CN112771376B - System and method for identifying and/or measuring a concentration of a substance in exhaled breath of a patient - Google Patents

Abstract

A system for identifying and/or measuring a concentration of a substance in exhaled breath of a patient (4), the system comprising a measuring device (20), the measuring device (20) being for performing an ion mobility spectrometry measurement of a sampled gas flow (a) obtained from exhaled breath of the patient (4), the measuring device (20) comprising a drift detector (22) and at least one gas circuit (23, 24) connected to the drift detector (22), the at least one gas circuit (23, 24) being for directing an analysis gas flow (B) towards an inlet end (220) of the drift detector (22) and/or for directing a drift gas flow (C) towards an outlet end (221) of the drift detector (22), a sample of the sampled gas flow (a) being injectable into the analysis gas flow (B), wherein the at least one gas circuit (23, 24) comprises a molecular sieve filter (233, 241) comprising a filter material (26) for filtering the analysis gas flow (B) and/or the drift gas flow (C). Herein, the filter material (26) includes zeolite NaY. In this way, a system for measuring the concentration of a substance in the exhaled breath of a patient is provided which allows accurate measurements to be made using Ion Mobility Spectrometry (IMS).

Description

System and method for identifying and/or measuring a concentration of a substance in exhaled breath of a patient

Technical Field

The present invention relates to a system for identifying and/or measuring a concentration of a substance in exhaled breath of a patient, and to a method for measuring a concentration of a substance in exhaled breath of a patient.

Background

Such a system includes a measurement device for performing ion mobility spectrometry measurements on a sampled gas stream obtained from the exhaled breath of a patient. The measuring device herein comprises a drift detector and at least one gas circuit connected to the drift detector for guiding an analysis gas flow into which a sample of the sampling gas flow can be injected towards an inlet end of the drift detector and/or for guiding the drift gas flow towards an outlet end of the drift detector. Herein, at least one gas circuit comprises a molecular sieve filter comprising a filter material for filtering the analysis gas stream and/or the drift gas stream.

Mechanical ventilation is used in conventional general anesthesia procedures, for example in surgical centers or during long-term sedation procedures on critically ill patients in intensive care units in hospitals. In the case of such general anesthesia procedures, the patient is intubated with an endotracheal tube in order to provide ventilation on the one hand and to administer gaseous anesthetic on the other hand.

As an alternative to inhalation anesthesia procedures using gaseous anesthetics, in the case of intravenous anesthesia, for example in the case of the so-called all-intravenous anesthesia (TIVA) procedure, an anesthetic such as propofol is administered intravenously to the patient. Such intravenous anesthesia may also be preferred, for example, for long-term sedation procedures in an intensive care unit.

In particular in the case of intravenous anaesthesia, for example using propofol as anaesthetic, it is very interesting to be able to monitor the concentration of anaesthetic and its associated effects in the patient, in particular with respect to the effects of anaesthesia. In general, conclusions regarding the concentration of drugs in a patient can be drawn by monitoring the presence and concentration of anesthetics and related substances in the patient's exhaled air. The concentration of the drug in the patient can be predicted from the concentration of the drug in the exhaled air using a suitable model, such as a pharmacokinetic/pharmacodynamic model. However, such predictions require an accurate model on the one hand and an accurate measurement of the concentration of the substance in the exhaled air on the other hand.

Detection of substances in the exhaled breath of a patient has been proposed, particularly when using anaesthetics such as propofol, using gas chromatography ion mobility spectrometry (GC-IMS) for monitoring during the anaesthetic process. Within the ion mobility spectrum, the components of the gas sample are ionized by means of ion molecular reactions and injected into the electrical drift field of the drift detector. By applying a considerable electric field strength, e.g. a few hundred volts per cm, to the drift detector, the ionized components are driven towards the detector, which is configured to generate a measurement signal when the ionized components arrive. Depending on, for example, the shape and cross-section of the ionized components, the ionized components encounter opposing forces as they travel through the drift detector, which forces originate from drift gas flowing through the same drift detector but in opposite directions, thus effectively providing an obstacle to the ionized components.

