Computer-implemented method of monitoring percutaneous sensor for measuring partial pressure of one or more blood gases of patient

Abstract

According to a first aspect of the present invention, a computer-implemented method of monitoring a transdermal sensor configured to measure partial pressure of one or more blood gases of a patient is presented. The method comprises the step of determining a response time parameter of the transcutaneous sensor (step S1). The method further comprises a step of determining whether the partial pressure measurement capability of the sensor is sufficient based on the determined response time parameter (step S2). The method not only can detect an increase in the response time of the sensor due to a dry membrane, which may occur after use of the membrane with the sensor for several days. The method may also detect degradation of the sensor, which may occur only several years after use of the sensor.

Description

Technical Field

[0001] The present invention relates to a computer-implemented method for monitoring a transcutaneous sensor configured to measure the partial pressure of one or more blood gases of a patient, to a computer program, to a non-transitory program storage medium storing such a program, to a transcutaneous blood gas monitor for transcutaneously monitoring one or more blood gases of a patient, and to the use of the determined results of the response time parameters of the transcutaneous sensor. Background Art

[0002] Transcutaneous monitoring is a method used in patients who require continuous and non-invasive monitoring of oxygenation and ventilation. Through a sensor applied to the body, the blood gases diffusing through the skin can be detected and measured. Specifically, transcutaneous monitoring is a useful and widely used trending tool for non-invasively monitoring the oxygenation (tcpO2) and ventilation (tcpCO2) status of a patient. It provides crucial real-time information, allowing immediate action to be taken when needed to improve patient safety and comfort. An exemplary transcutaneous monitor from Radiometer Medical is the TCM5 FLEX transcutaneous monitor, which is a compact and easy-to-use solution that gives accurate and continuous measurements of the oxygenation (tcpO2) and ventilation (tcpCO2) status in neonatal, pediatric, and adult patients in the intensive care unit (ICU).

[0003] Such transcutaneous monitors typically include a transcutaneous electrochemical sensor configured to measure the partial pressure of the blood gases of a patient. Such sensors often require re-membraning, i.e., replacing the membrane used within the sensor. Currently, the re-membraning interval of the sensor is usually fixed at a certain time period, such as 28 days, because the risk of the sensor membrane drying out becomes significantly increased or too high after this 28-day time period. When the sensor membrane dries out, the measurement will become incorrect.

[0004] During research and development, the inventors of the present invention have identified the need to extend the re-membraning interval beyond the current fixed time period. They have also identified the need to detect sensors that have dried out before the fixed time period has passed due to some reasons, and the need to detect sensors whose performance degrades over time and whose response time becomes too high due to use.

[0005] Therefore, there is a desire to provide improved monitoring of a transcutaneous sensor configured to measure the partial pressure of one or more blood gases of a patient. As will be explained in more detail hereinafter, this is achieved by the present invention.

[0006] Aspects, embodiments, examples, and exemplary steps of the present invention are disclosed below. Different embodiments, examples, and exemplary features of the present invention can be combined according to the present invention as long as it is technically appropriate and feasible. SUMMARY OF THE INVENTION

[0007] As described above, it is desirable to provide improved monitoring of a transcutaneous sensor configured to measure the partial pressure of one or more blood gases of a patient.

[0008] This is achieved by the subject matter of the independent claims, with further embodiments incorporated in the dependent claims as well as the following description and drawings.

[0009] Technical terms are used in their general meaning. If a specific meaning is conveyed to certain terms, the definition of the term will be given in the context in which the term is used hereinafter.

[0010] According to a first aspect of the present invention, there is provided a computer-implemented method for monitoring a transcutaneous sensor configured to measure the partial pressure of one or more blood gases of a patient. The method includes the step of determining a response time parameter of the transcutaneous sensor (step S1). The method further includes the step of determining whether the partial pressure measurement ability of the sensor is sufficient based on the determined response time parameter (step S2).

[0011] As will be apparent from the present disclosure, the proposed method uses the result of response time determination during the monitoring of the sensor. The method requires the determination of the response time parameter in step S1, and then its result is used to determine whether the ability of the sensor to measure the partial pressure of blood gases is sufficient, i.e., appropriate and / or acceptable. Different possibilities for determining whether the ability of the sensor is sufficient are disclosed, for example, comparing the measurement response time of an individual sensor with a response time threshold. Thus, step S2 of the proposed method can be regarded as an evaluation of the partial pressure measurement ability of the sensor. Specifically, an evaluation of the response time parameter is performed to decide whether the ability of the sensor for measuring the partial pressure of a gas is sufficient, appropriate, and / or acceptable / accepted. As those skilled in the art will understand, in the context of the present invention, the term "sufficient" should be used synonymously with the terms "appropriate" and "acceptable". Different possibilities for determining whether the ability of the sensor is sufficient are disclosed hereinafter, for example, comparing the measured response time with a response time threshold. Thus, generally, the method determines in step S2 whether the determined response time parameter meets or conforms to a sufficiency criterion, i.e., an acceptance criterion. The sufficiency criterion (i.e., the acceptance criterion) can preferably be predefined. Thus, as those skilled in the art will understand, in step S2, based on the determined response time parameter, it is determined whether the partial pressure measurement ability of the sensor is considered acceptable / accepted by the computer-implemented method. Therefore, step S2 should be understood as determining whether the partial pressure measurement ability of the sensor is sufficient based on the determined response time parameter, thereby determining whether the determined response time parameter meets or conforms to a sufficiency criterion, i.e., an acceptance criterion.

[0012] As will be described in detail in the specific embodiments below, determining whether the capabilities of the sensor are sufficient includes or can be implemented as determining whether to initiate re-membranation of the sensor, or replacement of the sensor, or maintenance of the sensor. In other words, in the said embodiments, the method determines in step S2 whether re-membranation, replacement or maintenance of the sensor is required based on the response time parameter determined in step S1. This will be explained in more detail in the context of the specific embodiments below.

