AU726908B2

AU726908B2 - Breath sampling bag and gas measuring apparatus

Info

Publication number: AU726908B2
Application number: AU26011/99A
Authority: AU
Inventors: Tamotsu Hamao; Eiji Ikegami; Yasuhiro Kubo; Takashi Maruyama; Masaaki Mori; Katsuhiro Morisawa; Kazunori Tsutsui; Yasushi Zasu
Original assignee: Otsuka Pharmaceutical Co Ltd
Current assignee: Otsuka Pharmaceutical Co Ltd
Priority date: 1995-10-09
Filing date: 1999-04-30
Publication date: 2000-11-23
Anticipated expiration: 2016-10-02
Also published as: AU2601199A

Description

AUSTRALIA

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

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

DESCRIPTION

BREATH SAMPLING BAG AND GAS MEASURING APPARATUS Technical Field The present invention relates to breath sampling bag and gas measuring apparatus for spectrometrically measuring the concentration of an isotopic gas on the basis of a difference in the light absorption characteristics of the isotope.

Background Art *4* Isotopic analyses are useful for diagnosis of a disease in a medical application, in which metabolic functions of a living body can be determined by measuring a change in the 15 concentration or concentration ratio of an isotope after S administration of a drug containing the isotope. In the other fields, the isotopic analyses are used for studies of the photosynthesis and metabolism of plants, and for ecological tracing in a geochemical application.

5*55** *0 It is generally known that gastric ulcer and gastritis are caused by bacteria called helicobacter pylori (HP) as well as by a stress. If the HP is present in the stomach of a patient, an antibiotic or the like should be administered to the patient for bacteria removal treatment. Therefore, it is indispensable to check if the patient has the HP. The HP has a strong urease activitY for decomposing urea into carbon dioxide arnd anurionia.

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

If the concentration of 13 C2(a final mtblcPout or the concentration ratio of 13 c02t 12 C02i raho patient is successfull Y measured after urea labeled with the isotope 130C is administered to the patient, the presence of the HP can be confirmed.

However, the concentration ratio of 1302t 1202i naturally ocrigcarbon dioxide is 1:100. Thrfrit i difficult to determine the concentration ratio in the breath of the patient with high accuracy.

There have been known methods for deter-mining the concent~Iiration ratio of132 2to C2by means of infrared specroscpy see PB61(1986)-..42219 adJB6(96-22) Intemethod disclosed in JPB 61(98two22 r spe tiv ly avi g a long path and a short path are provided, the path lengths of which are adjusted such that the light absorption by 1300 2 in one cell is equal to the light absoptin b 12O 2in the other cell. Light beams transmitted through the two cells are lead to spectrometric means, in which the light intensities are measured at wavelengths each providing the maximum sensitivity. In -3accordance with th accordance with th foris method, the light absorption ratio can be adjusted to for the concentration ratio of 13 C0 2 to in naturally occurring carbon dioxide If the CO t o

CO

ratio is changed, he light absorption ratio also changes by the amount of a change in the Ccentration ratio. Thus, the change in the concentration ratio can be determined by measuring a change in the light absorption ratio.

m n the infrared spectrosc 0 ic measurement, breath is sampled in breath sampling bags before and after a diagnostic S drug is administered to a living body, and the breath samples in ti e n d b in the breath sampling bags are respectively determination of the 13 COe ctively measured for 2 c o n c e n t r atin Or the 13c concentration ratio C2

S

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

More specifically breath samples obtained from one patient before and after the drug administration are mistaken for those obtained from another patient, or a breath sample o.I p a t i e n t o r m b r a t h forth obtained before the drug administration is mistaken for that obtained after the drug administration.

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

Further, if a breath sample includes a s..m5 the oral ea gas remaining in S he oral cavity of a patient, the measurement accuracy is S. reduced. To reduce a measurement erro breath from the lung of the patient should be sampled.

Still further si Still further, since moisture in a breath sample sic a breath sample adversely affects the optical measurement, the moisture should be removed from the breath sample. Furthermore, a consideration should be given to the breath sampling bag to prevent the breath sample from escaping from the bag.

5 It would therefore be advantageous if at least preferred embodiments of the present invention provide a breath sampling bag, which has a construction which reduces the possibility of a breath sample being mistakenly manipulated.

It would also be advantageous if at least preferred embodiments of the present invention provide a breath sampling bag, which prevents the sampling of air present in the oral cavity of a patient but allows the sampling of breath from the lung of the patient.

It would also be advantageous if at least preferred embodiments of the present invention provide a breath sampling bag, which is capable of removing moisture from breath blown therein.

15 It would also be advantageous if at least preferred embodiments of the present invention provide a breath sampling bag, which has a construction which prevents a breath sample escaping therefrom.

20 Summary of the Invention eves In one aspect, the present invention provides a o breath sampling bag, comprising a plurality of breath accumulating chambers joined together for respectively 25 accumulating a plurality of breath samples and a plurality of breath introduction pipes to be respectively connected to a plurality of breath inlets of a gas measuring apparatus for breath measurement to introduce the breath samples from the respective breath accumulating chambers into the gas measuring apparatus, and characterized in that the breath introduction pipes are each configured such that the breath introduction pipes are prevented from being connected to wrong breath inlets of the gas measuring apparatus (claim 1).

In another aspect, the present invention provides a gas measuring apparatus, which is adapted to measure a plurality of breath samples accumulated in a breath 6 sampling bag, comprising a plurality of breath inlets for introducing the breath samples from breath accumulating chambers of the breath sampling bag through breath introduction pipes, and characterized in that the breath inlets are each configured such that the breath inlets are prevented from being connected to wrong breath introduction pipes (claim With the breath sampling bag and gas measuring apparatus of the aforesaid constructions, such an inconvenient accident can be eliminated that one breath sample in one breath accumulating chamber of the breath sampling bag is introduced into the gas measuring apparatus mistakenly for another breath Sample in another breath accumulating chamber.

Where breath is sampled from a living body before and after a diagnostic drug is administered to the living body and the 13 13 the concentration or 13C2 concentration ratio of the breath samples is measured, for example, the manipulation mistake of the breath samples obtained before and after the administration of the diagnostic drug for measurement can be 25 prevented. Further, where a load test is performed and breath is sampled at a predetermined time interval after the administration of a diagnostic drug, breath samples thus obtained are prevented from being measured in a wrong order.

The breath introduction pipes or the breath inlets are, for example, asymmetrically configured for prevention of the connection mistake of the breath sampling bag. For asymmetrical configuration, the plurality of breath introduction pipes may have different diameters, lengths and cross-sections, and the plurality of breath inlets may have 7 different diameters, lengths and cross-sections correspondin to those of the respective breath introduction pipes.