Typically, the drift time of the ionized components through the drift detector depends on the applied voltage, the temperature and pressure in the drift detector, the mass of the ionized components, the shape and charge of the ionized components, etc., such that different components exhibit different velocities and therefore different components will travel through the drift detector at different drift times. Thus, the different ionized components will arrive at the detector at different times, such that signals separated in time and related to the different ionized components can be detected at the detector, resulting in a so-called drift spectrum (signal intensity over drift time) containing peaks related to the different components of the gas sample.

In GC-IMS, ion mobility spectrometry is combined with gas chromatography, wherein an analyte gas stream is directed through a separation column forming a capillary column, in which different components of the analyte gas stream are separated from each other, before being injected into a drift detector, because the different components travel through the separation column with different travel times (so-called residence times, which are indicative of the time that a particular component stays in the separation column) due to their chemical nature. By means of gas chromatography, different components of the analysis gas stream enter the drift detector at different times such that the components are separated before entering the drift detector, which improves the specificity of the components and thus the identification of the components in the measured drift spectrum.

A gas chromatography ion mobility spectrometry (GC-IMS) system is known, for example, from DE 198 56 784b4 and DE 102 28 912c 1.

In order to determine the concentration of a substance of interest, such as an anesthetic agent, in particular propofol, in the breath of a patient, peaks in a drift spectrum related to the substance of interest may be identified, and conclusions may be drawn regarding the concentration of the substance of interest in a gas sample obtained from the exhaled breath of the patient from the height of the peaks. Typically, using a suitable calibration, the height of the peak may be related to the concentration of the substance of interest, such that the concentration may be directly estimated from the height of the peak.

However, concentration values are typically in the parts per billion (ppb) range, such that the detected signal may interfere with certain contaminations in the analyte gas stream and the drift gas stream. The accuracy of the concentration measurement is therefore particularly sensitive to contamination in the analyte gas stream and the drift gas stream. In particular, it is to be ensured that the analysis gas stream and the drift gas stream do not comprise any remaining propofol content and additionally have a very low water content (e.g. below 1 ppm).

For this reason, the use of molecular sieve (also known as mole sieve) filters has been proposed, which are used both to remove propofol from an associated gas stream, and to reduce the water content in the gas stream by adsorption.

Because water may accumulate in the molecular sieve filter over time, the filter performance may deteriorate over time, thereby making it necessary to replace and renew the filter periodically. In this context, it is desirable to use filters with long durability, thus providing long service times before the filter needs to be replaced and renewed.

Disclosure of Invention

It is an object of the present invention to provide a system and method for measuring the concentration of a substance in exhaled breath of a patient, which allows accurate measurements using ion mobility spectrometry, in particular gas chromatography ion mobility spectrometry (GC-IMS).

This object is achieved by means of a system for identifying and/or measuring a concentration of a substance in exhaled breath of a patient, said system comprising: measuring device for performing an ion mobility spectrometry measurement of a sample gas flow obtained from exhaled breath of the patient, the measuring device comprising a drift detector and at least one gas circuit connected to the drift detector for guiding an analyte gas flow towards an inlet end of the drift detector and/or for guiding a drift gas flow towards an outlet end of the drift detector, the sample gas flow being injectable into the analyte gas flow, wherein the at least one gas circuit comprises a molecular sieve filter comprising a filter material for filtering the analyte gas flow and/or the drift gas flow, wherein the filter material comprises zeolite NaY, wherein the at least one gas circuit comprises first pump means for pumping the analyte gas flow towards an inlet end of the drift detector and/or the at least one gas circuit comprises second pump means for pumping the drift gas flow and the drift gas flow, wherein the sample gas flow and the drift gas flow are combined, and wherein the flow is again guided in the drift gas circuit by means of the respective filter, wherein the flow is cleaned, and/or the drift gas flow is guided along the closed circuit, wherein the flow is detected by means of the respective closed circuit.

Thus, the filter material of the molecular sieve filter comprises zeolite NaY.

Thus, the filter material is composed wholly or partly of zeolite material, i.e. NaY.

Conventionally, zeolites are grouped by category indicating their structure type. The zeolite material used as the filter material in this case belongs to the category "Y".

The zeolite of the class "Y" is a synthetically produced crystalline substance having a crystal structure consisting of so-called sodalite cages interconnected by means of hexagonal prisms. In this way, regularly shaped and sized holes are formed, the largest holes having a diameter of about 7A (angstroms), corresponding to about 0.7nm.