[0013] As will be explained in detail below, the proposed method can not only detect an increase in the response time of the sensor due to a dry membrane, which may occur after using the membrane with the sensor for several days. The method can also detect deterioration of the sensor, which may occur only after using the sensor for several years. Depending on the use and setting of the sensor, this may be less than several years. For example, the surface of the glass of the sensor may no longer be appropriate after several years. Thus, in addition to the measure of re-membranating the sensor, the sensor can be repaired or refurbished by using, for example, hydrofluoric acid on the glass to restore the glass surface. Thus, in addition to detecting the need for re-membranation, the proposed method can also detect the need for replacement or maintenance of the sensor. As mentioned before, this also covers repairing, refurbishing, servicing or reactivating the glass surface of the transcutaneous sensor. Generally, the method can detect any kind of sensor condition that interferes with or changes the ability of the sensor to measure the partial pressure of blood gases, and the change in this ability is detectable based on evaluating the response time parameter determined in step S1 in step S2.

[0014] Note that different response time parameters can be used for the determination performed in step S1. For example, the response time parameter determined in step S1 can be the value of the response time, specifically the absolute value. Note that in the context of the present invention, and if not stated otherwise, the response time should be understood as the so-called 10% to 90% response time, i.e., the time required for the sensor to detect a change from a first gas partial pressure to a second gas partial pressure, where 10% and 90% refer to the time difference between 10% and 90% of the difference between the detected first gas partial pressure and the second gas partial pressure. This can also be related to the time constant τ described herein, see for example Figure 4Description. The response time is not necessarily the 10% to 90% response time, but in other embodiments it can be, for example, the 20% to 80% response time, the 5% to 95% response time, or any other percentage selected on the response curve. A person skilled in the art knows the parameter of the (10% to 90% or other) response time. In addition, a person skilled in the art knows that the (10% to 90% or other) response time can be converted into a time constant τ by calculation, and this time constant τ is known to a person skilled in the art as the time constant of the exponential or double-exponential response of the transcutaneous sensor to a suddenly changed gas pressure. Therefore, in line with the understanding of a person skilled in the art, the response time as used herein preferably refers to the x% to y% response time, such as the 10% to 90% response time or the time constant τ. This will be explained in more detail below.

[0015] In addition, the response time parameter determined in step S1 can also be implemented as a trend parameter, which indicates the time development of the response time of the transcutaneous sensor. A non-limiting example of such a trend parameter is the time derivative of the measurement curve of the partial pressure value of the blood gas measured by the monitored sensor over time. This can be derived from Figure 2 and Figure 3 in the context of and will be further clarified in Figure 2 and Figure 3 in the context of. In addition, other examples of the response time parameter determined in step S1 can be used.

[0016] In addition, the method step S1 of "determining the response time parameter" can be implemented as calculating the response time parameter and / or measuring the response time parameter. This will be clarified below in the context of specific embodiments. Note that the step S1 of determining the response time parameter covers any calculation using a two-point model, and it also covers the use of, for example, regression analysis, as will be explained in more detail below. In another embodiment, this determination of step S1 is implemented as predicting the response time parameter by using a predictive maintenance module (for example, using an artificial intelligence module and / or machine learning).

[0017] The proposed method can be executed, for example, by a transcutaneous blood gas monitor and can be repeated regularly, such as every 24 hours, every 12 hours, every 8 hours, etc. Therefore, the method of monitoring the transcutaneous sensor can be regarded as a method for continuously checking the quality of the transcutaneous sensor. In addition, the proposed method of monitoring the transcutaneous sensor can be regarded as a method for calibrating the transcutaneous sensor, or can be part of a calibration method for calibrating the transcutaneous sensor.

[0018] In addition, in the context of the present invention, the term "transcutaneous sensor" should be understood to mean any kind of sensor configured to non-invasively measure the partial pressure of one or more blood gases of a human in / on the skin of a patient.

[0019] It should be noted that the proposed method can be used for several different types of transcutaneous sensors. Specifically, the proposed method can be used in conjunction with electrochemical transcutaneous sensors for measuring the partial pressure of one or more blood gases of a patient, particularly for electrochemical transcutaneous STOW-SEVERINGHAUS type CO2 sensors, amperometric O2 sensors, and other sensors. Additionally, the proposed method can also be applied to transcutaneous sensors using optical sensor technology. The operating principle of the optical sensor can be different from that of the electrochemical sensor described herein. However, the response time can still be useful for determining some conditions of the sensor.

[0020] As will be understood by those skilled in the art, the response time should generally be measured at the same temperature to make it comparable. Alternatively, the response times at different temperatures can be converted to a standard temperature through known conversion functions and thus made comparable. In other words, a prerequisite for making a meaningful comparison is to measure the response time at the same temperature (e.g., set by the user to 42 °C), or to convert the response times at different temperatures to make them comparable. This temperature is typically set for the entire measurement period. The monitor can be set to maintain this temperature between uses, or to enter standby when not in use if the temperature drops.

[0021] As will be understood by those skilled in the art, by implementing the response time parameter determination in the monitoring algorithm as suggested herein, notifications regarding re-membraning, sensor replacement, or sensor maintenance can be based on the actual sensor condition. This generally allows the re-membraning interval to be appreciably longer than, for example, the fixed number of days used in the prior art, such as 28 days.

[0022] This novel method of monitoring transcutaneous sensors offers specific advantages. First, the re-membraning interval can be extended beyond the fixed time periods of the prior art. Currently, re-membraning is one of the biggest drawbacks for customers using transcutaneous monitoring. Additionally, using the proposed method, sensors that have dried out before the fixed time period has passed due to some reason can be detected. Furthermore, sensors whose performance has degraded over time and whose response time has become too high due to use can be detected.

