MXPA00003957A - A method and apparatus for measuring pulmonary blood flow by pulmonary exchange of oxygen and an inert gas with the blood - Google Patents

Abstract

The invention relates to a method and apparatus for determining pulmonary blood flow in a subject which utilises a divided airway, such that isolated divisions of the respiratory system which together make up the whole of the gas exchanging part of the respiratory system are ventilated with different gas mixtures. The invention also provides a triple lumen cuffed endobronchial catheter useful in measuring pulmonary blood flow.

Description

A METHOD AND APPARATUS FOR MEASURING PULMONARY BLOOD FLOW THROUGH PULMONARY EXCHANGE OF OXYGEN AND A NORTH GAS WITH THE BLOOD This invention relates to the measurement of blood flow in a subject, more particularly to a method and apparatus for measuring pulmonary blood flow by pulmonary oxygen exchange and an inert gas with the blood using a divided respiratory system. The invention is especially suitable for monitoring pulmonary blood flow / cardiac output of a patient under general anesthesia and accordingly it will be convenient to describe the invention in relation to this application. However, it is understood that the method and apparatus described herein can be used to determine the pulmonary blood flow or cardiac output of a subject in a conscious state. The equation that links the cardiac performance of a subject to parameters measured more directly is as follows: Uß «» = Qc? (F? G «* - Fvßa«) where FA8 «« refers to the concentration of inert gas soluble in the alveolar gas mixture of the lungs expressed as a fraction of its partial pressure at barometric pressure (Bp), Fva "refers to the fraction of the inert gas soluble in the mixed venous blood expressed as a fraction of its partial pressure with the total pressure,? is the solubility coefficient of Ost ald of the inert gas soluble in the blood, Qo is the cardiac output that passes through the pulmonary capillaries in the walls of alveoli that contain gas, and Ußas is the intake in the blood from the alveoli measured in units of volume at body temperature and barometric pressure per unit of time. This equation is valid for inert gases only. In this respect, an inert gas dissolves in the blood proportionally to its partial pressure, that is, it obeys Henry's Law. In contrast, a reactive gas does not obey Henry's Law because of its chemical reactivity with constituents of the blood. Oxygen and carbon dioxide are examples of reactive gases. The term "cardiac production" as used herein refers to the amount of blood per unit time that passes through the pulmonary capillaries in the walls of the alveoli of the lungs. If the saturation of the hemoglobin with O2 of the subject is of balloon catheter% then the total cardiac production will be equivalent to the pulmonary blood flow, that is to say, the amount of oxygenated blood that passes through the pulmonary capillaries in the walls of the alveoli of the lungs. If this saturation is less than balloon catheter% total cardiac output includes moving blood in addition to pulmonary blood flow. Shunt blood does not carry O2 from the lungs to the tissue and therefore, can be ignored. The% shunt can be estimated from pulse oximetry. Most of the methods in use today or described in the literature refer to or depend on the above equation, but Fvgaß can not be measured exactly without obtaining a mixed venous blood sample, which would sacrifice the advantage of noninvasive blood vessels. large with catheters, as is necessary with the most widely used method of measuring cardiac output currently in use, namely the thermodisol method. Most of the gas exchange methods for measuring cardiac output that have been tried suffer from the problem of "recirculation" which limits them to intermittent determinations only of Qc separated by relatively long intervals to give gas introduced by the previous determination. This frequency restriction of taking readings of Q0 is necessary to ensure that Pvaa8 has returned to a value close to 0 before making another determination. The same constant also applies to methods that use reactive gases. The term "recirculation" refers to the return to the lungs in mixed venous blood gas that has previously been separated from the lungs in the arterial blood. It is an object of the present invention to overcome or at least alleviate one or more of the aforementioned difficulties of the prior art, or at least to provide the public with a useful selection. Accordingly, in a first aspect the present invention provides a method for measuring pulmonary blood flow in a subject that includes: Isolate two or more divisions of the respiratory system, said divisions comprising part of full gas exchange of said respiratory system, Ventilate each said division with a gas mixture separately, at least one said said gas mixtures including an inert gas soluble, Determine the intake of soluble inert gas in at least two of these divisions, Determine the intake of oxygen in each of said divisions, Determine the final current concentration of soluble inert gas in at least two of said divisions, and Calculate the pulmonary blood flow from determined values of intake and final current concentration of soluble inert gas, and oxygen uptake. Preferably, two or three divisions of the respiratory system are isolated, most preferably three divisions. When three divisions are isolated it is preferred that two of the divisions be ventilated with mixtures of gases that are substantially balanced with respect to the soluble inert gas, the concentration of the soluble inert gas in each of these two divisions being different between them, and the third Division is ventilated with a gas mixture that is unbalanced with respect to the soluble inert gas. A method to isolate two or more divisions of the respiratory system uses a multi-lumen balloon endotracheal catheter. Accordingly, in a second aspect of the invention there is provided an apparatus for measuring pulmonary blood flow in a subject which includes: A multi-lumen balloon endotracheal catheter adapted to allow s? To provide separate gas mixtures to two or more separate divisions of the subject's respiratory system, said separate divisions comprising the complete gas exchange part of said respiratory system, two or more breathing systems to supply different mixes to each lumen of said multi-lumen catheter at the same rate and the same total pressure, two or more gas delivery systems for providing gas mixtures to said two or more breathing systems, sampling means for sampling (i) gas aspirated and expired in each division and / or (ii) fresh flow gas and gas of exhaust of each division, and gas analyzer to determine the concentrations of gases in said samples, a means to determine flow to determine the flow regimes dß (i) said exhaled and expired gas and / or (ii) said fresh flow gas and exhaust gas and, processing system for calculating the pulmonary blood flow from said determined concentrations and flow rates. One method to ensure that gas mixtures are supplied to each lumen at the same rate and the same total pressure is to use a bag type fan in a box with each breathing system, and operate the ventilator supplying a common working gas. Other methods for synchronizing the rate and pressure of the mixed gas delivered to the lumens of the catheter would be apparent to a person skilled in the art. It should be noted that the defined apparatus is not essential to use the measurement method defined above, but represents a particularly convenient apparatus in making the required measurements. Endotracheal catheters having more than two lumens are novel and represent a third aspect of the present invention. Particularly accurate results can be obtained if the multi-lumen balloon endotracheal catheter has three lumens. Accordingly, in a fourth aspect of the invention a triple lumen endotracheal balloon catheter is provided to provide separate gas mixtures to each of the three separate divisions of the respiratory system of a subject, said three divisions comprising the complete part of gas exchange of said respiratory system, said catheter comprising: A primary tube having three lumens adapted to be inserted into the trachea of a subject, each of said lumens opening to an upper end thereof to a matching connector tube to be connected to a breathing system, and that opens to a bottom end thereof to an outlet to deliver a mixture of gases to one of said divisions, one or more inflatable balloons placed around said primary tube and / or said outlets adapted to form seals within the respiratory system so that each outlet is capable of delivering a mixture of gases to one of said three divisions separated in isolation from each of the other divisions. The outlet may be an opening in a tube, or a short tube with an opening, to deliver a mixture of gases to a division of the respiratory system from a lumen of the primary tube. The outlet may be an extension of a lumen of the primary tube or may be an opening at the bottom end of a lumen. The endobronchial catheter with triple lumen balloon preferably has an inflatable balloon placed around the primary tube and above the outlets which is adapted to form a seal within the trachea. In a particularly preferred embodiment the triple lumen catheter includes a first inflatable balloon as described above in combination with a second inflatable balloon placed between the first and third outputs to form a second seal in the right bronchus and a third seal in the hipartial bronchus , the third seal that allows the third outlet to provide a mixture of gases to the middle and lower lobes of the right lung and the second and third seals together that allow the second outlet to provide a mixture of gases to the upper lobe of the right lung. The second inflatable balloon preferably encloses the second outlet and falls into the right main bronchus and the hipartial bronchus. It is also possible to manufacture triple lumen catheters with inflatable balloons as described above which are adapted to deliver mixtures of gases to the right lung, the upper lobe of the left lung and the lower lobe of the left lung, although for technical reasons it is less convenient. According to the present invention the measurement of the xw or cardiac output can be done in short intervals for an extended period of time, while avoiding the problems of recirculation. Measurements can be made quickly and calculations can be made using appropriate software on a computer. Anesthesia is usually given through a single anesthetic breathing system, however, the present invention involves the use of more than one breathing system. Satisfactory results can be obtained with two respiratory systems, however, you can obtain more accurate results with three. It is theoretically possible an additional improvement with more than three breathing systems. Each breathing system delivers to the subject its own individual gas mixture of adjustable ventilation to a division of the alveolar volume of the subject through its particular branch of the bronchial tree. Such an arrangement ensures that each part of the total volume of alveolar gas (that is, the entire gas exchange part of the respiratory system) was being ventilated through one or other of the air passage divisions, but no part was being ventilated. through more than one air passage division. The number of such divisions that is possible is limited only by technical considerations.

