of t h e component gas which -16should basically be the same vary depending on the oxygen concentration, thereby improving the measurement accuracy of the concentration or concentration ratio of the component gas.

The oxygen concentration may be determined by means of any of various oxygen sensors or by spectrometrically measuring an absorbance in an oxygen molecular spectrum Still another method f Still another method for spectrometrically measuring an isotopic gas in accordance with the present invention is described in claim 8.

It is a conventional practice that a reference gas measurement in which a light intensity is measured with a S: reference gas filled in a cell and a sample measurement in which a light intensity is measured with a gaseous sample filled in the cell are each performed once for measurement of an absorbance. In the aforesaid method, however, the absorbance is determined on the basis of the light intensity measured in the sample measurement and an average of light intensity measured in the reference gas measurements performed before and after the sample measurement.

Therefore, a time-related variation of the absorbances measured before and after the sample measurement can be osample measurement can be corrected by using the average of the light intensity obtained in the referencs Sthe referen yas measurement. Thus, an influence of the time-related change of the measurement system can be eliminated.

-17- The result of the reference gas measurement performed after the sample measurement can serve as the result of the reference gas measurement performed before the next sample measurement. Therefore, one measurement result for the reference gas can be used twice.

Yet another method for spectrometrically measuring an isotopic gas in accordance with the present invention is described in claim In this method, an absorbance is determined on the basis of a light intensity measured in a reference gas measurement and an average of light intensity measured in sample measurements performed before and after the reference gas measurement.

Since the measurement should be performed twice on the same aseous ample, the operation efficiency is reduced. However, a time-related variation of the absorbances obtained .before and after the sample measurement can be corrected by using the average of the light intensity obtained in the sample measurement. Thus, an influence of the time-related change of the measurement system can be eliminated.

20 Still another method for spectrometrically measuring an a isotopic gas in accordance with the present invention is described in claim 12.

In this method, two breath test samples can be measured on condition that the C0 2 concentrations thereof are at the same level and, therefore, a range of a calibration curve to -18be used can be limited. The accuracy of the measurement can be improved as the range of the calibration curve to be used becomes narrower. Hence, the measurement accuracy can be improved by using a limited range of the calibration curve.

Yet another method for spectrometrically measuring an isotopic gas in accordance with the present invention is described in claim 13 or 14. This method is based on a premise that a first gaseous sample is filled in a cell for light intensity measurement thereof and, after the first gaseous sample is discharged from the cell, a second gaseous sample is filled in the same cell for light intensity measurement thereof.

To achieve the aforesaid objects, the present invention Sprovides an apparatus for spectrometrically measuring an isotopic gas, which includes a gas injection means for sucking therein a gaseous sample and then injecting the gaseous sample into a cell by mechanically pushing out the gaseous sample at a constant flow rate (claim With this construction, the gaseous sample is injected into the cell at a constant flow rate. Therefore, the gaseous sample uniformly flows within the cell, so that a highly accurate light detection signal free from fluctuation can be provided for more accurate concentration measurement.

Usable as the gas injection means for mechanically Pushing out the gaseous sample at the constant rate is, for example, a mechanism including a piston and a cylinder and -19adapted to move the cylinder at a constant rate.

In accordance with another aspect of the present invention, the apparatus for spectrometricall measuring an isotopic gas further includes a temperature maintaining mean for maintaining a cell forreceiving the gaseo sample r^ recei vin t h e gaseous sam p I introduced therein at a constant temperature (claim 16).

By keeping the temperature within the cell constant the temperature condition of the gaseou sample can be kept e gaseous sample can be ke t uniform, so.that a highly accurate light detection signal free from fluctuation can be provided.

To achieve the aforesaid objects the present invention Sprovides another apparatus for spectrometrically measuring an isotopic gas, which includes a cell for receiving a gaseous sample introduced therein c o r r e c e i v i n g a g a s e o u s sample introduced therein ositioned in the midst of a light Path between a light o a l g h t 5 path between a light source and a photoreceptor, and a reference cel disposed n a portion of the light path not occupied by the cell and filled with a reference gas having no absorption at a wavelength f he g a s h a v i n g n o absorption at a wavelength for measurement (claim 17).

Where a measuring vessel io Where a measuring vessel is not provided with the reference cell and filled with air which contains component gases of the same kinds as contained in thes mp adverse effect is causedgaseous sample, an caused due to the component gases present in the measuring vessel. With the aforesaid construction, h ever, the referencef o r e s a i d c o n s t r u c t i o n owever, the reference cell filled with the reference gas having no absorption at the measurement wavelength is disposed in the light path, thereby eliminating the opticall adverse effect. Th Ptically adverse effect. Thus, the concentration measurement can be performed more accurately.

Further another apparatus for spectrometricall measuring an isotopic gas in accordance with the present invention includes two cells each disposed parallel to a light pat between a light source and a photoreceptor and having different lengths for receiving a gaseous sample introduced therein, and a reference cell disposed between a shorter one of the two cells and the photoreceptor or between the shorter cell and t h e l i sheh rel cell and the light ource and filled with a reference gas Shaving no absorption at a wavelength for measurement (claim .e SWith the cells having different lengths a large space is *15 present between the shorter cell and the photoreceptor or between the light source and the shorter cell, and component gases of the same kinds as contained in the gaseous sample are present in the space and adversely affect the optical measurement. More accurate concentration measurement can be ensured by providing in the space the reference cell filled Lh me referen Sreference gas having no absorption at the measurement wavelength.

In accordance with further another aspect of the present invention, the aforesaid apparatuses for sectoetcally measuring an isotopic gas each further include a gas flow -21generating means for constantly Passing the reference gas through the reference cell at a onstant flow rate (claims 18 and 21). te (cai The Passing of the reference gas through the reference cell is based on the following consideration If the reference cell is sealed with the reference gas filled therein, the refere enc gas filled therein, the reference gas gradually leaks from a joint of the cell and is replaced with outside air. The air t hich has entered the cell contains component gases of the same kinds as 1 0 contained in the gaseou sample resulting in an tically a seous am p l e r e s u l t i n g l n B n adverse effect. Further the reference gas constantly flowing ":at a constant rate does reference gas constantly flowing at: a ntnt rae e de not generate a nonuniform gas flow within the reference cell, thereby preventing a light :.:detection signal from being fluctuated.

15 oThe igas flow generating means may comprise a valve for Sintroducing the reference gas from a gas con S: a flow meter for example gas container, a pipe and a flow meter, for example.

In accordance with yet another aspect of the present invention, the aforesaid apparatus for sectrometrica asring an isoto s p e c t r o m etrically measuring an isotopic gas further includes a temperature maintaining means for maintaining the cell for receiving the gaseous sample introduced therein and the refernce at constant temperature (claims 19 and 22).

By keeping the temperature within the cell and the reference cell constant, a temperature difference between the -22gaseous sample and the reference gas can be eliminated, so that the thermal conditions of the gaseous sample and the reference gas can be kept equivalent. Thus, the absorbances can be determined accurately.

To achieve the aforesaid objects, the present invention provides a breath sampling bag, which includes a plurality of breath accumulating chambers joined together for respectively accumulating a plurality of breath samples, and a plurality of breath introduction pipes for respectively introducing the breath samples from the plurality of breath accumulating chambers into a plurality of inlets of a gas measuring i apparatus for measuring a breath sample, the plurality of breath introduction pipes each being configured such as to be prevented from being connected to the inlets of the gas .:15 measuring apparatus in a wrong way (claim 23).

A gas measuring apparatus in accordance with the present invention is adapted to measure breath samples contained in a breath sampling bag which includes a plurality of breath accumulating chambers joined together and a plurality of breath introduction pipes for introducing therethrough a Plurality of breath samples from a living body into the respective breath accumulating chambers, and includes a ra Uy u breath inlets for respectively introducing the breath samples from the breath accumulating chambers through the breath introduction Pipes, the plurality of breath inlets -23each being configured such as to prevent the breath introduction pipes from being connected thereto in a wrong Way (claim 24).

With the breath sampling bag and gas measuring apparatus of the aforesaid constructions, such an inconvenient accident can be eliminated that one breath sample in one breath accumulating chamber of the breath sampling bag is introduced into the gas measuring apparatus mistakenly for another breath sample in another breath accumulating chamber.

Where breath is sampled from a living body before and after a diagnostic drug is administered to the living body and the

CO

2 concentration or 13C02 1 2 concentration ratio of the breath samples is measured, for example, the manipulation mistake of the breath samples obtained before and after the C: 15 administration of the diagnostic drug for measurement can be prevented. Further, where a load test is performed and breath S Pm is sampled at a predetermined time interval after the administration of a diagnostic drug, breath samples thus obtained are prevented from being measured in a wrong order.

The breath introduction pipes or the breath inlets are, for example, asymmetrically configured for prevention of the connection mistake of the breath sampling bag. For asymmetrical configuration, the plurality of breath introduction Pipes may have different diameters, lengths and cross-sections, and the plurality of breath inlets may have -24different diameters, lengths and cross-sections corresponding to those of the respective breath introduction pipes.