"Na" indicates modification of the structure of zeolite, and NaY is also denoted as "Na-form zeolite Y". Within NaY, sodium ions are intercalated into the crystal structure of the Y zeolite.

In this context, naY may be used as a filter material in different forms, for example in the form of binder-containing particles or binder-free particles (in the latter case also denoted as NaY BFK).

Filter materials comprising or consisting of, for example, naY in the form of particles exhibit a considerable dynamic adsorption capacity for adsorbing water, for example between 20% and 30%, for example about 25%.

The NaY filter material may have a pore size of between 0.6nm and 0.8nm, such as 0.7nm,

Corresponding to about 7A.

It has surprisingly been found that removal of substances of interest, in particular propofol, from a gas stream and removal of water from a gas stream can be effectively achieved with a NaY filter material, which offers the possibility of constructing filters with large water adsorption capacities and thus provides filters which allow long service times, for example for service times longer than a year.

The molecular sieve filter may, for example, have a cylindrical shape with a diameter in the range between 1cm and 10cm, for example in the range between 3cm and 6 cm. The filter may be, for example, 10cm to 20cm long, and the molecular sieve filter comprises a housing enclosing the filter material, the housing being, for example, made of stainless steel material. The volume of the filter is filled with NaY filter material through which the gas stream to be filtered passes in operation in order to remove water and the desired substances of interest, in particular propofol, from the gas stream.

In one embodiment, at least one gas circuit includes molecular sieve filters in both the portion that directs the flow of the analysis gas and the portion that directs the combined flow of the analysis gas and the flow of the drift gas, each molecular sieve filter including NAY filter material for filtering the associated flow of gas. In this context, the at least one gas circuit may additionally comprise a further filter device, such as a carbon filter, for providing further filtration of the analysis gas stream, for example with respect to organic compounds.

In one embodiment, at least one gas circuit comprises one or more fluid lines made at least in part of a PTFE material, the at least one gas circuit being for guiding an analysis gas flow and/or a drift gas flow. The fluid line may be entirely made of PTFE material, or the fluid line may include a coating of PTFE material, thereby preventing the formation of water droplets on the inside of the fluid line. The fluid line may for example comprise an inner diameter in the range between 1mm and 3mm, for example 2 mm.

In one embodiment, a portion of at least one gas circuit implemented to direct the flow of the analyte gas comprises a separation column for chromatographically separating components of the flow of the analyte gas from each other prior to injection of the flow of the analyte gas into the inlet end of the drift detector. Thus, ion mobility spectrometry and gas chromatography are combined to provide a significant separation of the components of the gas stream to be analyzed. The flow of analyte gas passes through a separation column having, for example, a capillary channel with a length of between 0.5m and 5m, for example about 1m, before being injected into the drift detector. The inner wall of the capillary channel forming the separation column comprises, for example, a liquid phase to provide different residence times of the different components within the separation column, so that the different components of the analyte gas stream need different times to travel through the separation column. Thus, different components of the analysis gas stream are injected into the drift detector at different times, such that the different components of the analysis gas stream have been separated before the different components of the analysis gas stream are injected into the drift detector. After traveling through and further separated within the drift detector, the different components are detected by suitable detection circuitry at the outlet end of the drift detector, allowing detection of the different components within the analyte gas stream and measurement of concentration by measuring the peak height of the peaks in the detected signal associated with the substance of interest, particularly propofol.

The separation column is advantageously heated to a predefined temperature, in particular to a temperature above 80 ℃, for example above 85 ℃, in order to provide a suitable difference in residence time between the different components of the analysis gas stream, in particular in residence time of water (H ₂ O) and propofol.

By using a combination of gas chromatography and ion mobility spectrometry, a rapid measurement time can be achieved, for example allowing the concentration of a substance of interest, in particular propofol, in the respiration of a patient to be reliably measured with a measurement time of less than 1 minute.

In one embodiment, the system includes an additional sampling gas circuit for directing a flow of sampling gas obtained from the patient's breath. The sample is obtained from the sample gas flow and injected into the analysis gas flow by means of a valve arrangement, which is switchable such that the sample of the sample gas flow (having a volume of e.g. 1 ccm) can be injected into the analysis gas flow via the valve arrangement by connecting at least one gas circuit to the sample gas circuit.