The simplest example of such an arrangement, quickly achievable with existing anesthetic equipment, has two such divisions, namely the left lung and the right lung. After placement of a double lumen endotracheal catheter, conventional double balloon (a "double lumen tube" - eg, Bronchocath or Robertshaw type) the left lung and right lung can each be ventilated with completely separate gas mixtures administered through entirely separate breathing systems served each by its own separate fresh gas supply through a dedicated gas delivery system. Alternatively, a custom-made double-lumen tube that ventilates (1) the right upper lobe of the lung and (2) the rest of the respiratory system along with the lines of the triple-lumen tube mentioned previously, but with first and third combined lumens. The subject on whom this method will be used to determine cardiac output could be, for example, a patient undergoing general anesthesia and the inert gas could be a nitrous oxide (N2O). In this case ßl N2O, which is an anesthetic drug, is contributing to the anesthetic state of the patient, but this need is not necessarily so for other inert gases. In this case the total alveolar volume is divided into two divisions, namely the left lung and the right lung and the air passage is similarly divided into two divisions, one for each lung.

Each lung is then ventilated with a gas mixture supplied to it by its own breathing system. Any usable breathing system would suffice. In a typical arrangement used for general anesthesia there would be admission of flow into the respiratory system of component gases under the control of the anesthetist through a needle valve for each. In this case two of the components would be O2 (used in all cases) and N2O. The anesthetist generally observes the flow regime of each gas flow that it controls by means of a gas rotameter or other flow meter for continuous measurement. The breathing systems may contain fresh lime cans to absorb the CO2 produced by the patient, for example semi-closed or closed circle absorber systems (SCCA or CCA). Alternatively they may not contain lime, v. g. , Mapleson A to E systems. A preferred type is the Humphrey ADE low flow multi-purpose breathing system, adaptable to both lime or Mapleson A or Mapieson D lime-free absorption systems. (One advantage of this make is a low volume of circuit made possible by its flexible tube design, it can also be quickly converted from spontaneous breathing mode to IPPV mode by flickering a switch). The most preferred type is the no-breath system because the fresh gas flow from the gas delivery system is also the inspiratory gas and the expiratory gas is the same as the exhaust gas. Except in a completely closed system, each breathing system has a spill valve to vent excess gas, that is, exhaust gas, from the circuit either under manual control or automatically operated. Each breathing system can be connected to the external opening of one of the lumens of the balloon endobronchial catheter, usually via a connecting tube, which may include a catheter assembly. The gas from the breathing system passes to the patient with each inspiration, and the gas expires the other form during expiration. The preferred form of the invention employs three breathing systems and three divisions of the respiratory system. One method to do this involves the use of a flexible small diameter balloon catheter passed underneath one or the other lumen of the double lumen tube. It pushes down on the lung until it does not advance further and the inflated balloon with a minimum volume of air or fluid. The upper end comes out near the upper end of the larger tube through an opening on its side. Ensuring that there is no leakage of the largest tube at the exit point. The small tube ventilates a segment of one lung and the larger tube the rest of that lung. The other lumen of the double lumen tube functions as described in relation to the double lumen system described above. A similar procedure can be carried out with two such small catheters passed through a balloon endobronchial tube. The flexible balloon catheter with a small diameter can be, for example, a Foley urinary catheter or a Swan-Ganz d-catheter or similar or custom-made type. The preferred way to subdivide the ventilation of the alveolar volume into three divisions consists of a preformed triple lumen catheter made to measure analogous in structure to a double lumen tube. This is called a "triple lumen tube" or "triple lumen catheter." A triple-lumen tube is preferred to the three-division methods described above because its position in the patient's bronchial tree can be reviewed by fibrotic optic bronchoscopy while a flexible balloon catheter is placed blindly and is also prone to migration after placement. because of its flexibility. This can result in the occlusion of the opening of a bronchus that branches off the lumen of the bronchus on which the inflated balloon of the catheter rests.

This will cause him to collapse a segment of a lung. Although this can happen without serious immediate effects, in the presence of lung pathology it could possibly cause v. g., local infection or other long-term local pathology. The following parameters can be monitored using techniques known in the art, v. g., using appropriate gas sampling and analysis equipment. (i) ta taking or excretion of one or more of the species of gas by the subject, from the flow of fresh gas, "FGFgas", between its point of entry into the system and its point of exit from the system in the flow of Exhaust gas, "XHgas" (ii) the final current concentrations of one or more of the soluble inert gases present In a preferred embodiment the intake or excretion of each gas species separated from each breath is measured at the outer end of the divisional lumen of the endotracheal tube The term "respiration" as used herein refers to a respiratory cycle. The term "take" as used herein refers to both taking and excretion, excretion being a negative value of the take. This last measurement considerably improves the response time of cardiac production measurement, that is, its response to fleeting or rapid changes in cardiac output, but cardiac output could be measured even though with a slower response time if it is last measurement was omitted. The arrangement described below follows the pattern of usual anesthetic equipment: Each divisional alveolar volume can be served, from top to bottom, by a gas delivery system, which consists of separate sources of gas flow, one for each type of gas , each with a flow control and, for safety reasons, a visual monitor of the instantaneous flow rate of each of the separated gas flows. These gas flows are united together in a single mixed flow and pass to a breathing system. The breathing system allows the inspiratory gas mixture to enter and leave the divisional alveolar volume either by normal breathing action, or (preferably) by the action of a ventilator. The exhaust gas leaves the respiratory system at the same point in it. The preferred point of departure is from the bag of the fan tank (concertina bag) in the case of the bag type fan in a box. The gas in the breathing system enters a lumen of a multi-lumen tube, with a lumen for each combination of gas delivery system / breathing system, and enters the divisional alveolar volume during inspiration. It comes out again during the expiration. As it enters and exits the tube lumen, the gas can be sampled and analyzed at a small continuous rate. Where a separate flow measurement device is in use for measuring body intakes, it is also preferably located here. For total system intakes, sampling for gas analysis and separate flow measurement devices can be in two locations - (1) in the gas delivery system, between the union of separate gas flow flows and the output of common gas and / or (2) in the pipe that moves the exhaust gas away. Whether the shots are being measured between FGFgas and divisional EXHgas (global system shots) or between the flow of inspiration and the divisional expiration flow of each breath (shots of the body) there is a range of ways by which they can be made These measurements of shots. The advantage of measuring body intakes over global system intakes is that the response time is faster because the change in volume dampening is only the volume of the divisional respiratory system. In the case of global system intakes, the volume buffer also includes the volume of the divisional breathing system.