Another breath sampling bag in accordance with the present invention includes a breath accumulating chamber for accumulating breath and a breath introduction pipe for introducing the breath from a living body into the breath accumulating chamber, the breath introduction pipe having a resistance generating means for generating a resistance to the blowing of the breath during the sampling of the breath (claim With this construction, the provision of the resistance 0 generating means prevents the sampling of breath present in the oral cavity of the living body, but enables the sampling of breath from the lung thereof. Thus, a measurement error can be reduced.

The resistance generating means is embodied by allowing the interior of the breath introduction pipe to have some change which generates a resistance to the blowing of the breath. For example, the inner diameter of the breath introduction pipe may be reduced or, alternatively, a resistance component may be provided on the interior of the breath introduction pipe.

Further another breath sampling bag in accordance with the present invention includes a breath accumulating chamber for accumulating breath and a breath introduction pipe for introducing the breath from a living body into the breath accumulating chamber, the breath introduction pipe having a detachable filter for removing moisture from the breath during the sampling of the breath (claim 26).

With this construction, the moisture in the breath can be removed therefrom by means of the filter, so that a reduction in the optical measurement accuracy can be Prevented. The removal of moisture isParticularly effective for infrared spectrometry.

'10 Still another breath sampling bag in accordance with the resent invention includes a breath accumulating chamber for accumulating breath and a breath introduction pipe for introducing the breath from a living body into the breath accumulating chamber, the breath introduction pipe having a :15 valve for Preventing the back flow of the breath during the sampling of the breath (claim 27).

With this construction, the provision of the back-flow S prevention valve in the breath introduction Pipe prevents the breath from leaking out of the breath sampling bag.

Another gas measuring apparatus in accordance with the present invention, which is adapted to measure a breath sample contained in a breath sampling bag including a breath accumulating chamber for accumulating the breath sample and a breath introduction pipe with a back-flow prevention valve for introducing the breath sample from a living body into the -26breath accumulating chamber, includes a breath inlet for introducing therein the breath sample from the breath samplin bag through the breath introduction Pipe, the breath inlet having means for disabling the function of the valve With the breath introduction pipe being connected to the breath inlet (claim 28).

With this construction, the function of the valve can be disabled with the breath introduction pipe being connected to the breath inlet when the breath sample is to be introduced 10 into the gas measuring apparatus through the breath introduction pipe. Therefore, the breath sample can be lgo.

smoothly introduced into the gas measuring apparatus.

T

The means for disabling the function of the valve is Sembodied, for example, by providing a long pin projecting from he breath inlet, which is adapted to forcibly open the valve when the breath introduction pipe is connected to the breath inlet.

The foregoing and other objects and features of the present invention will become apparent from the following description with reference to the attached drawings.

Brief Description of Drawings Hereinafte, concentration of 2C2 is called "12Conc concentration of 13 C0 2 is called "3nc absorbance of 12 is called "12Abs absorbance of COO 2 is called is called 2 Abs" and absorbance of 13 CO is called "3 C2 1 Abs'.

-27- Fig. 1 is a graphical representation in which concentrations 12 Conc and concentration ratios 1 3 Conc/12Cone are plotted as abscissa and ordinate, respectively the oncentrations 12 Con and 13 Con and the concentration ratios 1 3 Conc/12Conc having been determined by using calibration curves prepared on the basis of measurements of the absorbances 1 2 Abs and 13 Abs of component gases in gaseous samples having the same concentration ratio 13Conc/12Con but different concentrations of the component gases; 10 Fig. 2 is a graphical representation in which 13c concentration ratios are plotted with respect to oxygen ontents' the 13 2 concentration ratios having been .*determined by measuring gaseous samples containing 13C diluted with oxygen and nitrogen and having the same 13 2 15 concentration ratio but different oxygen concentrations the 13 oxyen concentrations, the C0 2 concentration ratios being normalized on the basis of a CO2 concentration ratio for an oxygen content of 0; Fig. 3 is a graphical representation illustrating the result of measurement in which gaseous samples having different 13CO2 concentration ratios and containing no oxygen were measured, in which graphical representation the actual CO2 concentration ratios and the measur 13 concentration ratios are plotted as abscissa and ordinate, respectively, and the 13C respectively and the 132 concentration ratios are normalized on the basis of the minimum 13 C0 2 concentration of th minim 1 2 concentration -28ratio; Fig. 4 is a graphical representation illustrating the result of measurement in which gaseous samples having different 13Co 2 concentration ratios and containing various concentration of oxygen (up to 90%) were measured, in which graphical representation the actual 13C02 concentration ratios and the measured 13C02 concentration ratios are plotted as abscissa and ordinate, respectively, and the 13C02 -concentration ratios are normalized on the basis of the minimum 13CO2 concentration ratio; Fig. 5 is a view illustrating the appearance of a breath sampling bag to be connected to nozzles of an apparatus for spectrometrically measuring an isotopic gas; Fig. 6 is a partial view illustrating pipes connected to an end of the breath sampling bag; Fig. 7 is a block diagram illustrating the overall construction of the spectrometric apparatus; S* Fig. 8 is a sectional view illustrating the construction of a cell chamber 11; Fig. 9 is a block diagram schematically illustrating a mechanism for adjusting the temperature of the cell chamber; Figs. 10A and 10B are a plan view and a side view, respectively, of a gas injector for quantitatively injecting a gaseous sample; Fig. 11 is a diagram illustrating a gas flow path through -29which a clean reference gas is passed for cleaning the gas flow path and the cell chamber of the spectrometric apparatus; Fig. 12 is a diagram illustrating a gas flow path through which the clean reference gas is passed for cleaning the gas flow path and the cell chamber of the spectrometric apparatus and for Performing a reference measurement; Fig. 13 is a diagram illustrating a state where a base ga i e sean farea sat wath ere a b gas is sucked from a breath sampling bag by means of the gas injector 21 with the reference gas prevented from g flowing 10 through first and second sample cells lla and llb; Fig. 14 is a diagram illustrating a gas flow path to be employed when the base gas sucked in the gas injector 21 is mechanically pushed out at a constant rate by the gas injector 21 for measurement of light intensity by detection elements 2 injector 21 with the reference gs prevented from flowing .Fig. 15 is a diagram illustrating a state where a sample employed when the begas sucked in thegas injector 21 is uced from the breath sampling bag by means of the gas Sinjector 21 with the reference gas prevented from flowing through the first and second sample cells lla and llb; Fig. 16 is a diagram illustrating a gas flow path to be employed when the sample gas sucked in the gas injector 21 is mechanically pushed out at rate by the gas injector 21 for measurement of light intensity by the detection elements 2 5a and Fig. 17A is a graphical representation in which 12 C0 2 concentrations and 12C02 absorbances are plotted as abscissa and ordinate, respectively, for preparation of a calibration curve, the 12CO2 absorbances having been measured for measuring points in a 12 C0 2 concentration range of about 0% to about 6%; Fig. 17B is a graphical representation in which 12C concentrations and 12CO 2 concentrations and 122 absorbances in five data points in a relatively narrow 12C0 relatively narrow 1 2 concentration range around a 12C02 concentration determined byusing the calibration curve of Fig. 17A are plotted as abscissa and ordinate, respectively; .:Fig. 18A is a graphical representation in which 13C02 concentrations and 130 concentrations and 13C02 absorbances are plotted as abscissa a n d rdinate, respectivel and spectvely for preparation of a calibration curve* the 13002 curve, the 13CO2 absorbances having been measured for 15 measuring points in a 13C02 concentration range of about 0.00% to about 0.07%; Fig. 18B is a graphical representation in which 13 C02 concentrations and 13CO2 absorbances in five data points in a relatively narrow 13CO2 concentration range around a 13CO 2 concentration determined by using the calibration curve of Fig. 18A are plotted as abscissa and ordinate, respectively; Fig. 19 is a graphical representation in which concentration ratios 13Conc/12Con plotted as ordinate are normalized on the basis of a concentration ratio 13 Conc/ 12 Conc obtained when 12 Conc is -31- Fig. 20 is a graphical representation illustrating the relationship of 12 Cnc (plotted as abscissa) versus 13CO2 concentration ratio 13Conc/12Conc (plotted as ordinate) which (plotted as ordinate) which was determined by measuring the CO2 concentrations 12 Conc and 13CO 2 concentrations 13 Conc of gaseous samples; Fig. 21 is a graphical representation illustrating the S relationship of 12 Conc (plotted as abscissa) o n (Plotted as abscissa) versus concentration ratio 13 Conc/1 10 ordinate) which was(plotted as was determined by measuring the 12C02 concentrations 12 Conc and 13C2 oncentrations 13 of *2 concentrations Conc of S gaseous samples and correcting obtained concentration ratios Conc/12Conc; Fig. 22 is a graphical representation illustrating the relationship of 1 2 Cone (plotted as abscissa) versus concentration ratio 13Conc/12nc (plotted as onc/ Cone (plotted as ordinate) which was obtained by determining the 1 2 co concentrations 12 Conc and 13CO2 concentrations 13 Conc of gaseous samples on the basis of absorbances measured on the gaseous samples by using the calibration curves shown in Figs.