In one embodiment, the sampling gas circuit further comprises one or more fluid lines at least partially made of PTFE material for directing the flow of the sampling gas, the sampling gas circuit being for example connected to a catheter device through which ventilation of the patient is provided. The fluid line may be made entirely of PTFE material, or the fluid line may include a PTFE coating or the like.

In one embodiment, the at least one gas circuit comprises a first pump means for pumping the flow of analyte gas towards the inlet end of the drift detector. The pump means may be, for example, a diaphragm pump. The first pump means may be located within the at least one gas circuit, in particular at a position before the separation column, when seen in the flow direction of the analyte gas flow, such that the first pump means generates a pressure to move the analyte gas flow through the separation column towards the inlet end of the drift detector.

In one embodiment, the at least one gas circuit comprises a second pump device for pumping a combined gas flow of the drift gas flow and the analysis gas flow, which second pump device is for example also a membrane pump. By means of a diaphragm pump, in particular, the combined gas stream may be pumped towards a separator which separates the combined gas stream into an analysis gas stream and a drift gas stream, which is then directed towards an outlet end of the drift detector to drift through the drift detector in a direction opposite to the injection of ionized components originating from the analysis gas stream into the drift detector at the inlet end. The drift gas flow that drifts through the drift detector advantageously consists of clean air.

In one embodiment, at least one gas circuit forms a closed circuit for guiding an analysis gas flow and/or a drift gas flow. Thus, the analysis gas flow and the drift gas flow through the at least one gas circuit along a closed loop, so that no gas needs to be fed into the gas circuit in particular from an external source. The respective gas flow flows along a closed loop through the gas circuit, the respective gas being cleaned by means of an associated filter device after passing the drift detector before being injected again into the drift detector. In this context, a sample of the sample gas of exhaled breath is injected into the analyte gas stream before passing through the separation column and before being injected into the drift detector in order to measure the concentration of the substance in the sample.

With the aid of the system, characteristic values relating to one or more drift spectra can be determined, which can then be used to output a concentration estimate indicative of the concentration of a substance in a gas sample with a suitable calibration. The substance(s) of interest may in particular be at least one anesthetic agent such as propofol, such that the system may be particularly adapted to provide monitoring during an anesthetic or sedative procedure, for example, during which anesthetic agent is administered intravenously to a patient, and ion mobility spectrometry is used on a gas sample of the patient's exhaled breath to monitor the concentration of anesthetic agent within the patient.

For this purpose, a gas sample may be obtained continuously or periodically in order to monitor the concentration(s) of at least one anesthetic agent, in particular propofol, in the exhaled breath of the patient.

The object is also achieved by a method for measuring a concentration of a substance in exhaled breath of a patient, the method comprising: obtaining a sample gas stream from the exhaled breath of the patient, and performing an ion mobility spectrometry measurement of the sample gas stream by means of a measurement device comprising a drift detector and at least one gas circuit connected to the drift detector for directing the analyte gas stream towards an inlet end of the drift detector and/or directing the drift gas stream towards an outlet end of the drift detector, a sample of the sample gas stream being injectable into the analyte gas stream, wherein the at least one gas circuit comprises a molecular sieve filter comprising a filter material for filtering the associated gas stream. Herein, the filter material includes zeolite NaY.

The advantages and advantageous embodiments described above for the system apply equally well to the method, so that it should be mentioned above.

Drawings

The basic idea of the invention will be described in more detail later with reference to an embodiment shown in the drawings. Herein, the following is the case:

FIG. 1 shows a schematic view of a system including an endotracheal tube and a ventilation system for providing ventilation to a patient;

FIG. 2A shows a graphical representation of a plurality of drift spectra recorded over time for a sample obtained from exhaled breath of a patient by using GC-ion mobility spectrometry;

FIG. 2B shows a graphical representation of a combined drift spectrum obtained from the drift spectrum of FIG. 2A;

FIG. 3 is a schematic depiction of the layout of a system for measuring the concentration of a substance in exhaled breath of a patient; and

Fig. 4 is a schematic depiction of a filter apparatus for filtering an associated gas stream.