The advantage of measuring global system intakes is that they are more easily realized because through the mixing of the gas flows it can be more easily secured and therefore greater accuracy is achieved. As there is a balance between the advantages, the preferred arrangement is to measure global system intakes and body shots in combination. This allows for optimal resulting accuracy and response. Examples of methods for measuring the necessary intakes are given below. Each of these methods can be applied to either global system taps or body taps, and either in whole or in part. The term "flow entry" applies either to divisional FGFgas or to the divisional inspiration flow in this section according to context, and similarly "flow out" applies to EXHgas or to divisional expiration flow.

The use of flow measuring devices Examples of flow measurement devices include the hot wire anemometer, the pneumotachograph and the turbine anemometer. Other devices that measure gas flow accurately are also suitable. The response time of the flow measurement device is relevant if the gas flow changes over time. The response time is preferably such that the device is able to follow flow changes closely. Incompatible response times will result in longer take measurement times even in the case of global system taps. Pollution will occur between inspiration and expiration measurements in the case of body shots that render them useless unless a special breathing circuit is used. In this respect, the inspiration and expiration sampling lines may be connected between the inspiration and expiration extremities respectively of an IPPV breathing system and a gas analyzer. The sampling and analysis of the gas mixtures could be coordinated with the fan so that the sampling and analysis of the inspired gas are triggered when the ventilator is in its inspiratory phase and vice versa. This could be achieved by an appropriate combination of sotenoid valves in the sampling lines which are operated by a sofenoid control unit which is coordinated with the fan operation. Where the response time of the instrument is compatible with flow changes, the rapid response of the flow measurement device can be used in conjunction with a rapid gas analyzer (RGA) to give flow rate signals of individual species of gases ( Vx). For example, a stream of signals digitized from a RGA that samples the gas mixture can represent individual values of Fx (the fractional concentration in the gas mixture of gas x). This current may be combined with a corresponding stream of signals Vi or VE which represent instantaneous inspiration and expiration signals respectively of such a flow measurement device so that each signal of the RGA corresponds in time to a signal from the device. Through a computation process the Fx det RGA signals can be multiplied by the corresponding Vr or Ve signals of the device to form a stream of resulting signals, each representing the instantaneous flow rate of x towards or outside the divisional air passage and volume alveolar def subject, Vlx or VEx. The integration of this resultant signal current with the measurement time interval, t, gives ßl volume of x that has passed in that time VT? X or VTEX- The chosen time interval is conveniently the duration of inspiration or the duration of expiration in the case of body shots, the instrument that detects the moment of change from inspiration to expiration as the zero flow moment that separates the positive (inward) flow values from the negative ones (outwards). If the volumes that pass in and pass out of x are thus measured with each breath then the difference between them is the intake with each breath, UTX- The regime dβ takes x, ÚX) is Utx multiplied by the regime of respiration, RR. Alternatively Ux can be determined more directly by taking the average of (V VEx) evaluated over an integral number of respiratory cycles.

Algebraically: Vlx Fx-V, and VCx = FX VE UTX = v Tlx "« TEx An insoluble gas, "marker gas", can be added to a known stable flow regime, Vmarc, dor, at a flow inlet, it can be mixed radially and then sampled periodically by means of a gas analyzer.The total gas flow rate, Vi, is: V m- arcade, rr / 'F > Imarcador where F? mark or is the fractional concentration of measured marker gas. If the sampling rate and the analyzer response time are sufficiently fast, the Vi signals can be used in exactly the same way as the Vi signals generated by a flow measurement device and can be measured from any gas of interest in a base breath by breath. To achieve this end, expiratory flows are measured in the most convenient way using a second marker gas (other species of insoluble gas). In a fix, a single sampling point no farther than the outer end of the divisional lumen of the multiple lumen tube can be crossed by two holes for delivery of marker gas to the air passage, one on each side. The distance between each orifice and the sampling point is sufficient to allow radial mixing of marker gas in the gas flow. The marker gases can be any non-toxic insoluble gas. Examples of such a gas include helium, nitrogen, argon, sulfur hexafluoride, neon and many others. It can be used at any convenient concentration taking into account reserves of body tissue in the case of a gas found naturally in the atmosphere. This applies particularly to nitrogen, but if you are going to use trace concentrations you can apply for other gases as well.

Volume displacement devices The VT? It can be measured in this way. A piston pump is an example when used as a ventilator when proper compliance correction is made within the respiratory system. Another more common example is the concertina bag of a bag fan in a box where the volume of gas delivered by the bag can be regulated by a mechanical stop inside the box. The VTe can also be measured by volume displacement so that a spirometer can be used, for example, or the concertina bag can be operated as a spirometer. Breathing patients can spontaneously breathe in and out of a spirometer. In all these cases, the displacement of the spirometer or the bag can be translated into an electrical signal for the purposes of later calculations.

Mixing devices The Fx and Fx measurements can be simplified considerably if volumes of gas are mixed longitudinally before measurement because complex mathematical processes and fast response times can then be dispensed. Mixing can be done by passing the gas streams through mixing boxes, or by stirring them with v. g., a fan, or employing other similar means of either mechanical deflectors or active mixing.

Obligation for uniform flow regime If inspiration and expiration occur at a constant flow rate and a sufficiently large number of gas analyzes are made during the course of a single breath, the simple averaging of inspiration and expiration of multiple values for Fxroador Fx simplifies the calculation of mass transfer because the unit of time in this case is exactly equivalent to the unit volume.

Suggested gas analysis techniques Gas concentrations can be measured by any suitable technique, but one form of rapid gas analysis can provide the best information by (a) rapid response regime to change and (b) averaging, giving a more precise determination. Suitable RGA devices include mass spectrometers, infrared spectrometers, photoacoustic devices, magnetic and acoustic devices for magnetic and Raman scattering analyzers.

