CA1113842A - Apparatus for determining the alcohol concentration of the blood - Google Patents
Apparatus for determining the alcohol concentration of the bloodInfo
- Publication number
- CA1113842A CA1113842A CA334,235A CA334235A CA1113842A CA 1113842 A CA1113842 A CA 1113842A CA 334235 A CA334235 A CA 334235A CA 1113842 A CA1113842 A CA 1113842A
- Authority
- CA
- Canada
- Prior art keywords
- threshold value
- signal
- stage
- alcohol
- flip
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
- G01N33/483—Physical analysis of biological material
- G01N33/497—Physical analysis of biological material of gaseous biological material, e.g. breath
- G01N33/4972—Determining alcohol content
Abstract
ABSTRACT OF THE DISCLOSURE
The present application discloses apparatus for deter-mining the alcohol concentration of the blood, having an alcohol measuring instrument that measures the alcohol con-centration of the respiratory air and a CO2-monitoring device which responds to the CO2-content of the respiratory air, said monitoring device having a threshold value stage which generates a signal representing the validity of the alcohol measurement when the CO2-content exceeds a pre-determined value, characterized in that the CO2-monitoring device includes a control stage which responds to the start of exhalation and then generates a signal representing in-validity of the alcohol measurement until the threshold value stage emits the signal representing validity.
The present application discloses apparatus for deter-mining the alcohol concentration of the blood, having an alcohol measuring instrument that measures the alcohol con-centration of the respiratory air and a CO2-monitoring device which responds to the CO2-content of the respiratory air, said monitoring device having a threshold value stage which generates a signal representing the validity of the alcohol measurement when the CO2-content exceeds a pre-determined value, characterized in that the CO2-monitoring device includes a control stage which responds to the start of exhalation and then generates a signal representing in-validity of the alcohol measurement until the threshold value stage emits the signal representing validity.
Description
13~g2 The invention concerns an appratus for determining the alcohol concentration of the blood, with an alcohol-measuring apparatus that measures the alcohol concentration of the res-piratory air and a C02-monitoring device that responds to the C02-content of the resplratory air and has a threshold stage which generates a signal representing the validity of the alcohol measurement when the C02-content exceeds a preset value.
An apparatus Or this kind is known from U.S. Pat. Spec.
3,830,630. This apparatus makes use of the principle that the alcohol concentration Or the blood bears a rixed relationship to the alcohol concentration Or the respiratory air when the latter, being red into the alcohol-measuring apparatus, is derived ~rom the alveoli of the lungs. In order to be sure that this alr ls alveolar air, the C02 content of the respiratory air is monitored, since it has been round that when it consists Or alveolar alr the respiratory air contains at least 4.5 % by vol. C02. The known apparatus includes a bridge circuit which contains a C02-sensitlve resistance in one Or its branches and an alcohol-sehsitive resistance in one Or its other branches. The brldge is so di-mensioned that the al¢ohol-sensitive resistance is errective when the C02-sensitive resistance has previously received su~ficient C02-laden respiratory air, in which case the C02-content Or the respiratory alr ~ust have exceeded the arorementioned 4.5 % by vol. A disadvantage of the known apparatus ls the fact that the sub~ect must breath lnto it several times, e.g. 3 to 5 times, before the alcohol measurement can be carried out.
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With the aid Or the known apparatus it is posslble to ensure that the alcohol measurement is carrled out on alveolar air.
However, the correlation factor between the alcohol-concentratlon of the blood and the alcohol concentration o~ the respiratory air also depends on the diffusion conditions o~ the lungs. Thus people whose blood-alcohol concentration is to be determined can falsify the results of the measurement by manlpulatlng the breath. -For example, the breath-alcohol concentration can be considerably reduced by vigorous hyperventllation before a breath-alcohol test, and thls holds true even if the alcohol measurem~ent is carried out on alveolar alr. Hyperventilation here means rapid, successive deep breathlng.
The purpose o~ the invention is to disclose a structural-ly slmple method whereby previous hyperventilation by the test subJect can be recognlzed during breath-alcohol measurements.
This problem is solved, proceeding from an apparatus as described ln detall above, by having the C02-monltoring equipment lnclude a control stage whlch responds at the start of exhalation and continues to respond as long as a slgnal lndicatin~ the lnvalldity Or the alcohol measurement i9 generated and until the threshold-value stage emits the signal representing valldlty.
- Surprlsingly lt has been found that monitoring the C02-content of the respiratory air will show not only whether the ex-pired air originates from the alveoll, but also whether the test subJect has previously hyperventilated. Unlike the apparatus known from U.S. Pat. Spec. 3,830,630, however, the measurement of the C02-content and the alcohol measurement must be carried out on one . . .
.
. . .
. . ' . ~ .