[0023] As previously mentioned, the current 28-day re-membraning interval is a number determined by a safety margin. As suggested herein, equivalent or better safety can be provided by regularly or continuously monitoring the response time of the sensor. This is particularly important for CO2 sensors, as shown and explained in the context of Figure 2 For CO2 sensors, the response time is closely related to the onset of incorrect measured values in the steady state. Figure 3The data therein shows a sudden change in the behavior of the sensor, such that some of the blood gas measurements of the sensor become less accurate. This occurs, for example, when the sensor membrane dries out and is related to a change in the response time. This correlation is explained by the fact that the slow evaporation of the electrolyte applied to the inner membrane of the transcutaneous sensor results in a more concentrated electrolyte. The phenomenon of having an increasing response time with respect to the electrolyte concentration is used in a specific embodiment of the present invention. Thus, using this correlation and / or phenomenon to detect a drying transcutaneous sensor provides improved monitoring of the sensor.

[0024] Note that the methods proposed herein are applicable to sensors calibrated on both a single gas concentration and two different gas concentrations.

[0025] According to another exemplary embodiment of the present invention, the response time parameter indicates the response time of the sensor when measuring the partial pressure of one or more blood gases of a patient.

[0026] According to another exemplary embodiment of the present invention, step S2 of determining whether the partial pressure measurement ability of the sensor is sufficient includes determining whether to initiate re-membraning of the transcutaneous sensor. The determination of re-membraning is based on the previously determined response time parameter.

[0027] A specific transcutaneous sensor for blood gas measurement includes a membrane. Specifically, a transcutaneous CO2 sensor is an electrochemical sensor, where the membrane is provided in an electrolyte that may evaporate. This evaporation may change the properties of the membrane, and if no additional electrolyte is added, the drying process of the membrane may start. However, this process may lead to a change in the ability of the sensor to measure the partial pressure of the patient's blood gases. Thus, using the proposed embodiments, the re-membraning interval can be extended beyond the currently used fixed time period in the prior art, and also sensors that have dried out before the currently used fixed time period due to some reason can be detected. Preferably, in step S2, based on the determined response time parameter, it is determined whether the partial pressure measurement ability of the sensor is sufficient, thereby determining whether the determined response time parameter meets or conforms to a sufficiency criterion, i.e., an acceptance criterion.

[0028] According to another exemplary embodiment of the present invention, step S2 of determining whether the partial pressure measurement ability of the sensor is sufficient includes determining whether to initiate replacement or maintenance of the transcutaneous sensor due to deterioration. Further, the determination of replacement or maintenance is based on the determined response time parameter.

[0029] In a particular embodiment, a transcutaneous sensor can be repaired or refurbished by using, for example, hydrofluoric acid on the glass to restore the glass surface of the sensor. Other repair or refurbishment measures can also be used. Thus, after determining that the sensor needs to be replaced or maintained, a signal or warning indicating that the sensor needs to be replaced, repaired, refurbished, or serviced or that the glass surface of the sensor needs to be reactivated can be generated for the user or monitor performing the proposed method. Further details regarding such a signal will be explained in the context of further embodiments below. Preferably, in step S2, based on the determined response time parameter, it is determined whether the partial pressure measurement ability of the sensor is sufficient, thereby determining whether the determined response time parameter meets or conforms to a sufficiency criterion, i.e., an acceptance criterion.

[0030] According to another exemplary embodiment of the present invention, the response time parameter determined in step S1 is the value of the response time, and the method includes a step of comparing the determined value of the response time with a response time threshold.

[0031] As previously mentioned, the value of the response time can be the value of the 10% to 90% response time of the transcutaneous sensor or the time constant τ of the exponential or double-exponential response underlying the transcutaneous sensor, see, for example Figure 4 and its explanation. As will be understood by those skilled in the art, in the context of the present invention, the specific absolute value of the response time is measured, determined, and / or used as opposed to a relative value. In other words, this embodiment details measuring and / or calculating the value of the response time and comparing it with the response time threshold. Then, the result of this comparison defines whether the monitoring method concludes that the sensor needs to be remembraned, replaced, and / or maintained or not.

[0032] Note that the response time threshold can be implemented in different ways as used herein. For example, the response time threshold can depend on the initial response time of the sensor. This means that the response time measured immediately after remembraning the sensor is used to set or define the response time threshold, for example, twice or three times the initial response time, or multiplied by any other factor set by the user or the system. Thus, the individual response time of a specific sensor can be measured and / or calculated, and the threshold can be set accordingly. In other words, the threshold can be set individually for each sensor, for example, set to a value that is twice the response time measured after remembraning. In another example, the response time threshold can be calculated or determined by adding a predetermined amount of time to the response time measured after remembraning. Additionally, in a particular embodiment, a predetermined threshold can be used. For example, the response time threshold can be set to a specific predetermined time period, such as 30 s, 40 s, 50 s, or 60 s. As will be understood by those skilled in the art, there are many different ways to use a predefined or individually set threshold in the context of the present invention.

[0033] According to another exemplary embodiment, the method includes the step of generating a control signal configured to cause remembranization of the sensor or configured to cause replacement or maintenance of the sensor if a determined value of the response time exceeds a response time threshold.

[0034] Such a control signal allows the device implementing the monitoring method to deactivate the sensor function and / or warn the user of the need for remembranization, replacement, and / or maintenance. Thus, when it is determined or decided that remembranization is necessary, i.e., when the determined response time of the sensor exceeds (i.e., is longer than) the response time threshold, a control signal will be generated. In an example, the response time of the sensor is 54 s and the response time threshold is 50 s. In this case, remembranization is required and a corresponding signal or warning is generated.