17A and 18A; Fig. 23 is a graphical representation illur.in relationship of 12 Conc (plotted as abscissa) and concentration ratio 13Conc/12Conc (plotted as ordinate) which was obtained by determining the concentration -32ratios 3 Conc/l2conc ratios 13Cnc/12Conc of gaseous samples first on the basis of the calibration curves shown in Figs. 17A and 18A and then on the basis of the calibration curves in limited ranges shown in Figs. 17B and 18B; and Fig. 24 is a graphical representation illustrating the result of measurement in which gaseous samples having different 13 co 2 concentration ratios and containing various concentration of oxygen (up to 90%) were measured and *measurements were subjected to a correction process accordin to the present invention, in which graphical representation the actual 13 C02 concentration ratios and the measured concentration ratios are plotted as abscissa and ordinate respectively, and the 13

CO

respectively, and the 1 concentration ratios are S normalized on the basis of the minimum 13

C

2 concentration 15 ratio.

Best Mode for Carrying Out the Invention A preferred embodiment of the present invention will hereinafter be described with reference to the attached drawings. The embodiment is adapted for a case where a 13C concentration or concentration ratio 13 Conc/12 in a breath tes- sam I ^nc/ Cone in a breath test sample is spectrometrically determined after administration of an urea diagnostic drug labeled with an isotope 13

C.

3x htc t -33- Before the urea diagnostic drug is administered to a patient, breath of the patient is sampled in a breath sampling bag. The volume of the breath samplingbag may be about mp li 2 50m. Then, the urea diagnostic drug is administered to the patient and, after a lapse of 10 to 15 minutes, breath of the patient is sampled in the breath sampling bag in the same manner as in the previous breath sampling.

*ie Fig. 5 is a view illustrating the appearance of the breath sampling bag to be connected to nozzles N and N 2 of 10 an apparatus for N 2 of apparatus for spectrometrically measuring an isotopic gas.

The breath sampling bag 1 includes a breath chamber a nreath sampling chamber la for sampling breath f the patient after the administration S of the urea diagnostic drug and a breath sampling chamber lb for sampling breath of the patient before the administration r" 15 o f th e ua gn i re th e a d m i nistration .15 of the urea diagnostic drug, the breath sampling chambers la and lb 9 h sampling chambers la and lb being integrally molded and joined togeth to form a l joined together to form a fed. single body.

A pipe 2a is attached to an end of the breath sampling chamber la, and a pipe 2b is attached to an end of the breath sampling chamber lb. Bottom ends 5a and 5b of the breath sampling chambers la and lb are closed. The ipes 2a and 2b each have two functions, the pipes 2a and 2h serve not only as breath blowing ports from which breath is blown into the breath sampling chambers la and lb, but also for introducing the breath samples from the breath sampling

_I~

-34chambers la and ib into the spectrometric apparatus when the breath sampling bag is connected to the nozzles

N

1 and

N

2 of the apparatus.

When breath is sampled, a cylindrical filter (like cigarette filter) 7a or 7b is fitted into the pipe 2a or 2b, and then the breath is blown into the breath sampling bag i.

The filters 7a and 7b are used to remove moisture in the breath.

As shown in Fig. 6, back-flow valves 3a and 3b are 0.i10 provided in the pipes 2a and 2b, respectively, for preventing the breath blown into the breath sampling bag from flowing back.

The pipes 2a and 2b each have a portion having a smaller inner diameter a smaller diameter portion 4a or 4b) for generating a resistance to the blowing of the breath. The resistance to the blowing of the breath allows the patient to exhale air from his lung. It has been experimentally confirmed that air exhaled from the lung of a patient provides a more stable

CO

2 concentration than air present in the oral cavity of the patient.

After the completion of the sampling of the breath, the filters are removed, and the pipes 2a and 2b are inserted into the nozzles

N

1 and

N

2 respectively, of the spectrometric apparatus. The nozzles

N

1 and

N

2 have different inner diameters, and the pipes 2a and 2b have different outer diameters corresponding to the inner diameters of the nozzles

N

1 and

N

2 This prevents the pipes 2a and 2b from being inserted into wrong nozzles

N

2 and

N

1 thereby preventing the breath samples obtained before and after the administration of the urea diagnostic drug from being mistakenly manipulated.

The nozzles

N

1 and N 2 of the spectrometric apparatus have projections 6a and 6b, respectively, which are adapted to disable the function of the back-flow valves 3a and 3b when the pipes 2a and 2b are inserted into the nozzles

N

1 and N 2 Although the outer diameters of the pipes 2a and 2b are made different in this embodiment, any other constructions may be employed to prevent the mistake of connection between the pipes 2a and 2b and the nozzles

N

1 and

N

2 For example, the S Pipes may have different lengths and the nozzles

N

1 and

N

2 of the spectrometric apparatus may have different depths corresponding to the lengths of the pipes. With this construction, a longer one of the pipes mistakenly inserted into a nozzle having a smaller depth fails to perfectly fit in the nozzle. Therefore, a user notices the connection mistake of the pipes. Alternatively, the pipes may have different cross sections round, rectangular or triangular cross sections).

Upon completion of the connection of the breath sampling bag 1, the spectrometric apparatus performs the following automatic control.

-36- Fig. 7 is a block diagram illustrating the overall construction of the apparatus for spectrometrically measuring an isotopic gas.

The breath sampling bag is set to the apparatus so that one breath sampling chamber thereof containing the breath sampled after the drug administration (hereinafter referred to as "sample gas") and the other breath sampling chamber thereof containing the breath (hereinafter referred to as "base gas") reitrrea to as "base gas") 10 sampled before the drug administration are connected to the S nozzles

N

1 and N 2 respectively. The nozzle

N

1 is connected to one port of a three-way valve

V

1 through a transparent resin pipe (hereinafter referred to simply as "pipe") and the nozzle

N

2 is connected to one port of a three-way valve V 2 through a pipe.

A reference gas (any gas having no absorption at a wavelength for measurement, nitrogen gas) is supplied S from a gas cylinder to the apparatus. The reference gas flows through a flow path diverged into two paths. One path is connected through a flow meter

M

1 to a reference cell lic.

The other path is connected through a flow meter

M

2 to one port of a three-way valve

V

3 The reference gas flows into the reference cell 11c, and discharged therefrom.

The other ports of the three-way valve

V

3 are connected to another port of the three-way valve

V

1 and to a first -37sample cell Ila for measuring a 12 C0 2 absorbance. The ther ports of the three-way valve V are nnected to the first 2 a r e connected to the firf sample cell la through a two-way valve

V

4 and to the other port of the three-way valve V 1 A gas injector 21 (volume: 60cc) for uantitatively injecting the sample gas or the b injecting the sample gas or the base gas is interposed between the three-way valve

V

3 and the first sample cell Ila. The gas injector 21 is a syringe-like device having a piston and a cylinder. The it g a p i s t o n a n d a cylinder. The piston is driven by cooperation of a motor, a 10 screw connected to the motor and a nut fixed to the piston (which will be described later).

As shown in Fig. 7, a cell chamber 11 has the first Ssample cell lla having a smaller length for measuring therein a absorbance, a second sample cell b having a greater length for measuring therein a 13 C0 2 absorbance, and the reference cell llc through which the reference gas is passed.

The first sample cell 11a communicates with the second sample cell lb. The sample gas or the base gas is introduced into the first sample cell The the first sample cell la and then into the second cell llb, and discharged therefrom. The reference gas is introduced into the reference cell 11c, and then discharged therefrom.

Specifica, h t h e n d i s c h arged therefrom.

Specifically, the first and second sample cells 11a and 11b ave lengths of 3mm and 2 5 0mm, respectively, and the reference cell llc has a length of 2 36mm.

A discharge Pipe extending from the second sample cell cod sm5e c l -38llb is provided with an 02 ensor 18. Usable as the 2 sensor 18 are commercially available xygen sensors uch as a solid electrolyte gas sensor zrconia sensor) and an electrochemical gas sensor galvanic cell sensor) A reference character L denotes an infrared light Source having two waveguides 2 3a and 23b for guiding infrared rays for irradiation. The generation of the infrared rays may be achieved in any way. For example, a ceramic heater (surface temperature: 450'C).and the like can be used. A rotary 0 .hp e 2 f o *a 10 chopper 22 for periodically blocking the infrared rays is provided adjacent to the infrared light source L. Infrared rays emitted from the infrared light source L are transmitted to the first sample cell 1a and the reference cell llc through a first light path, and to the second sample cell llb through a second light path (see Fig. 8).

A reference character D denotes an infrared detector for .detecting the infrared rays transmitted through the cells.

The infrared detector D has a first wavelength filter 24a and a first detection element 2 5a disposed in the first light path, and a second wavelength filter 24b and a second detection element 25b disposed in the second light path.

The first wavelength filter 2 4a (band width: about .asses an infrared ray having a wavelength of about 4 ,280nm to be used for measurement of a 12 2 absorbance Thesecond wavelength filter 24b (band width: about 5 0nm) passes an -39infrared ray having a wavelength of about 4 ,412nm to be used for measurement of a 13

C

2 absorbance. Usable as the first and second detection elements 2 5a and 25b are any elements capable of detecting infrared rays. For example, a semiconductor infrared sensor such as of PbSe is used.

