Respiratory rate measuring device

Abstract

Provided is a respiratory rate measurement device comprising: a patient connection unit for acquiring, from a user, biological information for detecting respiration; a conversion unit for converting the biological information detected by the patient connection unit into an electric signal; a respiration rate calculation unit for processing the converted electric signal to calculate a respiration rate; and a signal output unit that outputs the calculated respiration rate by at least one or more means among audio, a screen display, and a communication signal. The respiratory rate measurement device is characterized in that the respiratory rate calculation unit: calculates the respiration interval for individual respiration detected on the basis of the electric signal or respiratory supplementary information that includes the amplitude of the respiration waveform detected; calculates an index related to the reliability of the calculated respiratory rate, on the basis of the respiratory supplementary information; and outputs the index through the signal output unit. The respiratory rate measurement device calculates the respiratory rate, calculates an index related to the stability of respiration, and thereby makes it possible to determine that a situation is such that respiration detection is being performed in a stable manner.

Description

Technical Field

[0001] The present invention relates to a respiratory rate measuring device that monitors the respiratory rate of a user, etc.

Background Art

[0002] The respiratory rate is, like body temperature, blood pressure, heart rate, etc., the most basic numerical value as a vital sign representing the state of the body, and is particularly important in detecting changes in physical activity and abnormalities in ventilation function. The heart rate follows an accurate rhythm according to the amount of blood circulation required by the periodic signal from the sinoatrial node, whereas the state of breathing can be consciously changed. Especially during wakefulness, due to body movements, meals, conversations, etc., it changes significantly or is interrupted regardless of physiological situations such as the body's oxygen demand, so it is extremely difficult to always accurately measure the value of the respiratory rate. In most cases, for example, during a medical examination, doctors, nurses, etc. only measure the respiratory rate spot-check after confirming that the patient is in a resting state. Even for a measuring device having a function of continuously monitoring the respiratory rate, its utilization is limited to monitoring during sleep, etc., and the detected numerical value also does not exceed the category of reference values.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When continuously monitoring the respiratory rate using a respiratory rate measuring device, if it is possible to detect a state where breathing is stable, by comparing the detected respiratory rate values in the stable breathing state according to the monitoring period, it is possible to detect long-term changes in physical condition. Furthermore, it may be possible to detect a decrease in ventilation function due to chronic pulmonary disease, etc., from the period and frequency of a state where breathing cannot be stably detected.

[0005] Polysomnography (PSG) is an example of a device that allows for continuous monitoring of respiratory rate and identification of a resting state. Such a device can analyze respiratory disorders during sleep with high accuracy by attaching an airflow sensor for respiratory detection, a chest and abdominal band, an accelerometer for measuring body position, an electromyograph (EMG) sensor for determining sleep stages, and an electroencephalogram (EEG) sensor. On the other hand, it is not suitable for continuous monitoring over long periods, including day and night, because it places a high degree of constraint on the user and requires specialized skills to analyze the waveform data.

[0006] While it is possible to measure respiratory rate using only specific sensors, such as airflow sensors, within the PSG's measurement function, even in this case, long-term continuous monitoring results in an enormous amount of data, and analyzing it to determine whether or not respiration is being detected normally is extremely labor-intensive.

[0007] Oxygen therapy is used for patients with respiratory diseases such as COPD (chronic obstructive pulmonary disease) and ILD (interstitial lung disease). As disclosed in WO2020 / 067067 (Patent Document 1), a technology has been devised to improve the hypoxic state of such patients by incorporating a respiratory monitoring device into an oxygen concentrator and using the tube for delivering oxygen to the patient as a means for acquiring respiratory information. This allows for continuous monitoring of the respiratory state without the need for a separate sensor, and without the patient being particularly aware of it while inhaling oxygen. In the future, this technology is expected to have the potential to detect changes in the patient's disease state from continuous respiratory monitoring data.