[0035] According to another exemplary embodiment of the present invention, the response time parameter determined in step S1 is a trend parameter indicating the time development of the response time of the transcutaneous sensor. The method further includes the step of comparing the determined trend parameter with a trend threshold regarding the time development of the response time of the transcutaneous sensor (step S3b).

[0036] As will be explained in detail in the context of specific embodiments, the first and / or second time derivatives of a measurement curve such as any of those shown in Figures 2 to 4 can be used as the trend parameter. Further, in a preferred embodiment, the trend threshold used in step S3b is a set threshold of the first or second time derivative of the measurement curve shown in Figures 2 to 4 .

[0037] Figure 2 Shows the values of the partial pressure of CO2 measured by the monitored sensor when exposed to a significant change in gas pressure. For example, if the steepness (i.e., the first time derivative) of the partial pressure of blood gas measured by the sensor over time is too low in the first part of the curve of increasing pressure (see Figure 2 ), this can be used as a criterion for causing the control signal. The first part of the curve can be in a time period between 50 s and 300 s. As can be derived from, for example, Figure 2 , from the 10th day to the 50th day of using the sensor, the steepness of the partial pressure of blood gas curve over time decreases in the first part of the curve.

[0038] In another exemplary embodiment of the present invention, the control signal is configured to prevent the operator from further using the sensor by, for example, deactivating the sensor, and / or the control signal is configured to warn the operator of the need for remembranization, replacement, or maintenance of the sensor.

[0039] Accordingly, a device that performs the methods described herein, such as a transcutaneous blood gas monitor, can generate a control signal for sensor deactivation such that the user can no longer use the transcutaneous sensor for blood gas measurements. Additionally, a visual or audio signal (e.g., via a user interface of the transcutaneous blood gas monitor) can be used to alert the operator or user that the sensor needs to be re-membraned, or that the sensor needs to be replaced or maintained.

[0040] According to an exemplary embodiment of the present invention, the method includes the step (S4b) of generating a control signal configured to cause re-membraning of the sensor or configured for replacement or maintenance of the sensor if the determined trend parameter deviates from the trend parameter by at least a predetermined minimum amount.

[0041] Such a control signal can cause automatic re-membraning of the sensor, or automatic replacement of the sensor, or automatic maintenance of the sensor, such that the user is not troubled by these tasks.

[0042] According to another exemplary embodiment of the present invention, the method further includes the step of measuring the blood gas partial pressure value over time by the sensor. Additionally, the determined trend parameter is implemented as one or more time derivatives of the measurement curve of the measured blood gas partial pressure values over time.

[0043] In a preferred embodiment, a first-order time derivative and / or a second-order time derivative can be determined in the computer-implemented method. In Figure 2 a non-limiting example of the measurement curve of the measured blood gas partial pressure values over time is shown. As can be derived from Figure 2 and as will be explained in detail below, depending on the age of the sensor and / or depending on the age of the membrane on the sensor (i.e., the time the membrane has been used with the sensor), when the sensor is exposed to a pressure change, the steepness of the measurement curve becomes lower and lower over time, see Figure 2 the exemplary measurements from day 10 to day 50 shown therein. Accordingly, the proposed method can use the first-order time derivative of the measurement curve to detect the need for re-membraning, replacement, or maintenance of the sensor. For example, if the first-order time derivative is not steep enough / too low in a specific time period of the measurement curve (e.g., between 50 and 300 s), the method can detect the need for re-membraning. In other words, in this embodiment, the trend parameter is the time derivative of the measured blood gas partial pressure over time. For example Figure 2 a decrease in the slope of the curve shown in

[0044] According to another exemplary embodiment of the present invention, the response time parameter determined in step S1 is the value of the response time within a time period (preferably within at least multiple days). Additionally, the determined value of the response time describes the response time measurement curve of the value of the response time of the sensor within the time period. Furthermore, the determined trend parameter is the time derivative of the response time measurement curve.

[0045] In other words, in this embodiment, the trend parameter is the time derivative of the measurement curve as Figure 3 shown. The inventors of the present invention have recognized that a strong increase in the slope of the shown curve (i.e., the first derivative) indicates a phase change of the membrane. In Figure 3 the non-limiting example shown, Figure 3 a strong increase in the first-order time derivative / slope of the shown curve occurs at approximately 36 days. Thus, if the absolute value of the slope / first-order time derivative increases above a specific threshold, then the proposed method can determine that the partial pressure measurement ability of the sensor is no longer sufficient. Therefore, the specific threshold of the first-order time derivative is used as the trend threshold in this embodiment. Additionally, in another example, the value of the second-order time derivative can also be used as the trend threshold, and the determination of the sensor ability is based on the comparison of the value of the second-order time derivative with the trend threshold. As will be clear to those skilled in the art, in this embodiment, the method compares the determined trend parameter (i.e., the first-order or second-order time derivative) with a trend threshold (i.e., a set threshold of the first-order or second-order time derivative) regarding the time development of the response time of the transcutaneous sensor, as described herein as step S3b.

[0046] Therefore, by using the proposed method, the remembranation interval can be extended beyond the fixed time period used in the prior art. This improves one of the biggest drawbacks for customers using transcutaneous monitoring.

[0047] According to another exemplary embodiment of the present invention, the method includes the step of determining whether the sensor is inside a calibration chamber (preferably, the calibration chamber of a transcutaneous blood gas monitor) at the start of the monitoring method.

[0048] For a specific application, it may be beneficial to know whether the sensor to be monitored is currently inside the calibration chamber. In a preferred embodiment, the angle of the calibration chamber door can be used to indicate whether the sensor is inside. Since the door in this embodiment opens a bit more to accommodate the sensor, the angle of the calibration chamber door can be used for this indication.

[0049] According to another exemplary embodiment of the present invention, the method includes the step of ensuring that the sensor is exposed to a minimum amount of gas pressure change during the monitoring method.

