AU2017100108A4

AU2017100108A4 - Method for Monitoring Gas Analyser and Breathing Apparatus

Info

Publication number: AU2017100108A4
Application number: AU2017100108A
Authority: AU
Inventors: Christer Ahlmen
Original assignee: Maquet Critical Care AB
Current assignee: Maquet Critical Care AB
Priority date: 2017-01-30
Filing date: 2017-01-30
Publication date: 2017-03-02
Anticipated expiration: 2025-01-30

Abstract

Herein a method (100) for monitoring a gas analyser (24) of a breathing apparatus (2) is disclosed. The breathing apparatus (2) comprising the gas analyser (24) and a further sensor device (28) fluidly connected in series with the gas analyser (24). The method (100) 5 comprises steps of: - conducting (102) expiratory gas from a patient (8) through the gas analyser (24) and the further sensor device (28), - providing (104) gas analyser measurement data related to the expiratory gas from the gas analyser (24), 10 - providing (106) sensor measurement data related to at least one aspect of the expiratory gas from the further sensor device (28), and - comparing (108) at least one parameter related to the gas analyser measurement data with at least one parameter related to the sensor measurement data. Fig. 1

Description

1

Method for Monitoring Gas Analyser and Breathing Apparatus

TECHNICAL FIELD

The invention relates to a method for monitoring a gas analyser of a breathing apparatus. The invention further relates to a breathing apparatus comprising a gas analyser.

BACKGROUND A breathing apparatus may comprise a gas analyser for analysing e.g. expiratory gas from a patient. Automatic control and/or manual control of the breathing apparatus may rely on the gas analysis provided by the gas analyser. It is important that the gas analyser provides correct gas analysis. US 7290544 discloses a combination gas mixer and ventilator. The combination gas mixer and ventilator comprises a controllable gas dispenser, a gas monitor, a controlling device and a user interface by which the controlling device can be monitored by means of set values. The gas monitor is adapted to measure a measuring value from a measuring point, which measuring value is dependent on the operation of the controllable gas dispenser and the controlling device is adapted to monitor the controllable gas dispenser on the basis of the measuring value and set values. To improve safety, the arrangement comprises means adapted to feed a reference gas, e.g. a fresh gas sample, to the gas monitor periodically.

The controlling device is adapted to compare a measuring value obtained from the reference gas with the real concentration value of the reference gas and adapted to take a safety measure when the measuring value and the real concentration value differ substantially from each other.

During periods of feeding the reference gas to the gas monitor, the gas monitor is not available for monitoring gas in a patient circuit of the combination gas mixer and ventilator. US 8978652 discloses an anaesthetic breathing apparatus. The anaesthetic breathing apparatus comprises a first gas analyser arranged to provide gas measurement data related to a first sample point to a control unit that is arranged in a servo or feedback control system configured to adjust delivery of a vaporized aesthetic agent from an anaesthetic vaporizer to a delivery point in an inspiratory branch of a breathing circuit of the anaesthetic breathing apparatus. The first sampling point is arranged in the breathing circuit downstream and close to the delivery point. A second gas analyser is arranged to be operated in a first mode of operation to provide gas measurement data for patient monitoring, and in a second mode of 2 operation to provide gas measurement data to the control unit. A switch over unit is fluidly connected to the second gas analyser and arranged to switch fluid communication of the second gas analyser between the first sample point for the second mode of operation and a second sample point for the first mode of operation. The second sample point is arranged in a patient tubing close to a Y-piece at a patient connected to the breathing circuit.

Thus, the second gas analyser is connected in parallel with the first gas analyser when measurement data from one of the gas analysers is to be verified. The second gas analyser is used for redundantly measuring the gas concentrations, at least when a deviation is detected. Providing a second gas analyser is a costly solution to verify proper function of the first gas analyser. Moreover, during expiratory gas analysis, the relevant gas analyser cannot be verified.

SUMMARY

It is an object of the invention to provide an alternative solution for verifying the functionality of a gas analyser in a breathing apparatus, which alleviates at least one of the above mentioned problems.

According to an aspect of the invention, the object is achieved by a method for monitoring a gas analyser of a breathing apparatus according to claim 1, see below.

According to a further aspect of the invention, the object is achieved by a breathing apparatus according to claim 3, see below.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects and/or embodiments of the invention, including its particular features and advantages, will be readily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which:

Fig. 1 illustrates embodiments of a breathing apparatus comprising a gas analyser, and Fig. 2 illustrates a method for monitoring a gas analyser of a breathing apparatus.