3~
and the same respiratlon stroke. Thls ls guaranteed by the control stage whlch responds to the start Or exhalatlon. In contrast, in the case Or the apparatus known from U.S. Pat. Spec. 3,830,630 the sub~ect must breath out several times berore the alcohol measurement can be carried out. l~lth several successlve resplra-tlons there is even an increased ~danger Or hyperventilatlon.
Of baslc lmportance are embodlments ln whlch lt ls indi-cated that hyperventilation has taken place prior to the measure-ment. The criterion for this ls that the slgnal representlng _ invalidity of the measurement continues to be present even arter conclusion Or the respiratory stroke determined by the controlstage, i.e. no signal representlng validity has been generated prior to the end of this respiratory stroke. The end Or the respiratory stroke can also be determined by the control stage analogously to the beginning o~ exhalation; however a timing circuit can also be provided whose tlme constant corresponds to the mean d~ratlon Or a respiratory stroke and at the end of which the end Or this stroke is assumed. The indicatlon o~ the erroneous measurement caused by hyperventllatlon can take place ln a separate error-lndicating apparatus, e.g. in an opti-cal slgnalllng apparatus, or the llke. Embodlments are preferred ~ ln ~hich the indicating apparatuses givlng the test results areblocked or at least dimmed out in the case of hyperventilation, so that the erroneous test value is not indicated at all.
.
.
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So as to be able to determine the start of exhalation, the control stage may include e.g. a flow meter which responds to a preset minimum flow. However, this calls for additional sensors in the test duct of the apparatus through which the respiratory air flows, a feature that is in itself undesirable owing to the fact that such sensors bring about fluctuations of respiratory air pressure and lead to condensation of the breath alcohol and hence to test errors. Better, therefore, are embodiments in which no supplementary sensors are re~uired. In such an embodiment the control stage possesses a second threshold value stage that re-sponds to the CO2-content of the respiratory air and generates a signal representing the start of exhalation when the CO2-content exceeds a second predetermined value, the first predetermined value being below the first predetermined value monitored by the aforementioned threshold value stage~ This utilizes the principle that the CO2-content of the surrounding air is usually low and only starts to rise with the start of exhalatian.
In the presence of irregular breathing it may happen that the CO2-content fluctuates, especially at the beginning of exhal-ation. If the second threshold value is here exceeded by several times in the same respiratory stroke, this will result in an un-stable operation of the apparatus. This disadvantage will not arise if a flip-flop circuit is coupled to the first and second threshold value stages, and if this circuit is put by the signal from t~e second threshold Yalue stage into a setting in which it generates the signal representing invalidity of the measurement, and w~ere the flip-flap can be returned by the signal of the first threshold stage ta its other setting.
1 .
.
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The testing of the respiratory air for hyperventilation is preferably carried out independently of the measurement of the maximum alcohol concentration of the respiratory air. The alcohol measuring apparatus measures the alcohol concentration of the respiratory air preferably in a continuous manner and possesses a storage unit for thema~mum value of the measured alcohol concen-tration and indicating equipment for the value stored in said unit.
In such alcohol measuring apparatuses it has been found expedient for the indicating apparatus then to indicate the test result only when the measurement is considered valid. The test subject in this case has no possibility of checking whether his manipulation of the breath has falsified the test result. In the embodiment heretofore described this goal is most easily achieved by having the signal of the flip-flop representing invalidity of the measure-ment block or dim out the indicating apparatus.
Expediently, the signal representing invalidity of the measurement is shown, e.g. optically, on an error-indicating de-vice. This expedient is of importance especially in the case of dimming-out indicators.
In order to facilitate the handling of the equipment the error indicator will preferahly not light up as soon as the signal representing invalidity of the measurement is generated, but only when this signal is present e.g. at the end af a respiratory stroke. In a first embodiment making this possible, provision is made for a timing circuit, that is settable by the signal from the second threshold value stage, to be connected to that stage, thé output signal of which tim$ng circuit is connected by an and-gate to the flip-flop signal representing invalidity of the alcohol _ 5 _ :
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measurement, and sets the error-indicating device to indication of error whenever the signal representing invalidity still continues after the expiry of the time span determined by said timing cir-cuit. The time span of the timing circuit is chosen such that alveolar air will certainly have been exhaled, independently of the vital lung capacity of the test subject.
The signal of the first threshold value stage can be linked via another and-gate to the output signal of the timing circuit, whereby the flip-flop is returned to the other position when the signal from the first threshold value stage appears during the time span established by the timing circuit. If the threshold value that rules out hyperventilation is reached by the first threshold value stage, e.g. owing to breath manipulation, only after expiry of the time span of the timing circuit, then the test-value indicating apparatus will nevertheless not be released to indicate the alcohol concentration.