The first wavelength filter 2 4a and the first detection element 25a are housed in a ackage 2 6a filled with an inert gas such as Ar Similarly an inert gas such as Ar. Similarly, the second wavelength filter 24b S" and the second detection 2 S t ection element 25b are housed in a ackage 10 26b filled with an inert gas.

SThe whole infrared detector D is maintained at a onstant temperature (25oC) by means of a heater and a Peltier element.

The inside temperatures of the Packages 2 6a and 26b are kept S* at OC by means of a Peltier element.

5 The cell chamber 11 is formed of a stainless steel, and vertically and laterally sandwiched between metal plates brass plates) 12.

brass plates) 12. A heater 13 is provided on upper, lower and lateral sides of the cell chamber. The cell chamber 11 is sealed with insulators 14 such as of polystyrene foam with the heater 13 interposed therebetween. Though not shown, a temperature sensor a platinum temperature sensor) for measuring the temperature of the cell chamber 11 is provided in the cell chamber 11.

The cell chamber 11 has two tiers. The first sample cell l1a and the reference cell lic are disposed in one tier, and the second sample cell llb is disposed in the other tier.

The first light path extends through the first sample cell lla and the reference cell llc which are disposed in series, and the second light path extends through the second sample cell b. Reference characters 15, 16 and 17 denote sapphire transmission windows through which the infrared rays are transmitted.

Fig. 9 is a block diagram illustrating a mechanism for adjusting the temperature of the cell chamber 11. The temperature adjustment mechanism is constituted by the temperature sensor 32 provided in the cell chamber 11, a temperature adjustment substrate 31 and the heater 13. The temperature of the temperature adjustment substrate 31 may be adjusted in any manner. For example, the temperature adjustment can be achieved by changing the duty ratio of a pulse current flowing through the heater 13 on the basis of a temperature measurement signal of the temperature sensor 32.

:The heater 13 is controlled on the basis of this temperature adjustment method so as to maintain the cell chamber 11 at a constant temperature Figs. 10A and 10B are a plan view and a side view, respectively, of the gas injector 21 for quantitatively injecting a gaseous sample.

The gas injector 21 includes a cylinder 2lb disposed on a base 2 1a, a piston 2 1c inserted in the cylinder 2 1c, and a -41movable nut 21d connected to the piston 2 1c, a feed Screw 21e threadingly meshed with the nut 21d and a motor 21f for rotating the feed screw 2 1e which are disposed below the base 21a.

The motor 21f is driven for forward and backward rotation by a driving circuit not shown. As the feed screw 2 le is rotated by the rotation of the motor 21f, the nut 21d moved forward or backward depending on the rotational direction of the feed screw 21e. The Piston 2 1c advances toward a position 1 0 indicated by a dashed line in Fig. 10A. Thus, the gas injector 21 can be flexibly controlled to introduce and S" extract the gaseous sample in/from the cylinder 21b.

TT. MBT a Surin procedure 1 The measuring procedure includes reference gas measurement, base gas measurement, reference gas measurement, sample gas measurement and reference gas measurement, which are to be performed in this order. Alternati ase gas measurement, reference gas measurement and base gas measurement, and sample gas measurement, reference gas measurement and sample gas measurement may be performed in this order. In the latter case, the base gas measurement and the sample gas measurement are each performed twice and, herefore, the operation efficiency is reduced. The former measuring procedure which is more efficient will hereinafter be described.

i -42- During the measurement, the reference gas constantly flows through the reference cell lic, and the flow rate thereof is always kept constant by the flow meter

M

1 TIIa-1 Reference mstrem nt As shown in Fig. 11, the clean reference gas is passed through a gas flow path and the cell chamber 11 of the spectrometric apparatus at a rate of 20 0 ml/minute for about seconds for cleaning the gas flow path and the cell chamber 11.

In turn, as shown in Fig. 12, the gas flow path is changed, and then the reference gas is passed therethrough for cleaning the gas flow path and the cell chamber 11. After a lapse of about 30 seconds, light intensity are measured by means of the detection elements 2 5a and On the basis of the reference measurement, absorbances are calculated.

The light intensity thus obtained by the first and second detection elements 25a and 25b are represented by 12 R and 3R 1 respectively.

TTIa-2. Base gas measuremnt The base gas is sucked into the gas injector 21 from the breath sampling bag with the reference gas prevented from flowing through the first and second sample cells 11a and lib (see Fig. 13).

base gas is echanically p ed out at a Thereafter, the base gas is mechanically pushed out at a -43constant rate (60ml/minute) by the gas inector 21 as hown in Fig. 14 and at the as shown in Fig. 14 and, at the same time, light intensity are measured by means of the detection elements 2 5a and 25b.

d b The light intensity thus obtained by the first and second detection elements 2 5a and 25b are represented by 12 B and 13 respectively.

TTa-

L

R

l efp e rnc^e ur met The cleaning of the oac ^i The cleaning of the gas flow path and the cells and the light intensity measurement on the reference gas are perfored 10 again (see Figs. 11 and 12).

are p e r f o r m The light intensity thus obtained by the first and second detection elements 2 5a and 25b are represented by and 13 a r e presented by 12R 3

R

2 respectively. 2 0 The sample gas is sucked into the gas injector 21 from the breath sampling bag with the reference gas prevented from flowing through the first and second sample cells a and Fig. SThereafte r the sample gas is mechanically pushed out at a constant rate 6 0ml/minute) by the gas injector 21 as shown in Fig. 16 and, at the same time, light intensity are measured by means of the detection elements 2 5a and dt e light intensity thus obtained by the first and second detection elements 2 5a and 25b are represented by 12 S and 13S, respectively.

-44- Reference mP-surp ment The cleaning of the gas flow path and the cells and the light intensity measurement on the reference gas are performed again (see Figs. 11 and 12).

The light intensity thus obtained by the first and second detection elements 2 5a and 25b are repesented by 12 and

R

3 respectively.

Illb. MEsrement prcc^hre 2 In the measurement procedure 1 the CO 2 concentrations of 10 the base gas and the sample gas are not adjusted to the same level.

SIf the base gas and the sample gas are at the same CO2 concentration level, the ranges of 12C02 and 13CO 2 C2 calibration curves to be used for determination of the concentrations can be narrowed. By using limited ranges of the calibration curves, the measurement accuracy can be increased.

In accordance with the measurement procedure 2, the CO2 Sconcentrations of the base gas and the sample gas are adjusted to substantially the same level. First, the CO2 concentrations of the base gas and the sample gas are measured in a preliminary measurement. If the C02 concentration of the base gas obtained in the preliminary measurement is higher han the CO2 concentration of the sample gas obtained in the Preliminary measurement, the base gas is diluted to a CO2 concentration level equivalent to that of the sample gas, and the measurement of the concentration is perfoed on the base gas and then on the sample gas in a main measurement.

If the

CO

2 concentration of the base gas obtained in the preliminary measurement is lower than the C taine in t h the sample gas obtained in h 2 c o n c e n t r ation of 5 the sample gas obtained in the preliminary measurement, the concentration of the base gas is measured in the main measurement. The sample gas is diluted to a C 2 concentration level equivalent to that of the base gas, and then the C concentration thereof is measured a s a n d t h e n t h e 10 The measurement procedure 2 includes preliminar base gas measurement, preliminary sample gas measurement reference gas gas measurement, S measurement base gas meaurement reference gas measurement, sa pe gas measurement re Sample gas measurement and reference gas measurement, which are performed in this order.

o° o 15 h The clean reference gas is passed through the gas flow S path and the cell chamber ii of the spectrometric apparatus for cleaning the gas flow path and the cell chamber 11 and, at the same time, a reference light intensity is measured.

20 In turn, the base gas is sucked into the gas injector 21 from the breath sampling bag, and then mechanically pushed out a t a constant mechanically pushed o u t at a constant flow rate by means of the gas injector 21

A

t h i s time i n a s s e c t o r 2 1 S ethe intensity of light transmitted through the base gas is measured by means of the detection element 2 5a to determine an absorbance, and the C0 2 concentration of the base

I

-46gas is determined on the basis of the absorbance by using a calibration curve.

The clean reference gas is passed through the gas flow path and the cell chamber 1 1 of the spectrometric apparatus for cleaning the gas flow path and the cell chamber 1i and at the same time, a reference light intensity is measured.

In turn, the sample gas is sucked into the gas injector 21 from the breath sampling bag, and then mechanically pushed out at a constant flow rate by means of the gas injector 21 i At this time, the intensity of light transmitted through the sample gas is measured by means of the detection element to determine an absorbance, and the C02 concentration of the 2 concentration of the sample gas is determined on the basis of the absorbance by 15 using the calibration curve.

SThb-3. Ref nc-fmPasmant The gas flow path is changed, and then the reference gas is passed therethrough to clean the gas flow path and the cell S chamber 11. After a lapse of about 30 seconds, light intensity are measured by means of the detection elements 25a and The light intensity thus obtained by the first and second detection elements 2 5a and 25b are represented by 1 2

R

1 and R respectively.