DETAILED DESCRIPTION

Aspects and/or embodiments of the invention will now be described more fully. Like numbers refer to like elements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and/or clarity. 3

Fig. 1 illustrates embodiments of a breathing apparatus 2 comprising a gas analyser 24. The breathing apparatus 2 comprises an inspiratory section 4 and an expiratory section 6. The inspiratory section 4 is configured for providing fresh gas, and recirculated breathing gas to a Y-piece 17. The expiratory section 6 is configured for conducting expiatory gas from the Y-piece. From the inspiratory section 4 fresh gas is provided to a patient 8 at the Y-piece 17. The expiratory section 6 leads gas from the patient 8 and the Y-piece to an exhaust port 10 of the breathing apparatus 2. Seen in a direction of gas flow towards the patient 8, the inspiratory section 4 comprises at least one gas inlet 11, at least one inlet gas pressure and/or flow regulator 12, an anaesthetic agent vaporizer 14, a patient inspiration tube 16, and the Y-piece 17. Seen in a direction of gas flow from the patient 8, the expiratory section 6 comprises the Y-piece 17, a patient expiration tube 18, a volume reflector 20 or similar device, and an expiratory pressure control valve 21 (PEEP valve). A C02 absorber 22 is arranged between the expiratory section 6 and the inspiratory section 4. The C02 absorber absorbs C02 from expiratory gas, which is recirculated to the inspiratory section 4. The C02 absorber is fluidly connected at a recirculation connection point 23 at the inspiratory section 4. The inspiratory and expiratory section 4, 6 connected to the patient 8 and the C02 absorber 22 may be referred to as an anaesthesia breathing circuit. The anaesthesia breathing circuit also contains check valves, not shown.

The breathing apparatus 2 comprises a patient gas analyser, PGA, also referred to as a gas analyser 24. The gas analyser 24 may analyse gas based e.g. on light absorption techniques, or other techniques. The gas analyser 24 is configured to be fluidly connected to the Y-piece 17. The gas analyser 24 is configured for providing gas analyser measurement data related to expiratory gas from the patient 8. Samples of expiratory gas from the Y-piece 17 are lead to the gas analyser 24. The gas analyser measurement data may be provided to a control unit 26 of the breathing apparatus 2. The gas analyser measurement data, e.g. may relate to anaesthetic agent content in the expiratory gas and to the content of, or other measurement data, of other gas components, such as Oxygen, Nitric Oxide, Carbon Dioxide, and perhaps further gases.

The breathing apparatus 2 comprises a further sensor device 28 fluidly connected in series with the gas analyser 24. In the illustrated embodiments, the further sensor device 28 is arranged downstream of the gas analyser 24 fluidly connected to a gas sample outlet conduit 30 of the gas analyser 24. In alternative embodiments, the further sensor device 28 may instead be arranged fluidly connected to a gas sample inlet conduit 32 of the gas analyser 24. The further sensor device 28 is configured for providing sensor measurement data related to at least one aspect of expiratory gas flow from the patient 8. 4

The breathing apparatus 2 also comprises a control unit 26. The control unit 26 is configured to compare at least one parameter related to the gas analyser measurement data with at least one parameter related to the sensor measurement data.

Since the further sensor device 28 is connected in series with the gas analyser 24, the further gas sensor 28 can provide sensor measurement data simultaneously with the gas analyser 24. Thus, gas analysis measurement data from the gas analyser 24 can be provided while simultaneously, the sensor measurement data from the further sensor device 28 can be utilised by the control unit 26 to verify that the gas analyser 24 is providing correct gas analyser measurement data. Accordingly, during ordinary operation of the gas analyser 24, the gas analyser 24 may be checked. No interruption for conducting fresh gas through the gas analyser 24 has to be performed for verifying the operation of the gas analyser 24 while expiratory gas from the patient is analysed. A flow directing unit 25 is configured to directs either samples of expiratory gas, or samples of fresh gas, to the gas analyser 24. Accordingly, as an alternative to expiratory gas samples, samples of fresh gas from the inspiratory section 4 may be led to the gas analyser 24, and may be analysed therein.