In some embodiments of the breath sampling bag of the resistance generating means for generating a resistance to the blowing of the breath during the sampling of the breath (claim 2).

With this construction th With this construction, the provision of the resistance generating means prevents the sampling of breath present in Sthe oral cavity of the living body, but o y but enables the sampling of breath from the lung thereof. Thus, a measurement error can be reduced.

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

In some embodiments of the breath sampling bag of the present invention, 8 the breath introduction pipe has a detachable filter for removing moisture from the breath during the sampling of the breath (claim 3).

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

In some embodiments of the breath sampling bag of the present invention, the breath introduction pipe has a valve for preventing the back flow of the sampled breath (claim 4).

With this construction, the provision of the backflow prevention valve in the breath introduction pipe 15 prevents the breath from leaking out of the breath sampling bag.

In some embodiments of the gas measuring apparatus of the present invention, the breath inlet has means for disabling the function of a back-flow prevention valve in 20 the breath introduction pipe when the breath introduction pipe is connected to the breath inlet (claim 6).

go *.oe oo 0 a

B

ooo.

9 With this construction the function of the valve can be disabled with the breath introductionip being connected t the breath inlet when the breath sample is to be introduced into the gas measuring apparatus through the breath introduction pipe. Therefore the breath sample can be te breath sample can be smoothly introduced into the gas measuring apparatus.

The means for apparatus.

T m e a n s f o r disabling the function of the valve is embodied for example, by providing a long pin rojecting from the breath inlet, which is adapted to forcibly open the valve when the breath introduction pipe is connected to the breath inlet.

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

Brief Description of Drawings Hereinafter, concentration of 12 is called 12 concentration of 13

CO

2 is called o o c o 225 is called "12A absorbance of 2 i 1 S is called Abs" and absorbance of 1 3 2 is called 13 Abs.

andC0 abooac o 3^ Fig.1 is a graphical representation ill which Concentrations 1 2 Conc and concentration ratios 13Conc/12Con c are plotted as abscissa and ordinate, respectively, the concentrations 12Conc and 13conc and the concentration ratios 1 3 iCOnc/12Conc having been determined by using calibration cur-ves prepared on the basis of measurements of the absorbances 12Abs and 1 3 Abs of component gases in gaseous samples having the same concentration ratio 13Conc/12Conc 13 C0 2 concentration/12C 0 2 concentration 1.077%) but different concentrations of the component gases; Fig. 2 is a graphical representation in which 13 C0 0 F g02 concentration ratios are Plotted with respect to oxygen contents, the 13Co 2 concentration ratios having been determined by measuring gaseous samples containing 13 dilutednOxynCO 2 diluted with oxygen and nitrogen and having the same C02 15 concentration ratio but different oxygen concentrations, the 9.9.

9 1 3 C0 2 concentration ratios being normalized on the basis of C0a 2 concentration ratio for an oxygen content of 0%; Fig.3.. graphical representation illustrating the argFg result of measurement in which gaseous samples. having different 13C02 concentration ratios and containing no oxygen were measured, in which graphical representation the actual 13C02 concentration ratios and the measured 13C02 concentration ratios are plotted as abscissa and ordinate, respectively, and the 13C02 concentration ratios are normalized on the basis of the minimum 13C02 concentration 11 ratio; Fig. 4 is a graphical representation illustrating the result of measurement in which gaseous samples having different 13 C0 2 concentration ratios and containing various concentration of oxygen (up to 90%) were measured, in hich graphical representation the actual 13 C0 2 concentration ratios and the measured 13 C0 2 concentration ratios are plotted as abscissa and ordinate, respectively, and the 13c 2 S concentration ratios are normalized on the basis of the minimum 130 2 concentration ratio; o; Fig. 5 is a view illustrating the appearane of a breath S. sampling bag to be connected to nozzles of an apparatus for spectrometrically measuring an isotopic gas; a Fig. 6 is a partial view illustrating pipes connected to an end of the breath sampling bag; Fig. 7 is a block diagram illustrating the overall construction of the spectrometric apparatus; 0 Fig. 8 is a sectional view illustrating the construction of a cell chamber 11; Fig. 9 is a block diagram schematically illustrating a mechanism for adjusting the temperature of the cell chamber; Figs. 10A and 10B are a plan view and a side view, respectively, of a gas injector for quantitatively injecting a gaseous sample; Fig. 11 is a diagram illustrating a gas flow path through 12 which a clean reference gas isassed for leaning the gas gas is passed for ci nt flow path and the cell chamber of the ectroetri apparatus; Fig.-12 is a diagram illut a p p a r a t u s Fig. 12 is a diagram illustrating a gas flow path through which the clean reference gas is assed for cleaninthe g flow path and the cell chamber of the pectrometr aaats and for performing a reference measuree ct r aratus measurement- Fig. 13 is a diagram illustrating a state where a base Ssucked fro a breath a base gas is sucked from a breath sampling bag by means of the gas injector 21 with the reference gas prevented from flowing 10 through afirst ndfromflowing through first and second sample cells 11a and 11b Fig.saeeis and lb; :oFig 14 is ha diagram illustrating a as flow path to be .empln te base gas sucked in the g mechanically pushed out atas injector 21 is mechanically pushednt out at a constant rate by the gas injector 21 fr m o ight intensity by detection elements 2 I and 25b; F i g 1 5 is a diagram illustrating a state where a sample gas is sucked from the breath sampling b by means of the gas injector 21 with the ref y m e a n s o f t h e g a s injetou 21 with the reference gas prevented from flowing through the first and second sample cells lla and -11b; Fig. 16 is a diagram illustratin S a diagra illustrating a gas flow path to be employed when the sample gas sucked in the gas injector 21 is mechanically pushed out at a onstant rate by the gas injector 21 for measurement of light intensity by the detection elements 2 5a and 25b;etection elements Fig. 17A is a graphical representation in which 12 C02 252 13 concentrations and 12C02 absorbances are plotted as abscissa and ordinate, respectively or reparation of a calibration curvePPation f a calibration curve, the 12C02 absorbances having been measured for measuring points in a 12C02oncentration 2 concentration rane abt 0% t about 6%; Fig. 17B is a graphical representation in which 1202 concentrations and 120 22 concentrations and 12C2 absorbances in five data points in a relatively narrow 12C02 oncentration range around a 12CO concentration determined by Using the calibration curve of Fig. 17A are plotted as abscissa and ordinate respectively; Fig. 18A is a graphical representation in which 13CO concentrations and 13 2 and ordinations and absorbances are plotted as abscissa and ordinate respectively, for preparation of a calibration .r C02 absorbances having been measured for measuring points in a concentration of about 0.00 to about 0.07; r a n u 0.00 Fig. 18B is a graphical representation in which 13o 2 concentrations and 13CO absorb2 Srconcentrations and CO2absorbances in five data points in a relatively narrow 2 concentration range around a 13CO 2 concentration determined by using the calibration curve of Fig. 18A are plotted as abscissa and ordinate respectively; Fig. 19 is a graphical representation in which concentration ratios 13 Conc/12,.