The C 0 2 concentration of the base gas obtained by the -47first detection element 2 5a in "IIIb-. Priminary base gas m e a s u r e me n t is r e l i mi n a r y base gas measurement", is compared with the C0 2 concentration of the sample gas obtained by the first detection element 2 5a in "IIb-2. Prelimnary samp l e ement 25a in "Ib-2 Preliminary sample gas measurement". If the C02 concentration of the base gas is higher than the 2 gas i s higher than the

CO

concentration of the sample gas, the base gas is diluted ith the reference gas in the gas injector 21 to a 2 gas injector 21 to a CO concentration level 0 2 concentration level equivalent to that of the sample gas, and then the light intensity measurement is performed on the bae as thus diluted.

Since the CO2 concentrations of the two breath samples are adjusted to substantially the same level by dilution the ranges of the 12C02 and 13C 2 calibration curves to be used can be narrowed.

15 It should be noted that the measuring procedure 2 of this embodiment is characterized in that the Co p o ce d r e 2 o f t the two breath samples 2 concentrations of the two breath samples are adjusted to substantially the same level, and does not necessarily require to employ a step of -maintaining the CO t o e m p l o y a step o f maintaining the C02 concentration at a constant level as described in JPB 4(1992)-12441 The use oftt lmted ranges of calibration curves can b u s e o f l i m i t e d r a n g e s o f calibration curves can be achieved simply by adjusting the C02 concentrations of the base gas and the sample oa s to substantially the same level. Since the 2 concentrations of the base gas and th 2 concentrations of the base gas and the sample gas vary within a range of 1% to in actual measurement is very troublesome to always ~r -48maintain the

CO

2 concentrations at a constant level.

If the CO2 concentration of the base gas is lower than the CO2 concentration of the sample gas, the base gas is not diluted, and the measurement is performed on the base gas The base gas is mechanically pushed out at a constant flow rate by the gas injector 21, and light intensity are measured by means of the detection elements 2 5a and The light intensity thus obtained by the first and second detection elements 2 5a and 25b are represented by 12B and 13

B,

respectively.

i mea.- Rurnct X r ment The cleaning of the cleaning of the gas flow path and the cells and the light intensity measurement on the reference gas aanerence gas are performed again.

1: 15 The light intensity thus obtained by the first and second detection elements 2 5a and 25b are represented by 12R 2 and a r e rprented by 1 and :i 3R2, respectively.

2 If the base gas is diluted in "IIIb-4. Base gas 20 measurement, the sample gas is sucked from the breath sampling bag, and then mechanically pushed out at a constant flow rate by the gas injector 21. At this time light intensity are mthetdetec tion are measured by the detection elements 2 5a and If the base gas is not diluted in "IIIb-4. Base gas measurement" the sample gas is diluted with the reference gas -49to a CO 2 concentration level equivalent to that of the base gas in the gas injector 21, and then the intensity of light transmitted through the Sample gas is measured by means of the detection elements 25a and The light intensity thus obtained by the first and second detection elements 2 5a and 25b are represented by 12 s and 13 respectively.

The cleaning of the gas flow path and the cells and the 10 light intensity measurement on the reference gas are erformed erence gas are performed again.

*The light thus .The light intensity thus obtained by the first and second Sdetection elements 2 5a and 25b are represented by 12R 3 and

R

3 respectively.

the base gas are calculated on the basis of the transmitted h tlight intensity 1 r 13 12 1 :light intensity 12R" 1 1 R 2 and

R

2 for the reference gas and the transmitted light intensity 12 B and 13B for the base gas obtained in the measuring procedure 1 or in the measuring procedure 2.

The absorbance 12 Abs(B) of 12

CO

2 is calculated from the following equation: 12 Abs(B) -log[2.12B/(2R112R2 The absorbance 13Abs(B) of 13 C0 2 is calculated from the following equation: 13Abs(B)=-log[2.

13 B/(13R+13R2)] Since the calculation of the absorbances is based on the light intensity obtained in the base gas measurement and the averages (12R1 12R2)/2 and (13R1+13R2)/2 of the light intensity obtained in the reference measurements performed before and after the base gas measurement, the influence of a drift (a time-related influence on the measurement) can be eliminated. Therefore, when the apparatus is turned on, there is no need for waiting until the apparatus reaches a thermal equilibrium (it usually takes several hours).

Where the measuring procedure of the base gas measurement, the reference gas measurement and the base gas 15 measurement, and the sample gas measurement, the reference gas measurement and the sample gas measurement as describe at the beginning of "IIla" is employed, the absorbance 12 Abs(B) of 1C02 in the base gas is calculated from the following equation: 20 12Abs(B)=-log[( 12B+B 2 )/2.12R and the absorbance 13 Abs(B) of 13C02 is calculated from the following equation: 3Abs(B)=-log[( 3 B 13B2) 3

R

wherein 1 2 R and 13 R are the transmitted light intensity for the reference gas, 12B and 13 1 n B 1 are the transmitted light I_

I

-51ntensity for the base gas obtained before the reference gas east,B 2 and 1

B

2 are the transmitted light intensity or the base gas obtained after the reference gas measurement.

V-2.-Caim i a ion o f ahscnrhannc! r s Absorbances 12 Abs(S) and 13 Abs(S) of 12C02 and 13 C0 2 in the sample gas are calculated on the basis of the transmitted light intensity 12

R

2 13

R

2 12

R

3 and 13

R

3 for the reference gas and the transmitted light intensity 12 S and 13 S for the 10 sample gas obtained in the measuring procedure 1 or in the S measuring procedure 2.

S

T

he absorbance 12 Abs(S) of 122 is calculated from the 2 is calculated from the following equation: 12Abs(S)=-log[2.12s/(12R2+12R3) The absorbance 1 3 Abs(S) of 13C The absorbance Abs(S) f 2 is calculated from the following equation: 13 Abs(S)=-log[2.3S/(13R213R3)] Since the calculation of the absorbances is based on the light intensity obtained in the sample gas measurement and the averages of the light intensity obtained in the reference measurements performed before and after the sample gas measurement, the influence of a drift can be eliminated.

Where the measuring procedure of the base gas measurement, the reference gas measurement and the base gas measurement and the sample gas measurement the reference gas the sample gas measurement, the reference gas -52measurement and the sample gas measurement as describe at the beginning of "IIIa" is employed, the absorbance 12 Abs(S) of 12 C0 2 in the sample gas is calculated from the following equation: 1 2 Abs(S)=-log[(12S 1 +12s2)/2.12R] and the absorbance 13Abs(S) of 13C2 is calculated from the of CO 2 is calculated from the following equation: 13 Abs(S)=-log[( 13 s 1 +13s 2 /2.

13

R]

wherein 1 2 R and 13 R are the transmitted light intensity for the reference gas, 12S and 13 transitted light S are the transmitted light intensity for the sample gas obtained before the reference gas Smeasurement, and 1 2

S

2 and 13

S

2 are the transmitted light Sintensity for the sample gas obtained after the reference gas measurement.

15 IV-3. Calclation of concentrails 1 2 The CO2 concentration and the 13C2 concentration are calculated by using calibration curves.

The calibration curves for 12C02 and 13C02 are prepared on the basis of measurement performed by using gaseous samples 20 of known 12 C 0 2 concentrations and gaseous samples of known 13C02 concentrations, respectively.

For preparation of the calibration curve for 12C02, the 12 r2, the 1O2 absorbances for different 12C02 concentrations within a range of about 0% to about 6% are measured. The 1 2CO absorbanes are plotted as 5 concentrations and the 2 c 2 absorbances are plotted as I -53abscissa and ordinate, respectively, and the curve is determined by the method of least squares. An nr--.dxe quadratic curve, which includes relatively small errors, is employed as the calibration curve in this embodiment.

For preparation of the calibration curve for 13C02, the 13CO2 absorbances for different 13C02 concentrations within a range of about 0.00% to about 0.07% are measured. The 13C02 concentrations and the 13C02 absorbances are plotted as abscissa and ordinate, respectively, and the curve is determined by the method of least squares. An approximate 0 O quadratic curve, which includes relatively small errors, is employed as the calibration curve in this embodiment.

e Strictly speaking, the C02 absorbance determined by individually measuring gases respectively containing 12CO2 and 1302 may be different from the 13C02 absorbance determined by measuring a gas containing both 12C02 and 13C02 This is because the wavelength filters each have a bandwidth and the 12C02 absorption spectrum partially overlaps 13CO2 absorption spectrum. Since gases containing both 12C02 and 13C0 are to be measured in this measurement method, the overlap of these spectra should be corrected for preparation of the calibration curves. The calibration curves to be employed in this measurement are subjected to the correction for the overlap of the absorption spectra.

For preparation of the calibration curve for the 12CO2 -54concentration, the 1C02 absorbances for 20 different 1202 conlu---. on within a range of about 0% to about 6% are measured. The 12C02 concentrations nd the 12C02 absorbances are plotted as abscissa and ordinate respectively, as shown in Fig. 17A.

The curve, which passes through the respective data points, is determined by the method of least squares. An approximate quadratic curve includes the least error.

