US-12616808-B2 - Process and device for detection of a leak in a ventilation circuit

US12616808B2US 12616808 B2US12616808 B2US 12616808B2US-12616808-B2

Abstract

A process for monitoring a measuring system ( 110 ) for mechanical ventilation of a patient ( 20 ) is carried out while a fluid connection ( 40 ) is established between the patient ( 20 ) and a medical device ( 100 ). A gas sample is suctioned from the fluid connection ( 40 ) and is sent through a gas sensor fluid-guiding unit ( 52 ) to a gas sensor array ( 50 ). A time curve of the CO2 concentration and O2 concentration in the suctioned gas sample are determined. A concentration change curve of the change over time of the CO2 concentration and the O2 concentration are calculated. A search is made for a time period in which the two concentration change curves continuously have the same sign. Upon detecting such a time period it is checked whether a predefined first leak criterion is met. When this is the case, an indication of a leak (L) is detected.

Inventors

Gerd Peter
Martin Kroh

Assignees

Drägerwerk AG & Co. KGaA

Dates

Publication Date: 20260505
Application Date: 20210428
Priority Date: 20200429

Claims (10)

1 . A process for monitoring a measuring system for mechanical ventilation of a patient, the process comprising the steps of: providing the measuring system, wherein the measuring system comprises: a gas sensor array and a gas sensor fluid-guiding unit, and wherein the process is performed while a fluid connection, between the patient and a medical device, is established, using a patient-side fluid-guiding unit; with the measuring system, measuring a concentration of a gas flowing in the fluid connection between the patient and the medical device; providing a signal processing unit and a control device; automatically controlling a parameter of the mechanical ventilation, via the control device, as a function of the concentration of the gas; suctioning a gas sample from the patient-side fluid-guiding unit and guiding the gas sample through the gas sensor fluid-guiding unit to the gas sensor array, with the fluid connection, between the patient and the medical device, being established; with the signal processing unit, calculating an indicator of a progress over time of a concentration of carbon dioxide, as a carbon dioxide concentration time curve, in the suctioned gas sample and an indicator of a progress over time of a concentration of an other gas, different from carbon dioxide, as an other gas concentration time curve, in the suctioned gas sample, using measured values of the gas sensor array; with the signal processing unit, calculating an indicator of a progress over time of a temporal change of the carbon dioxide concentration, as a carbon dioxide concentration change curve, and an indicator of a progress over time of a temporal change of the concentration of the other gas, as an other concentration change curve, using the carbon dioxide concentration time curve and the other gas concentration time curve; with the signal processing unit, searching for time periods with a same sign, wherein throughout the same sign time period the two concentration change curves have the same sign, with both concentration change curves being greater than zero or both less than zero; with the signal processing unit, checking, upon at least one same sign time period being detected, whether the two concentration change curves meet a predefined first leak criterion in the detected same sign time period; with the signal processing unit, determining that a leak has occurred, the leak occurring between the patient-side fluid-guiding unit and the gas sensor array, or determining that there is an indication of such a leak, if the predefined first leak criterion is met; and if the signal processing unit has determined that the leak or leak indication has occurred, with the control device, generating an alarm and transmitting the alarm to a receiver located at a distance in space and outputting the alarm, wherein the alarm is configured to be perceptible to a person, and while the patient is mechanically ventilated, the mechanical ventilation is continued without using the results of the gas measurement of the concentration of the gas flowing in the fluid connection between the patient and the medical device.
2 . The process in accordance with claim 1 , wherein the predefined first leak criterion depends on at least one of the following parameters: a duration of the same sign time period; an entire duration of all same sign time periods detected since a predefined reference time; an arithmetic product of the two values that the two concentration change curves assume at least one sample time in the same sign time period; an arithmetic sum of a plurality of such arithmetic products of values with the same sign within the same sign time period; and a sum of all such arithmetic products for all sample times within at least one same sign time period.
3 . The process in accordance with claim 1 , wherein a calculation of a phase shift of the carbon dioxide concentration change curve in relation to the other concentration change curve is carried out such that, after the calculated phase shift, a maximum of the carbon dioxide concentration change curve falls at the same time point as a maximum or minimum of the other concentration change curve.