Detailed Description

Fig. 1 shows an embodiment of a system as it may be used in general, for example, in the case of an anesthesia procedure.

For example, during intravenous anaesthesia, an anesthetic such as propofol is administered intravenously to patient 4 and thus into the patient's blood stream. For monitoring the concentration of an anesthetic substance in a patient, the gas detector 2 connected to the connection 11 of the endotracheal tube 1 in a lateral flow arrangement continuously or periodically measures the concentration of a drug in a gaseous flow obtained from the patient's lungs 41 via the tube 10 of the endotracheal tube 1 inserted into the trachea 40 of the patient 4 and possibly connected to the ventilation system 3 for providing ventilation of the patient 4. Thus, with such concentration measurements, monitoring of the concentration of the substance in the exhaled air of the patient 4 may be performed, allowing conclusions regarding the concentration of the anaesthetic substance in the patient to be drawn, e.g. using a suitable pharmacokinetic/pharmacodynamic model or the like.

In an embodiment, the gas detector 2 comprises a processing means 21 and a measuring device 20, the measuring device 20 being designed to: ion mobility spectrometry measurements are performed on gas samples obtained via lateral flow line 12 connected to connector 11 of endotracheal tube 1 at port 110.

By means of the side flow line 12, gas samples can be obtained from the gas flow through the connection 11 in a continuous or periodic manner. In order to measure the concentration of a substance of interest in a gas sample obtained from exhaled breath of the patient 4, ion mobility spectrometry is used, in which components of the gas sample are ionized and injected into a drift detector, by means of which they are driven to drift towards the detector by a considerable voltage, for example a voltage of more than 100 volts or even a few hundred volts per cm. The measurement signal is obtained by means of a detector, the measurement signal being generated by a component that reaches the detector and causes ionization of the low voltage signal at the detector. Because different components exhibit different drift velocities through the drift detector, e.g. depending on the temperature and pressure in the drift detector, the mass of the components, and the shape and charge of the components, the different components will reach the detector at different drift times, resulting in a drift spectrum in which peaks related to the different drift times of the different components appear. Thus, from the signal intensity at the peak associated with a particular component associated with a substance of interest, a conclusion can be drawn regarding the concentration of the substance of interest in a gas sample obtained from the gas stream.

To draw conclusions about the concentration of the species in the gas sample, characteristic values relating to the drift spectrum are determined, such characteristic values allowing concentration estimates to be inferred (e.g. by calibrating a range of characteristic values to a range of concentration values in an initial calibration phase). However, recorded data obtained from ion mobility spectrometry is often affected by noise, making it impossible to accurately determine characteristic values immediately with sufficient accuracy, such as the height of peaks in the drift spectrum that are related to the substance of interest.

Fig. 2A and 2B show an example of a recorded drift spectrum S obtained by ion mobility spectrometry using the measurement device 20 of the gas detector 2. Fig. 2A herein shows a plurality of drift spectra S recorded over time for samples obtained from exhaled breath of a patient 4, which in particular shows how peaks in the measured drift spectra S relating to the substance of interest, in the present case propofol, evolve over time. Fig. 2B shows a combined drift spectrum S obtained from the drift spectrum of fig. 2A (e.g. by summation). As can be seen in fig. 2B, the resulting drift spectrum S contains various peaks, different peaks being associated with different components of the gas sample, the peak of interest P being associated with, for example, propofol.

Fig. 3 shows an embodiment of the layout of the detection device 2 with a measurement apparatus 20 and a processing device 21 for measuring the concentration of a substance of interest, in particular propofol, in a sample of exhaled breath of a patient by using ion mobility spectrometry information in combination with gas chromatography (so-called GC-IMS).

The measurement device 20 comprises a gas circuit for guiding different gas flows from and towards the drift detector 22.

The sampling gas circuit 25 is for guiding a side flow of exhaled breath of the patient 4 (see fig. 1) through the side flow line 12 of the catheter device 1 towards the detection device 2 by means of a fluid line 251, the sampling gas circuit 25 for example comprising a pump device 250 in the shape of a diaphragm pump for conveying the sampling gas flow a through the sampling gas circuit 25.