In another embodiment it is provided that two triggering stages are connected to the second threshold value stage, the first of which triggering stages responds to the change of signal of the second threshold value stage that occurs ~hen the second predetermined threshold value is exceeded, and puts the flip-flop into its position corresponding to invalidity of the alcohol measurement, and the second of which triggering stages responds to the change of signal of the second threshold value stage in the opposite direction, and it is provided that the output signal of the second triggering stage is linked through an and-gate to the flip-flop signal representing invalidity of the alcohol measurement and sets the error-indicating instrument at error-- .: - . . :, . ., , .- - . : ~ - .
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indication. This embodiment has the advantage that it responds to breath manipulations, e.g. short breathing. The first trigger-ing stage determining the startof the exhalation process when the C02-content rises above the threshold value of the second threshold value stage, while the second triggering stage is re-leased when the threashold value of the seonc threshold value stage is exceeded again towards the end of the exhalation pro-cess. The triggering stages can be monoflops which generate brief triggering impoulses compared with the duration of the respira-tion stroke when they are released by side parts of the output signal of the second threshold value stage, In what follows embodiments of the invention are explainedin greater detail with reference to drawings.
Fig. 1 shows the time curve of the C02-content of the emitted air with and without previous hyperventilation, in a schematic diagram;
Fig. 2 is a block circuit diagram of a first embGdiment of a measuring apparatus that recognizes the previous hyper-ventilation, and !a Fig, 3 is a block circuit diagram of a secand embodiment.
In Fig. 1 the time curve of C02-concentration of the air emitted by a test subject is denoted by 1. The breath-emission process begins at the time t = 0 and ends at the time tl. The C02-concentration increases after the start of breath emission and exceeds a threshbld value Sl when air is emitted from the alveoli of the lungs. It is known that the alcohol concentration of the respiratory air stands in a constant ratio to the alcohol concentrat~on of the blood when the alcohol concentration is ' .
~t ~ 7 ~
, t ~
.
.
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measured in alveolar air. The concentration ratio changes, however, when the test subject has hyperventilated vigorously before the alcohol measurement. It has been found that the maxi-mum value of the CO2-concentration attainable during exhalation decreases considerably when there has been previous hyperventi-lation. Curve 3 in Fig. 1 shows the variation of CO2-concentra-tion with the time when there has been previous hyperventilation.
Curve 3 fails to reach the threshold value Sl. This criterion can be utilized for the recognition of a previous hyperventila-tion.
Fig. 2 shows a first embodiment of a ~reath-alcohol tester which avoids measuring error~ caused by previous hyperventilation of the test subject. The subject breathes out in the direction of arrow 5 through a test duct 7, in which an alcohol-measuring sensor 9 of a continuously measuring alcohol tester is located.
Through an analog-digital converter 11 a maximum-value storing unit 13 is connected to alcohol sensor 9. This stores the maxi-mum alcohol concentration value measured during the exh~lation of the test subject. The CQntentS ofmaximu~value storage unit 13 are indicated in a dimming-out indicating instrument 15.
The test duct also contains a CO2-sensor 17 whose signa'l, corresponding to the CO2-concentration of the respiratory air is fed to two threshold value stages 19, 21. Threshold value stage 19 determines the start of exhalation and responds at a threshold , value S2 (Fig. 1~, which corresponds to a smaller CO2-concentra- '~
tion than the threshold value Sl (,Fig. 1) of threshold value stage 21, Threshold value stage 19 triggers a timing circuit 23 to the Q-output of which a triggering stage 25, e.g. a monoflop, is connected, which converts the ascending flank of the output ,,.. -. . . . . . .. .
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signal of timing circuit 23 into a short, e.g. needle-shaped triggering impulse. The triggering impulse fed to a setting input S of a flip-flop 27, sets the latter. The indicating instrument 15 of the alcohol tester is connected to the Q-output of flip-flop 27 and remains dimmed out as long as flip-flop 27 remains set.
Flip-flop 27 is reset when the CO2-concentration exceeds threshold value Sl of threshold value stage 21. The output signal of threshold value stage 21, which is connected in an AND-gate 29 to the output signal of the Q-output of timing circuit 23 is fed for this purpose via an or-gate 31 to the reset input R of flip-flop 27. Flip-flop 27 i5 thus reset when the CO2-concentration exceeds the threshold value Sl within the time span determined by the timing circuit. With flip-flop 27 reset the dimming signal which temporarily indicates invalidity of the alcohol-concentrat.ion measurement is shut off and indicating instrument 15 shows the alcohol-concentration value retained in maximum-value storage unit 13.
In order to be ahle to show the signal indicating invalid-ity o~ the alcohol-concentration measurement even after expiry of the time span of timing unit 23 in an optical indicating apparatus 33, an and-gate 35 connects the signal of the negated output Q' of timing unit 23 with the signal of the output Q of flip-flop 27.
The setting input S of a flip-flop 37 is connected to the output of the and-gate 35. The output Q' of flip-flop 37 controls indic-ating instrument 33. Indicating instrument 33 shows an error, i.e. invalidity o~ the alcohol-concentration measurement, when-ever threshold value Sl of threshold value stage 21 is not reached during the time span established by timing unit 23. The reset ~!
