Method for monitoring a volumetric flow of respiratory air in an analyzer

Abstract

The invention relates to a method (100) for monitoring a volumetric flow (10) of respiratory air in an analyzer, in particular for measuring fractionated exhaled nitrogen monoxide, wherein the respiratory air is exhaled in the form of the volumetric flow (10), preferably via an orifice in the analyzer, wherein the volumetric flow (10) is monitored during a monitoring period (130) for deviation with regard to a specified quantity (20, 21), characterized in that the specified quantity (20, 21) is time-dependent.

Description

[0001] Description

[0002] title

[0003] Method for monitoring a volume flow of breathing air in an analysis device

[0004] State of the art

[0005] The measurement of fractional nitric oxide (NO) in exhaled air (FeNO) has become established as a measure of lung inflammation, particularly in connection with asthma. The proportion of NO in the exhaled air depends significantly on the respiratory flow during exhalation. To measure FeNO with an analyzer, it is therefore necessary to provide the breath sample at a defined flow (volume flow). With the help of suitable feedback (visual and / or acoustic) in real time, the user can monitor and adjust the strength of their exhaled flow. If the required flow cannot be maintained, the analyzer preferably aborts sampling to prevent incorrect measured values ​​from being generated and output. One such FeNO analyzer is based, for example, on the device described in EP 1384069 B1 and is marketed under the brand name Vivatmo®.

[0006] Typically, a constant value of + / - 10% is set for the permissible flow tolerance, based on a fixed volume flow of 50 milliliters per second (ml / s), as also specified in the so-called guideline for measuring FeNO (ATS / ERS recommendations for standardized procedures for the online and offline measurement of exhaled lower respiratory nitric oxide and nasal nitric oxide, 2005. Am J Respir Crit Care Med. 2005;171 (8):912-930. doi:10.1164 / rccm.200406-71 OST). Due to this relatively narrow range, inexperienced users often require several attempts to provide a correct breath sample. Disclosure of the Invention

[0007] Advantages of the invention

[0008] Against this background, the invention relates to a method for monitoring a volume flow of respiratory air in an analysis device, wherein the respiratory air is exhaled in the form of the volume flow, preferably through an opening into the analysis device. The volume flow is monitored during a monitoring period for a deviation from a predetermined, time-dependent measure. In particular, the method can be used to measure fractionated exhaled nitric oxide (FeNO). Furthermore, the invention relates to an analysis device configured in this way, i.e. in particular an analysis device with a correspondingly programmed control unit, and to a computer program, i.e. software comprising instructions which, when the program is executed by a computer, in particular by the control unit of the analysis device, cause the computer to carry out the method according to the invention.

[0009] The analyzer according to the invention and the associated method utilize the fact that different deviations of the volume flow from the target values ​​can be tolerated in different time periods. Depending on the parameter of interest to be measured in the exhaled air, in particular the analytes to be measured, such as NO, CO2, or alcohol, and their physiological background, the time dependence of the measurement can be determined.

[0010] Preferably, the measure can represent a deviation tolerance for a tolerable deviation of the volume flow from one or more target values. The target values ​​can in particular be a predetermined volume flow, i.e. a volume moved through an area per unit of time. In the case of FeNO, for example, the above-mentioned guideline specifies a volume flow of 50 ml / s. Preferably, the measure has a higher deviation tolerance during a second interval of the monitoring period than during a previous first interval. In the case of FeNO measurement, the fact can be exploited that the part of the exhaled air relevant for the measurement, i.e. the relevant breath sample, originates from the lower respiratory tract, in particular from the bronchi, and the parts exhaled first, namely the breath from the oropharynx and from the trachea (also referred to as dead space volume), are not to be taken into account for the measurement.This dead space volume means that the relevant breath sample only reaches the sensor in the analyzer with a delay. This means that flow fluctuations during the exhalation process only have a delayed effect on the measurement signal, and thus a higher deviation tolerance can advantageously be set for the second interval. This has the advantage of making it easier for the user to maintain the correct flow or volume flow. Due to the dead space volume described above, users must generally maintain a relatively constant volume flow during exhalation for a relatively long time, which is particularly difficult for users with smaller lung volumes. By adjusting the tolerated degree of deviation from the specified volume flow, the strict requirements for an exhaled sample to be classified as correct can advantageously be relaxed.Furthermore, the method facilitates the rapid performance of multiple valid measurement trials, if necessary. In addition to FeNO measurements, the method is also particularly well-suited for measuring other analytes in breath from the lower respiratory tract.