concentration ratios Cnc/12Conc plotted as ordinate are normalized on the basis of a concentration ratio 13Conc/12Conc obtained when 12Cone is 14 Fig. 20 is a graphical representation illustrating the relationship of 12 Conc (plotted as abscissa) versus 3 CO 2 concentration ratio 1 3 Conc/l2Conc (plotted as ordinate) which was determined by measuring the 12 C0 2 concentrations 12 Conc and 1 3 o 2 concentrations i3conc of gaseous samples; Fig. 21 is a graphical representation illustrating the relationship of 12 COnc (plotted as abscissa) versus concentration ratio 1 3 Conc/12Conc (Plotted as :flj ordinate) which was determined by measuring the 12 c0 3 C 2 L~t1 fls 1 0 2n o concentrations 12

C

onc and

C

S2 concentrations Conc of S" gaseous samples and correcting obtained concentration ratios i l 3 Conc/12Conc; Fig. 22 is a graphical representation illustrating the relationship of 1 2 Conc (Plotted as abscissa) versus concentration ratio 1Conc/12COnc i~ c nc/1 C~ nc (plotted as ordinate) which was obtained by determining the 12C02 concentrations 1 2 Conc and 13 C0 2 concentrations 1 3 Conc of on e t a i n 1 Co c o "gaseous samples on the basis of absorbances measured on the gaseous samples by Using the calibration curves shown in Figs.

17A and 18A; Fig. 23 is a graphical representation illustrating the relationship of 12 Conc (plotted as abscissa) and concentration ratio 1 3 Conc/12Conc (plotted as ordinate) which was obtained by determining the concentration 15 a t i o s 1 3 C o n c /12C of l5 ratios 13Conc/12Conc of gaseous samples first on the basis of the calibration curves shown in Figs. 17A and 18A and then on the basis of the calibration rves in limited ranges shown in on c u r v e s i n limited Figs. 17B and 18B; and Fig. 24 is a graphical representation llustrating the result of measurement in which gaseous samples having different 13C02 concentration ratios and containing various concentration of oxygen (up to 90%) were measured and easurements were subjected to a correctionrocess according to the present invention, in which graphical representation the actual 13 i c a l representation the actua C02 concentration ratios and the measured 13C oncentraton ratios are plotted as abscissa and ordinate respectively, and the 13 s c s s a a n o r d n a respectively, concentration ratios are normalized on the basis of the minimum 13

CO

ratio. 2 concentration ratio.

Best Mode for Carrying Out the Invention A preferred embodiment of the present invention will S hereinafter be described with reference to the attached drawings. The embodiment is adapted for a case where a 13C02 concentration or concentration ratio 13 Conc/12Con i a breath test sample is spectrometrically determined after administration of an urea diagnostic drug labeled with an isotope 13 t 16 Before the urea diagnostic drug is administered to a patient, breath of the patient is sampled in a breath sampling bag. The volume of the breath sampling bag may be a mp l i n bout 250m. Then the n s a m d p l ing b a g m a y b e a b o ut 2 50m. Then, the urea diagnostic drug is administered to the patient and, after a lapse of 10 to 15 minutes breath of the patient is sampled i lap of 10he l patient is sampled in the breath sampling bag in the same manner as in the previous breath sampling.

Fig. 5 is a view illustrating the breath sampling bag 1 to be breath sampling bag 1 to be connected to nozzles

N

1 and N 2 of S an apparatus for pectrometricall measuring an isotopic gas The breathc gas.

*The br h sampling bag 1 includes a breath sampling chamber la for sampling breath of the atient after the administration of the urea diagnostic drug and a breath sampling chamber Sreath sampling c h a m b e r l b for sampling breath of the patient before the administration of the urea rt- ^"inistration S of the urea diagnostic drug, the breath sampling chambers la and bbmpling chambers la eing integrally molde a n d and b being integrally molded and joined together to form a single body.

SA pipe 2a is attached to an end of the breath sampling chamber la, nd a pipe 2b is attached to an end of the breath sampling chamber lb. Bottom ends 5a and 5b of the breath sampling chambers la and ib are closed. The Pipes 2a and 2b each have two functions, the ipes 2a and 2b serve not otly as breath blowing ports from which breath is blown into the breath sampling chambers la and ib, but also for introducing the breath samples from the breath sampling 17 chambers la and lb into the spectrometric apparatus when the breath sampling bag is connected to the nozzles

N

1 and N 2 of the apparatus.

When breath is sampled, a cylindrical filter (like cigarette filter) 7a or 7b is fitted into the pipe 2a or 2b, and then the breath is blown into the breath sampling bag 1i.

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

As shown in Fig. 6, back-flow valves 3a and 3b are Provided in the pipes 2a and 2b,, for reventing respectively, f S the breath blown into the breath sampling bag from flowing back.

The pipes 2a and 2b each have a portion having a smaller inner diameter a smaller diameter portion 4a or 4b) for generating a resistance to the blowing of the breath. The resistance to the blowing of the breath allows the patient to S exhale air from his lung. It has been experimentally filters are removed, and the pipes 2a and 2b are inserted into confirmed that air exhaled from the u a more stable'CO 2 concentration than air present in the oral cavity of the patient.

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

N

1 and

N

2 respectively, of the spectrometric apparatus. The nozzles

N

1 and

N

2 have different inner diameters, and the pipes 2a and 2b have different outer 18 diameters corresponding to the inner diameters of the nozzles

N

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

N

2 and

N

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

bei n g mistakenly manipulated The nozzles

N

1 and

N

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

N

1 and N2 0 Although the outer diameters of the pipes 2a and 2b are made different in th is made different in this embodiment, any other constructions may S be employed to prevent the mistake of connection between the pipes 2a and 2b and the nozzles Nl and N2. For example the pipes may have different lengths and the nozzles

N

1 and

N

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

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

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

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

N

1 and N 2 respectively. The nozzle

N

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

V

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

N

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

V

2 through a pipe.

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

M

1 to a reference cell llc.

The other path is connected through a flow meter

M

2 to one port of a three-way valve

V

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

The other ports of the three-way valve

V

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

V

1 and to a first 20 sample cell 1a for measuring a 12C0 2 absorbance The other ports of the three-way valve

V

2 are connected to the first -2 are connected to th sample cell lla through a two-way valve V 4 and to the other port of the three-way valve V 1 4 e A gas injector 21 (volume: 60cc) foruantitative injecting the sample gas or the base gas is interposed between the three-way valve

V

3 and the first sample cell la. The gas inj e c t o r 2 1 i s a cine-^la- The gas injector 21 is a syringe-like device having a piston and a cylinder. The n p i s t o n nd a Slinder The ston is driven by cooperation of a screwca motor, a 10 screw connected to the motor and a nut fixed to the Piston a S (which will be described later).