[0050] In a specific embodiment, this can be ensured by using a calibration chamber into which the calibration gas is flushed by the device performing the monitoring method. For example, the transcutaneous blood gas monitor described herein can cause the calibration gas to be delivered from a calibration gas reservoir into the calibration chamber, see for example Figure 5 . In a specific non-limiting embodiment, an outlet tube may be present between the calibration chamber and the ambient air. Thus, when the flow from the calibration gas reservoir is shut off, the air inside the calibration chamber will slowly exchange with the atmospheric air by simple diffusion. The inventors of the present invention have determined this exchange rate. Preferably, the monitoring method proposed herein may generally be required only after more than 30 minutes after a previous successful monitoring, so the change in gas pressure should generally be sufficient to determine the response time. However, there may be some special cases / events where the previously described scenario does not hold (e.g., if the sensor temperature changes less than 30 minutes after monitoring / calibration).

[0051] Furthermore, the step of ensuring that the sensor is exposed to a minimum amount of gas pressure change during the monitoring method can also be implemented by looking at the monitoring curve at the end of the monitoring. Take the difference between the initial gas pressure value (which should be the minimum) and the final gas pressure value (which should be the maximum), and check whether this is at least a specific desired amount of gas pressure change.

[0052] As described above, the monitoring method proposed herein can be performed by a transcutaneous monitor that includes a transcutaneous sensor, a calibration chamber, and a calibration gas reservoir. In this embodiment, the method includes the step of flushing the calibration gas from the calibration gas reservoir into the calibration chamber, and the transcutaneous sensor is placed in the calibration chamber for monitoring of the sensor.

[0053] According to another exemplary embodiment of the present invention, the step S1 of determining the response time parameter includes providing data of the sensor and / or data about the sensor as input data to a predictive maintenance module. Such data can be considered monitoring data. Such a predictive maintenance module can be implemented as an artificial intelligence module and / or a module trained by machine learning. The method of this embodiment may further include predicting the response time of the transcutaneous sensor by the predictive maintenance module. Furthermore, in step S2, the predicted response time of the transcutaneous sensor is used to determine whether the partial pressure measurement ability of the sensor is sufficient, in particular whether remembranation of the transcutaneous sensor or replacement or maintenance of the sensor is necessary or required.

[0054] Therefore, such a predictive maintenance module can predict, for example, the values of the measurement curves shown in Figure 2 and Figure 3 . In other words, instead of measuring the blood gas partial pressure as performed in Figure 2 , and / or instead of Figure 3The response time within the measured / determined membrane age performed in [description] can be predicted by the predictive maintenance module for such a measurement curve. Then, these predicted response time values of the transcutaneous sensor can be used to make a decision in step S2 as to whether the partial pressure measurement ability of the sensor is still sufficient or will be sufficient at a future time point. Preferably, in step S2, it is determined whether the partial pressure measurement ability of the sensor is sufficient based on the determined response time parameter, that is, whether the determined response time parameter meets or conforms to a sufficiency criterion, namely an acceptance criterion.

[0055] Generally, an artificial intelligence module is an entity that processes one or more inputs into one or more outputs by means of an internal processing chain that typically has a set of free parameters. The internal processing chain can be organized in interconnected layers that are traversed sequentially as one progresses from the input to the output. Many artificial intelligence modules are organized to process inputs with high dimensions into outputs with much lower dimensions. A common task of an artificial intelligence module is to classify data into one or more categories. Such a module is called "intelligent" because it can be "trained". The module can be trained using a record of training data. The record of training data includes training input data and corresponding training output data. The training output data of the record of training data is the result that is expected to be produced by the module when the training input data of the same record of training data is given as input. The deviation between the expected result and the actual result produced by the module is observed and rated with the aid of a "loss function". The loss function is used as feedback for adjusting the parameters of the internal processing chain of the module. For example, the parameters can be adjusted with the optimization goal of minimizing the value of the loss function, which value is produced when all the training input data is fed into the module and the results are compared with the corresponding training output data. The result of this training is that, given a relatively small number of records of training data as "ground truth", the module can perform its work well for a much larger number of records of input data. In the context of the present embodiment, neural networks, convolutional neural networks, and generative adversarial networks can be used.

[0056] According to another exemplary embodiment of the present invention, the method is applied to a transcutaneous electrochemical sensor for measuring the partial pressure of one or more blood gases of a patient.

[0057] Although the optical sensors have been described above as being also monitorable with the present invention, the specific embodiment relates to an electrochemical sensor. Specifically, electrochemical sensors are often used to measure the partial pressure of CO2 in a patient. As described in detail above, for an electrochemical sensor, the effects of membrane drying can be avoided or reduced. The remembranation interval can be extended beyond the fixed time periods used in the prior art. In addition, with the proposed method, an electrochemical sensor that has dried out before the expiration of the fixed time periods used in the prior art can be detected due to some reasons.

[0058] According to another aspect of the present invention, a program which, when run on a computer or when loaded onto a computer, causes the computer to perform the method steps of the method as disclosed herein.

[0059] The program can be part of a computer program, but can also be the entire program by itself. For example, the program can be used to update an already existing computer program to achieve the present invention.

[0060] According to another aspect of the present invention, a non-transitory program storage medium storing such a program is provided.

[0061] A computer-readable medium can be regarded as a storage medium, such as for example a data storage device, a USB stick, a CD, a DVD, a hard disk or any other medium on which the program as described above can be stored.

[0062] According to another exemplary embodiment of the present invention, a transcutaneous blood gas monitor for transcutaneously monitoring one or more blood gases of a patient is provided. The monitor includes a transcutaneous (preferably electrochemical) sensor configured to measure the partial pressure of one or more blood gases of the patient. The monitor further includes a control circuit configured to determine a response time parameter of the transcutaneous sensor during monitoring of the transcutaneous sensor. In addition, the control circuit is configured to determine whether the partial pressure measurement ability of the sensor is sufficient based on the determined response time parameter.