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inputs R of flip-flops 27 and 37 are connected via a key 39 or the like *o-a-source of operating voltage V , reset input R of flip-flop 27 having its connection made through OR-gate 31. With the aid of key 39 flip-flops 27 and 37 can be put to a defined switch-ing position at the start o~ the measuring procedure.
The embodiment according to Fig. 3 differs from that according to Fig. 2 basically only in the CO2-monitoring apparatus.
Wherever functionally similar parts are involved, these are de-noted by the same reference numbers multiplied by 100. For explanation of these parts see the description above.
The alcohol tester again contains a test duct 107, an analog-digital converter 111, a maximum-value storage unit 113 and a dimmable indicating instrument 115.
The CO2-monitoring apparatus, like the embodiment accord-ing to Fig. 2, includes a threshold value stage 119 for a smaller threshold value S2 of the CO2-concentration and a threshold value stage 121 for a larger threshold value Sl of the CO2-concentration.
To threshold value stage 19, unlike this embodiment, however, two triggering stages 141 and 143 are connected which are released by the flanks of the output signal of threshold value stage 119 and then emit brief triggering impulses in both cases. The triggering stages 141, 143 can be designed as monoflops. Triggering stage 141 determines the ascent o~ the output signal of threshold value stage 119 when it exceeds the value S2 at the start of the exhal-ation process. The triggering impulse of triggering stage 141 sets a flip-flop 145 corresponding to flip-flop 27 of Fig. 2, the Q-output signal af which dims out indicating instrument 115. The back-setting input R Q~ flip-~lop 145 i connected, through an x,, , , l'' ,, ' ' :
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or-gate 147 corresponding to or-gate 31 of Fig. 2, to the threshold value stage 121, whereby flip-flop 145 is set back whenever threshold value Sl is reached, and indicating instrument 115 is released so as to show the value of the alcohol concentration that has been stored in maximum-value storage unit 113.
Triggering stage 143 receives the flanks of the output signal of threshold value stage 119 that occur when it falls below the threshold value S2. Triggering stages 141, 143 thus respond to flanks of opposite polarity. An or-gate 149 connects the Q-output signal of flip-flop 145 to the output signal of triggering stage 143 and sets a flip-flop 151, the output of which in turn controls an error-indicating instrument 153 corresponding to the indicating instrument 33 of Fig. 2. Error-indicating instrument 153 thus shows invalidity of the alcohol-concentration measure-ment when the CO2-concentration threshold Sl is not exceeded between the start and finish of the exhalation process determined by triggering stages 141, 143. Reset inputs R of flip-flops 145, 151 are again connected through a key 155 to a source of operating voltage V~, so that it is possible to switch flip-flops 145, 151 to a defined position at the start of the measurement.
Threshold value Sl s~ould lie approximately in the range of 4 to 7% by volume CO2, preferably at approximately 5% by volume.
For thres~old value S2 values around 1% by volume CO2 are suit-a~le, . ' :
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An apparatus Or this kind is known from U.S. Pat. Spec.
3,830,630. This apparatus makes use of the principle that the alcohol concentration Or the blood bears a rixed relationship to the alcohol concentration Or the respiratory air when the latter, being red into the alcohol-measuring apparatus, is derived ~rom the alveoli of the lungs. In order to be sure that this alr ls alveolar air, the C02 content of the respiratory air is monitored, since it has been round that when it consists Or alveolar alr the respiratory air contains at least 4.5 % by vol. C02. The known apparatus includes a bridge circuit which contains a C02-sensitlve resistance in one Or its branches and an alcohol-sehsitive resistance in one Or its other branches. The brldge is so di-mensioned that the al¢ohol-sensitive resistance is errective when the C02-sensitive resistance has previously received su~ficient C02-laden respiratory air, in which case the C02-content Or the respiratory alr ~ust have exceeded the arorementioned 4.5 % by vol. A disadvantage of the known apparatus ls the fact that the sub~ect must breath lnto it several times, e.g. 3 to 5 times, before the alcohol measurement can be carried out.
.' ' ~
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With the aid Or the known apparatus it is posslble to ensure that the alcohol measurement is carrled out on alveolar air.
However, the correlation factor between the alcohol-concentratlon of the blood and the alcohol concentration o~ the respiratory air also depends on the diffusion conditions o~ the lungs. Thus people whose blood-alcohol concentration is to be determined can falsify the results of the measurement by manlpulatlng the breath. -For example, the breath-alcohol concentration can be considerably reduced by vigorous hyperventllation before a breath-alcohol test, and thls holds true even if the alcohol measurem~ent is carried out on alveolar alr. Hyperventilation here means rapid, successive deep breathlng.