As s hown in Fia 7 sn Fig. 7, a cell chamber 11 has the first sample cell 11a h a i e nt sample cell lla having a smaller length for measuring there a 1C 2 abhence, absorbance a second sample cell llb having a greater 1 length for h a v ing a greater length for measuring therein a 13 measuring therein a 2 absorbance, and the reference cell llc through which th reference ga is assed.

The first sample cell l1a co cate werence as is eosape.

cell lb. Th second sample smp etgas or the basehe cell lb. The sample gas or the base gas is introduced into S the first sample there a en into the second cell llb, and discharged therefrom. The reference gas is introduced into the reference cell lc, and then discharged therefrom.

Specifically, the first and second sample cells la and llb have lengths ofh3m s t a n d S e c o n d s a mp l e c e l ls 11a and 11b have lengths of mm and 2 5 0mm, respectively, and the reference cell llc has a length of 23 6mm.

A discharge pipe extending from the second sample cell a2r5 h e o n a p e c l 21 llb is provided with an 02 sensor 18. sab as the 2 sensor 18 are commercially available oxygen sensors uch as a olid electrolyte gas sensor zirconia sensor) and an electrochemical gas sensor galvanic cell sensor) A reference character L denotes an infrared light Source having two waveguides 2 3a and 2b for guiding infrared s o u r c e for irradiation Th guiding infrared rays for irradiation The generation of the infrared rays may be achieved in any way p e d r a y s may be achieved in any way. For example, a ceramic heater (surface temperature: 450oC) and the like can be used. A rota 1O chopper 22 fr A r o t a y S chopper 22 for periodically blocking the infrared ray rovided adjacent to the infrared light source L nfrared S rays emitted from the infrared light source L are transmitted light source L tr to the first sample cell a and the reference cell lic through a first light path, and to the second sample cell through a second light path (see Fig. 8).ll A reference character D denotes an infrared detector for detecting the infrared rays transmitted through the cells.

e The infrared detector Dr h S f detect o haa irst wavelength filter 24a and a first detection element 2 5a disposed in the first light path, and a second wavelength filter 24b and a second detection element 25b disposed in the second light path.

The first wavelength filter 2 4a (band width: about passes an infrared ray having a wavelength of about 4 ,280nm to be used for measurement of a 12 2 absorbance Thesecond aelength filter 24b (b ab s o r b a n c e The secon wavelength filter 24b (band width: about 5 0nm) passes an 22 infrared ray having a wavelength of about 4,412nm to be used for measurement of a 13 CO2 absorbance. Usable as the first and second detection elements 25a and 25b are any elements capable of detecting infrared rays. For example, a semiconductor infrared sensor such as of PbSe is used.

The first wavelength filter 2 4a and the first detection element 25a are housed in element 2 5a are housed in a package 26a filled with an inert gas such as Ar. Similarly, the second wavelength filter 24b and the second detection element 25b are housed in a package 26b filled with an inert gas.

The whole infrared detector D is maintained at a constant *temperature (25cC) by means of a heater and a Peltier element.

The inside temperatures of the packages 2 6a and 26b are kept at O*C by means of a Peltier element.

15 The cell chamber ii is formed of a stainless steel, and vertically and laterally sandwiched between metal plates brass plates) 12. A heater 13 is provided on upper, eer 13 is provided on upper, lower and lateral sides of the cell chamber. The cell chamber 11 is sealed with insulators 14 such as of polystyrene foam with the heater 13 interposed therebetween. Though not shown, a temperature sensor a platinum temperature sensor) for measuring the temperature of the cell chamber 11 is provided in the cell chamber 11.

The cell chamber 1 1 has two tiers. The first sample cell a and the reference cell 1lc are disposed in one tier, and 23 the second sample cell llb is disposed in the other tier.

The first light path extends through the first sample cell lla and the reference cell lIc which are disposed in series, and the second light path extends through the second t p a h e x t e n d s through the second sample cell b. Reference characters 15, 16 and 17 denote sapphire transmission windows through which the infrared rays are transmitted.

Fig. 9 is a block diagram illustrating a mechanism for adjusting the temperature of the cell chamber i. The sensor 32 provided in the cell chamber 11 a 0 temperature adjustment substrate 1 and the heater 13. The t e m p e r a t u r e o f thh e ^be 11^ S. temperature of the temperature adjustment substrate 31 may be S adjusted in any manner. For example, the temperature adjustment can be achieved by changing the duty ratio of a S'S: pulse current flowing through the heater 13 on the basis of a temperature measurement signal of the temperature sensor 32.

The heater 13 is controlled on the basis of this temperature 0 adjustment method so as to maintain the cell chamber 1 1 at a constant temperature Figs. 10A and 10B are a plan view and a side view, respectively, of the gas injector 21 for quantitatively injecting a gaseous sample.

The gas injector 21 includes a cylinder 21b disposed on a base 2 1a, a piston 2 1c inserted in the cylinder 21c, and a 24 movable nut 21d connected to the piston 21c, a feed screw 21e threadingly meshed with the nut 21d and a motor 21f for rotating the feed screw 21e which are disposed below the base 21a.

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

The measuring procedure includes reference gas 15 measurement base gas measurement, reference gas measurement, sample gas measurement and reference gas measurement, which are to b ence gas measurement, which are to be Performed in this order Alternatively, base gas rd Aternativel b measurement, reference g a s r e f e r e gas measurement and base gas measurement, and sample easurement and sample gas measurement, reference gas measurement and sample gas measurement may be Performed in this order. In the latter case, the base gas measurement and the sample gas measurement are each performed twice and, therefore, the operation efficiency is reduced. The former measuring rocedure which is more eficent will hreinafter be described.

25 During the measurement the reference gas constantl flows through the reference cell lic, and the flow rate thereof is always kept constant by the flow meter Mi.

TJITa-] -l eferep meaurement As shown in Fig. 11, the clean reference gas is passed through a gas flow path and the cell chamber 11 of the spectrometric apparatus at a rate of 20 0ml/minute for about seconds for cleaning the gas flow path and the cell chamber 10 In turn, as shown in Fig. 12 the gas flow path is 9 gas flow path is changed, and then the reference gas is passed therethrough f ch lean ing an for cleaning the gas flow path and the cell chamber 11. After a lapse of about 30 seconds, lightintensity are measured by means of the detection elements 2 5a and 15 On the basis of the reference measurement, absorbances .o are calculated.