The sampling gas circuit 25 is connectable to the analysis gas circuit 23 by means of a valve arrangement 230, the valve arrangement 230 being switchable such that a sample of the sampling gas flow a (having a volume of e.g. 1 ccm) flowing through the sampling gas circuit 25 can be injected into the analysis gas circuit 23 for analysis.

The analyte gas loop 23 directs the analyte gas stream B through the separation column 231 by means of the fluid line 235 and from the separation column 231 towards the drift detector 22 for injection into the drift detector 22 at the inlet end 220. After injection into the drift detector 22 at the inlet end 220, the component B 'of the analysis gas flow B is ionized by means of ionizing radiation and driven by a voltage applied to the drift detector 22, drifts through the drift detector 22 towards the outlet end 221, at the outlet end 221 the arrival time of the ionized component B' is recorded by suitable detection circuitry to obtain a drift spectrum as shown in fig. 2 and analyzed by means of the processing means 21.

The separation column 231 provides separation of the components of the analyte gas stream B prior to injection into the drift detector 22. The separation column 231 provides gas chromatography by forming a capillary column having a length, for example, in the range of between 0.5m and 5m, for example, 1m, and having an inner diameter, for example, between 0.1mm and 1mm, for example, about 0.5 mm. Within the capillary column, a liquid phase is provided that causes the components to reside within the capillary column, which causes different residence times of different components within the capillary column, such that the components leave the separation column 231 at different times due to their different residence times.

Thus, when the analyte gas stream B is injected into the drift detector 22, the relevant component B ' of the analyte gas stream B has been separated in time, drift through the drift detector 22 due to ionization and drive voltages provides further separation of the component B ', and the ionized component B ' can then be detected by means of suitable detection circuitry associated with the processing circuitry 21 at the outlet end 221.

Such gas portion of the analysis gas flow B that is not ionized leaves the drift detector 22 at the inlet end 220 and enters the drift gas loop 24, where the analysis gas flow B is guided together with the drift gas flow C. By means of the drift gas loop 24, the combined gas flow of the analysis gas flow B and the drift gas flow C is directed towards the separator 243, where the analysis gas flow B and the drift gas flow C are separated, such that the clean air shaped drift gas flow C is directed towards the outlet end 221 of the drift detector 22 and injected into the drift detector 22 at the outlet end 221, such that the drift gas flow C flows through the drift detector 22 in a direction opposite to the direction in which the ionized component B' of the analysis gas flow B drifts through the drift detector 22 driven by the applied electric field in order to provide a (constant) counter-current for the ionized component within the drift detector 22. The drift gas circuit 24 comprises a pump means 240 in the form of a membrane pump for driving a combined gas flow of the analyte gas flow B and the drift gas flow C and a filter means 241 in the form of a molecular sieve filter. Fluid line 242 is used to direct the combined gas flow to and from drift detector 22, drift gas flow C flowing via separator 243 toward outlet end 221 of drift detector 22 for injection into drift detector 22.

After separation of the analyte gas stream B from the drift gas stream C by means of the separator 243, the analyte gas stream B is driven by the pump means 232 in the shape of a diaphragm pump through the filter means 233, 234, the filter means 233 being shaped as a molecular sieve filter and the filter means 234 being shaped as a carbon filter for removing water and substances, in particular propofol, from the analyte gas stream B. The analysis gas stream B (now present as substantially clean air) then re-enters the valve means 230, and a sample of the sample gas stream a can be injected into the analysis gas stream B via the valve means 230.

The fluid lines 235, 242, 251 of the system may each be made, in whole or at least in part, of a PTFE material. For example, the fluid lines 235, 242, 251 may be all made of PTFE material. Alternatively, the fluid lines 235, 242, 251 may include a PTFE coating at the inner side thereof. By such material selection, water droplets can be prevented from forming within the fluid lines 235, 242, 251.

Within the analysis gas circuit 23, the analysis gas stream B is cleaned before flowing through the valve arrangement 230 and thus before processing the (further) sample of the sampling gas stream a for analysis by means of the separation column 231 and the drift detector 22. In particular, prior to injecting another sample of sample gas stream a into analysis gas stream B, the analysis gas stream B is purged of water and the substance of interest, i.e., propofol, so that the analysis gas stream B is substantially free of water and propofol prior to flowing through valve device 230. In order to obtain accurate measurements, this is necessary for analyzing the concentration of propofol in the gas stream B to indicate the concentration of propofol in the breath of the patient 4.