[0008] However, a disadvantage of using the oxygen delivery tube as a respiratory detection means is that noise associated with the operation of the oxygen concentrator is superimposed on the input to the respiratory monitoring device. Generally, oxygen concentrators use an adsorbent such as X-type zeolite that preferentially adsorbs nitrogen over oxygen, and employ a pressure swing adsorption method in which pressurized air is supplied to an adsorption cylinder containing the adsorbent to adsorb nitrogen, and the adsorbed nitrogen is desorbed and discharged by depressurizing the adsorption cylinder. Due to pressure fluctuations associated with switching between adsorption and desorption, slight periodic fluctuations occur in the flow rate of the delivered oxygen. Although Patent Document 1 discloses a technology to reduce periodically occurring noise, the operating timing of mechanisms that operate passively due to pressure, such as check valves and pressure regulating valves installed in oxygen concentrators, does not fluctuate perfectly periodically, but rather varies. Patent Document 1 does not disclose a technology to remove aperiodic noise that depends on these operational variations.

[0009] Furthermore, when using the oxygen delivery tube as a means of detecting respiration, it is susceptible to noise caused by patient movement, conversation, and eating. In addition to detecting respiration using the oxygen delivery tube, it is possible to obtain the most reliable respiratory information by using multiple detection methods, such as chest and abdominal bands, in combination and comparing the data from these methods. However, such methods lose the advantage of being able to monitor respiration without the patient being aware of it.

[0010] Therefore, there is a need for technology that can distinguish such non-periodic noise from the waveform caused by respiration and reliably acquire the respiratory rate. [Means for solving the problem]

[0011] The present invention solves the problems described above and provides a respiratory rate measuring device or an oxygen supply device equipped with such a respiratory rate measuring function that calculates the respiratory rate based on information from a single respiratory sensor capable of measuring respiratory waveforms, calculates an index related to respiratory stability, and thereby makes it possible to determine a situation in which respiration can be detected stably.

[0012] In other words, the present invention provides a respiratory rate measuring device comprising: a patient connection unit for acquiring biological information from a user for detecting respiration; a conversion unit for converting the biological information detected by the patient connection unit into an electrical signal; a respiratory rate calculation unit for processing the converted electrical signal and calculating the respiratory rate; and a signal output unit for outputting the calculated respiratory rate by at least one of the following means: voice, screen display, or communication signal. The respiratory rate calculation unit calculates respiratory ancillary information, including the interval between each breath and / or the amplitude of the detected respiratory waveform, based on the electrical signal; calculates an index related to the reliability of the calculated respiratory rate based on the respiratory ancillary information; and outputs this index through the signal output unit.

[0013] The present invention also provides an oxygen supply device comprising: an oxygen concentrator that concentrates and generates oxygen from the air using a pressure swing method; a patient connection unit that delivers concentrated oxygen gas to the user and is equipped with a detection means for detecting changes in gas pressure associated with the user's breathing; a respiratory rate measurement unit equipped with a conversion unit for converting the pressure change value detected by the patient connection unit into an electrical signal; a respiratory rate calculation unit for processing the converted electrical signal and calculating the respiratory rate; and a signal output unit that outputs the calculated respiratory rate by at least one of the means of voice, screen display, or communication signal, wherein the respiratory rate measurement unit calculates respiratory information including the respiratory interval for each breath and / or the amplitude of the detected respiratory waveform in addition to the respiratory rate calculated by the respiratory rate calculation unit based on the electrical signal, calculates an index related to the reliability of the calculated respiratory rate based on the respiratory information, and outputs it through the signal output unit. Such an oxygen supply device can be realized by integrating the functions of the respiratory rate measurement device of the present invention into a pressure swing type oxygen concentrator and incorporating it as a respiratory rate measurement unit.

[0014] The respiratory rate calculation unit is characterized by calculating information representing the fluctuation in the respiratory interval or the amplitude of the respiratory waveform for each detected breath, as an indicator related to the reliability of the respiratory rate. In particular, the respiratory rate measuring device is characterized in that the respiratory rate calculation unit calculates the variability of the respiratory interval for each detected breath as an indicator related to the reliability of the respiratory rate, determines that the reliability of the respiratory rate calculation value is low when the variability value exceeds a predetermined threshold, and outputs the result of the determination. The respiratory rate measuring device is characterized in that the respiratory rate calculation unit calculates the variance, standard deviation, or interquartile range of the respiratory interval for each breath, or a value obtained by dividing these values ​​by the mean or median of the respiratory interval, as the variability value of the respiratory interval for each breath. The respiratory rate measuring device is characterized in that the respiratory rate calculation unit outputs the value obtained by averaging the absolute value of the difference between the i-1th respiratory interval t(i-1) and the ith respiratory interval t(i) of a series of detected breaths over a plurality of i values, or by taking the square root of the mean square of the difference over a plurality of i values.