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

R

1 respectively.

l A 2 B a Jg a maasrament The base gas is sucked into the gas injector 21 from the breath sampling bag with the reference gas prevented from flowing through the first and second sample cells lla and llb (see Fig. 13).

Thereafter, the base gas is mechanically pushed out at a 26 constant rate (60ml/minute) by the as inector 21 as hown in meansFig. 14 and, at the same time, light intensity are measured by means of the detection elements 2 5a and The light intensity thus obtained by the first and second detection elements 2 5a and 25b are represented by 12 B and 13 s respectively.

The cleaning of the gas flow path and the cells and the light intensity measurement on the reference gas are rformed 10 again (see Figs. 11 and 12).

The light intensity thus obtained b the first and second detection elements 2 5a and 25b are represented by 12 d 13 a r e p ented by 12 and 1 3 2 R2 respectively.

15 The sample gas is sucked into the gas injector 21 from a s injector 21 from the breath sampling bag with the reference gas prevented from Sflowing through the first and econd sample cells la and llb (see Fig. Thereafter th 20 cThereafter, the sample gas is mechanically pushed out at a constant rate 6 ml/minute) by the gas injector 21 as shown in Fig. 16 and, at the same time, light intensity are measured by means of the detection elements 2 5a and The light intensity thus obtained by the first and second detection elements 2 5a and 25b are represented by 12S and 13S respectively.

27 Refprenee mem E te The cleaning of the gas flow path and the cells and the light intensity measurement on the reference gas are performed again (see Figs. 11 and 12).

The light intensity thus obtained by the first and second detection elements 25a and 25b are rresented by 12 and 13

R

3 respectively.

In the measurement procedure 1, the CO 2 concentrations of the base gas and the sample gas are not adjusted to the same level.

o If the base gas and the sample gas are at the same CO2 concentration level, the ranges of 1 2 2 and 1 3 2 calibration curves to be used for determination of the concentrations can be narrowed. By using limited ranges of the calibration curves, the measurement accuracy can be increased.

In accordance with the measurement procedure 2, the CO 2 concentrations of the base gas and the sample gas are adjusted to substantially the same level. First, the CO2 concentrations of the base gas and the sample gas are measured in a preliminary measurement. If the CO2 concentration of the base gas obtained in the preliminary measurement is higher than the CO 2 concentration of the sample gas obtained in the Preliminary measurement, the base gas is diluted to a CO2 concentration level equivalent to that of the sample gas, and 28 the measurement of the concentration is performed on the base gas an then on the sample gas in a main measurement.

If the CO2 concentration of the base gas obtained in the preliminary measurement is lower ta e 2 o b t n e d n t he ower than the

CO

the ample gas obtained in the prelimina meaurent r t of CO2 concentration of the base gas is measured in the n measurement. The sample gas is diluted to a t e m a in pe gas is diluted t level equivalent to that o2 concentration level equivalent to that of the base gas, and then the co 2 concentration thereof is measured.

The measurement The measurement procedure 2 includes prelimin 10measurement, preli n e s rr se gas measurement, reliminary sample gas measurement, reference gas m u gas measurement, reference gas ample gas measurement and reference gas measurement, which are performed in this order.

S The clean reference PaThe clean reference gas is passed through the gas flow path and the cell chamber 11 of the spectrometric apparatus for cleaning the gas flow pathtrometric apparatusand for leaning the gas flow path and the cell chamber 11 and, at the same time, a reference light intensity is measured.

In turn, the base gas is sucked into the gas injector 21 from the breath sampling bag, and then mechanically pushed out ow rate by means of th at a constant flow rate by means of the gas injector 21. At ths time, the intensity of light transmitted through th base gas is measured by means of the detection element 2 5a to determine an absorbance, and the C02 concentration of the base 29 gas is determined on the basis of the absorbance by Using a calibration curve.

The clean reference gas is passed through the gas flow path and the cell chamber 11 of thepectrometric aparatus for cleaning the gas flow path and the cell chamber 11 and, at the same time, a reference light intensity is measured.

In turn, the sample gas is sucked into the gas injector 21 from the breath sampling bag, and then mechanically pushed *0 out at a constant flow rate by means of thegas injector 21.

At this time, the intensity of I g At this time, thof light transmitted through the s ample gas is measured by means of the detection element 25a s pl ga detection elem ent 2 to determine an absorbance, and the CO concentration of the ample gas is determined on the basis of the absorbance by using the calibration curve.

.The gas flow path is changed, and then the reference gas is passed therethrough to clean the gas flow path and the cell chamber 11. After a lapse of about 30 seconds, light intensity are measured by means of the detection elements 25a and The light intensity thus obtained by the first and second detection elements 2 5a and 25b are represented by 12

R

1 and 1 3 R, respectively.

The C0 2 concentration of the base gas obtained by the a25a otiedb h 30 first detection element 25a in 'IlIb-. Preliminary base gas measurement', is compared with the Co02 concentratio Of the sample gas Obtained by the first detection element 25 a in "IIlb-2. Preliminary sample gas measurement,, If the 00 2 concentration of the base gas is higher than the Co 2 concentration of the sample gas, the base gas is diluted with the reference gas in the gas injdector 21 to a

C

concentration level equivalent to that Of the sample gas, and then the light intensity measurement is performed on the base gas 010J thus diluted.

Sine te 02 Concentration Of the two breath samples aeadjusted to substantially the same level b iuin ranges of the and caibato C 0 2 a n d 1 3 0 2 a l i r a t o n c u r v e s t o b e u s e d Can be narrowed.

1 It should be noted that the measuring Procedure 2 of this embodiment is characterized in that the 002 concentrations of *the two breath samples are adjusted to substantially tesm Sn. level, and does not necessarily require to employ a step of maintaining 00eCo2 cnetainat a constant level as described in JPB 4(1992)-124141. The use of limited ranges of calibration curves can be achieved simply by adjusting the 00 2 concentrations Of the base gas and the sample gas to subsantillythe same level. Since the 00 2 concentrations of the base gas and the sample gas vary within a range .of 1 to 5% in actual measurement, it is very troublesome to always 31 maintain the 002 concentrations at a constant level If the C02 concentration of the base gas is lower than the 02 concentration of the sample gas, the base gas is not diluted, and the measurement is performed on the base gas.

The base gas is mechanically pushed out at a onstant flow rate by the a constant flow rate by the gas injector 21, and light intensity are measured by means of the detection elements 2 5a and The light intensity thus obtained by the first and second detection elements 2 5a and 25b are represented by 12 B and respectively. an "eferne SThe cleaning of the gas flow path and the cells and the intensity onthereference S light te t measurement gas are performed again.as e r 2 The light intensity thus obtained by the first and second e mea e b elements 2 5a and 25b are represented by 1 2

R

2 13and .R2, respectively.