Calculation of Qc The ratios of O2 intakes of subdivisions of the total alveolar volume are assumed to accurately reflect their relative pulmonary blood flows. This will be true if pulse oximetry shows a high saturation of O2 in hemoglobin (v. G, 95% - 100%). (Pulse oximetry is universally used as a modality for the supervision of anesthetized and severely ill patients). If the saturation of Oz in hemoglobin is not high, the relationships represent oxygenated blood flows through the subdivisions. From the preceding measurements and from the final current FAN * O values, Qc can be calculated as follows. The calculations will be illustrated by reference to the two-division model previously profiled, but there are corresponding equations to apply to any number of divisions. For the purpose of the following mathematical discussion N2O will be used as the type of gas, but any soluble inert gas "x" will also give a valid result. The N2O (UNIOL and ÚN2OR) intakes for the left and right lung respectively are governed by their respective fractional partial alveolar pressures of N2O (FAN2O_ and FAN2OR), the fractional pressure. mixed venous dß N2O (F N2O). the Ostwald solubility coefficient for N2O,?, and the respective lung share cardiac production (Qei and QcR): ÜNZOL = Qot? (FAN20L FvN2?) .1 UN2QR = QcR? (FAN20R FvN2?) .2 The respective intakes in the left and right lungs are measured simultaneously so that FtfN2o is the same in each. The most effective values for use with FAN2OR and FAN2o ?. they are when the two values are as widely separated between them as possible, in order to maximize the transfer of N2O in the lungs and thus make measurements of N2O intake more accurate. Preferably a lung is ventilated with a gas mixture containing 60% to 80% N2O (soluble inert gas) while the other lung is ventilated with a gas mixture containing 0-20% N2O, preferably 0 %. More preferably, a lung is ventilated with a gas mixture containing: BpfmmHa) -150 x 100%? 2 Bp (mmHg) while the other lung is ventilated with a gas mixture that does not contain N2O. In preference there is positive take in one lung and negative take (excretion) in the other lung. The relation of the respective oxygen intakes, UO? and U02L, equals the ratio of QcR to QoL: this can be shown as follows: Under anesthesia there may be areas of the lung that are poorly ventilated so that the hemoglobin in the blood that passes through such an area is less than 100% saturated with oxygen when it enters the arterial system. The "SpO2" measures the saturation in the arterial system and is a universal monitor. If the S? O2 indicates that the hemoglobin is saturated (SpO2 ~ 100%) this indicates that there are no poorly ventilated areas. If this is the case (which is usual) the oxygen uptake from any given area of the lung, or from the right lung to the left lung, is strictly proportional to the blood flow through that area of the lung. This statement is not true for taking N2O or any other gas that does not saturate a carrier molecule such as hemoglobin. In these cases less N2O is collected by poorly ventilated areas than by well ventilated areas even if the respective blood flows are equal, because the N20 obeys Henry's Law and less of it dissolves in the blood when there is less in the alveolar gas , more of this when better regional ventilation produces more in the alveolar gas of that region. To summarize when O2 completely saturates its carrier molecule with hemoglobin, its concentration in the blood is always the same. All mixed venous blood that returns to the heart from the rest of the body has the same level of unsaturation at a particular time in time (usually around 75%). Therefore, the taking of O2 from particular places in the lung must depend on the blood flow regime to that place and only in this one, whereas for N2O, which obeys Henry's Law, the intake will depend on both, the regime of regional blood flow and the regional concentration of N2O in the regional alveolar gas. Therefore, equations 1, 2 and 3 above are simultaneous and contain three unknowns, namely QoR l QcL and FVN2O- Now: The calculations can be carried out online using a computer. The previous set of simultaneous equations, when resolved, lead to the following equation: The claim that the most effective values for FAN2OR and FAN2OL are when the two values are separated from each other as widely as possible can be demonstrated with the help of this equation. The values of FAN2OL and FAN2OR that are widely separated are achieved when FAN2OR and FAN2o ?. will be as widely separated as possible too, FAN2OR and F? ZOL that are the concentration of N2O fracciona! Inspired by the left and right lungs respectively. (FAN2OL and FAN2OR) are measured by the RGA as the concentration of N2O in the expired gas at the end of the expiration). As these two values become less widely separated the quantity (FAN20? - FAN2OR) s? Becomes smaller. Since this is the difference between two measured quantities, the relative error of this difference becomes larger and larger, tending toward infinity as (FAN2OL - FAN2OR) tends toward its lower limit of zero. Therefore, the Qc error also approaches at infinity as the final expiration concentrations of N2O are equalized in the two divisional alveolar volumes (which in this case are the left lung and the right lung). More than one inert gas soluble in the gas mixture can be used. In this case it is possible to calculate cardiac output by the two separate sets of results and then combine the measured cardiac output of each inert gas calculation into a single value by weighing each according to its estimated margin of error in the appropriate manner. These calculations are They are preferably carried out by a computer. The double lumen endotracheal balloon tube can be modified to a triple lumen tube. The third lumen may serve the bronchus of the right upper lobe or the bronchus of the left upper lobe. An advantage of a third lumen is that it can be ventilated with air or a gas mixture containing insoluble gas. The inflow of fresh gas to a closed-circle breathing system without lime that is connected to the third lumen (third division of the respiratory system), it could be cut for prolonged periods because the intake could be very slow due to the presence of insoluble gas. (Any gas removed from this system through sampling needs to be replaced with insoluble gas or air). The mixed venous partial pressure of each gas dissolved in the mixed venous blood would rapidly come into equilibrium with the gas in the re-breathing system of the third lumen, from which the lime is omitted so that the CO2 is also in equilibrium. In this way the mixed venous tensions of all relevant gases, which would be of interest and value to the anesthetist in his own rights, could be given to him. This can be done by ventilating the division and sampling final gas flow. Furthermore, a direct knowledge of the partial pressure fraction of the inert gas soluble in the mixed venous blood would increase the accuracy of the Qc determination when compared to the independent determination calculated as in the preceding equations, and used to correct it. An additional advantage of a third lumen is that it can reduce errors associated with a phenomenon called V / Q inequality. This is an imperfection in the physiology of the lung that essentially involves a failure to equalize the ventilation of each portion of the lung exactly to its perfusion with blood. The term "perfusion" refers to the rate of blood flow through the unit volume of the lung. Normally the lung is irrigated with blood rather than uniformly ta! that the most dependent parts of the lung, that is, the lower parts, have a greater perfusion than those that are not dependent. A change in the position of the body means that any small region of the lung in particular will probably change its perfusion by changing its vertical distance from the heart, which is a controlling factor. The distribution of blood flow through all the lungs will change. Along with this there is a change also in the regional distribution of ventilation that equals very closely the change in blood flow. Normally all parts of the lung have a relationship of ventilation to blood flow, the ratio V / Q, which is approximately the same, and normally around 0.8 at rest. This value of 0.8 is likely to change, with exercise for example, but its uniformity - much less, ventilation is matched by the body for perfusion. If the equalization of V / Q is perfect it can be shown mathematically that the partial pressure of all the gases of interest in the final expired breath (excluding the terminal space, namely the bronchial tree, within which there is no gas exchange) is equal to the partial pressure of those gases in the arterial blood. In addition, these partial pressures are the same in all parts of the lung. The equalization of V / Q is very close to perfect in the lungs of healthy young adults. In childhood and in later life it is less than perfect. In all people it is not perfect under anesthesia. Also in various forms of disease and even in such states of the body as obesity is probably worse. Thus, in all human patients under anesthesia unequal V / Q will be found, and when anesthesia is combined with factors of age, body weight, and body position (resting in a flat position is worse in this respect than sitting or standing) and the effect on the lungs of, v. g., smoking, yes they can find very considerable degrees of this. It can be shown mathematically that in the presence of unequal V / Q the partial pressure of a gas in the final expired breath (excluding the terminal space gas, namely the first part of the expired breath) will no longer be iguat to its partial pressure. in the blood artery !. It is reasonably close, but it is not exactly the same anymore. The prior art has accepted the errors inherent therein and a number of published documents show Reasonable agreement between the cardiac outputs measured by prior art gas sampling methods to measure cardiac output and alternative methods for measuring it have been tested again. The present method is expected to be able to demonstrate reasonable agreement with existing methods that do not depend on gas exchange (the most widely used being thermo-dissolution being the latter). A study in older and sicker patients where appreciable V / Q inequality is expected has confirmed this. NeverthelessApart from technical errors, the V / Q inequality remains a source of error that is not quantified. It is believed that this problem can be overcome by using one of the possible methods that makes a triple lumen tube possible.