In addition, the drift gas stream C must also be substantially free of water and the substance of interest, i.e., propofol.

To this end, both the analysis gas circuit 23 and the drift gas circuit 24 comprise filter means 233, 241 in the form of molecular sieve filters, as schematically shown in fig. 4, the filter means 233, 241 comprising a housing 260 made of, for example, stainless steel material enclosing a filter material 26 comprising or consisting of NaY.

The zeolite NaY filter material 26 provides for the removal of water and propofol from the respective gas streams and exhibits a large water adsorption capacity, thus allowing for a considerable period of use of the system before the filter means 233, 241 are replaced.

Zeolite NaY may be used in the form of particles, wherein binder-containing particles or binder-free particles (NaY BFK) may be used.

In particular, by using such a filter material, the water content in the respective gas stream can be kept below one part per million, and the substance of interest (propofol) is substantially completely removed from the respective gas stream.

As shown in fig. 4, the molecular sieve filter has a cylindrical shape with a diameter D, for example, between 1cm and 10cm, in particular between 3cm and 6cm, and a length L, for example, between 10cm and 20 cm. The volume of the filter device is filled with filter material 26, and the size D, L of the filter is selected according to the required volume for achieving the desired filter performance.

In the embodiment shown in fig. 3, the analysis gas circuit 23 and the drift gas circuit 24 are formed as a combined gas circuit, which represents a closed circuit. The separation column 31 of the analyte gas loop 23 herein is heated to a temperature above 80 ℃, advantageously above 85 ℃, to provide for efficient separation of components within the capillary column formed by the separation column 231.

The underlying idea of the invention is not limited to the embodiments described above but can be implemented in completely different ways.

By means of the proposed design, a compact system can be provided which allows measuring the concentration of a substance of interest in the respiration of a patient, in particular propofol, with a measuring time of less than 1 minute, so that on-line examinations and controls can be performed, for example in the case of an anesthetic procedure.

List of reference numerals

1 Endotracheal tube

10 Catheter

11 Connecting piece

110 Port

12 Side stream line

2 Detection device

20 Measuring device

21 Treatment device

22 Drift detector

220, 221 Ends

23 Analysis gas Loop

230 Valve device

231 Separation column

232 Pump device

233 Filter device (molecular sieve filter)

234 Filter device (charcoal filter)

235 Pipeline

24 Drift gas loop

240 Pump device

241 Filter device (molecular sieve filter)

242 Pipeline

243 Separator

25 Sample gas loop

250 Pump device

251 Pipeline

26 Zeolite filter material

260 Shell

3 Ventilation system

4 Patients

40 Trachea

41 Lung

A sample gas flow

B analysis of gas flows

B' ionized component

C drift gas flow

Diameter D

L length

Peak of P attention (Propofol)

S drift spectrum

Claims (16)

1. A system for identifying and/or measuring a concentration of a substance in exhaled breath of a patient (4), comprising:

measuring device (20) for performing an ion mobility spectrometry measurement of a sampled gas flow (a) obtained from exhaled breath of the patient (4), the measuring device (20) comprising a drift detector (22) and at least one gas circuit (23, 24) connected to the drift detector (22), the at least one gas circuit (23, 24) for guiding an analysis gas flow (B) towards an inlet end (220) of the drift detector (22) and/or for guiding a drift gas flow (C) towards an outlet end (221) of the drift detector (22), a sample of the sampled gas flow (a) being injectable into the analysis gas flow (B), wherein the at least one gas circuit (23, 24) comprises a molecular sieve filter (233, 241) comprising a filter material (26) for filtering the analysis gas flow (B) and/or the drift gas flow (C),

It is characterized in that the method comprises the steps of,

The filter material (26) comprises zeolite NaY, wherein the at least one gas circuit (23, 24) comprises a first pump means (232), the first pump means (232) for pumping the analysis gas flow (B) towards the inlet end (220) of the drift detector (22), and the at least one gas circuit (23, 24) comprises a second pump means (240), the second pump means (240) for pumping the combined gas flow (b+c) of the drift gas flow (C) and the analysis gas flow (B), and wherein the at least one gas circuit (23, 24) forms a closed circuit for guiding the analysis gas flow (B) and/or the drift gas flow (C) along a closed loop, wherein the respective gas is cleaned by means of an associated filter means after passing the drift detector before being injected again into the drift detector.