[0011] According to a special embodiment, the respiratory air is exhaled into the analyzer during a bypass period and a subsequent measurement period. A measurement period is understood to be a period during which the respiratory air is measured by one or more sensors of the analyzer and the data recorded thereby is considered valid. A bypass period, on the other hand, is understood to be a period during which no measurement is taken or recorded measurement data is considered invalid. Depending on the specific structural design of the analyzer, the respiratory air can be passed past the sensor during the bypass period without contact with the sensor and / or the sensor can be deactivated. Particularly in the case of FeNO measurement, the monitoring period can cover at least parts of the bypass period and the measurement period. Typically, the monitoring period covers at least the measurement period.In the case of FeNO measurement, due to the time delay described above, a portion of the bypass period immediately preceding the measurement period is also covered. According to a special design, particularly for FeNO measurement, the monitoring period can end before the end of the measurement period, so that the monitoring period covers, in particular, a portion of the bypass period and a first portion of the measurement period immediately adjacent to it, and does not cover a second portion of the measurement period.

[0012] In an advantageous embodiment, the measure increases or decreases during at least one interval of the monitoring period. The measure can increase or decrease continuously, in particular linearly or exponentially, or in steps, at least in sections. For example, the measure can decrease at the beginning of the first interval and increase towards the end of the second interval.

[0013] According to an advantageous development of the invention, the analyzer issues a warning if a deviation in the volume flow exceeds a predefined value during the monitoring period. The predefined value can, in particular, correspond to the deviation tolerance. Preferably, the user is informed of the current volume flow value and warned if the deviation approaches or exceeds the specified value, for example, via a visual and / or acoustic signal from the analyzer, in order to reduce the deviation.

[0014] Short description of the drawings

[0015] Embodiments of the invention are schematically illustrated in the drawings and explained in more detail in the following description. The same reference numerals are used for the elements shown in the various figures and have a similar effect, whereby a repeated description of the elements is omitted.

[0016] Figure 1 shows an embodiment of the analysis device according to the invention for analyzing respiratory air,

[0017] Figure 2 shows a division of the exhalation process into a bypass period and a measurement period with a partially simultaneous monitoring period and

[0018] Figure 3 shows an exemplary volume flow curve and the time-dependent degree of deviation tolerance according to embodiments of the method according to the invention.