Although one does not wish to be limited by theory, it is believed that the invention will give more reliable results if three divisions of alveolar volume are used on the basis of a technique that can overcome the uneven V / Q problem.

Theoretical source of error 1. Unequal V / Q is a phenomenon exhibited by all functioning lungs. If we consider a young adult at rest in the supine position there is a small discrepancy between ßl FN20, in the case of N2O (as a soluble inert gas), as measured by a gas analyzer in a gas sample taken from the end of expiration , FAN2o, and the FN2o of the blood that is draining the lungs, FaN2Q- In this example the subject is breathing a mixture of gases of uniform composition in both lungs. The FN2o (of the blood) can be measured accurately by specialized techniques. The discrepancy is evaluated as A-aDN2O. If this discrepancy is large enough, it will interfere with the accuracy of the Qc measurement because the equation dβ where Qc is derived contains the variables FAN2OL and FAN20R. The variables that are measurable quickly are taken to be equal to the equivalent variables in the blood, FaN2oR and F, N2O and the equation referred to must be written appropriately with FaN20L and F »N2OR in the place of FAN20L and FAN2O - It would be completely impractical to measure the variables F8 2O and FaN20L directly since this would involve sampling blood from the pulmonary veins, very deep inside the chest.

However, this source of error can be completely eliminated if all the alveoli in a single alveolar division can be caused to have exactly the same concentration of gases in them. The usual situation is that there is a diffusion of FN20 concentrations within a division because there is a diffusion of V / Q ratios within the division. The term V / Q means the ventilation ratio, V, that a particular cell obtains with its perfusion, Q. The value of FAN20 found within its contained gas mixture will be different from that found inside another cell if the V / Q is different. 2. Balanced intake theory If, however, the component gases of the inspired gas mixture, particularly the most abundant ones, N2O and O2, are entering the blood at the same relative regime in which they are being delivered to the alveolus above, the regimen to which these two gases are taken by blood becomes dependent only on the flow of blood. The ventilation becomes irrelevant because in this case (and only in this case) the mixture of aspirated gases, becomes identical in composition. This state is described here as a balanced take. It can be described mathematically and it is found that for values of normal adult dβ Qc and U02, and of total body it can be d + no more dβ approximately 0.37 in value. In this value of FvN20 there is a possible gas mixture that can be given to the subject that will produce the balanced intake. Below this value of FvN20 and exactly below a zero value of FvN20 there are always two possible aspirated gas mixtures of O2 and N2O that can be given to the subject which will result in the occurrence of balanced intake. In PvN2o = O for example the two gas mixtures are 0% N2O and approximately 80% N2O. As the PvN20 increases towards 0.37 the value of F | N20 (the level of N2O aspirated) rises from zero in a mixture while it falls of 80% in the other, becoming the same in FVN? O = 0.37 where it comes to fall between 60 and 70%. For complete balanced intake, carbon dioxide (CO2) must also be added to the gas mixture aspirated in physiological concentration. It has now been discovered that the composition of the correct breathing mixture, the "balanced intake" mixture, can be calculated from a knowledge of both the cardiac output and the mixed venous fractional pressure of N2O, FvN20 (and also the hemoglobin concentration). It turns out that for FvN20 values in the range that will be present in most patients, for each specific value there are two possible gas compositions, that is, two possible ratios of nitrous oxide to oxygen in the balanced intake mixture. This is the case when it is impossible to find these relationships simultaneously by trial and error using two lumens of a triple lumen tube, one for each of the two balanced intake mixtures. The third lumen would ventilate either a segment of a lung or a whole lung with an unbalanced mixture. The need for this arises because the dv FvN2o value needs to be kept stable over time and under appropriate control. Such a system ensures that the mixture of alveolar gases in each compartment (whole lung or segment thereof) is uniform in composition throughout that compartment and that the perfusion blood leaves the compartment (to mix with the blood leaving the other two compartments and forms the arterial current) has values of fractional pressures of N2O that are the same as the FN20 of the breathing gas mixture for the two compartments of balanced intake mixture. Consequently, it is believed that this innovation would improve the precision and accuracy of the method very considerably. The invention will now be described with reference to some examples and drawings which illustrate some preferred aspects of the present invention. However, it should be understood that the particularity of the examples and accompanying drawings is not to replace the generality of the foregoing description of the invention.