Therefore, the approximate quadratic curve is employed as the calibration curve for 12C n 02 emb 2in this embodiment.

In turn, five data points are selected which are located around the C2 concentration of the base gas reviously determined on the basis of the calibration curve for 12CO e2e The five data points fall within a concentration range of ,io a concentratiocn range of S 15 which accounts for 25% of the entire concentration range 0 the limited data range improves the conformity of the data to of the absorbance 12Abs(B) of the bas calibra n e a s by using he ne, data within the limited concentration range are used for the preparation of a new calibration curve (see Fig. 17B). It is confirmed that the preparation of the calibration curve within the limited data range improves the conformity of the data to the approximate curve, thereby remarkably reducing errors associated with the preparation of the calibration curve. The Cnentration of the base gas is determined on the basis of the absorbance 12 Ab(B) of the base calibration curve for 1 2 CO2.

The 12CO2 concentration of the sample gas is determined in the same manner.

For preparation of the calibration curve for the 13CO 2 concentration, the 13C02 absorbances for 20 different 13CO2 concentrations within a range of about 0.00% to about 0.07% are measured. The 13C02 concentrations and the 13CO2 absorbances are plotted as abscissa and ordinate, respectively, as shown in Fig. 18A.

The curve, which passes through the respective data points, is determined by the method of least squares. An approximate quadratic curve includes the least error.

Therefore, the approximate quadratic curve is employed as the curve is employed as the Scalibration curve for 1C02 in this embodiment.

In turn, five data points are selected which are located around the 13C02 concentration of the base gas previously determined on the basis of the calibration curve for 13

CO

2 The five data points fall within a concentration range of 0.015%, which accounts for about 1/4 of the entire concentration range of the calibration curve shown in Fig. 18A. Then, the data within the limited concentration range are used for the preparation of a new calibration curve (see Fig. 18B). It is confirmed that the reparation of the calibration curve within the limited data range improves the conformity of the data to the approximate curve, thereby remarkably reducing errors associated with the preparation of -56the calibration curve. The 13

CO

2 concentration of the base gas is determined on the basis of the absorbance 13 Abs(B) of the base gas by using the new calibration curve for 13C02.

The 13

CO

2 concentration of the sample gas is determined in the same manner.

The 12 C0 2 concentration and 13

CO

2 concentration of the base gas are represented by 12 Conc(B) and 13Conc(B), respectively. The 12 CO2 concentration and 13 C0 2 concentration of the sample gas are represented by 12 Conc(S) and 13 Conc(S), respectively.

0 TV-4. Cn]ulotion of concentration ratic The concentration ratio of 13C0 2 to 12 C0 2 is determined.

The concentration ratios in the base gas and in the sample gas are expressed as 13Conc(B)/12Conc(B) and 13Conc(S)/12Conc(S), respectively.

o 0 Alternatively, the concentration ratios in the base gas and in the sample gas may be defined as 13 Conc(B)/ 1 2 Conc(B)+13Conc(B) and 13Conc(S)/1 2 Conc(S)+13Conc(S), respectively. Since the 12C0 2 concentration is much higher than the 13 C0 2 concentration, the concentration ratios expressed in the former way and in the latter way are substantially the same.

C.orrect-in of roncentration ratins As described in "BACKGROUND ART", the concentration ratios obtained in the aforesaid manner deviate from actual

I

-57concentrations, depending on the 12C02 concentration.

Although the cause of the deviation has not been elucidated yet, the deviation supposedly results from changes in the spectroscopic characteristics such as reflectance, refractive index and stray light in dependence on the 12C02 concentration and from the error characteristics of the least square method employed for preparation of the calibration curves.

If the concentration ratio is determined without correcting the deviation, a critical error may result.

Therefore, absorbances 2 Abs and iAbs of C02 and C1302 in oo gaseous samples having the same concentration ratio but 12 13 different C0 2 concentrations are measured, and the CO2 and 12 C0 2 concentrations and 13 C0 2 concentration ratios of the gaseous samples are determined by using the calibration o curves. Then, the 12C02 concentrations 1 2 Conc and the concentration ratios 1Conc/1Conc are plotted as abscissa and ordinate, respectively.

The result is shown in Fig. 1.

iO0 The concentration ratios plotted as ordinate in the graph of Fig.l are not normalized. The concentration ratios may be normalized for easy processing of data. Fig. 19 illustrates a graph obtained by way of standardization of the concentration ratios in which a concentration ratio in a gaseous sample of the lowest CO 2 concentration is regarded as (The concentration ratios thus normalized are hereinafter referred to as "normalized concentration ratios".) To obtain an approximate curve accommodating these plotted data, the method of least squares is employed for approximation of the data. It is experientially known that a function of the fourth degree expressed by the following equation provides the most accurate approximate curve.

F(x) ax 4 bx 3 cx 2 dx e (1) wherein F is a normalized concentration ratio, a to d are coefficients, e is a constant, and x is a 12CO2 concentration.

Therefore, the fourth-order function is used as a correction equation. Alternatively, a spline function may be used.

S:

1 5 Standardized 13 CO2/12C0 2 concentration ratios are calculated from the correction equation on the basis of the 12CO2 concentrations 1 2 Conc(B) and 12Conc(S) in the breath samples of the patient. Then, the concentration ratios 3Conc(B)/12Conc(B) and 13Conc(S)/12Conc(S) of the base gas and the sample gas obtained in the measurement are respectively divided by the normalized concentration ratios calculated from the correction equation Thus, corrected concentration ratios are obtained as follows: Corrected concentration ratio =13Conc(B)/[12Conc(B).F(12Conc(B))] -59- Corrected concentration ratio =13Conc(S)/[12Conc(s).F(12Conc(S))] Correction of concentration ratios The 1CO 2 concentration ratios of the base gas and the sample gas are subjected to a correction for oxygen concentration according to the present invention.

The 13C02 concentration ratios are corrected by using a graph (Fig. 2) in which measurements of the 13 C0 2 concentration ratio are plotted with respect to the oxygen contents of gaseous samples.

More specifically, normalized 13C02 concentration ratios are obtained from the graph shown in Fig. 2 on the basis of the concentrations of oxygen in the breath samples which are measured by means of the 02 sensor. Then, the 13 CO2 concentration ratios of the base gas and the sample gas are respectively divided by the normalized 13C02 concentration ratios. Thus, the 13C02 concentration ratios corrected depending on the oxygen concentrations can be obtained.

IV-6. ete r-mintion of change in 13r A difference in 13 C between the sample gas and the base gas is calculated from the following equation:

A

1 3 C [Concentration ratio of sample gas Concentration ratio of base gas] x 10 3 [Concentration ratio of base gas] (Unit: per mill) M -difi af Lto The present invention is not limited to the embodiment described above. In the above-mentioned embodiment, the 12CO and 13C02 concentrations of the base gas and the sample gas are determined, then the concentration ratios thereof are calculated, and the concentration ratios are subjected to the oxygen concentration correction. Alternatively, the concentration ratios may be determined after the 12CO2 and 13CO concentrations of the base gas and the sample gas are determined and the 12C0 and 13C concentrations are 2 andt02 concentrations are corrected by way of the oxygen concentration correction.

YI. RExperiment *i The absorbances of gaseous samples respectively containing 12C02 in concentrations 12 Conc of 4%, :15 5% and 6% with a concentration ratio 13Conc/12Conc of 1.077% were measured in accordance with the method for spectrometrically measuring an isotopic gas. The 12CO 2 concentrations 1 2 Cone and 13C02 concentrations 13 Conc of the gaseous samples were determined on the basis of the measured absorbances by using the calibration curves. The 12CO2 concentrations 12 Conc and the concentration ratios 13Conc/12Conc were plotted as abscissa and ordinate, respectively, as shown in Fig. The maximum and minimum Values of the concentration ratios 3 Conc/12Conc were 1.083% and 1.076%, respectively, and -61the difference therebetween was 0.007%.

In turn, the concentration ratios 13Conc/12Conc were corrected by using the correction equation thus providing a less undulant curve as shown in Fig. 21. In Fig. 21, the maximum and minimum values of the concentration ratios onc/ 2Conc were 1.078% and 1.076%, respectively, and the difference therebetween was 0.0015%.

Therefore, the correction with the correction equation remarkably reduced the variation in the concentration 10 ratio 13Conc/12Conc.

The absorbances of gaseous samples respectively .1 containing 1 2

C

2 in concentrations 12 Conc of 4%, and 6% with a concentration ratio 1 3 Conc/12Conc of 1.065% were measured in accordance with the method for spectrometrically measuring an isotopic gas. The 12 Conc and •13 the 13 Cone were determined on the basis of the measured absorbances by using the calibration curves shown in Figs. 17A and 18A. The 12 12 and 18A. The 12 02 concentrations 12 Conc and the concentration ratios 13Conc/12Conc were plotted as abscissa and ordinate, respectively, as shown in Fig. 22.

The maximum and minimum values of the concentration ratios 1 3 Conc/12Conc were 1.077% and 1.057%, respectively, and the difference therebetween was 0.02%.