[0019] Embodiments of the invention

[0020] Figure 1 shows an exemplary embodiment of the analysis device 1000 according to the invention for analyzing breath, in particular for measuring fractionated exhaled nitrogen monoxide, which can be based on a device as described in patent specification EP 1384069 B1. The analysis device 1000 comprises a mouthpiece 300 through which a user can exhale breath into the analysis device 1000. The mouthpiece 300 can be attached to the actual analysis device, also referred to as a handheld device 200, preferably in an interchangeable manner. The handheld device 200 comprises, in addition to a suitable sensor, such as a sensor described in EP 1384069 B1 for measuring NO converted to NO2 in the analysis device, among other things, a control device 210 for carrying out the measurement and a memory in which commands for carrying out the method according to the invention are stored as software.The handheld device 200 further comprises a sensor 220 connected to the control unit 210 for measuring the correct volume flow of the exhaled air, for example, the BME280 combination sensor from Robert Bosch GmbH, and preferably an output device 230 for outputting optical and / or acoustic feedback to the user, in particular via a display or a loudspeaker. The method 100 according to the invention will now be described by way of example with reference to Figure 2 and especially Figure 3. Figure 2 schematically shows time periods elapsed during a measurement of exhaled air, for example, during a measurement of fractionated exhaled nitric oxide (FeNO) in exhaled air using a breath analyzer based on a device as described in patent EP 1384069 B1. The user exhales continuously for several seconds, for example, 10 seconds, into a designated opening of the analyzer 1000.The first portion of exhaled air, which is exhaled during a predefined period referred to as bypass period 110, should cover the portion of exhaled air originating from the dead space volume described above. The second portion of exhaled air, which immediately and without interruption follows, should, if possible, exclusively comprise the breath sample originating from the bronchi and relevant for the measurement. This second portion is exhaled during the predefined measurement period 120 and used for the measurement. In the following, bypass period 110 and measurement period 120 last, for example, seven seconds and three seconds, respectively.

[0021] To obtain a breath sample suitable for measurement, the user must exhale as evenly as possible during the measurement period. According to the above-mentioned guideline, the user should provide a volume flow of 50 milliliters per second with a tolerated deviation of + / - 10% for a FeNO measurement. To ensure this, the appropriately configured analyzer monitors whether the volume flow exceeds the specified tolerance level of 10% based on 50 ml / s during a monitoring period 130. As shown in Figure 2, the monitoring period 130 covers the entire measurement period and a portion of the bypass period preceding the measurement period. For example, the monitoring period can begin after the first three seconds of the bypass period, thus covering the remaining four seconds of the bypass period and the three seconds of the measurement period, and then end simultaneously with the measurement period.Preferably, the user is informed of the current value of the volume flow and warned if the deviation approaches or exceeds the limit, for example via an optical and / or acoustic signal from the analysis device 1000, in order to reduce the deviation. The limit can also comprise two different values, for example a tolerance value of + / - 10% and a threshold value of + / - 20%, so that, for example, if the tolerance value is exceeded initially only the warning is issued and only if the threshold value is exceeded is the measurement classified as invalid, wherein in special embodiments a minimum duration for the exceedance of one or both values ​​can also be provided (if applicable in each case) for the warning to be issued or the invalidation to be classified. The output can in particular be acoustic and / or optical, for example as a color output, for example in orange and red if the tolerance value is exceeded.the threshold value, via (LED) lamps or the display.

[0022] According to the invention, the degree of tolerated deviation is to be specified as a function of time. In particular, the degree can be relaxed, i.e., widened, in the last seconds of the measurement period 120, as shown in Figure 3. This is particularly less critical in the case of FeNO measurement or, in general, the measurement of a breath sample from the lower respiratory tract (bronchi) due to the time delay described above, but advantageously provides noticeable relief for the user. For example, the tolerance can be increased from + / -10% to + / -30% in the last two seconds of the measurement period 120. The increase in the tolerance can occur abruptly or, alternatively, continuously. Figure 3 shows, alongside an exemplary volume flow 10, such a time-dependent degree 20, which is increased abruptly from + / -10% to + / -30% eight seconds after the start of the exhalation process, i.e., one second after the start of the measurement phase.The measure can also be increased in several steps, for example to 15% after the first half second, to 25% after 1.5 seconds and to 35% after 2.5 seconds after the start of the measuring period. A continuous increase can in particular have a linear or exponential gradient and can also end, for example, at a measure of + / -30% or + / -35%. As an example, Figure 3 (dashed line) also shows a continuous increase in the measure 21 to + / - 30% starting six seconds after the start of the exhalation process, i.e. still in the bypass period 110 and one second before the start of the measuring period 120. In the example according to Figure 3, the volume flow 10 of the exhaling user would deviate more than the specified measure between seconds 7 and 8 despite a sudden loosening 20 from second 8, whereas in the alternative example of constant loosening 21 from second 6 it would remain within the tolerance.If the measure comprises multiple values ​​as described above, these values ​​can preferably be increased in parallel, to the same or, alternatively, to a different extent. If, in particular, the associated measurement uncertainty is acceptable, the increase in the measure can also begin during the last part of the bypass period, as shown by way of example in Figure 3 for the steady increase 21 starting at second 6, and, for example, an increase can occur in smaller steps or with a smaller gradient. Alternatively or additionally, the monitoring period 130 can also end before the end of the measurement period 120, for example, half a second or a full second before the end of the measurement period, which would be equivalent to an infinitely large measure.