[0015] The present invention also provides a respiratory rate measuring device characterized in that the respiratory rate calculation unit includes either the amplitude value of the detected respiratory waveform or the amplitude increase / decrease range as an indicator related to the reliability of the respiratory rate, and determines that the reliability of the respiratory rate calculation value is low if the amplitude increase / decrease range or the amplitude variation exceeds a threshold, or if the amplitude value falls below a threshold, and outputs the result of the determination.

[0016] In particular, the present invention provides a respiratory rate measuring device characterized in that the respiratory rate calculation unit calculates, as an increase / decrease in amplitude, the difference between the average or median of the amplitude values ​​over a certain period in the past and the average or median of the amplitude values ​​over a certain period most recent than the aforementioned period, or the ratio of the two. Alternatively, the present invention provides a respiratory rate measuring device characterized in that the respiratory rate calculation unit outputs, as a variation in amplitude for each detected breath, the variance, standard deviation, or interquartile range of the amplitude value calculated for each detected breath.

[0017] Furthermore, the present invention provides a respiratory rate measuring device characterized in that the respiratory rate calculation unit determines that the reliability of the respiratory rate calculation value is low if the length of time and / or frequency of time during which no respiration is detected during the respiratory rate calculation period is greater than a predetermined value.

[0018] In particular, the present invention provides a respiratory rate measuring device characterized in that the respiratory rate calculation unit calculates the period during which no respiration was detected using either the period during which the detected respiratory interval was above a certain value, or the period during which the amplitude of the respiratory waveform was below a certain value.

[0019] The present invention provides a respiratory rate measuring device characterized in that, when the respiratory rate calculation unit calculates a value greater than a predetermined threshold for the length of time during which no breathing was detected, or when the variation in the length of time during which no breathing was detected is greater than a predetermined threshold, and the variation in the amplitude of the respiratory waveform during the period during which breathing was detected is greater than or equal to a predetermined threshold, it outputs a signal indicating the possibility of apnea occurring. Alternatively, the present invention provides a respiratory rate measuring device characterized in that, when the value of the length of time during which no breathing was detected is greater than a predetermined threshold that is greater than the threshold for detecting the occurrence of apnea, it outputs a signal indicating the possibility of a malfunction in the attachment of the patient connection part.

[0020] The present invention provides an oxygen supply device that integrates an oxygen supply source for supplying oxygen to the user's mouth or nose, with the patient connection part also serving as an oxygen supply means. [Effects of the Invention]

[0021] By using the respiratory rate measuring device of the present invention, users can continuously monitor their respiration over a long period of time with minimal restraint. From the long-term monitoring results, it is possible to exclude respiratory disturbances unrelated to physiological oxygen demand caused by conversation or body movement, and to extract values ​​detected at times when respiration is stable, compare long-term fluctuations, and objectively judge changes in physical condition.

[0022] In addition, especially during sleep, it becomes possible to estimate the likelihood of the occurrence of a breathing disorder from the frequency and duration in which stable breathing has not been detected. Furthermore, as breathing-related information, by using both a value related to the amplitude of breathing and a value related to the frequency, for example, it may be possible to utilize it for determining factors for unstable signals such as discrimination between apnea and unstable detection due to poor attachment of patient connection means.

[0023] In the breathing rate measuring device of the present invention, in order to determine the stability of breathing detection based only on the detected breathing data, for example, when combined with an oxygen concentrator or the like, it is also possible to detect pressure fluctuations associated with breathing through oxygen supply means such as a cannula that supplies oxygen from the oxygen concentrator to the patient, and it is possible to continuously monitor breathing with high reliability without wearing anything other than the cannula that is essential for the patient to continue treatment. This can be said to be an extremely important effect of the invention because many patients who require oxygen inhalation have severe lung diseases such as COPD and restrictive ventilation disorders, and the need for breathing monitoring is higher than that of other patients.