The purpose o~ the invention is to disclose a structural-ly slmple method whereby previous hyperventilation by the test subJect can be recognlzed during breath-alcohol measurements.
This problem is solved, proceeding from an apparatus as described ln detall above, by having the C02-monltoring equipment lnclude a control stage whlch responds at the start of exhalation and continues to respond as long as a slgnal lndicatin~ the lnvalldity Or the alcohol measurement i9 generated and until the threshold-value stage emits the signal representing valldlty.
- Surprlsingly lt has been found that monitoring the C02-content of the respiratory air will show not only whether the ex-pired air originates from the alveoll, but also whether the test subJect has previously hyperventilated. Unlike the apparatus known from U.S. Pat. Spec. 3,830,630, however, the measurement of the C02-content and the alcohol measurement must be carried out on one . . .
.
. . .
. . ' . ~ .
3~
and the same respiratlon stroke. Thls ls guaranteed by the control stage whlch responds to the start Or exhalatlon. In contrast, in the case Or the apparatus known from U.S. Pat. Spec. 3,830,630 the sub~ect must breath out several times berore the alcohol measurement can be carried out. l~lth several successlve resplra-tlons there is even an increased ~danger Or hyperventilatlon.
Of baslc lmportance are embodlments ln whlch lt ls indi-cated that hyperventilation has taken place prior to the measure-ment. The criterion for this ls that the slgnal representlng _ invalidity of the measurement continues to be present even arter conclusion Or the respiratory stroke determined by the controlstage, i.e. no signal representlng validity has been generated prior to the end of this respiratory stroke. The end Or the respiratory stroke can also be determined by the control stage analogously to the beginning o~ exhalation; however a timing circuit can also be provided whose tlme constant corresponds to the mean d~ratlon Or a respiratory stroke and at the end of which the end Or this stroke is assumed. The indicatlon o~ the erroneous measurement caused by hyperventllatlon can take place ln a separate error-lndicating apparatus, e.g. in an opti-cal slgnalllng apparatus, or the llke. Embodlments are preferred ~ ln ~hich the indicating apparatuses givlng the test results areblocked or at least dimmed out in the case of hyperventilation, so that the erroneous test value is not indicated at all.
.
.
1~13~
So as to be able to determine the start of exhalation, the control stage may include e.g. a flow meter which responds to a preset minimum flow. However, this calls for additional sensors in the test duct of the apparatus through which the respiratory air flows, a feature that is in itself undesirable owing to the fact that such sensors bring about fluctuations of respiratory air pressure and lead to condensation of the breath alcohol and hence to test errors. Better, therefore, are embodiments in which no supplementary sensors are re~uired. In such an embodiment the control stage possesses a second threshold value stage that re-sponds to the CO2-content of the respiratory air and generates a signal representing the start of exhalation when the CO2-content exceeds a second predetermined value, the first predetermined value being below the first predetermined value monitored by the aforementioned threshold value stage~ This utilizes the principle that the CO2-content of the surrounding air is usually low and only starts to rise with the start of exhalatian.
In the presence of irregular breathing it may happen that the CO2-content fluctuates, especially at the beginning of exhal-ation. If the second threshold value is here exceeded by several times in the same respiratory stroke, this will result in an un-stable operation of the apparatus. This disadvantage will not arise if a flip-flop circuit is coupled to the first and second threshold value stages, and if this circuit is put by the signal from t~e second threshold Yalue stage into a setting in which it generates the signal representing invalidity of the measurement, and w~ere the flip-flap can be returned by the signal of the first threshold stage ta its other setting.
1 .
.
~3a~
The testing of the respiratory air for hyperventilation is preferably carried out independently of the measurement of the maximum alcohol concentration of the respiratory air. The alcohol measuring apparatus measures the alcohol concentration of the respiratory air preferably in a continuous manner and possesses a storage unit for thema~mum value of the measured alcohol concen-tration and indicating equipment for the value stored in said unit.
In such alcohol measuring apparatuses it has been found expedient for the indicating apparatus then to indicate the test result only when the measurement is considered valid. The test subject in this case has no possibility of checking whether his manipulation of the breath has falsified the test result. In the embodiment heretofore described this goal is most easily achieved by having the signal of the flip-flop representing invalidity of the measure-ment block or dim out the indicating apparatus.
Expediently, the signal representing invalidity of the measurement is shown, e.g. optically, on an error-indicating de-vice. This expedient is of importance especially in the case of dimming-out indicators.
In order to facilitate the handling of the equipment the error indicator will preferahly not light up as soon as the signal representing invalidity of the measurement is generated, but only when this signal is present e.g. at the end af a respiratory stroke. In a first embodiment making this possible, provision is made for a timing circuit, that is settable by the signal from the second threshold value stage, to be connected to that stage, thé output signal of which tim$ng circuit is connected by an and-gate to the flip-flop signal representing invalidity of the alcohol _ 5 _ :
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.