If the base gas is diluted in "IIIb-4. Base gas measurement", the sample gas is sucked from the breath sampling bag, and then mechanically pushed out at a constant flow rate by the gas injector 21. At this time, light intensity are measured by the detection elements 2 5a and If the base gas is not diluted in "IIIb-4. Base gas measurement the sample gas is diluted with the reference gas 32 to a CO 2 concentration level equivalent to that of the base gas in the gas injector 21, and then the intensity of light transmitted through the sample gas ese y Semp e g a s is measured by ^n detection elements 2 5a and The light intensity thus obtained by the first and second detection elements 2 5a and 25b are represented by 12S and 13 respectively.

The cleaning of the gas flow path and the cells and, the 10 light intensity measurement on the reference gas again. t h e r e f e r e gas are performed againe.lihin The light intensity thus obtained by the first and second S detection elements 25a and 25b are represented by 12 and 13 a r e represented b 12 3 respectively.

Absorbances 12Abs(B) and 13 of 12

S

and Abs(B) of 1 2 and 13 "athe base gas are

C

2 i n the base gas are calculated on the basis of the transmitted light intensity 1 2 R 1 13 R 12 R and R 2 for the reference gas and the 1 2 a n d R2 f o r the reference 20 gas and the transmitted light intensity 12 B and 13 for the base gas obtained in the f o r t h e ase gas obtained in the measuring procedure 1 or in the measuring procedure 2.

The absorbance 1 2 Abs() 1 2

CO

ll e asAbs(B) of 12 C2 is calculated from the following equation: 12 Abs(B)_log[2 12B/( 12

R

1 +12R 2 33 The absorbance i 3 Abs(B) of 13 Co 2 is calculated from the following equation: 13Abs(B)=-log[ 2 .13SB/(1SR+3R2)] Since the calculation of the absorbances is based on the light intensity obtained in the base gas measurement and the avraes 12 R±12R) 3 R13::: averages (12RI+12R2)/2 and 1 RI+l3R 2 of the light intensity obtained in the reference measurements performed before and after the base gas measurement, the influence of a drift (a time-related influence on the measurement) can be eliminated. Therefore, when the apparatus is turned on, there S is no need for waiting until the apparatus reaches a thermal egx: equilibrium (it usually takes several hours).

Where the measuring procedure of the base gas measurement, the reference gas measurement and the base gas 5 measurement, and the sample gas measurement, the reference gas measurement and the sample gas measurement as describe at the l as describe at the S beginning of "IIIa" is employed, the absorbance 12 Abs(B) of 1 2 C 0 in the base gas is calculated from the following a.a equation: 12 Abs(B)=-log[( 1 2 BI+2B 2 12

R

and the absorbance 13 Abs(B) of 1 3 C0 2 is calculated from the following equation: 1 3 Abs(B)=-Iog[(13BI+13B2)/2.13R] wherein 12 R and 1 3 R are the transmitted light intensity for the reference gas, 12B 1 and 1B are the transmitted light 34 intensity for the base gas obtained before the reference gas measurement and 12B2 and 13 2 are the transmitted light i n t e n s i t y f o r t h e b a s e intensity for the base gas obtained after the reference gas measurement.

Absorbances 1 2 Abs(S) and 13 Abs(S) of 12C02 and 132 in the sample gas are calculated on the basis of the transmitted li g h t i n t e n s i t y 1 2 R 1 3 R 12 13 light intensity 12

R

2 R2 12R 3 and 13

R

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

The absorbance 1 2 Abs(S) of 1202 is calculated from the following equation: 12 12Abs(S)=-log[ 2 .12S/(12R2+2R 3 The absorbance 13 Abs(s) of 13C 2 is alculadro is calculated from the following equation: 1 3 Abs(S)=-log[2.13S/(13R213R3) SSince the calculation of the absorbances is based on the light intensity obtained in the sample gas measurement and the averages of the light intensity obtained in the reference measurements performed before and after the sample gas measurement, the influence of a drift can be eliminated.

Where the measuring procedure of the base gas measurement the reference gas measurement and the base gas measurement, and the sample gas measurement, the reference gas 35 measurement and the sample gas measurement as describe at the beginning of "IIa' is employed, the absorbance 12 Abs(S) of 12C02 in the sample gas is calculated from the following equation: 1 2 Abs(S)=-log[(12Ss 1 2)/ 2 .12] and the absorbance 13 Abs(S) of 13C02 is calculated from the following equation: Abs(s)=-log[(S l l 3s 2 13

R]

wherein 12 R and 13 R are the transmitted light intensity for the reference gas, 12

S

1 and 1 3 are the transmitted light intensity for the sample gas obtained before the reference gas e me s re e-.ad 1'2I

S

S measurement, and 1 2 S and 1S are the transmitted light intensity for the sample gas obtained after the reference gas measurement.

S*-

To 12 0 The 2 concentration and the CO concentration are an te l^2 concentrationar S calculated by using calibration curves.

The calibration curves for 12 and 13 co are prepared S on the basis of measurement performed by using gaseous samples of known 12Co02 concentrations and gaseous samples of known 13C02 concentrations, respectively.

For preparation of the calibration curve for 12C02, the 12C02 absorbances for different 12C02 concentrations within a reren co^concentrations within a range of about 0% to about 6% are measured. The 12C2 concentrations and the 12C02 absorbances are plotted as 36 abscissa and ordinate, respectively, and the curve is determined by the method of least squares. An approximate quadratic curve, which includes relatively small errors, is employed as the calibration curve in this embodiment.

For preparation of the calibration curve for 13CO2, the 13C02 absorbances for different 13C02 concentrations within a range of about 0.00% to about 0.07% are measured. The 13C2 concentrations and the 13C02 absorbances are plotted as abscissa and ordinate, respectively, and the curve is Q: determined by the method of least squares. An approximate quadratic curve, which includes relatively small errors, is 9 employed as the calibration curve in this embodiment.

Strictly speaking, the 13C02 absorbance determined by individually measuring gases respectively containing 12CO2 and r13 df 13 co S C02 may be different from the CO2 absorbance determined by measuring a gas containing both 12C02 and 13C2. This is because the wavelength filters each have a bandwidth and the S 12C02 absorption spectrum partially overlaps 13C02 absorption spectrum. Since gases containing both 12 C0 2 and 13C02 are to be measured in this measurement method, the overlap of these spectra should be corrected for preparation of the calibration curves. The calibration curves to be employed in this measurement are subjected to the correction for the overlap of the absorption spectra.

For preparation of the calibration curve for the 12CO2 37 oncentration, the 12C02 absorbances for 20 different 12C2 concentrations within a range of about 0% to about 6% are measured. The 12C measured The 12C02 concentrations and the 12 C0 2 absorbances are plotted as abscissa and ordinate, respectively, as shown in Fig. 17A.