Brief Description of the Drawings

[0024] [Figure 1] Schematic diagram showing an embodiment of the breathing rate measuring device of the present invention. [Figure 2] Schematic diagram showing another embodiment of the breathing rate measuring device of the present invention. [Figure 3] Schematic diagram showing another embodiment of the breathing rate measuring device of the present invention. [Figure 4] Flowchart of the calculation in the breathing rate calculation unit of the breathing rate measuring means of the present invention. [Figure 5] Another flowchart of the calculation in the breathing rate calculation unit of the breathing rate measuring means of the present invention. [Figure 6] Comparison data between the breathing rate calculated value calculated by the breathing rate measuring means of the present invention and the breathing rate obtained by PSG. [Figure 7] Schematic diagram of the breathing rate measuring system of the present invention.

Mode for Carrying Out the Invention

[0025] One embodiment of the respiratory rate measuring device of the present invention is shown in a schematic diagram in Figure 1.

[0026] The respiratory rate measuring device of the present invention comprises a patient connection unit 2 for acquiring biological information from the user to detect respiration, a conversion unit 3 for converting the biological information detected by the patient connection unit into an electrical signal, a respiratory rate calculation unit 4 for processing the converted electrical signal and calculating the respiratory rate, and a signal output unit 5 for outputting the calculated respiratory rate by at least one of the following means: voice, screen display, or communication signal.

[0027] The patient connection unit 2, for example, is a nasal cannula and is attached to the nose of the user 1, who is the patient. The other end of the nasal cannula is connected to the converter unit 3, which transmits the pressure changes in the nasal cavity associated with breathing to the converter unit 3. The converter unit 3 can use, for example, a differential pressure sensor that detects the difference between atmospheric pressure and the pressure inside the cannula, and can detect pressure with a sensitivity of 0.1 Pa or less. In addition to the above combination of patient connection unit 2 and converter unit 3, any well-known means of detecting respiration can be used, such as a thermistor-type respiratory sensor in which a thermistor placed close to the mouth and nose is used as the patient connection unit 2 and a circuit for measuring the resistance of the thermistor is used as the converter unit 3, or a combination of a chest and abdominal band with an elastic conductive material woven into a band placed on the chest and abdomen, and a converter unit 3 that measures the resistance value and impedance of the band.

[0028] The patient connection unit 2 detects airflow and pressure associated with breathing, the temperature difference between inhalation and exhalation, and the expansion and contraction of the chest and abdomen. The breathing-related signals, converted into electrical signals by the conversion unit 3, are input to the respiratory rate calculation unit 4, where the respiratory rate is calculated internally. There are various methods for calculating the respiratory rate, including detecting the pressure peaks associated with exhalation and inhalation, detecting the zero-crossing point where the breath switches from exhalation to inhalation or vice versa, detecting the peak of the autocorrelation value using the similarity of the waveform shape of each breath, and detecting the frequency using the Fourier transform and taking its reciprocal. Any method that can calculate the interval between each breath can be used.

[0029] In addition to calculating the respiratory rate, the respiratory rate calculation unit 4 also calculates an index related to the reliability of the calculated respiratory rate and simultaneously calculates the result of the reliability determination of the respiratory rate based on that index. Details of how these values ​​and determination results are calculated will be described later.

[0030] In the signal output unit 5, the respiratory rate value calculated by the respiratory rate calculation unit 4, along with indicators related to reliability and the reliability judgment result, are displayed on the screen display unit 6 and the communication output unit 7, respectively, and simultaneously transmitted to an external server via the communication line. In addition to the above, other methods such as voice output can also be used for outputting the calculation results. Furthermore, to reduce the burden on the communication line, a storage means can be built in to store data for a certain period and transmit it to the server in batches at regular intervals.

[0031] As shown in Figure 7, a respiratory rate measurement system can be constructed in which the respiratory rate measurement device, an external server, and an external terminal of the present invention are connected by a communication network, and the patient's respiratory rate measured and calculated by the respiratory rate measurement device, indicators related to the reliability of the respiratory rate, and the reliability judgment results are stored on the external server, and trend data regarding the patient's respiratory rate for a predetermined period and the data of the reliability judgment results are made viewable via an external terminal installed in a medical institution or other facility. In such a system, it is also possible to transfer some or all of the functions of the respiratory rate calculation unit 4, which are responsible for calculating the respiratory rate value, indicators related to reliability, and determining the reliability, to the external server side.