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measurement, and sets the error-indicating device to indication of error whenever the signal representing invalidity still continues after the expiry of the time span determined by said timing cir-cuit. The time span of the timing circuit is chosen such that alveolar air will certainly have been exhaled, independently of the vital lung capacity of the test subject.
The signal of the first threshold value stage can be linked via another and-gate to the output signal of the timing circuit, whereby the flip-flop is returned to the other position when the signal from the first threshold value stage appears during the time span established by the timing circuit. If the threshold value that rules out hyperventilation is reached by the first threshold value stage, e.g. owing to breath manipulation, only after expiry of the time span of the timing circuit, then the test-value indicating apparatus will nevertheless not be released to indicate the alcohol concentration.
In another embodiment it is provided that two triggering stages are connected to the second threshold value stage, the first of which triggering stages responds to the change of signal of the second threshold value stage that occurs ~hen the second predetermined threshold value is exceeded, and puts the flip-flop into its position corresponding to invalidity of the alcohol measurement, and the second of which triggering stages responds to the change of signal of the second threshold value stage in the opposite direction, and it is provided that the output signal of the second triggering stage is linked through an and-gate to the flip-flop signal representing invalidity of the alcohol measurement and sets the error-indicating instrument at error-- .: - . . :, . ., , .- - . : ~ - .
~13~
indication. This embodiment has the advantage that it responds to breath manipulations, e.g. short breathing. The first trigger-ing stage determining the startof the exhalation process when the C02-content rises above the threshold value of the second threshold value stage, while the second triggering stage is re-leased when the threashold value of the seonc threshold value stage is exceeded again towards the end of the exhalation pro-cess. The triggering stages can be monoflops which generate brief triggering impoulses compared with the duration of the respira-tion stroke when they are released by side parts of the output signal of the second threshold value stage, In what follows embodiments of the invention are explainedin greater detail with reference to drawings.
Fig. 1 shows the time curve of the C02-content of the emitted air with and without previous hyperventilation, in a schematic diagram;
Fig. 2 is a block circuit diagram of a first embGdiment of a measuring apparatus that recognizes the previous hyper-ventilation, and !a Fig, 3 is a block circuit diagram of a secand embodiment.
In Fig. 1 the time curve of C02-concentration of the air emitted by a test subject is denoted by 1. The breath-emission process begins at the time t = 0 and ends at the time tl. The C02-concentration increases after the start of breath emission and exceeds a threshbld value Sl when air is emitted from the alveoli of the lungs. It is known that the alcohol concentration of the respiratory air stands in a constant ratio to the alcohol concentrat~on of the blood when the alcohol concentration is ' .
~t ~ 7 ~
, t ~
.
.
' , ` '' . , ' , . ' 1~38~
measured in alveolar air. The concentration ratio changes, however, when the test subject has hyperventilated vigorously before the alcohol measurement. It has been found that the maxi-mum value of the CO2-concentration attainable during exhalation decreases considerably when there has been previous hyperventi-lation. Curve 3 in Fig. 1 shows the variation of CO2-concentra-tion with the time when there has been previous hyperventilation.
Curve 3 fails to reach the threshold value Sl. This criterion can be utilized for the recognition of a previous hyperventila-tion.
Fig. 2 shows a first embodiment of a ~reath-alcohol tester which avoids measuring error~ caused by previous hyperventilation of the test subject. The subject breathes out in the direction of arrow 5 through a test duct 7, in which an alcohol-measuring sensor 9 of a continuously measuring alcohol tester is located.
Through an analog-digital converter 11 a maximum-value storing unit 13 is connected to alcohol sensor 9. This stores the maxi-mum alcohol concentration value measured during the exh~lation of the test subject. The CQntentS ofmaximu~value storage unit 13 are indicated in a dimming-out indicating instrument 15.
The test duct also contains a CO2-sensor 17 whose signa'l, corresponding to the CO2-concentration of the respiratory air is fed to two threshold value stages 19, 21. Threshold value stage 19 determines the start of exhalation and responds at a threshold , value S2 (Fig. 1~, which corresponds to a smaller CO2-concentra- '~
tion than the threshold value Sl (,Fig. 1) of threshold value stage 21, Threshold value stage 19 triggers a timing circuit 23 to the Q-output of which a triggering stage 25, e.g. a monoflop, is connected, which converts the ascending flank of the output ,,.. -. . . . . . .. .
'. ' . ~ : : . :' ': ' ., : : .
:. : ,. ,:: . . . .:
` - :
1~L1384`;~
signal of timing circuit 23 into a short, e.g. needle-shaped triggering impulse. The triggering impulse fed to a setting input S of a flip-flop 27, sets the latter. The indicating instrument 15 of the alcohol tester is connected to the Q-output of flip-flop 27 and remains dimmed out as long as flip-flop 27 remains set.