The curve, which passes through the respective data points, is determined by the method of least squares. An a m proi m a t e s u a d r a t i c

A

approximate quadratic curve includes the least error.

Therefore, the approximate quadratic curve is employed as the 10 calibration curve for 1202 in this embodiment.

gg ^2 i n this embodiment.

In turn, five data points are selected which are located around the 12o around the 12 0 2 concentration of the base gas reviously detemined on the b determined on the basis of the calibration curve for 12C The five data points fall within a concentration range of 1.5,which accounts for 25% of the entire concentration range of the calibration curve shown in Fig. 17A. Then, the data within the limited concentration range are used for the preparation of a new calibration curve (see Fig. 17B). It is confirmed that the preparation f the calibration curve within the limite data range improves the conformity of the data to the approximate curve, thereby remarkably reducing errors associated with the preparation of the calibration curve. The 2C2 concentration of the base gas is determined on the basis of the absorbance 12Abs(B) of the base gas by using the new calibrationgas by usng the new calibration curve for 12C02 38 The 12CO 2 concentration of the sample gas is determined in the same manner. determi For preparation of the calibration curve for the 1 concentration, the 13C 2 concentration the absorbances for 20 different 13CO concentrations within a r-2 concentrations within a range of about 0.009 to about 0.07 are measured The 1 3 a b o u t Se CO2 concentrations and the 13

CO

absorbances are plotted as abscissa and ordinate, respectively, as shown in Fig. 18A.

The curve, which passes through the respective data points is determined by the method of least spetive d a t a east squares An approximate uadr.a.0 approximate quadratic curve includes the least error.

Therefore, the approximate quadratic curve i employed as the calibration curve for 13 C02 in this embodiment.

02 in this embodiment.

In turn, five data points are selected which are located eeo around the 13 S around 2 concentration of the base detem-,e base gas previously terned on the basis of th Son the basis of the calibration curve for 1C The five data points fall within within a concentration range of 0.015%, which accounts for about 1/4 of the entire concentration range o concentration range (0.07) of the calibration curve shown in Fig. 18A. Then, the data within the limited concentration range are used for the preparation of a new calibration curve (see Fig. 18B). It is confirmed that the preparation of the calibrate Preparation of the calibration curve within the limited data range improves the conformity of the data to the approximate curve, thereby remarkably reducing errors associated with the preparation of witn the preparation of 39 1-1, cli1Drptjon Curve. The 13002 concentratio~n of the base gas is determined On the basis of the absorbance 1 3 Abs(B) of the base gas by using the new calibration curve for 13002.

The 130C02 concentration of the sample gas is determined in the same manner.

The12O2concentration and 13~ C2concentration of the base gas are represented by 12 COnc and 1 3 C0nc(B), respectively. The 12002 concentration and 13 co 2 concentration of the sample gas are represented by 12 C0nc(S) and 1 3 00flc(s), *00 10 respectively.

TV-. a]cti a i n f coe trat on ratio The cocnrtonrtoo 13CO2 to 12 co2idermn The concentration ratios ithbaegsndin the sample gas a r e e x p r s s e g a s a n d are xprssedasl 3 Conc(B)/l2Conc(B) ad1Cn()1Cn() respectively.

Alternatively, the concentration ratios in the base gas and in the sample gas may be defined as 13 C0nc(B)/ 1 2 c cD13 and1 ConcB)+ConcB) nd 3 C0nc(S)/l20nc(S)+1Cn(S 9 respectively. Since the 12 co concentration is much higher *C02 than the 13 C 02 concentration, the concentration ratios expressed in the former way and in the latter way are substantially the same.

TV-pCr cti f on-nttinr t o The concentration ratios obtained in the aforesaid manner deviate from actual 40 concentrations, depending on the 12

C

2 concentration.

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

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

Therefore, absorbances 12Abs and 13 Abs of 12C 2 and 13 C0 2 in gaseous samples having the same concentration ratio but different 12COZ concentrations are measured, and the 13CO 2 and 12 C02 concentrations and 3C2 concentration ratios of the gaseous samples are determined by using the calibration pope curves. Then, the 12 c 2 concentrations 1 Conc and the Sconcentration ratios 13Conc/12Conc are plotted as abscissa and ordinate, respectively.

The result is shown in Fig. 1.

The concentration ratios plotted as ordinate in the graph of Fig.l are not normalized. The concentration ratios may be normalized for easy processing of data. Fig. 19 illustrates a graph obtained by way of standardization of the concentration ratios in which a concentration ratio in a gaseous sample of the lowest

CO

2 concentration is regarded as 41 (The concentration ratios thus normalized are hereinafter referred to as "normalized concentration ratios".) To obtain an approximate curve accommodating these plotted data, the method of least squares is employed for approximation of the data. It is experientially known that a function of the fourth degree expressed by the following equation provides the most accuate approximate rve.

F(x) ax 4 bx 3 cx 2 dx e (1) S wherein is a normalized concentration ratio, a to d are S coefficients e is a constant, and x is a 1202 concentration Therefore, the fourth-order function is used as funti c o r r e c t i a uation.

rection equation. Alternatively, a spline function may be used.

Standardized 13CO/12 SStandardize 13C2/1C0 2 concentration ratios are calculated from tho :l from the correction equation on the basis of the 1CO concentrations 12Conc(B 12 Sonc(B) and Conc(S) in the breath samples of the patient Then the concentration ratios 13Conc(B)/12Conc(B) and 13Conc( 12f the base gas and the sample gas obtained in the measurement are respectively divided by the normalized concentration ratios calculated from the correction equation Thus, corrected concentration ratios are obtained as follows: Corrected concentration ratio =13Conc(B)/[12Conc(B).F(12Conc(B))] 42 Corrected concentration ratio

=I

3 Conc(S)/[12Conc(S).F(12Conc(S))] The 13C02 concentration ratios of the base gas and the sample gas are subjected to a correction for oxygen concentration according to the present invention.

The

ISCO

2 concentration ratios are corrected by using a graph (Fig. 2) in which measurements of the 13

CO

2 concentration ratio are plotted with respect to the oxygen C 10 contents of gaseous samples.

More specifically, normalized 13Co 2 concentration eog.

ratios are obtained from the graph shown in Fig. 2 on the basis of the concentrations of oxygen in the breath samples which are measured by means of the 02 sensor. Then, the 13 C0 5 ratiosrtio concentration ratios of the base gas and the sample gas are respectively divided by the normalized 13C0 2 concentration ratios. Thus, the concentration ratios corrected depending on the oxygen concentrations can be obtained.