[0063] Figure 5 A specific non-limiting example of such a blood gas monitor is depicted and will be explained in more detail below. Preferably, the control circuit is configured to determine whether the partial pressure measurement ability of the sensor is sufficient based on the determined response time parameter, and thus is configured to determine whether the determined response time parameter meets or conforms to a sufficiency criterion, i.e., an acceptance criterion.

[0064] According to another exemplary embodiment of the present invention, the transcutaneous blood gas monitor includes a calibration chamber and a calibration gas reservoir. The transcutaneous blood gas monitor is configured to flush calibration gas from the calibration gas reservoir into the calibration chamber for calibrating the transcutaneous sensor.

[0065] In a specific embodiment, the transcutaneous blood gas monitor is configured to ensure that the sensor is exposed to a minimum amount of gas pressure change during the monitoring method.

[0066] According to another aspect of the present invention, it is proposed to use the result of determining the response time parameter of the transcutaneous sensor for monitoring the use of the sensor, where the transcutaneous sensor is configured to measure the partial pressure of one or more blood gases of a patient. Specifically, this can be used to determine the need for re-membraning the transcutaneous sensor or the need for replacing the sensor due to deterioration. Preferably, the result is used in a transcutaneous blood gas monitor, a computer-implemented method, or by a transcutaneous blood gas monitor, a computer-implemented method, a program, and / or used by a computer. Note that the result of determining the response time parameter of the transcutaneous sensor is preferably data that can be used as input for such a transcutaneous blood gas monitor, a computer-implemented method, a program, and / or by a computer. Therefore, the disclosed use should not be construed as a mental act, but as a technical use of the data generated by the determination.

[0067] According to an exemplary embodiment of the present invention, the transcutaneous blood gas monitor is configured to periodically perform the method as proposed herein, for example, every 24 hours, every 12 hours, every 8 hours, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Hereinafter, the present invention will be described with reference to the drawings that give a background description and illustrate specific embodiments of the present invention. However, the scope of the present invention is not limited to the specific features disclosed in the context of the drawings.

[0069] Figure 1 A flowchart of a computer-implemented method for monitoring a transcutaneous sensor according to an embodiment of the present invention is schematically shown.

[0070] Figure 2 Four measurement curves of the partial pressure of CO2 over time that can be used in one or more embodiments of the present invention are shown.

[0071] Figure 3 A measurement curve of the response time of a transcutaneous sensor over membrane age that can be used in one or more embodiments of the present invention is schematically shown.

[0072] Figure 4 A theoretical response curve of a transcutaneous sensor for measuring the partial pressure of one or more blood gases of a patient when exposed to a pressure change that can be used in one or more embodiments of the present invention is schematically shown.

[0073] Figure 5 A transcutaneous blood gas monitor for transcutaneously monitoring one or more blood gases of a patient according to an embodiment of the present invention is schematically shown.

[0074] Figure 6 A flowchart schematically showing a computer-implemented method for monitoring a transcutaneous sensor according to an embodiment of the present invention is presented. Detailed implementation

[0075] Figure 1 A flowchart schematically showing a computer-implemented method for monitoring a transcutaneous sensor configured to measure the partial pressure of one or more blood gases in a patient is presented. Preferred blood gases are oxygen and carbon dioxide. However, other blood gases can also be measured. As already explained above, Figure 1 the proposed method shown in [reference] can be applied to transcutaneous electrochemical sensors, but the method is also applicable to transcutaneous sensors that use optical techniques to measure the partial pressure of blood gases in a patient. Figure 1 The proposed method includes step S1, in which a response time parameter of the transcutaneous sensor is determined. The response time parameter can be one or more absolute values of the response time of the sensor, but can also be a trend parameter, such as Figure 2 and Figure 3 the first derivative or second derivative of the measurement curve shown in [reference], for example. Furthermore, in a second step S2, the method determines, based on the previously determined response time parameter, whether the partial pressure measurement ability of the sensor is sufficient, appropriate, or acceptable. As will be understood by those skilled in the art, in the context of the present invention, the term "sufficient" should be used synonymously with the terms "appropriate" and "acceptable". Different possibilities for determining whether the ability of the sensor is sufficient are disclosed, such as comparing the measured response time with a response time threshold. Thus, generally, the method determines in step S2 whether the determined response time parameter meets or conforms to a sufficiency criterion, i.e., an acceptance criterion. The sufficiency criterion (i.e., the acceptance criterion) can preferably be predefined. Thus, as will be understood by those skilled in the art, in step S2, based on the determined response time parameter, it is determined whether the partial pressure measurement ability of the sensor is considered acceptable / accepted by the computer-implemented method. Thus, step S2 should be understood as determining whether the partial pressure measurement ability of the sensor is sufficient based on the determined response time parameter, and thus determining whether the determined response time parameter meets or conforms to the sufficiency criterion, i.e., the acceptance criterion. Figure 1 The method shown in [reference] can be executed by, for example, a control circuit, a processor, or a computer. Such a control circuit, processor, or computer can be included in the transcutaneous blood gas monitor 500 shown in the non-limiting example of Figure 5 [reference].