In the drawings: Figure 1 is a perspective view of an endobronchial catheter with triple lumen baffle, according to the invention. Figure 2 is a partial cross-sectional view of the triple lumen catheter of Figure 1 inserted into the subject's respiratory system. Figure 3 is a diagrammatic representation of the apparatus useful for measuring pulmonary blood flow in a subject. Referring to the drawings, Figure 1 shows an endobronchial catheter 1 with triple lumen balloon having a primary tube 2 that includes three lumens (not visible). The three lumens are to provide mixtures of individual gases to bronchus 3 of the right upper lobe that feeds the upper lobe of the right lung 4, the right hipartorial bronchus (or right truncal) that feeds the middle and lower lobes of the right lung 6, and the left main bronchus 7 (or bronchus of the left lung) which feeds the left lung 8, as shown in Figure 2. On the top of the primary tube 2 the three volumes are converted into three tubes 9, 10 and 1 1 connectors Dependents which are placed outside the mouth when the catheter is in place within the trachea 12 of a subject. The primary tube 2 is molded with a fold 13 toward the center of its proximal half designed to overlap the tongue posteriorly down the opening of the glottis. Distally there is a tracheal balloon 14 which, when in position, rests entirely from the trachea 12 and when inflated through the funnel 15 d inflation firmly seals the primary tube 2 within the trachea 12. Immediately below the distal margin of the balloon 14 tracheal the output 16 of one of the internal lumens opens to the outside of the tube on its left side and ends. This outlet 16 is at the bottom of the end of the lumen fed by the connecting tube 1 1 and provides gas mixture to the left lung 8. Its upper margin 17 falls approximately 2 cm distal to the tracheal balloon 14. Beyond the outlet 16 a tube 18 that contains exits 19 and 20 curves to the right and slightly later. Outlets 19 and 20, which are in the form of 2 lumens or tubes, extend from the lumens of the primary tube 2 to which the connecting tubes are associated 9 and 10 respectively. Two centimeters below the lower margin 21 of the outlet 16 and on the left side is the upper margin 22 of an inflatable distal balloon 23. This upper margin 22 then encloses the tube 18 obliquely such that in the oblique cross section along the line of the balloon margin the margin 22 extends proximally to the tube 18. In the right side tubes the margin is proximal at its level in the tubes on the left side by 1 cm. The distal margin 24 of the distal balloon 23, on the other hand, obliquely crosses the tube 18 in the other direction so that on the right side the margin 24 is distal by 1 cm and the width of the balloon 23 on the right side is much larger than its width on the left side - 3 cm wide compared to 1 cm wide on the left. When the distal balloon 23 is in position, it falls around the right main bronchus. The right part of the balloon 23 also extends to the hipartial bronchus, which is the extension of the right main bronchus beyond the origin of the bronchus 3 of the right upper lobe. On the right side of the tube 18 and intermediate part centered between the upper and lower margins of the distal balloon 23 the outlet 19 opens to the outside. The outlet 19 is elongated in the axis of the tube 18 and approximately 6-8 mm long by approximately 1 - - 4 mm wide. The distal balloon 23 surrounds the opening 19 which opens to the upper lobe of the right lung 4. The distal balloon 23 is firmly attached to the external surface of the tube 18 at a distance of 1-2 cm around the perimeter of the opening 19. Et tube 18 ends one to two mm distal to the distal margin 24 of the distal balloon 23 at the outlet 20. The cross section at the outlet 20 is oblique as it is parallel with the distal oblique marking of the balloon and the outlet 20 is oval in shape accordingly. The tracheal balloon 14 and the distal balloon 23 are inflated by two tubes 25 and 26 respectively to inflate the balloon which open to them distantly while proximally extending into the body of the primary tube 2 (as two small additional mini lumens) towards the proximal bifurcations 27 and 28 respectively. Beyond the bifurcations they extend 10 cm as independent tubes. Within this independent part of each tube 25 and 26 there are pilot balloons 29 and 30 and at the proximal ends funnels for inflation 15 and 31, which can be replaced by balloon valves mounted beyond the female Luer connections. The respective internal diameters of the three lumens would be 1: 2: 2 with the lumen feeding the right upper lobe which is the smallest. Figure 3 is a diagrammatic representation of part of a preferred embodiment of the invention.