4 . The process in accordance with claim 1 , further comprising the steps of: measuring a progress over time, as a pressure change curve, of a pressure at a measuring point in or at the gas sensor array or in or at the gas sensor fluid-guiding unit; and calculating an indicator of a progress over time of a temporal change of the measured pressure; calculating an indicator of a phase shift between the carbon dioxide concentration time curve and the other gas concentration time curve; calculating an indicator of a progress over time of a temporal change of the calculated phase shift indicator; and checking whether a predefined second leak criterion is met, wherein: the predefined second leak criterion depends on the phase shift change curve and the pressure change curve; upon detecting that at least one of the predefined first and second leak criteria is met, determining that the leak has occurred between the patient-side fluid-guiding unit and the gas sensor array or determining that there is the indication of the leak.
5 . The process in accordance with claim 4 , wherein the predefined second leak criterion depends on: the phase shift change curve at a first sample time and the pressure change curve at a second sample time, wherein the time interval between the two sample times depends on the distance between the measuring point, at which the pressure is measured, and a measuring point, at which the two concentrations are measured.
6 . The process in accordance with claim 5 , wherein the predefined second leak criterion is met if: the phase shift curve at the first sample time is above a first predefined threshold; and the pressure change curve at the second sample time is above a second predefined threshold.
7 . The process in accordance with claim 1 , wherein: upon detecting that at least one of the predefined first leak criterion and the predefined second leak criterion is met, carrying out a check; the check comprises: interrupting the step of suctioning the gas sample from the patient-side fluid-guiding unit; measuring a pressure in the patient-side fluid-guiding unit and measuring a pressure at a measuring point in or at the measuring system while the suctioning of the gas sample is interrupted; comparing the two measured pressures; and upon the result that the comparison of the two pressures meets a predefined third leak criterion, determining that a leak has occurred.
8 . A measuring system for a mechanical ventilation of a patient, the measuring system comprising: a gas sensor array; a gas sensor fluid-guiding unit connected or connectable to a patient-side fluid-guiding unit, wherein, using the patient-side fluid-guiding unit, a fluid connection is established or establishable, the fluid connection configured to be between the patient and a medical device, wherein the patient is mechanically ventilated while a process for monitoring the measuring system is performed, wherein the measuring system is configured to suction gas from the patient-side fluid-guiding unit through the gas sensor fluid-guiding unit to the gas sensor array, wherein the gas sensor array is configured to measure a concentration of a gas flowing in the fluid connection between the patient and the medical device; a control device, wherein the control device is configured to automatically control a parameter of the mechanical ventilation as a function of the concentration of the gas; and a signal processing unit configured to: calculate an indicator of progress over time of a concentration of carbon dioxide, as a carbon dioxide concentration time curve, in the suctioned gas sample using measured values of the gas sensor array; calculate an indicator of progress over time of a concentration of an other gas, different from carbon dioxide, as an other gas concentration time curve, in the suctioned gas sample using measured values of the gas sensor array; calculate an indicator of a progress over time of a temporal change of the carbon dioxide concentration, as a carbon dioxide concentration change curve, using the carbon dioxide concentration time curve; calculate an indicator of a progress over time of a temporal change of the concentration of the other gas, as an other gas concentration change curve, using the other gas concentration time curve; search for time periods with a same sign, wherein throughout the same sign time period the two concentration change curves have the same sign, with both concentration change curves being greater than zero or both less than zero; upon detecting at least one same sign time period, check whether the two concentration change curves meet a predefined first leak criterion in the detected at least one same sign time period; upon the predefined first leak criterion being met, determining that a leak has occurred between the patient-side fluid-guiding unit and the gas sensor array or determining that there is an indication of such a leak, wherein the control device is configured to generate an alarm if the signal processing unit determines that the leak has occurred or that there is the indication of the leak and to transmit the alarm to a receiver and to provide the alarm as output such that the alarm is configured to be perceptible to a person, and wherein the mechanical ventilation is configured to be continued without using the results of the gas measurement of the concentration of the gas flowing in the fluid connection between the patient and the medical device if the signal processing unit determines that the leak has occurred or that there is the indication of the leak.