Flip-flop 27 is reset when the CO2-concentration exceeds threshold value Sl of threshold value stage 21. The output signal of threshold value stage 21, which is connected in an AND-gate 29 to the output signal of the Q-output of timing circuit 23 is fed for this purpose via an or-gate 31 to the reset input R of flip-flop 27. Flip-flop 27 i5 thus reset when the CO2-concentration exceeds the threshold value Sl within the time span determined by the timing circuit. With flip-flop 27 reset the dimming signal which temporarily indicates invalidity of the alcohol-concentrat.ion measurement is shut off and indicating instrument 15 shows the alcohol-concentration value retained in maximum-value storage unit 13.
In order to be ahle to show the signal indicating invalid-ity o~ the alcohol-concentration measurement even after expiry of the time span of timing unit 23 in an optical indicating apparatus 33, an and-gate 35 connects the signal of the negated output Q' of timing unit 23 with the signal of the output Q of flip-flop 27.
The setting input S of a flip-flop 37 is connected to the output of the and-gate 35. The output Q' of flip-flop 37 controls indic-ating instrument 33. Indicating instrument 33 shows an error, i.e. invalidity o~ the alcohol-concentration measurement, when-ever threshold value Sl of threshold value stage 21 is not reached during the time span established by timing unit 23. The reset ~!
_ g _ . ' . :. . ,. -':
' . . ' ' . . . ~ ~
- : . ;. - , : ~ ~ .
- . . .
~il3~
inputs R of flip-flops 27 and 37 are connected via a key 39 or the like *o-a-source of operating voltage V , reset input R of flip-flop 27 having its connection made through OR-gate 31. With the aid of key 39 flip-flops 27 and 37 can be put to a defined switch-ing position at the start o~ the measuring procedure.
The embodiment according to Fig. 3 differs from that according to Fig. 2 basically only in the CO2-monitoring apparatus.
Wherever functionally similar parts are involved, these are de-noted by the same reference numbers multiplied by 100. For explanation of these parts see the description above.
The alcohol tester again contains a test duct 107, an analog-digital converter 111, a maximum-value storage unit 113 and a dimmable indicating instrument 115.
The CO2-monitoring apparatus, like the embodiment accord-ing to Fig. 2, includes a threshold value stage 119 for a smaller threshold value S2 of the CO2-concentration and a threshold value stage 121 for a larger threshold value Sl of the CO2-concentration.
To threshold value stage 19, unlike this embodiment, however, two triggering stages 141 and 143 are connected which are released by the flanks of the output signal of threshold value stage 119 and then emit brief triggering impulses in both cases. The triggering stages 141, 143 can be designed as monoflops. Triggering stage 141 determines the ascent o~ the output signal of threshold value stage 119 when it exceeds the value S2 at the start of the exhal-ation process. The triggering impulse of triggering stage 141 sets a flip-flop 145 corresponding to flip-flop 27 of Fig. 2, the Q-output signal af which dims out indicating instrument 115. The back-setting input R Q~ flip-~lop 145 i connected, through an x,, , , l'' ,, ' ' :
-.
~13B4~
or-gate 147 corresponding to or-gate 31 of Fig. 2, to the threshold value stage 121, whereby flip-flop 145 is set back whenever threshold value Sl is reached, and indicating instrument 115 is released so as to show the value of the alcohol concentration that has been stored in maximum-value storage unit 113.
Triggering stage 143 receives the flanks of the output signal of threshold value stage 119 that occur when it falls below the threshold value S2. Triggering stages 141, 143 thus respond to flanks of opposite polarity. An or-gate 149 connects the Q-output signal of flip-flop 145 to the output signal of triggering stage 143 and sets a flip-flop 151, the output of which in turn controls an error-indicating instrument 153 corresponding to the indicating instrument 33 of Fig. 2. Error-indicating instrument 153 thus shows invalidity of the alcohol-concentration measure-ment when the CO2-concentration threshold Sl is not exceeded between the start and finish of the exhalation process determined by triggering stages 141, 143. Reset inputs R of flip-flops 145, 151 are again connected through a key 155 to a source of operating voltage V~, so that it is possible to switch flip-flops 145, 151 to a defined position at the start of the measurement.
Threshold value Sl s~ould lie approximately in the range of 4 to 7% by volume CO2, preferably at approximately 5% by volume.
For thres~old value S2 values around 1% by volume CO2 are suit-a~le, . ' :
, ~',-- 11 - ,~
.~ ~
.
-' ' "' ~
. ' - :
-,. ~ . . . :
Claims (10)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for determining the alcohol concentration of the blood, having an alcohol measuring instrument that measures the alcohol concentration of the respiratory air and a CO2-monitoring device which responds to the CO2-content of the respiratory air, said monitoring device having a threshold value stage which generates a signal representing the validity of the alcohol measurement when the CO2-content exceeds a predetermined value, characterized in that the CO2-monitoring device includes a control stage which responds to the start of exhalation and then generates a signal representing invalidity of the alcohol measurement until the threshold value stage emits the signal represent-ing validity.