In turn, concentration ratios 13Conc/12Conc were -62determined by using the calibration curves shown in Figs. 17A and 18A and then using the limited-range calibration curves shown in Figs. 17B and 18B, thus providing a less undulant curve as shown in Fig. 23. In Fig. 23, the maximum and minimum values of the concentration ratios 13Conc/12Conc were 1.066% and 1.064%, respectively, and the difference therebetween was 0.002%.

Therefore, the method of the present invention, in which the calibration curves were produced again, remarkably reduced 10 the variation in the concentration ratio 13Conc/12Conc.

The absorbances of gaseous samples having different known 13C C02 concentration ratios and containing various concentration of oxygen (up to 90%) were measured, and then 13 the C0 2 concentration ratios were determined on the basis of the measured absorbances by using the calibration curves.

Further, the 13C02 concentration ratios thus determined were corrected by using a correction line as shown in Fig. 2.

The actual 13C02 concentration ratios and the 13CO concentration ratios thus corrected were normalized, and plotted as abscissa and ordinate, respectively, as shown in Fig. 24.

In Fig. 24, the relationship between the actual 13C02 concentration ratio and the measured 13C02 concentration ratio is about 1:1 (or the scope of the fitting curve in Fig. 24 is -63about In comparison with the prior art shown in Fig. 4, in which the relationship between the actual 13C02 concentration ratio and the measured 13 C0 2 concentration ratio is about 1:0.3 (or the.scope of the fitting curve is about the measurement accuracy was drastically improved by performing the correction.

Thus, the correction using the correction line remarkably improved the accuracy of the measurement of the 13CO 2 concentration ratio.

:10 VI-4.

The 12C 0 2 concentration of the same sample gas containing carbon dioxide was measured a plurality of times by means of S. the apparatus for spectrometrically measuring an isotopic gas.

After one hour warming-up of apparatus, a measuring procedure consisting of the reference gas measurement, the sample gas measurement, the reference gas measurement, the sample gas measurement and the reference gas measurement were performed ten times on the same sample gas. The 12CO2 concentration was determined in each cycle of the measuring procedure in accordance with the method A of the present invention in which the absorbance of 12C02 in the sample gas was determined on the basis of an average of values obtained in the reference gas measurements performed before and after the sample gas measurement, and in accordance with the prior art method B in which the absorbance of 12 C0 2 in the sample -64gas was determined on the basis of a value obtained in the reference measurement only before the sample gas measurement.

The results of the calculation of the concentrations in accordance with the method A are shown in Table 1. In Table 1, the concentrations obtained in the second and subsequent measurements were normalized by regarding a concentration obtained in the first measurement as The standard deviation of the concentration data calculated in accordance with the method A was 0.0009.

Table 1 1 2 3 4 1 1.0011 0.9996 0.9998 1.0011 6 7 8 9 0.9982 1 1.0014 1.0005 1.0006 The results of the calculation of the concentrations in accordance with the method B are shown in Table 2. In Table 2, the concentrations obtained in the second and subsequent measurements were normalized by regarding a concentration obtained in the first measurement as The standard deviation of the concentration data calculated in accordance with the method B was 0.0013.

Table 2 1 2 3 4 1 1.0024 1.0001 0.9996 1.0018 6 7 8 9 0.9986 1 1.0022 1.0014 1.0015 As can be understood from the foregoing, the method of the present invention, in which the absorbances are determined on the basis of the light intensity measured on the sample gas and an average of the light intensity measured on the reference gas, provides concentration data with little variation.

1 o o* gg

Claims (28)

1. A method for spectrometrically measuring an isotopic gas, comprising the steps of introducing a gaseous test sample containing a plurality of component gases into a cell, measuring intensity of light transmitted through the gaseous test sample at wavelengths suitable for the respective component gases, and processing data of the light intensity to determine concentrations of the component gases in the gaseous test sample, the method characterized by: a first step of introducing the gaseous test sample into the cell and measuring absorbances of the respective component gases in the gaseous test sample; a second step of determining determining concentrations and concentration ratios of the component gases in the gaseous test sample on the basis of calibration curves; and a third step of obtaining concentration ratio correction values for the component gases on the basis of the concentrations of the component gases obtained in the second step by using correction curves preliminary prepared by measuring absorbances of the component gases in gaseous samples containing the respective component gases in known concentrations with known concentration ratios, determining concentrations and concentration ratios of the component gases in the gaseous samples on the basis of the calibration curves, and by plotting the thus determined concentrations and concentration ratios of the component gases in the gaseous -67- samples, and respectively dividing the concentration ratios of the component gases obtained in the second step by the concentration ratio correction values for the component gases, thereby correcting the concentration ratios of the component gases in the gaseous test sample.

2. A method as set forth in claim i, wherein the correction curves prepared in the third step are approximate fourth-order curves respectively representing the relationships between the 10 concentrations and concentration ratios of the component gases in the gaseous samples determined in the third step.

3. A method as set forth in claim 1, wherein the plurality of component gases include 12 C 2 and 13C0 2

4. A method for spectrometrically measuring an isotopic gas, comprising the steps of introducing a gaseous test sample containing a plurality of component gases into a cell, measuring intensity of light transmitted through the gaseous test sample at wavelengths suitable for the respective component gases, and processing data of the light intensity to determine concentrations of the component gases in the gaseous test sample, the method characterized by: a first step of introducing the gaseous test sample into the cell and measuring absorbances of the respective component gases in the -68- gaseous test sample; a second step of tentatively determining concentrations of the component gases in the gaseous test sample on the basis of calibration curves prepared by using data obtained by measuring gaseous samples respectively containing the component gases in known concentrations within a predetermined range; and a third step of preparing new calibration curves by using some of the data within limited ranges around the concentrations of the component gases in the gaseous test sample tentatively determined in the second step, and determining concentrations of the component gases in the gaseous test sample by using the calibration curves thus prepared. A method as set forth in claim 4, wherein the plurality of component gases include 12C02 and 13CO

06. 6. A method for spectrometrically measuring an isotopic gas, comprising the steps of introducing a gaseous test sample containing 13C02 into a cell, measuring an intensity of light 2: transmitted through the gaseous test sample at a wavelength suitable for 13C02, and processing data of the light intensity to determine a concentration of 13C02 in the gaseous test sample, the method characterized by: a first step of introducing the gaseous test sample into the cell and measuring an absorbance of 13C02 in the gaseous test sample; a -69- second step of determining a concentration of 13 CO 2 in the gaseous test sample on the basis of a calibration curve; and a third step of measuring an oxygen concentration in the gaseous test sample, obtaining a concentration correction value for C0 2 on the basis of a correction curve and the measured oxygen concentration, said correction curve being preliminary prepared by measuring absorbances of 13 C0 2 in gaseous samples containing 13C02 and oxygen in known concentrations, determining concentrations of 13 C0 2 in the gaseous samples on 10 the basis of the calibration curve, and by plotting the concentrations of 13C02 thus determined with respect to the oxygen concentrations, and dividing the concentration of 13C02 S obtained in the second step by the concentration correction value for 13CO 2 determined on the basis of the correction 15 curve, thereby correcting the concentration of 13C 2 in the gaseous test sample.

7. A method for spectrometrically measuring an isotopic gas, comprising the steps of introducing a gaseous test sample containing 02 and 13 2 into a cell, measuring intensity of light transmitted through the gaseous test sample at wavelengths suitable for 1 2 C0 2 and 13C2, and processing data of the light intensity to determine concentrations of or a concentration ratio between 13C and 122 in the gaseous test sample, the method characterized by: a first step of introducing the gaseous test sample into the cell and measuring absorbances of 12C02 and 13C02 in the gaseous test sample; a second step of determining concentrations of or a concentration ratio between 13C0 2 and 12C0 2 in the gaseous test sample on the basis of calibration curves; and a third step of measuring an oxygen concentration in the gaseous test sample, obtaining concentration correction values or a concentration ratio correction value for 13C02 and 12C02 on the basis of correction curves and the measured oxygen concentration, said correction curves being preliminary prepared by measuring absorbances of 12C02 and 13C02 in gaseous samples containing 12 CO 13C and oxygen in known concentrations, determining concentrations of or concentration ratios between 13C02 and 12C02 in the gaseous samples on the 15 basis of the calibration curves, and by plotting the concentrations of or the concentration ratios between 1C02 and 12C02 thus determined with respect to the oxygen concentrations, and respectively dividing the concentrations of or the concentration ratio between 13C02 and 12C02 20 determined in the second step by the concentration correction values or the concentration ratio correction value determined on the basis of the correction curves, thereby correcting the concentrations of or the concentration ratio between 13C02 and 1202 in the gaseous test sample. CO2 in the gaseous test sample. -71-

8. A method for spectrometrically measuring an isotopic gas, comprising the steps of introducing a gaseous test sample containing a plurality of component gases into a cell, measuring absorbances of light transmitted through the gaseous test sample at wavelengths suitable for the respective component gases, and determining concentrations of the respective component gases on the basis of calibration curves prepared by measuring gaseous samples respectively containing the component gases in known concentrations, the method characterized in that a reference gas measurement in which a light intensity is measured with a reference gas filled in the S.i cell and a sample measurement in which a light intensity is measured with the gaseous test sample filled in the cell are alternately performed; and the absorbances are determined on the basis of the light intensity obtained in the sample measurement and an average of light intensity obtained in the reference gas measurements performed before and after the ample measurement.