9 . A connection device for mechanical ventilation of a patient, the connection device comprising: a patient-side fluid-guiding unit; and a measuring system comprising: a gas sensor array; a gas sensor fluid-guiding unit connected or connectable to the patient-side fluid-guiding unit, wherein, using the patient-side fluid-guiding unit, a fluid connection is established or establishable, the fluid connection configured to be between the patient and a medical device, and whereby the patient is mechanically ventilated while a process for monitoring the measuring system is performed, wherein the measuring system is configured to suction gas from the patient-side fluid-guiding unit through the gas sensor fluid-guiding unit to the gas sensor array, the gas sensor array being configured to measure a concentration of a gas flowing in the fluid connection between the patient and the medical device; a control device, wherein the control device is configured to automatically control a parameter of the mechanical ventilation as a function of the concentration of the gas; and a signal processing unit configured to: calculate an indicator of progress over time of a concentration of carbon dioxide with respect to time, as a carbon dioxide concentration time curve, in the suctioned gas sample using measured values of the gas sensor array; calculate an indicator of progress over time of a concentration of an other gas, different from carbon dioxide, as an other gas concentration time curve, in the suctioned gas sample using measured values of the gas sensor array; calculate an indicator of a progress over time of a temporal change of the carbon dioxide concentration, as a carbon dioxide concentration change curve, using the carbon dioxide concentration time curve; calculate an indicator of a progress over time of a temporal change of the concentration of the other gas, as an other gas concentration change curve, using the other gas concentration time curve; search for time periods with a same sign, wherein throughout the same sign time period the two concentration change curves have the same sign, with both concentration change curves being greater than zero or both less than zero; upon detecting at least one same sign time period, check whether the two concentration change curves meet a predefined first leak criterion in the detected at least one same sign time period; and upon the predefined first leak criterion being met, determine that a leak has occurred between the patient-side fluid-guiding unit and the gas sensor array or determine that there is an indication of such a leak; wherein the control device is further configured to generate an alarm if the signal processing unit determines that the leak has occurred or that there is the indication of the leak and to transmit the alarm to a receiver and to provide the alarm as output such that the alarm is configured to be perceptible to a person; and wherein the mechanical ventilation is continuable or continued without using the results of the gas measurement of the concentration of a gas flowing in the fluid connection between the patient and the medical device if the signal processing unit determines that the leak has occurred or that there is the indication of the leak.
10 . A medical system comprising: a medical device; and a connection device comprising: a patient-side fluid-guiding unit; and a measuring system comprising: a gas sensor array; a gas sensor fluid-guiding unit connected to or connectable to the patient-side fluid-guiding unit, wherein, using the patient-side fluid-guiding unit, a fluid connection is establishable, the fluid connection configured to be between the patient and the medical device, and whereby the patient is mechanically ventilated while a process for monitoring the measuring system is performed, wherein the measuring system is configured to suction gas from the patient-side fluid-guiding unit through the gas sensor fluid-guiding unit to the gas sensor array, wherein the measuring system is configured to measure a concentration of a gas flowing in the fluid connection between the patient and the medical device; and a signal processing unit configured to: calculate an indicator of a progress over time of a concentration of carbon dioxide, as a carbon dioxide concentration time curve, in the suctioned gas sample using measured values of the gas sensor array; calculate an indicator of a progress over time of a concentration of an other gas, different from carbon dioxide, as an other gas concentration time curve, in the suctioned gas sample using measured values of the gas sensor array; calculate an indicator of a progress over time of a temporal change of the carbon dioxide concentration, as a carbon dioxide concentration change curve, using the carbon dioxide concentration time curve; calculate an indicator of a change over time of a temporal change of the concentration of the other gas, as an other concentration change curve, using the other gas concentration time curve; search for time periods with a same sign, wherein during the same sign time period the two concentration change curves have the same sign throughout the same sign time period, with both concentration change curves being greater than zero or both less than zero; upon detecting at least one same sign time period, check whether the two concentration change curves meet a predefined first leak criterion in the detected at least one same sign time period; and upon the predefined first leak criterion being met, determine that a leak has occurred between the patient-side fluid-guiding unit and the gas sensor array or determine that there is an indication of such a leak, wherein the medical device is configured: to receive from the measuring system of the connection device measured time curves of the carbon dioxide concentration and of the concentration of the other gas; and at least one of: to process the received time curves, and to output the received time curves in a form configured to be perceptible by a person; a control device, wherein the control device is configured to automatically control a parameter of the mechanical ventilation as a function of the concentration of the gas; wherein the control device is further configured to generate an alarm if the signal processing unit determines that the leak has occurred or that there is the indication of the leak and to transmit the alarm to a receiver and to provide the alarm as output such that the alarm is configured to be perceptible to a person; and wherein the mechanical ventilation is continued without using the results of the gas measurement of the concentration of the gas flowing in the fluid connection between the patient and the medical device if the signal processing unit determines that the leak has occurred or that there is the indication of the leak.