Notes: 1. Pipes carrying gas are indicated as follows: = 2. Arrows together at side, or entering, or exiting indicate direction of flows. 3. Ordinary arrows (-) indicate a direction only and increasing flow. 4. Arrows with two ends (< - >) indicate respiratory flow, that is, of a current nature, with or without pauses of no flow, associated with inflation and deflation of a division of the respiratory system. 5. Electrical connections are indicated by simple black lines. The direction of the current is indicated by arrowheads in these lines (- »-). An O2 gas source under high pressure 32 that can be contained, for example, in a cylinder, passes gas through a gas regulator or reducing valve 33 to a conductive tube where it is at some lower pressure, typical being 400 kPa . From here it passes through a flow control valve and a visual flow screen 34, v. g., a rotameter. Beyond this the gas, now just above the environmental pressure, joins with a similar flow of N2O. The N2O source is similar as well, high pressure supply 35, gas regulator 36, control valve and visual flow screen 37. In addition, the conductive tube is divided in two after the regulator 36 and the second conductive path circumvents the control valve and visual flow screen 37. Instead it passes through a stepped solenoid valve 38 or similar electronic flow control device capable of regulating the flow rate in response to electronic signals, which come, in this case, from the computer 39. Now the flow of the control valve and visual flow screen 37 and then it joins with the O2 flow mentioned above just above the ambient pressure and also, in the case of divisional gas delivery systems that supply the upper right division RULD and the division of the middle and lower right lobes RMLD, is joined by a conduit carrying CO2 whose source is similar to that of O2. It is derived from a high pressure supply 40, gas regulator 41, and control valve and visual gas screen 42 before the gas flows O2 and N2O are united just above the ambient pressure. The combined flow now passes through an anesthetic vaporizer 43, in the case of the divisional delivery system of LLD gas only, where it can collect the vapor of a powerful anesthetic agent in a marked percentage of the flow regime therethrough. The gas mixture with steam containing the potent anesthetic agent if it has been added now passes more than the common gas outlet 50 to the breathing system 51 comprising a wide caliber breathing tube 52, 53, and ventilator 45 for a patient of bag in a box equipped with a gas overflow mechanism 55 designed to allow the concertina bag of the ventilator to remain gas-tight while it is being filled (expiration), but by activating the gas overflow mechanism 55 as soon as it is full (until the top of his career) so that the additional inflow gas after this point in time, but before the inspiration starts to escape from the bag as overflow 56 of bag gas from the fan having the gas composition FGF. When the aspiration begins, the gas ftuye of the concertina bag down to the wide caliber breathing tube 53 to the non-breathing inflation valve 54, down the patient connection 57 and independent part of the triple lumen tube 58 (which consists of one of the independent tube part of the right superior lumen 9, of lumen 10 of the middle and lower right lobes or of 1 1 lumen of the left lung). From here the aspiration passes to the appropriate alveolar volume division where the gas exchange takes place. Although the suction gas is flowing to the non-breathing inflation valve 54, there is added an inflow of marker gas (1) for suction gas at a steady flow rate 59. The suction gas passes forward a sufficient distance for radial mixing to occur and then blasts to a constant flow rate at a sampling point, suction gas (1 to division) 60 which transports it to a solenoid (not shown). ) of solenoid bank (1). The solenoid bank (1) is a solenoid bank consisting of three solenoids that pass FGF gas from each of the three divisions to the gas analyzer 49. (The suction gas is also shown as it passes below the patient connection 57, but this sampling is not used for fear of expiration gas contamination which could fail to pass the non-respiratory inflation valve 54). The expiration gas passes after returning through the same path as far as the non-respiratory inflation valve 54. In this way it is sampled for the purpose of determining individual concentrations of gas present at the end of respiration at the sampling point, suction and expiration gases (1 to division) 61. The sample current passes to a solenoid el which is shown from the bank (2) of solenoids 44. This bank of solenoids consists of three solenoids which pass suction and expiration gas from each of the three divisions to the gas analyzer 49. The solenoids of the second bank of solenoids, 44, the cuat shown, pass suction or expiration gas along sampling lines 61, 46 and 47 of the three divisions. Finally, the solenoids of the third bank of solenoids, bank of solenoids (3), not shown either, pass EXH gas from the aspiration gas 63 from the sampling point of each of the three divisions, to a gas analyzer 49. After passing the non-breathing inflation valve 54, the patient becomes discharged gas, 40, and has the gas composition EXH which receives inflow of marker gas (2) 62. This is sampled as before, this time to a solenoid of the solenoid bank (3) which is not shown. It is sampled at a sampling point, expiration gas (1st division) 63. It is important that the non-respiratory inflation valve 54 be of demonstrable efficiency in its construction. Other shapes of these valves, v. g. , Ruben's valves were leaking and were not adequate. Efficiency is important because retrograde flow leads to inaccuracy due to double sampling. The solenoids of the sotenoid banks (1), (2) and (3) open in rotation and close at the same time that the next sotenoid is opened so that the flow of gas through! Analyzer is continuous. The gas analyzer must be a fast gas analyzer able to define the ßxpíratory waveform. The solnnoids are controlled by the computer 39 through the electrical connections 64-72 inclusive. The gas analyzer signals are sent to the computer through a computer 73 analyzer driver. The gas discharged from the gas analyzer is lost from the system for most analyzers and must be taken into account as a false intake component in the case of suction gas sampled from the breathing system, 51, and gas for inspiration and expiration sampled from connection 57 of the patient. In the case of expiration gas sampled from the gas discharged from the patient, 40, the loss of gas need not be taken into account. The overall operation of the system is conducted both manually and by operation of the computer 39. In an example of the operation of the apparatus shown in Figure 3a division of the right upper lobe, RUD 4, it is initially ventilated with a gas mixture containing 79% N2O, 14% O2 and 7% CO2. The left lung division, LLD 8, is initially ventilated with 100% O2 to which a powerful anesthetic agent vapor (v. G., Isoflurane) has been added via the anesthetic vaporizer 43 to produce a correct level of anesthesia. Its ventilation has been adjusted to produce a final current value (FETCO2LL, D) of 0.05 to 0.055. Ventilation is monitored by the system operator (in general, the anesthetist). The ventilation of the RUD 4 is then set at a level of V * of the ventilation level of the LLD 8. Division 6 of the middle lobe and lower right sß initially ventilates with 0% N2O, 93% O2 and 7% CO2. Your ventilation is set at an SA level of the ventilation level of LLD 8. After a period of five to ten minutes you can do the following. From the aspirated and final N2O concentrations in the RUD 4 (FtN2? RUD and FETN? ORUD), the difference between the aspirate and the final current is calculated. The same is done in RMLD 6. This difference is called the I BTDRUD and ta I ETDRMLD-AS Í, FIN2ORUD - FETN2ORUO - IETDRUD FLN2QRMLD "FETN20RMLD = IETDR LD If IETDRUD is negative in value, the N2O flow of its gas delivery system (1) is reduced by the stepped solenoid valve (3). The degree of reduction is related to the type of breathing system. The preferred type is a non-respiratory system. In this case, the degree of reduction is calculated, according to the percent reduction of the desired N2O, by means of a formula: reduction in VFGFN2ORUD =% deduction x 0.01 current F | N2QRUD X? FOFN2ORUD where VPGPN? ORUD is the current flow regime of fresh N2O gas in the RUD that is delivered by the gas delivery system. The desired percent reduction is the absolute value of IETDRUD- After passing a period (for stabilization of the new IETD up to one minute) the new IETD is evaluated- The stabilization may not actually occur if either FVN2O or QC continues to change, but the evaluation of the new I ETD must still be done. Based on this, additional adjustment of VFG N20RUD should be done in a similar manner. If IETDRUD is positive, VFGFN2ORUD must be adjusted again, increasing the VFGFN20RUD in a similar way, but it must be adjusted to increase FIN2ORUD above its initial value of 79%. If IETDRUD is positive and FIN2ORUD = 79% of balanced take in the RUD gas (IETDRUD = 0) it can be obtained by raising the N2O) to the RMLD until IETDRUD is = 0. This process can disturb the balance in the RUD and some tracking back and forth it may be necessary to adjust the flow of N2O to the RMLD and the RUD. Small adjustments to VFQFN2ORUD will be more responsible for the alteration of IETDRUD than for the equal increases or decreases of VFGFN2ORMLD in the alteration of IETDR LD due to the mathematical relationship. In addition, because the RUD is the smallest division the adjustments to it will at least disturb the value of FvN2o- As such a disturbance it may take a few minutes to manifest itself completely it is preferable as a matter of policy to make the adjustment to the VFOF first , wait for the stabilization and then make the adjustment to the VFGFN2OR LD being guided by the value of the increase in the VFGN? ORUD reached. The rise or fall of the value of FAN20RUD (FAN2ORMLD of final current are likely to occur together, but in opposite directions after initial stabilization because they are more likely to be caused by a change in cardiac output or a change in O2 intake The increase in VFGFN20R LD: increase in VFGFN2ORUD is expected to be 15-20 for most of the range of FAN2ORMLD and FAN2ORUD values (which are approximately 0-65 and 65-80 respectively). The strategy of adjusting the VFG FN20RUD can first be computerized, although it is probably best to do the initial stabilization manually, for this purpose manual adjustment under visual control is available, but a parallel system of finer control is also provided through a computer through of a stepped solenoid valve in the preferred system The initial process of adjusting the two balance values to be selected, the most high in the RUD and lowest in the RMLD gives the system operator the selection over a range of values of FvN20, FvN2D higher causing them to be closer to each other, the lower ones very far apart. The value of FvN2o that determines that this can be set independently allowing a flow of N2O to the left lung from its delivery system dß gas (positive value dß VFGFN2OL-.D) - The selection of FvN20 to be selected is a matter of judgment. The computer can be programmed to set a particular value of FV 2O, a parameter which can be calculated from Qc once it is known first. It can be programmed to track and defend this value through the dfs VFGFN2OLI.D setting, and sß can program to defend the balanced state in both the RUD and the RMLD by adjusting to both, VFGFN2ORUD and VFQFN2ORMLD when imbalance appears spontaneously. The output of the computer, 39, to the visual screen 74, printer 75 or interface RS232 76 and gives a. other electronic devices, and / or any other useful output mode and will also be able to carry information concerning any of the values of the different parameter variables observed by the measuring instruments or calculated from their readings and / or other data stored in your memory or communicated to it from other sources v. g. , manual input or RS232 communication from other electronic devices.

Numerical Example Suppose that the relevant variables listed below have the established plausible values: FN2O inspired, left * 0.8 PN2O inspired, right = 0 Alveolar ventilation left »2L / m Vent. Alveolar right = 2L / m QCL «2.5 L / m QßR = 2.5 L / m FVNZO ~ 0-4 (The value of FvN20 falls halfway between ta FN2o aspirated on the left and FN20 on the right if enough time has passed since the induction of anesthesia due to saturation of body tissues with N2O).

? N2O «0.5 U02R = 0.125 L / m The alveolar FN20 on both sides can now be calculated. The alveolar gas can be considered to be formed by the direct mixing of the fluid streams containing N2O. (This is true because the alveolar-capillary membrane that separates the blood from the gas is freely permeable to) N2O). Putting an equation of mass balance such that the mass of N2O transported in each lung is equal to the mass removed. So: where FBUOL is the left inspired FNÜO and VAH is the left alveolar ventilation.