[0032] Another embodiment of the respiratory rate measuring device of the present invention is shown schematically in Figure 2. The difference from the embodiment in Figure 1 is that it further has an oxygen supply source 8, and instead of the patient connection part 2, an oxygen supply means 9 such as a nasal cannula is attached to the user 1, and the other end of the oxygen supply means 9 is connected to the oxygen supply source 8 and further branched to the conversion unit 3. In this case, the oxygen supply means 9 performs both the supply of oxygen to the user 1 and the detection of the pressure associated with the user 1's breathing. For this reason, the pressure generated by the flow of oxygen is superimposed on the pressure associated with breathing on the conversion unit 3, so it is necessary to extract the pressure associated with breathing. As a technique for performing such an operation, the technique described in WO2020 / 067067 can be utilized. In this embodiment, the operation from the respiratory rate calculation unit 4 onwards is the same as in the embodiment in Figure 1.

[0033] Another embodiment of the respiratory rate measuring device of the present invention is shown in a schematic diagram in Figure 3. The difference from the embodiment in Figure 2 is that the series of means from the oxygen supply means 9 onward are integrated with the oxygen supply source 8 to form a respiratory rate measuring device 10, housed in a single housing. Since respiratory rate measuring devices are usually much smaller than the oxygen supply source 8, they can be integrated without significantly changing the size of the oxygen supply source 8. Furthermore, since the branching of the oxygen supply means 9 can be done inside the integrated housing, there are advantages such as not needing to branch the tube connected to the user midway.

[0034] Figure 4 shows an example of the detailed calculation flow within the respiratory rate calculation unit 4 of the respiratory rate measuring device of the present invention.

[0035] The respiratory rate calculation unit 4 converts the biological information detected by the patient connection unit 2 into an electrical signal in the conversion unit 3, calculates the respiratory rate based on the converted electrical signal, and also calculates respiratory ancillary information including the respiratory interval for each breath or the amplitude of the detected respiratory waveform in the detected respiration. Based on this respiratory ancillary information, it calculates an index related to the reliability of the calculated respiratory rate and outputs it through the signal output unit 5.

[0036] In the first step, the respiratory waveform signal sent from the conversion unit 3 is received, and the timing of exhalation, inhalation, or both is detected from it. Detection methods include detecting the timing when the waveform changes from a positive value to a negative value, or vice versa, as the start of exhalation or inhalation, or detecting the timing when the respiratory waveform signal takes on positive or negative peak values ​​as the exhalation or inhalation peaks. Alternatively, the relative time difference from the previous exhalation or inhalation may be detected using autocorrelation, etc. Furthermore, the peak values ​​of inhalation and exhalation are simultaneously acquired in this step.

[0037] In the second step, the respiratory interval between breaths is calculated based on the inhalation or exhalation timing determined in the first step. From the calculated respiratory interval, the respiratory rate is calculated by dividing 60 by the respiratory interval [seconds]. The respiratory rate can be calculated for each breath, or it can be calculated using the average or median value over a certain period, for example, one minute.

[0038] In the third step, the reliability of the calculated respiratory rate is determined based on the inhalation or exhalation timing and the peak values ​​of inhalation and exhalation determined in the first step. As the reliability of breathing is determined by whether the variability of the respiratory interval determined in the second step falls within a certain range, since breathing is usually regular when one is not consciously thinking about it.

[0039] However, since respiratory rate fluctuates over the long term in response to oxygen demand, setting an excessively long period for evaluating variability in respiratory intervals can lead to normal fluctuations in oxygen demand being detected as disturbances in respiratory detection. Furthermore, even if the sensitivity to detection disturbances is reduced to prevent this, the respiratory fluctuations will be averaged out, making it impossible to track actual respiratory fluctuations. Therefore, variability in respiratory intervals must be evaluated as variability within a specific, fixed period.