*0oo* V-6 teterin "13 A difference in 13 C between the sample gas and the base gas is calculated from the following equation:

A

13 c [Concentration ratio of sample gas Concentration ratio of base gas] x 103 [Concentration ratio of base gas] (Unit: per mill) V Mndifictinn 43 The present invention is not limited to the embodiment described above. In the above-mentioned embodiment, the 1 and 13c02 concentrations of the base gas and the sample gas are determined, then the concentration ratios thereof are calculated, and the Concentration ratios are subjected to the oxygen concentration correction. Alternatively, the concentration ratios may be determined after the 12CO2 and .IC02 concentrations of the base gas and the sample gas are determined and the 12 C0 2 and 13 CO concentrations are 0 10 corrected by way of the oxygen concentration correction.

The absorbances of gaseous samples respectively containing C0 2 in concentrations

I

2 conc of 29, 4%, 52 and 6. 12 with a concentration ratio of 1.077% were measured in accordance with the method for spectrometrically measuring an isotopic gas. The 1200 cocetrtins121 1 c0 concentrations 12 Conc and 13C02 concentrations i 3 Conc of the gaseous samples were determined on the basis of the measured absorbances by using the calibration curves. The 12C02 concentrations 12 Conc and the concentration ratios l 3 C0nc/12Conc were plotted as abscissa and ordinate, respectively, as shown in Fig. The maximum and minimum Values of the concentration ratios 13Conc/12Conc were 1.083% and 1.076%, respectively, and 44 the difference therebetween was 0.007%.

In turn, the concentration ratios 1 3 Conc/12Conc were corrected by using the correction equation thus iding a less undulant curve as shown in Fig. 21. In Fig. 21, the maximum and minimum values of the concentration ratios 3 Conc/2 Conc were 1.078% and 1.076%, respectively, and the difference therebetween was 0.0015%.

Therefore, the correction withe correction equation remarkably reduced the variation in the concentration 10 ratio 13Conc/12concn n The absorbances of gaseous samples respectively containing 1 2 in concentrations 12 Conc of 2% 4% 5% and 6% with 6 with a concentration ratio 1 3 Conc/12 **onc/ Cone of 1.065% were measured in accordance with the method for S spectrometrically measuring an isotopic gas. The 1 2 Conc and the Conc were determined on the basis of the measured absorbances by using the calibration curves shown in Figs. 17A and 18A. The 12 pn in gs. I/A and 18A. The 12 C2 concentrations 1 2 Cone and the concentration ratios 13Conc/12Conc were plotted as abscissa and ordinate, respectively, as shown in Fig. 22.

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

In turn, concentration ratios 13Conc/12Conc were 'nC/ Conc were 45 determined by using the calibration curves shown in Figs. 17A and 18A and then using the limited-range calibration curves shown in Figs. 17D and 18B, thus providing a less undulant curve as shown in Fig. 23. In Fig. 23, the maximum and minimum values of the concentration ratios 1 3 Conc/l2 Onc were 1.066-% and 1.06496, respectively, and the difference therebetween was 0.002t.

Therefore, the method ofthe present invention, in which calibration curves were produced again, remarkably reduced S the variation in the concentration ratio 1 3 0c/2COnc.

.The absorbances of gaseous samples having different known O concentration ratios and containing various concentration ooxgn(up t90)were measured, and then o is the 13002 concentration ratios were determined on the basis of S the measured absorbances by using the calibration curves.

Further, the 1C2concentration ratios thus determined were corrected by using a correction line as shown in Fig. 2.

The actual 1 3 C0 2 concentration ratios and the 32 concentration ratios thus corrected were normalized, and plotted as abscissa and ordinate, respectively, as shown in Fig. 24.

In Fig. 24, the relationship between the actual 130C02 concentration ratio and the measured 13CO2 ocnrto ai is about 1:1 (or the scope of the fitting curve in Fig. 24 is -46 about In comparison with the prior art shown in Fig. 4, in which the relationship between the actual 13

CO

2 concentration ratio and the measured 13

CO

2 concentration ratio is about 1:0.3 (or the scope of the fitting curve is about the measurement accuracy was drastically improved by performing the correction.

Thus, the correction using the correction line remarkabl improved the accuracy of the measurement of the e measurement of the 13 concentration ratio.

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

After one hour warming-up of apparatus, a measuring procedure consisting of the reference gas measurement, the S sample gas measurement th reference gas measurement, the sample gas measurement and the reference gas measurement were performed ten times on the same sample gas. The 12 CO2 concentration was determined in each cycle of the measuring procedure in accordance with the method A of the present invention in which the absorbance of 12 CO in the sample as was determined on the basis of an average of values obtained in the reference gas measurements performed before and after the sample gas measurement, and in accordance with the prior art method B in which the absorbance of 12CO in the 2 in the sample sus 47 gas was determined on the basis of a value obtained in the reference measurement only before the sample gas measurement.

The results of the calculation of the concentrations in accordance with the method A are shown in Table 1. In Table 1, the concentrations obtained in the second and subsequent measurements were normalized by regarding a concentration obtained in the first measurement as 111--. The standard deviation of the concentration data calculated in accordance 0 too e: with the method A was 0.0009.

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

Table 2 2 3 4 1.0024 1.0001 0.9996 1.0018 48 6 7 8 0.996 1.0022 1.0014 1.0015 As can be understood from the foregoing, the method of the present invention, the present ivention, in which the absorbances are determined on the basis of the light intensity measured on the sample gas and an average of the light intensity measured on the reference gas, provides concentration data with little variation.

In the claims which follow and in the preceding description of the invention, except where the context 0: requires otherwise due to express language or necessary implication, the word "comprising" is used in the sense of "including", i.e. the features specified may be associated with further features in various embodiments of the invention.

C

-U

Claims

2. A breath sampling bag according to claim 1 characterized in that the breath introduction pipe has resistance generating means for generating a resistance to the blowing of the breath during sampling of the breath.
3. A breath sampling bag according to claim 1 or 2 characterized in that the breath introduction pipe has a S"detachable filter for removing moisture from the breath S•during sampling of the breath.
4. A breath sampling bag according to any one of claims 1 to 3, characterized in that the breath introduction pipe has a valve for preventing the back flow of the sampled breath. A gas measuring apparatus, which is adapted to measure a plurality of breath samples accumulated in a breath sampling bag, comprising a plurality of breath inlets for introducing the breath samples from breath accumulating chambers of the breath sampling bag through breath introduction pipes, and characterized in that the breath inlets are each configured such that the breath 50 inlets are prevented from being connected to wrong breath introduction pipes.
6. A gas measuring apparatus according to claim characterized in that the breath inlet has means for disabling the function of a back-flow prevention valve in the breath introduction pipe when the breath introduction pipe is connected to the breath inlet. Dated this 23rd day of August 2000 OTSUKA PHARMACEUTICAL CO., LTD By their Patent Attorneys GRIFFITH HACK o o