In a similar way: F m * rßnR ».- 'UmR + FV N" end''Q * íccR »' -? NNp r? N2? ß Km * Yes? "?? UNSOL and UN2O are calculated from the equations: U «* J« (F? JpL -Fv ^ -Q ^ -?, ^ Üw? -FvNaP) -QoR- ?, NjO using the values established for the variables on the right: 0, ^ = 0.307692 L / m Thus, the expected intake regimens in normal human subjects in health will be close to 300 mls / min. (When the tissues are not saturated with N2O, the intake on the left will be increased in some way.The output on the right will be decreased in some way.The intake rate will be approximately 615 mls / min on the left side at the beginning. With a small outlet on the right, the 10-minute intake is approximately 340 m / min and the right exit is approximately 280 m / min, after which the intake declines more slowly. only 25 minutes per minute greater than the right output, it is not necessary to consider the taking of tissue as a cause of any loss in the accuracy of the intake and output measurement). The calculated values for FAN20L and FAN20R after tissue saturation are: The equation of cardiac output derived previously is: Inserting the values for the variables in this equation: , 2x0.615384 0.5x0.492308 l ?? = 5.00 L / min. - I > Saw Throughout this specification and the claims that follow, unless the context otherwise requires, the word "comprises", or variations such as "comprise" or "comprising", shall be understood to imply the inclusion of an integer established or group of integers, but not the exclusion of any other integer or groups of integers. Those skilled in the art will appreciate that the invention described herein is susceptible to other variations and modifications than those specifically described. It should be understood that the invention includes all such variations and modifications. The invention also includes all the steps and aspects alluded to or indicated in this specification, individually or collectively, and any and all combinations of any of two or more of said steps or aspects.

Claims (27)

1. REVIVAL DICATIONS 1. A method for measuring pulmonary blood flow in a subject that includes: isolating two or more divisions of the respiratory system, said divisions comprising the part of the gas exchange complete said respiratory system, ventilate each said division with a mixture of gases separately, at least one of said gas mixtures including a soluble inert gas, determine the intake of soluble inert gas in at least two of said divisions, determine the intake of oxygen in each of said divisions, determine final current concentration of inert gas soluble in at least two of said divisions, and calculate the pulmonary blood flow from determined values of intake and final current concentration of soluble inert gas, and oxygen uptake.
2. 2. A method according to claim 1 wherein two divisions of the respiratory system are isolated.
3. 3. A method according to claim 2 wherein said two divisions comprise the left and right lungs respectively.
4. 4. A method according to claim 1 wherein said soluble inert gas comprises nitrous oxide.
5. 5, A method according to claim 1 wherein at least one of said gas mixtures comprises two or more soluble inert gases.
6. 6. A method according to claim 1 wherein said soluble inert gas comprises sevoflurane and / or desfturane.
7. 7. A method according to claim 1 wherein at least one of said gas mixtures comprises nitrous oxide and sevoflurane or dßsflurane.
8. 8. A method according to claim 1 wherein the subject is under anesthesia.
9. 9. A method according to claim 1 wherein said intakes of soluble inert gas are determined using a soluble inert gas as a marker gas.
10. A method according to claim 1 wherein a gas mixture comprises from 60% to 80% by volume of soluble inert gas and the other gas mixture comprises from 0 to 20% soluble inert gas. eleven .
11. A method according to claim 10 wherein said other gas mixture does not contain any of said soluble inert gas.
12. 12. A method according to claim 1 wherein a mixture of gases comprises soluble inert gas and the other gas mixture does not comprise any of said soluble inert gases.
13. 13. A method according to claim 1 wherein three divisions of the respiratory system are isolated.
14. A method according to claim 13 wherein two of said divisions are ventilated with gas mixtures that are substantially balanced with respect to said soluble inert gas, the concentration of soluble inert gas in each of the two divisions being different on the other, and said third division is ventilated with a mixture of gases which is unbalanced with respect to the soluble inert gas.
15. 15. A method according to claim 14 wherein said two divisions are substantially balanced with respect to the soluble inert gas and carbon dioxide.
16. 16. A method according to claim 14 wherein the balanced concentrations of inert gas soluble in said two divisions are determined by: determining the expired current concentration of soluble inert gas in said third division, estimating the cardiac output of the subject, calculating concentrations Balanced major and minor soluble inert gas from the estimated cardiac output and the final current concentration of soluble inert gas in said third division, adjust the concentration of soluble inert gas in said two divisions to said higher and lower approximate balanced concentration, adjust the concentration of soluble inert gas, in each of said two divisions until a balance is obtained, calculate the pulmonary blood flow while the gas mixtures provided to said two divisions are substantially balanced with respect to the soluble inert gas.
17. 17. A method according to claim 14 wherein said third division is supplied with a gas mixture that does not contain any of said soluble inert gases.
18. 18. A method according to claim 1 or claim 14 wherein the pulmonary blood flow is calculated in a plurality of time intervals.
19. 19. A method according to claim 16 wherein the pulmonary blood flow is calculated in a plurality of time intervals and the balanced concentration of soluble inert gas in said two divisions is readjusted in response to changes in cardiac output or total intake of oxygen.
20. 20. An apparatus for measuring pulmonary blood flow in a subject that includes: an endobronchial catheter with multiple lumen balloon adapted to allow separate gas mixtures to be provided to two or more isolated divisions of the subject's respiratory system, said isolated divisions comprising the complete part of gas exchange of said respiratory system, two or more breathing systems to supply different mixes to each lumen of said multiple lumens catheter at the same rate and the same total pressure, two or more gas delivery systems to provide mixtures of gases to said two or more breathing systems, sampling means for sampling (i) gas aspirated and expired in each division and / or (ii) the fresh flow gas and the exhaust gas of each division, and gas analyzer To determine the gas concentrations in these samples, a means to determine flow to determine the flow regimes of (i said exhaled and expired gas and / or (ii) said fresh flow gas and determined exhaust gas, and processing system for calculating pulmonary blood flow from said concentrations and flow rates.
21. 21. An apparatus according to claim 20 further including a sampling means for sampling composition of gases delivered to the respiratory system of the gas delivery system.
22. 22. An apparatus according to claim 20 which further includes a sampling means for sampling exhaust gas from the respiratory system.
23. 23. An apparatus according to claim 20 wherein the endobronchial catheter with multiple lumen balloon has two or three lumens.
24. 24. A triple lumen endobronchial balloon catheter to provide separate gas mixtures to each of three separate divisions of the respiratory system of a subject, said three divisions comprising the complete gas exchange part of said respiratory system, said catheter comprising: A primary tube having three lumens adapted to be inserted into the trachea of a subject, each said lumen opening at an upper end thereof to a connector tube adapted to be connected to a breathing system, and opening at the bottom end thereof to an outlet for delivering a mixture of gases to one of said divisions, one or more inflatable balloons placed around said primary tube and / or said outlets adapted to form seals within the respiratory system in a manner that each outlet is capable of delivering a mixture of gases to one of said three divisions separated in isolation from each of the other divisions ions.
25. 25. An endobronchial balloon catheter, triple lumen according to claim 24 having a first inflatable balloon positioned around the primary tube and above the outlets which is adapted to form a first seal within the trachea.
26. 26. A triple lumen endobronchial balloon catheter according to claim 25 having a second inflabte balloon placed between the first and third outlets and around the second outlet to form a second seal in the right bronchus and a third seal in the the hipartial bronchus, the third seal that allows the third outlet to provide a mixture of gases to the middle and lower lobes of the right lung and the second seal that allows the second outlet to provide a mixture of gases to the upper lobe of the right lung.
27. 27. A triple lumen bronchobronchial balloon catheter according to claim 25 having a second inflatable balloon placed between the first and third exits and around the second outlet to form a second seal in the left bronchus and a third seal in the bronchus hiparterial, the third seal that allows the third outlet to provide a mixture of gases to the lower lobe of the left lung and the second seal that allows the second outlet to provide a mixture of gases to the upper lobe of the left lung.