The control unit 26 may be configured to preform calculations of parameters and/or comparisons of parameters related to the gas analyser measurement data and/or to the sensor measurement data. Such parameters may be actual measurement data and/or parameters calculated based on the measurement data. The control unit 26 may further be configured to control various functions of the breathing apparatus 2

For instance, the control unit 26 may form part of a servo, or feedback, control system based on analysis of the expiratory gas by the gas analyser 24, and provided for regulating the amount of anaesthetic agent delivered to the patient. Expiratory gas is at least partially reflected back to the patient and the amount of fresh gas may be kept at a suitable low value that still is enough for keeping gas concentrations at set values. The control unit 26 may form part of a patient monitoring system based on analysis of expiratory gas by the gas analyser 24, and provided for monitoring the condition of the patient. A healthcare person may supervise the condition of the patient on the basis of the patient monitoring system and, when necessary, adjust set values of the breathing apparatus 2 such that the measurement data correspond to one or more desired values. 5

In order to provide a cost-efficient solution, the further sensor device 28 may be a simpler device than the gas analyser 24, such as a gas analyser may be able to analyse gas content with respect to only one aspect of the gas, or fewer aspects of the gas than the gas analyser 24. Such aspect or aspects of the gas may be one or more constituents of the gas. Other such aspect or aspects of the gas may be one or more properties of the gas. Thus, sensor measurement data related to at least one aspect of expiratory gas flow from the patient 8 may be provided by the further sensor device 28. According to alternative embodiments, the further sensor device 28 may be a further gas analyser of the same kind as the gas analyser 24. Alternatively, the further sensor device 28 may be a different kind of gas analyser having similar gas analysis capabilities as the gas analyser 24. Thus, sensor measurement data related to at least one aspect of expiratory gas flow from the patient 8 may be provided by the further sensor device 28.

As discussed above, the control unit 26 is configured to compare at least one parameter related to the gas analyser measurement data with at least one parameter related to the sensor measurement data. Accordingly, parameters related to measurement data from the gas analyser 24 and the further sensor device 28 are compared. If the compared parameters are within a predefined range, the gas analyser 24 is assumed to provide reliable gas analyser measurement data. If the compared parameters lie outside the predefined range, at least one of the gas analyser 24 and the further sensor device 28 may be faulty, and may require maintenance or replacement. This comparison may be done continuously, or intermittently, without interrupting gas analysis of the expiration gas from the patient 8. An alarm signal may be triggered if the compared parameters lie outside the predefined range.

According to embodiments, the further sensor device 28 may be an ultrasonic sensor for measuring the speed of sound in the expiratory gas. The gas analyser 24 or the control unit 26 calculates a theoretical speed of sound in the expiratory gas based on the concentrations of gas measured by the gas analyser 24. Thus, the calculated theoretical speed of sound in the expiratory gas forms one parameter related to the gas analyser measurement data, and the measured speed of sound in the expiratory gas form one parameter related to the sensor measurement data. The calculated theoretical speed of sound is compared to the measured speed of sound from the further sensor device 28. If the measured speed of sound lies within a predefined range of the calculated theoretical speed of sound, the gas analyser 24 is assumed to provide reliable measurement data. If the measured speed of sound lies outside the predefined range of the calculated theoretical speed of sound, at least one of the gas analyser 24 and the further sensor device 28 may be faulty, and may require maintenance or 6 replacement. This comparison may be done continuously, or intermittently, without interrupting gas analysis of the expiration gas from the patient 8. The advantage of using an ultrasonic sensor is a low price and that it forms a robust component.

According to a further aspect, the invention also relates to a method 100 for monitoring a gas analyser 24 of a breathing apparatus 2. Fig. 2 illustrates embodiments of such a method 100. In the following reference is also made to Fig. 1.

Again, the breathing apparatus 2 comprises an inspiratory section 4 for providing fresh gas to a Y-piece, an expiratory section 6 for conducting expiatory gas from the Y-piece 17, and the gas analyser 24 configured to be fluidly connected to the Y-piece 17. The inspiratory section 4 comprises at least one inlet gas pressure and/or flow regulator 12 and an anaesthetic agent vaporiser 14. The breathing apparatus 2 comprises a further sensor device 28 fluidly connected in series with the gas analyser 24.

The method 100 comprises steps of: - conducting 102 expiratory gas from a patient 8 through the gas analyser 24 and the further sensor device 28, - providing 104 gas analyser measurement data related to the expiratory gas from the gas analyser 24, - providing 106 sensor measurement data related to at least one aspect of the expiratory gas from the further sensor device 28, and - comparing 108 at least one parameter related to the gas analyser measurement data with at least one parameter related to the sensor measurement data.

According to embodiments, the at least one parameter related to the gas analyser measurement data may be a theoretically calculated speed of sound of the expiratory gas based on the gas analyser measurement data, and wherein the at least one parameter related to the sensor measurement data may be a measured speed of sound of the expiratory gas measured by the further sensor device 28.