9. A method as set forth in claim 8, wherein the plurality of component gases include 1 2 CO 2 and 13CO2. A method for spectrometrically measuring an isotopic gas, comprising the steps of introducing a gaseous test sample containing a plurality of component gases into a cell, -72- measuring absorbances of light transmitted through the gaseous test sample at wavelengths suitable for the respective component gases and determining concentrations of the respective component gases on the basis of calibration curves prepared by measuring gaseous samples respectively containing the component gases in known concentrations, the method characterized in that a reference gas measurement in which a light intensity is measured with a reference gas filled in the cell and a sample measurement in which a light intensity is 10 measured with the gaseous test sample filled in the cell are alternately performed, and the absorbances are determined on the basis of the light intensity obtained in the reference gas measurement and an average of light intensity obtained in the -sample measurements performed before and after the reference gas measurement.

11. A method as set forth in claim 10, wherein the plurality of component gases include 12C02 and 13C02

12. A method for spectrometrically measuring an isotopic gas, comprising the steps of introducing a gaseous test sample containing 12 C0 2 and 13 C0 2 as component gases into a cell, measuring absorbances of light transmitted through the gaseous test sample at wavelengths suitable for the respective component gases, and determining concentrations of the -73- respective component gases on the basis of calibration curves prepared by measuring gaseous samples respectively containing the component gases in known concentrations, the method characterized in that two gaseous test samples obtained from one body are measured an, if a concentration of 12C0 in one of the two gaseous test samples is higher than a concentration of 12 C0 2 in the other gaseous test sample, said one gaseous test sample is diluted to a 12 C0 2 concentration level equivalent to that of the other gaseous test sample, and then S 10 C, 2 CO 2 concentration ratios in the respective gaseous test samples are determined.

13. A method as set forth in claim 12, further characterized by a preliminary measurement and a main measurement, wherein concentrations of C02 in first and second gaseous test samples obtained from one body are respectively measured in the preliminary measurement and, if the measured concentration of CO 2 in the first gaseous test sample is higher than the measured concentration of CO 2 in the second gaseous test sample, the first gaseous test sample is diluted to a CO 2 concentration level equivalent to that of the second gaseous test sample, then a 13 CO 2 /12C02 concentration ratio in the first gaseous test sample thus diluted is determined and a C02/ 12C02 concentration ratio in the second gaseous test sample is determined in the main measurement. -74-

14. A method as set forth in claim 12, further characterized by a preliminary measurement and a main measurement, wherein concentrations of C0 2 in first and second gaseous test samples obtained from one body are respectively measured in the preliminary measurement, and if the measured concentration of C02 in the first gaseous test sample is lower than the measured concentration of C0 2 in the second gaseous test sample, a 13CO 2 /12C0 2 concentration ratio in the first gaseous test sample is determined, then the second gaseous test sample :i10 is diluted to a CO2 concentration level equivalent to that of the first gaseous test sample, and a 13C02/12C02 concentration ratio in the second gaseous test sample thus diluted is determined in the main measurement.

15. An apparatus for spectrometrically measuring an isotopic gas, which is adapted to determine concentrations of a plurality of component gases in a gaseous test sample by introducing the gaseous test sample into a cell, then measuring intensity of light transmitted through the gaseous test sample at wavelengths suitable for the respective component gases, and processing data of the light intensity, characterized by gas injection means for sucking therein the gaseous test sample and then injecting the gaseous test sample into the cell by mechanically pushing out the gaseous test sample at a constant rate.

16. An apparatus as set forth in claim 15, further characterized by temperature maintaining means for maintaining the cell receiving the gaseous test sample introduced therein at a constant temperature.

17. An apparatus for spectrometrically measuring an isotopic gas, which is adapted to determine concentrations of a plurality of component gases in a gaseous test sample by introducing the gaseous test sample into a cell, then 10 measuring intensity of light transmitted through the gaseous test sample at wavelengths suitable for the respective component gases and processing data of the light intensity, characterized in that the cell receiving the gaseous test sample introduced therein is positioned in the light path between a light source and a photoreceptor, and a reference cell filled with a reference gas having no absorption at the wavelengths for measurement is disposed in a portion of the light path not occupied by the cell.

18. An apparatus as set forth in claim 17, further characterized by gas flow generating means for constantly passing the reference gas through the reference cell at a constant flow rate.

19. An apparatus as set forth in claim 17, further characterized by temperature maintaining means for maintaining -76- the cell receiving the gaseous test sample introduced therein and the reference cell at a constant temperature. An apparatus for spectrometrically measuring an isotopic gas, which is adapted to determine concentrations of a plurality of component gases in a gaseous test sample by introducing the gaseous test sample into two cells, then measuring intensity of light transmitted through the gaseous test sample at wavelengths suitable for the respective 10 component gases and processing data of the light intensity, characterized in that the two cells for receiving the gaseous test sample introduced therein are disposed along light paths between a light source and a photoreceptor and have different lengths, and a reference cell filled with a reference gas 15 having no absorption at the wavelengths for measurement is disposed between a shorter one of the two cells and the photoreceptor or between the light source and the shorter cell.

21. An apparatus as set forth in claim 20, further characterized by gas flow generating means for constantly passing the reference gas through the reference cell at a constant flow rate.

22. An apparatus as set forth in claim 20, further characterized by temperature maintaining means for maintaining -77- the cells receiving the gaseous test sample introduced therein and the reference cell at a constant temperature.

23. A breath sampling bag, comprising a plurality of breath accumulating chambers joined together for respectively accumulating a plurality of breath samples and a plurality of breath introduction pipes to be respectively connected to a plurality of breath inlets of a gas measuring apparatus for breath measurement to introduce the breath samples from the ooo 10 respective breath accumulating chambers into the gas measuring apparatus, and characterized in that the breath introduction pipes are each configured such that the breath introduction pipes are prevented from being connected to wrong breath inlets of the gas measuring apparatus.

24. A gas measuring apparatus, which is adapted to measure a plurality of breath samples accumulated in a breath sampling bag comprising a plurality of breath accumulating chambers joined together and a plurality of breath introduction pipes through which the breath samples are respectively introduced from a living body into the plurality of breath accumulating chambers, comprising a plurality of breath inlets for introducing the breath samples from the breath accumulating chambers through the breath introduction pipes, and characterized in that the breath inlets are each configured -78- such that the breath inlets are prevented from being connected to wrong breath introduction pipes. A breath sampling bag, comprising a breath accumulating chamber for accumulating breath and a breath introduction pipe for introducing the breath from a living body into the breath accumulating chamber, and characterized in that the breath introduction pipe has resistance generating means for generating a resistance to the blowing of the breath during 00000: sampling of the breath.

26. A breath sampling bag, comprising a breath accumulating chamber for accumulating breath and a breath introduction pipe for introducing the breath from a living body into the breath 15 accumulating chamber, and characterized in that the breath introduction pipe has a detachable filter for removing moisture from the breath during sampling of the breath.

27. A breath sampling bag, comprising a breath accumulating chamber for accumulating breath and a breath introduction pipe for introducing the breath from a living body into the breath accumulating chamber, and characterized in that the breath introduction pipe has a valve for preventing the back flow of the sampled breath. -i -79-

28. A gas measuring apparatus, which is adapted to measure a breath sample accumulated in a breath sampling bag comprising a breath accumulating chamber and a breath introduction pipe with a back-flow prevention valve through which the breath sample is introduced from a living body into the breath accumulating chamber, comprising a breath inlet for introducing the breath sample from the breath sampling bag through the breath introduction pipe, and characterized in that the breath inlet has means for disabling the function of 0 0 the valve when the breath introduction pipe is connected to ooooo the breath inlet.

29. A breath sampling bag as set forth in claim 23 characterized in that the breath introduction pipe has resistance generating means for generating a resistance to the blowing of the breath during sampling of the breath. 00 A breath sampling bag as set forth in claim 23, characterized in that the breath introduction pipe has a detachable filter for removing moisture from the breath during sampling of the breath. Sa

31. A gas measuring apparatus, which is adapted to measure a plurality of breath samples accumulated in a breath sampling bag, comprising a plurality of breaths inlets for introducing the breath samples from breath accumulating chambers of the breath samnling bag through breath introduction pipes, and characterized in that the breath inlets are each configured such that the breath inlets are prevented from being connected to wrong breath introduction pipes. 1 80

32. A breath sampling bag as set forth in claim 23, characterized in that the breath introduction pipe has a valve for preventing the back flow of the sampled breath.

33. A gas measuring apparatus as set forth in claim 32, characterized in that the breath inlet has means for disabling the function of a back-flow prevention valve in the breath introduction pipe when the breath introduction pipe is connected to the breath inlet. Dated this 28th day of April 1999 OTSUKA PHARMACEUTICALS CO., LTD. By their Patent Attorneys GRIFFITH HACK o9 *9 0