2. Apparatus according to claim 1, characterized in that the control stage possesses a second threshold value stage responding to the CO2-content of the respiratory air, which threshold value stage generates a signal representing the start of exhalation whenever the CO2-content exceeds a second predetermined value (S2), said second predetermined value (S2) being smaller than the first predetermined value (S1) monitored by the first-mentioned threshold value stage.
3. Apparatus according to claim 2, characterized in that a flip-flop is connected to the first and to the second thres-hold value stages, which flip-flop is set by the signal of the second threshold value stage into a position in which it generates the signal representing invalidity of the measurement, and where the flip-flop can be reset by the signal of the first threshold value stage into its other position.
4. Apparatus according to claim 3, characterized in that the alcohol-measuring instrument measures the alcohol con-centration of the respiratory air continuously and possesses a storage unit for the maximum value of the measured alcohol concentration and an indicating instrument for the value stored in the storage unit, and that the signal of the flip-flop representing invalidity of the measurement blocks or dims out the indicating instrument.
5. Apparatus according to claim 3, characterized in that an error-indicating instrument for the signal representing invalidity of the measurement is connected to the flip-flop.
6. Apparatus according to claim 5, characterized in that a timing unit that is settable by the signal of the second threshold value stage is coupled to said second threshold value stage, the output signal of which is linked through an and-gate with the flip-flop signal representing invalidity of the alcohol measurement, and sets the error-indicating instrument so as to indicate error when the signal represent-ing invalidity persists after expiry of the time span deter-mined by the timing unit.
7. Apparatus according to claim 6, characterized in that the signal of the first threshold value stage is linked through a second and-gate with the output signal of the timing unit and resets the flip-flop to the other position when the signal of the first threshold value stage appears during the time span established by the timing unit.
8. Apparatus according to claim 5, characterized in that two triggering stages are connected to the second threshold value stage, the first of which triggering stages responds to the change of signal of the second threshold value stage that occurs when the second predetermined threshold value is exceeded and puts the flip-flop into its position correspond-ing to invalidity of the alcohol measurement, and the second of which triggering stages responds to the change of signal of the second threshold value stage in the opposite direction, and that the output signal of the second triggering stage is linked through an and-gate with the signal of the flip-flop representing invalidity of the alcohol measurement and puts the error-indicating instrument to error-indication.
9. Apparatus according to claim 1, characterized in that an error-indicating instrument and/or a device for blocking or dimming the indicating instrument for the measured alcohol concentration are provided which indicate the occurence of the signal representing invalidity of the alcohol measure-ment even after termination of the respiratory stroke deter-mined by the control stage, whenever the threshold value stage fails to generate a signal representing validity.
10. Apparatus according to claim 1, characterized in that a device is provided which blocks or dims an indicating in-strument for indicating the measured alcohol concentration when the signal representing invalidity of the alcohol measurement occurs even after the end of the respiratory stroke determined by the control stage, whenever the threshold value stage fails to generate a signal represent-ing validity.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19782836886 DE2836886A1 (en) | 1978-08-23 | 1978-08-23 | Tamperproof breathalyser - with carbon di:oxide analyser to prove hyperventilation attempts |
| DEP2836886.7 | 1978-08-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1113842A true CA1113842A (en) | 1981-12-08 |
Family
ID=6047755
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA334,235A Expired CA1113842A (en) | 1978-08-23 | 1979-08-22 | Apparatus for determining the alcohol concentration of the blood |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1113842A (en) |
| DE (1) | DE2836886A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5376555A (en) * | 1994-02-25 | 1994-12-27 | Intoximeters, Inc. | Method for testing breath alcohol with discrimination between alveolar and upper respiratory tract alcohol |
| FI102511B (en) * | 1995-06-26 | 1998-12-31 | Instrumentarium Oy | Contents measurement from respiratory air |
| DE19619763A1 (en) * | 1996-05-17 | 1997-11-20 | Univ Ludwigs Albert | Device for taking inspiratory and / or expiratory gas samples |
| DE10061881C2 (en) * | 2000-12-12 | 2003-08-28 | Karl-Heinz Kraus | Device for measuring and displaying the breath alcohol content |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3830630A (en) * | 1972-06-21 | 1974-08-20 | Triangle Environment Corp | Apparatus and method for alcoholic breath and other gas analysis |
-
1978
- 1978-08-23 DE DE19782836886 patent/DE2836886A1/en active Granted
-
1979
- 1979-08-22 CA CA334,235A patent/CA1113842A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2836886A1 (en) | 1980-03-13 |
| DE2836886C2 (en) | 1990-08-30 |
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| MKEX | Expiry |