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority under 35 U.S.C. § 119 of German Application 10 2020 002 570.6, filed Apr. 29, 2020, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present invention pertains to a process and to a device for automatically detecting a leak during a mechanical ventilation of a patient, wherein this leak may have an effect on the measurement of gas concentrations, which occur in a fluid connection between a medical device and the patient. TECHNICAL BACKGROUND A fluid connection is established between a ventilator and the patient to mechanically ventilate and optionally to sedate a patient. During mechanical ventilation, the ventilator feeds a breathing gas to the patient via the fluid connection, and the exhaled breathing gas is led away from the patient. The ventilator may be configured as an anesthesia apparatus, which adds an anesthetic to the breathing gas being fed to the patient. The exhaled air, which may contain anesthetic in one embodiment, is optionally fed again to the ventilator, so that a ventilation circuit is generated. In order to be able to carry out the mechanical ventilation automatically to the extent desired, it is necessary to measure the concentrations of a plurality of gases in the ventilation circuit, especially the concentrations of O2 and CO2, as well as optionally of N2O (nitrous oxide) and/or of at least one anesthetic. As a rule, these gas concentrations are variable over time. The concentration of O2 is especially greater during an inhalation process (inspiration) than during an expiration (exhalation) process (expiration), while the concentration of CO2 is, as a rule, greater during the expiration process than during the inhalation process. An exception may occur when the concentration of a component of the gas mixture, which is being fed to the patient, is rapidly reduced during a mechanical ventilation of the patient. This component is, for example, oxygen or a breathing gas. One possibility of measuring the gas concentrations which is frequent and is also applied according to the present invention is as follows: A gas sample is suctioned from the ventilation circuit at a branching-off point close to the patient, is fed to a gas sensor array and is subsequently again fed into the ventilation circuit. This branching-off point is embodied, for example, in a Y-piece close to the patient. The gas sensor array measures the sought gas concentrations in the branched-off gas sample. Such a procedure is described, for example, in DE 10 2017 011 625 A1 (corresponding to US2020353197 A1). A leak may occur between the branching-off point and the gas sensor array, for example, because components, which are being used for the mechanical ventilation or the gas measurement, are not connected to one another in a fluid-tight manner because of an error. Ambient air can be suctioned in due to such a leak. The suctioned-in ambient air may distort the measurement results of the gas sensor array. Hence, detection must be immediate, so that the leak is eliminated or the ventilation is continued without the results of the gas measurement. In particular, a leak has to be immediately detected when at least one parameter of the mechanical ventilation is automatically controlled as a function of the measured concentration of at least one gas or when a user adjusts or changes this parameter as a function of the measured gas concentration. A plurality of processes and devices have become known for automatically detecting a leak in a fluid connection to a gas sensor array during the mechanical ventilation of a patient. It is proposed in DE 10 2017 011 625 A1 to measure the time curve (concentration with respect to time) of CO2 and the time curve (concentration with respect to time) of another gas, especially of O2, and to compare the two time curves with one another. In case no leak has occurred, then the two curves are phase-shifted in relation to one another. A statistical indicator of the phase shift between the two curves, especially the covariance, is calculated and compared to a predefined threshold. In case no leak has occurred, then this covariance is ideally −1 and is between −0.6 and −0.8 for all practical purposes. It is proposed in U.S. Pat. No. 8,033,280 B2 and EP 1961439 A1 to measure the respective time curve of two gases. In case these two time curves move simultaneously in the direction of likewise measured or known gas concentrations in the ambient air, then a leak is detected. It is proposed in WO 2004/076944 A2 to measure the time curve of a pressure in a patient monitor and the time curve of a pressure in a ventilation circuit and to compare these two time curves with one another. SUMMARY A basic object of the present invention is to provide a process for monitoring a measuring system, wherein the measuring system is used for the mechanical ventilation of a patient and a gas sam