[0023] Thus, as illustrated in these examples, the degree of deviation tolerance can be increased during a second interval of the monitoring period (time interval between seconds 6 or 8 and 10 in the examples according to Figure 2). Depending on the application and the resilience of the measurement, the second interval can begin during the measurement period or already during the bypass period. During the first interval of the monitoring period, the degree can remain constant (time interval between seconds 1 and 8 or 6 in the examples according to Figure 2). Alternatively, the degree can also change during the first interval. For example, the degree could be set higher at the beginning of the first interval and thus at the beginning of the monitoring period, for example to + / -20% or + / -15%, and then reduced, either gradually or continuously, to + / -10% if an increased tolerance at the beginning of the exhalation process is acceptable for the measurement.

Claims

Claims 1 . Method (100) for monitoring a volume flow (10) of respiratory air in an analysis device (1000), in particular for measuring fractionated exhaled nitrogen monoxide, wherein the respiratory air is exhaled in the form of the volume flow (10), preferably via an opening (300) into the analysis device (1000), wherein the volume flow (10) is monitored during a monitoring period (130) for a deviation with respect to a predetermined measure (20, 21), characterized in that the predetermined measure (20, 21) is time-dependent.

2. Method (100) according to claim 1, wherein the breathing air is exhaled into the analysis device (1000) during a bypass period (110) and a subsequent measuring period (120), and wherein the time-dependent measure (20, 21) changes during the measuring period (120).

3. Method (100) according to one of the preceding claims, wherein the measure (20, 21) represents a deviation tolerance for a tolerable deviation of the volume flow (10) from one or more target values ​​and wherein preferably the measure (20, 21) has a higher deviation tolerance during a second interval of the monitoring period (130) than during a temporally preceding first interval, wherein the second interval lies in particular in the measuring period (120).

4. The method (100) according to any one of the preceding claims, wherein the monitoring period (130) covers a part of a bypass period (110), the part immediately preceding a measurement period (120) 5. Method (100) according to one of the preceding claims, wherein the monitoring period (130) covers part of the measurement period (120) 6. The method (100) according to any one of the preceding claims, wherein the monitoring period (130) ends before the end of the measurement period (120).

7. Method (100) according to one of the preceding claims, wherein the measure (20, 21) increases, preferably increases continuously, at least during an interval of the monitoring period (130).

8. Method (100) according to one of the preceding claims, wherein the increase in the measure (20, 21) is at least partially linear or exponential.

9. Method (100) according to one of the preceding claims, wherein the increase in the dimension (20, 21) is at least partially step-like.

10. Method (100) according to one of the preceding claims, wherein the measure (20, 21) decreases, preferably decreases continuously, at least during an interval of the monitoring period (130).

11. Method (100) according to one of the preceding claims, wherein the analyzer (1000) issues a warning if a deviation of the volume flow (10) during the monitoring period (130) exceeds a predetermined value of the measure (20, 21).

12. Analysis device (1000) for analyzing respiratory air, in particular for measuring fractionated exhaled nitrogen monoxide, wherein the analysis device (1000) is configured to carry out a method (100) according to one of the preceding claims.

13. A computer program comprising instructions which, when executed by a computer, cause the computer to carry out the method (100) according to any one of claims 1 to 11.

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