[0076] Figure 2 A measurement curve of a transcutaneous sensor for measuring the partial pressure of carbon dioxide (CO2) over time is shown. From Figure 2It can be concluded that four different measurements were performed on the 10th, 36th, 40th, and 50th days. The number of days indicates the age of the membrane used on the sensor. At each measurement, the sensor was exposed to an external gas pressure. As can be seen from Figure 2 what can be concluded, the slope of the corresponding curve is significantly different between the measurements of the sensor used on the 10th day and the sensor used on the 50th day. Thus, in the exemplary embodiment, the steepness of the measurement curve (i.e., the first-order time derivative of the mathematical function describing the depicted curve) can be used as a criterion for determining whether the partial pressure measurement ability of the sensor is sufficient in Figure 1 step S2. Figure 2 A decrease in the slope of the curve shown in Figure 2 indicates a bad or old sensor. Then, this is used by the proposed method for decision-making, for example, for re-membraning. In other words, according to a specific embodiment of the present invention, the first-order and / or second-order time derivatives of the measurement curve shown in Figure 2 can be used as the trend parameters described herein. Furthermore, in a preferred embodiment, the trend threshold used in step S3b is

[0077] Figure 3 the set threshold of the first-order and / or second-order time derivatives of the measurement curve shown in Figure 4 . Figure 3 As can be seen from Figure 3 , a strong increase in the slope (i.e., the first derivative of the shown curve) indicates a phase change in the properties of the membrane. In the Figure 3 example, the strong increase occurs at a membrane age of approximately 36 days. Thus, the method provided herein can detect the need for re-membraning that occurs only after 36 days, rather than after 28 days (28 days is currently used as a fixed interval for re-membraning in the prior art). For this detection, an embodiment of the proposed method determines one or more values of the first-order time derivative and / or second-order time derivative (as Figure 3 the trend parameters of the response time curve over time shown in

[0078] This example clearly shows that using the method proposed herein, the re-membranation interval can be extended beyond the known prior art time period. In addition, the proposed method can detect sensors that have dried out before the prior art time period has elapsed due to some reasons. In addition, the method proposed herein can detect sensors whose performance degrades over time and due to use, such that the response time is too high. In such a case, the method described in the context of Figure 3 can generate a control signal to initiate replacement or maintenance of the transcutaneous sensor due to deterioration.

[0079] Figure 4 Shows the theoretical response curve of a transcutaneous sensor to a change in gas pressure using the model parameters listed in Figure 4 . Also shown in Figure 4 are the two points used to calculate the response time in the two-point estimation. The method proposed herein can utilize the fact that the transcutaneous sensor has a double-exponential or exponential response to a sudden change in gas pressure p(t) = (p end - p(0))(1 - e (-t / τ) ) + p(0), and the time constant (τ) in the exponential response can be determined by the following formula:

[0080]

[0081] where p end is the steady-state value of the gas pressure in the exponential function, p(t1) and p(t2) are the gas pressures of the exponential function at time points t1 and t2, as shown in Figure 4 . In addition, those skilled in the art know that this time constant τ can be converted by calculation into the so-called 10% to 90% response time. Note that in the context of the present invention, and if not stated otherwise, the response time should be understood as the so-called 10% to 90% response time, that is, the time required for the sensor to detect a change from a first gas partial pressure to a second gas partial pressure, where 10% and 90% refer to the time difference between 10% and 90% of the difference between the first gas partial pressure and the second gas partial pressure. This can also be related to the time constant τ described herein, see for example the description in Figure 4 . The response time is not necessarily the 10% to 90% response time, but in other embodiments it can be, for example, the 20% to 80% response time, the 5% to 95% response time, or any other percentage selected on the response curve.

[0082] Figure 5Schematically shown is a transcutaneous blood gas monitor 500 for transcutaneously monitoring one or more blood gases of a patient. The monitor 500 includes a transcutaneous sensor 501 configured to measure the partial pressure of one or more blood gases of the patient. The monitor 500 further includes a control circuit 502 configured to determine a response time parameter of the transcutaneous sensor during monitoring of the sensor 501. The control circuit 502 is further configured to determine whether the partial pressure measurement ability of the sensor 501 is sufficient, appropriate or acceptable based on the determined response time parameter. The monitor 500 includes a calibration chamber 503 into which calibration gas can be flushed from a calibration gas reservoir 504. The calibration gas 505 ensures that the sensor 501 is exposed to a minimal amount of gas pressure change during the monitoring method performed by the monitor 500 when being flushed through a pipe 506 into the calibration chamber 503. The control circuit 502 is connected to the calibration gas reservoir 504 via an electrical connection 507 to initiate the flushing. In addition, the control circuit 502 is connected to the sensor 501 via a connection 508 such that the measured value generated by the sensor 501 can be transmitted from the sensor 501 to the control circuit 502.

[0083] Figure 6 Schematically shown is a computer-implemented method for monitoring a transcutaneous sensor according to another embodiment of the present invention. In step S1, a response time parameter of the transcutaneous sensor is determined. In Figure 6 the embodiment, the value of the 10% to 90% response time is determined, preferably as an absolute value. In addition, in step S3a, the determined value of the 10% to 90% response time is compared with a response time threshold. As has been explained in detail above, the threshold can be predefined as, for example, a certain fixed amount of time, such as 50 s. However, the threshold can also be implemented as a value calculated based on the response time measured when the sensor has been re-membraned. For example, the threshold can be set to 1.5 times the value of the response time measured after re-membraning of the said individual sensor. Other possibilities have been disclosed above. In addition, in Figure 6 the method, the determined value of the response time is compared with the response time threshold in step S3a. In addition, based on the comparison in step S3a, it is determined in step S2 whether the partial pressure measurement ability of the sensor is sufficient. In other words, the determination is based on the comparison of the response value with the threshold in step S3a. Specifically, depending on the comparison of the response time determined in step S3a with the threshold, it can be decided whether re-membraning is necessary. For example, if the response time exceeds the threshold, it is determined by the method that re-membraning should be initiated. Therefore, a control signal for causing re-membraning is generated in step S4a.

[0084] The described embodiments are similarly directed to computer-implemented methods of monitoring a percutaneous sensor configured to measure the partial pressure of one or more blood gases of a patient, to computer programs, to non-transitory program storage media storing such programs, to percutaneous blood gas monitors for percutaneous monitoring of one or more blood gases of a patient, and to the use of the determined results of response time parameters of the percutaneous sensor. Synergistic effects can be produced by different combinations of the embodiments, although they may not be described in detail.