2. The system of claim 1, wherein the filter material comprises NaY of particles containing a binder or NaY of particles not containing a binder.

3. The system of claim 1 or 2, wherein the zeolite NaY filter material has a pore size between 0.6nm and 0.8 nm.

4. A system according to claim 3, wherein the zeolite NaY filter material has a pore size of 0.7 nm.

5. The system according to claim 1 or 2, characterized in that the molecular sieve filter (233, 241) has a cylindrical shape with a diameter between 1cm and 10 cm.

6. The system of claim 5, wherein the diameter of the cylindrical shape is between 3cm and 6 cm.

7. The system of claim 1 or 2, wherein the molecular sieve filter (233, 241) comprises a housing (260) surrounding the filter material, the housing (260) being made of stainless steel.

8. The system according to claim 1 or 2, characterized in that the at least one gas circuit (23, 24) comprises a fluid line, which is at least partially made of PTFE, the at least one gas circuit (23, 24) being used for guiding the analysis gas flow (B) and/or the drift gas flow (C).

9. The system according to claim 1 or 2, characterized in that the at least one gas circuit (23, 24) comprises a separation column (231) for chromatographically separating components of the analysis gas stream (B) from each other before injecting the analysis gas stream (B) into the inlet end (220) of the drift detector (22).

10. The system according to claim 9, characterized in that the separation column (231) forms a capillary channel for guiding the flow of the analysis gas (B), the capillary channel having a length of between 0.5m and 5 m.

11. The system of claim 10, wherein the capillary channel has a length of 1 m.

12. A system according to claim 1 or 2, characterized by comprising a sampling gas circuit (25) for guiding the sampling gas flow (a) obtained from the patient's breath and a valve means (230), said at least one gas circuit (23, 24) being connectable to the sampling gas circuit (25), a sample of the sampling gas flow (a) being injected into the analysis gas flow (B) by means of the valve means (230).

13. The system according to claim 12, characterized in that the sampling gas circuit (25) comprises a fluid line, which is at least partially made of PTFE, the sampling gas circuit (25) being used for guiding the sampling gas flow (a).

14. The system according to claim 1 or 2, characterized in that the substance concentration measured by the measuring device (20) is indicative of the concentration of anesthetic agent in the patient's breath.

15. The system of claim 14, wherein the concentration of the substance measured by the measuring device (20) is indicative of the concentration of propofol in the patient's breath.

16. A method for identifying and/or measuring a concentration of a substance in exhaled breath of a patient (4), the method comprising:

Obtaining a sample gas flow (A) from the exhaled breath of said patient (4), and

-Performing an ion mobility spectrometry of the sampled gas flow (a) by means of a measuring device (20), the measuring device (20) comprising a drift detector (22) and at least one gas circuit (23, 24) connected to the drift detector (22), the at least one gas circuit (23, 24) being for guiding an analysis gas flow (B) towards an inlet end (220) of the drift detector (22) and/or for guiding a drift gas flow (C) towards an outlet end (221) of the drift detector (22), a sample of the sampled gas flow (a) being injectable into the analysis gas flow (B), wherein the at least one gas circuit (23, 24) comprises a molecular sieve filter (233, 241), the molecular sieve filter (233, 241) comprising a filter material (26) for filtering the analysis gas flow (B) and/or the drift gas flow (C),

It is characterized in that the method comprises the steps of,

The filter material (26) comprises zeolite NaY, wherein the at least one gas circuit (23, 24) comprises a first pump means (232), the first pump means (232) for pumping the analysis gas flow (B) towards the inlet end (220) of the drift detector (22), and the at least one gas circuit (23, 24) comprises a second pump means (240), the second pump means (240) for pumping the combined gas flow (b+c) of the drift gas flow (C) and the analysis gas flow (B), and wherein the at least one gas circuit (23, 24) forms a closed circuit for guiding the analysis gas flow (B) and/or the drift gas flow (C) along a closed loop, wherein the respective gas is cleaned by means of an associated filter means after passing the drift detector before being injected again into the drift detector.