According to further embodiments, if comparison leads to that the compared parameters lie outside the predefined range, a further check of the gas analyser 24 and the further sensor device 28 may be performed before any conclusions with respect to the performance of the gas analyser 24 and/or the further sensor device 28 is drawn. A switch from gas sampling of patient expiratory gas to gas sampling of fresh gas is done. The flow directing unit 25 is utilised for switching between gas flow from the Y-piece 17 and gas flow from upstream of 2017100108 30 Jan 2017 7 the recirculation connection point 23. The fresh gas is a more stable gas-mixture than the expiratory gas mixture at the Y-piece 17 and does not contain humidity or C02. Thus, a more stable condition for the comparison between the readings from the gas analyser 24 and the further sensor device 28 may be provided. 5

According to further embodiments, in order to check functions in the inspiratory section 4, e.g. of the regulators 12 and the vaporiser 14, the gas sampling is switched from gas sampling at the Y-piece 17 to gas sampling in the inspiratory section 4, upstream of the recirculation connection point 23. The concentration of the delivered gases in the fresh gas 10 may then be checked with the gas analyser 24 and the further sensor device 28. The check of the functions in the inspiration section 4 may be done during a pre-use-check, i.e. before the breathing apparatus 2 is connected to the patient 8, as well as when a new vaporizer 14 is connected to the inspiratory section 4. The check of the functions in the inspiratory section 4 may also be done whenever concentration readings at the Y-piece 17 differ substantially 15 from expected values. This may be done in order to check whether the fresh gas composition is incorrect. Namely, upstream of the recirculation connection point 23, the fresh gas composition should be stable without moisture and/or C02.

It is to be understood that the foregoing is illustrative of various example embodiments and 20 that the invention is defined only by the appended claims. A person skilled in the art will realize that the example embodiments may be modified, and that different features of the example embodiments may be combined to create embodiments other than those described herein, without departing from the scope of the invention, as defined by the appended claims. 25 As used herein, the term "comprising" or "comprises" is open-ended, and includes one or more stated features, elements, steps, components or functions but does not preclude the presence or addition of one or more other features, elements, steps, components, functions or groups thereof.

Claims

1. A method (100) for monitoring a gas analyser (24) of a breathing apparatus (2), the breathing apparatus (2) comprising an inspiratory section (4) for providing fresh gas to a Y-piece (17), an expiratory section (6) for conducting expiatory gas from the Y-piece (17), and the gas analyser (24) configured to be fluidly connected to the Y-piece (17), wherein the inspiratory section (4) comprises at least one inlet gas pressure and/or flow regulator (12) and an anaesthetic agent vaporiser (14), wherein the breathing apparatus (2) comprises a further sensor device (28) fluidly connected in series with the gas analyser (24), and wherein the method (100) comprises steps of: - conducting (102) expiratory gas from a patient (8) through the gas analyser (24) and the further sensor device (28), - providing (104) gas analyser measurement data related to the expiratory gas from the gas analyser (24), - providing (106) sensor measurement data related to at least one aspect of the expiratory gas from the further sensor device (28), and - comparing (108) at least one parameter related to the gas analyser measurement data with at least one parameter related to the sensor measurement data.

2. The Method according to claim 1, wherein the at least one parameter related to the gas analyser measurement data is a theoretically calculated speed of sound of the expiratory gas based on the gas analyser measurement data, and wherein the at least one parameter related to the sensor measurement data is a measured speed of sound of the expiratory gas measured by the further sensor device (28).

3. A breathing apparatus (2) comprising an inspiratory section (4) for providing fresh gas to a Y-piece (17), an expiratory section (6) for conducting expiatory gas from the Y-piece (17), and a gas analyser (24) fluidly connected to the Y-piece (17), wherein the inspiratory section (4) comprise at least one inlet gas pressure and/or flow regulator (12) and an anaesthetic agent vaporiser (14), and wherein the gas analyser (24) is configured for providing gas analyser measurement data related to expiratory gas from a patient (8), characterised in that the breathing apparatus (2) comprises a further sensor device (28) and a control unit (26), wherein the further sensor device (28) is fluidly connected in series with the gas analyser (24), and is configured for providing sensor measurement data related to at least one aspect of the expiratory gas from the patient (8), and wherein the control unit (26) is configured to compare at least one parameter related to the gas analyser measurement data with at least one parameter related to the sensor measurement data.