[0085] Furthermore, it should be noted that all embodiments of the method of the present invention can be performed in the order of the described steps, however this is not necessarily the only and necessary order of the steps of the method. Unless explicitly stated to the contrary hereinafter, the methods presented herein can be performed in another order of the disclosed steps without departing from the corresponding method embodiments.

[0086] In cases where an indefinite or definite article is used in reference to a singular noun (e.g., "a", "an", or "the"), this includes a plurality of such nouns, unless otherwise specifically stated. The term "about" or "approximate" in the context of the present invention means an accuracy interval that a person skilled in the art will understand still ensures the technical effect of the feature being discussed. The term generally indicates a deviation of ±20% from the indicated value, preferably ±15%, more preferably ±10%, and even more preferably ±5%.

[0087] By studying the drawings, the present disclosure, and the appended claims, a person skilled in the art can understand and implement other variations of the disclosed embodiments when practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit can fulfill the functions of several items or steps recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously. A computer program can be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but can also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope of the claims.

Claims

1. A computer-implemented method for monitoring a transcutaneous sensor configured to measure the partial pressure of one or more blood gases of a patient, the method comprising the steps of: Determining a response time parameter of the transcutaneous sensor (step S1), and Based on the determined response time parameter, determining whether the partial pressure measurement ability of the sensor is sufficient (step S2).

2. The method according to claim 1, Wherein the response time parameter indicates the response time of the sensor when measuring the partial pressure of the one or more blood gases of the patient.

3. The method according to any one of the preceding claims, Wherein the step S2 of determining whether the partial pressure measurement ability of the sensor is sufficient includes: Based on the determined response time parameter, determining whether to initiate remembranation of the transcutaneous sensor.

4. The method according to any one of the preceding claims, Wherein the step S2 of determining whether the partial pressure measurement ability of the sensor is sufficient includes: Based on the determined response time parameter, determining whether to initiate replacement or maintenance of the transcutaneous sensor due to deterioration.

5. The method according to any one of the preceding claims, Wherein the response time parameter determined in step S1 is the value of the response time; and the method further comprises the step of: Comparing the determined value of the response time with a response time threshold (step S3a).

6. The method according to claim 5, the method further comprising the step of: If the determined value of the response time exceeds the response time threshold, generating a control signal configured to cause remembranation of the sensor or configured to cause replacement or maintenance of the sensor (step S4a).

7. The method according to any one of the preceding claims, Among them, The response time parameter determined in step S1 is a trend parameter indicating the time development of the response time of the transcutaneous sensor; and the method further comprises the step of: Comparing the determined trend parameter with a trend threshold regarding the time development of the response time of the transcutaneous sensor (S3b).

8. The method according to claim 7, the method further comprising: If the determined trend parameter deviates from the trend by at least a predetermined minimum amount, generating a control signal configured to cause remembranation of the sensor or configured to cause replacement or maintenance of the sensor (S4b).

9. The method according to any one of claims 7 to 8, the method further comprising the step of: Measuring the partial pressure value of the blood gas by the sensor over time, and Wherein the determined trend parameter is one or more time derivatives of the measurement curve of the partial pressure value of the blood gas measured over time, specifically the first-order time derivative and / or the second-order time derivative.

10. The method according to any one of claims 7 to 9, Wherein the response time parameter determined in step S1 includes the value of the response time within a time period, preferably at least multiple days, Wherein the determined value of the response time describes the response time measurement curve of the value of the response time of the sensor within the time period, and The determined trend parameter is the time derivative of the response time measurement curve.

11. The method according to any one of the preceding claims, wherein the step S1 of determining the response time parameter comprises: providing the data of the sensor and / or data regarding the sensor as input data to a predictive maintenance module, predicting, by the predictive maintenance module, the response time of the transcutaneous sensor; and wherein the predicted response time of the transcutaneous sensor in step S2 is used to determine whether the pressure measurement ability of the sensor is sufficient, in particular whether re-membranation of the transcutaneous sensor or replacement or maintenance of the sensor is necessary.

12. The method according to any one of the preceding claims, wherein the method is applied to a transcutaneous electrochemical sensor for measuring the partial pressure of one or more blood gases of a patient.

13. The method according to any one of the preceding claims, wherein the sensor is exposed to a pressure change from a first gas partial pressure to a second gas partial pressure during the monitoring method, and wherein the first gas partial pressure and / or the second gas partial pressure is known.

14. A program which, when run on a computer or when loaded onto a computer, causes the computer to execute the method steps of the method according to any one of the preceding claims.

15. A non-transitory program storage medium storing the program according to claim 14.

16. A transcutaneous blood gas monitor (500) for transcutaneously monitoring one or more blood gases of a patient, the monitor comprising: a transcutaneous, preferably electrochemical, sensor (501) configured to measure the partial pressure of one or more blood gases of the patient, a control circuit (502) configured to, during monitoring of the transcutaneous sensor: - determine a response time parameter of the transcutaneous sensor and configured to: - determine whether the pressure measurement ability of the sensor is sufficient based on the determined response time parameter.

17. The transcutaneous blood gas monitor according to claim 16, the monitor further comprising: a calibration chamber (503), a calibration gas reservoir (504) containing a calibration gas (505), and wherein the transcutaneous blood gas monitor is configured to flush the calibration gas from the calibration gas reservoir into the calibration chamber for calibrating the transcutaneous sensor.

18. A use of the result of the determination of the response time parameter of a transcutaneous sensor for monitoring the sensor, specifically for determining the need for re-membranation of the transcutaneous sensor or for determining the need for replacement of the sensor due to deterioration, the transcutaneous sensor being configured to measure the partial pressure of one or more blood gases of a patient.

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