[0040] Furthermore, even after removing the periodic fluctuations generated by the oxygen concentrator, the fluctuations, although non-periodic, still occur at a certain point within the adsorption / desorption switching cycle of the oxygen concentrator. Therefore, if reliability is evaluated over a period significantly longer than the adsorption / desorption cycle, some noise will be generated in every evaluation period, making it impossible to obtain highly reliable data. In oxygen concentrators for home oxygen therapy, the adsorption / desorption switching time is often several tens of seconds to several minutes, so from this perspective, it is desirable that the data period for evaluating reliability be several minutes or less. For similar reasons, it is more advantageous to evaluate reliability using data over a certain period of time than to evaluate reliability using data for a certain number of breaths.

[0041] During wakefulness, it is rare to maintain a constant breathing pattern for extended periods due to body movement or conversation. Therefore, it is necessary to detect short periods of stable breathing between such movements and conversations, and setting a long period for evaluating respiratory interval variability is undesirable. Accordingly, a period of 5 minutes, and more preferably 3 minutes or less, is suitable for evaluating respiratory interval variability, as respiratory responses to changes in oxygen demand due to exercise are generally within a few minutes, and the period of typical respiratory disturbances such as Cheyne-Stokes respiration and obstructive apnea is also within a few minutes. On the other hand, since calculating variability requires statistical processing of multiple respiratory intervals, the shortest period for calculating variability is approximately 20 seconds, equivalent to 3 breaths, and more preferably 30 seconds or more.

[0042] Alternatively, even if the respiratory state changes, the respiratory interval and amplitude do not change significantly between adjacent breaths. Therefore, the average or median difference in respiratory intervals between adjacent breaths can be used as the variability of the respiratory interval. This method has the advantage that even if the oxygen demand changes significantly, a gradual change in respiratory rate can be judged as normal breathing. On the other hand, it may detect single respiratory disturbances caused by movement, etc., as disturbances even though they can actually be compensated for by preceding and succeeding data, leading to a judgment of low reliability in the respiratory rate detection value. For these reasons, it is best to use different methods depending on the purpose of respiratory rate detection.

[0043] Specifically, for an integer i representing a breath, if t(i-1) is the time interval between the (i-1)th adjacent breaths and t(i) is the time interval between the i-th breath, then in normal breathing, even when the number of breaths changes significantly, the variation in the breathing interval between adjacent breaths, i.e., the difference between t(i-1) and t(i), does not change significantly. Therefore, the statistical value (mean or median) obtained by processing the absolute value of the difference, |t(i)-t(i-1)|, over a certain number of breaths or a certain time will be larger when noise is detected or breathing is significantly irregular than when breathing is detected normally. Therefore, by setting a threshold, if the mean or median of |t(i)-t(i-1)| exceeds the threshold, it can be determined that breathing is not being detected normally. In the above explanation, the difference in breathing intervals was calculated as an absolute value, but the squared value can also be used instead of the absolute value. In that case, the square root of the result of calculating the mean or median is usually used, but the operation of calculating the square root is not always necessary.

[0044] Similarly, since the depth of breathing is approximately constant when unconscious, the variation in the amplitude of inhalation and exhalation for each breath may be assessed. In addition, if the tip of the cannula is shifted from or detached from the nose, the detectable respiratory pressure value will be significantly smaller, so a decrease or sudden change in amplitude may be detected.

[0045] In addition to the above, other methods for calculating the reliability of respiratory rate include methods that compare the detected pressure waveform with a standard respiratory waveform and calculate the degree of agreement, and methods that estimate how likely a waveform matches a respiratory waveform based on specific indicators derived from the waveform, such as waveform sharpness and the ratio of inhalation to exhalation. However, in methods that combine the oxygen supply path and the respiratory detection means, factors such as oxygen supply airflow noise and differences in the pressure response to the respiratory airflow when exhaling against the oxygen supply airflow versus inhaling in the same direction as the airflow mean that the respiratory waveform cannot be faithfully reproduced by the output of the conversion unit 3. For this reason, in a respiratory rate measuring device integrated with an oxygen concentrator, as in the present invention, it is desirable to calculate the reliability using a method that does not depend on the respiratory waveform.

[0046] In the fourth step, the reliability of the respiratory rate is determined according to the reliability index calculated in the third step. A predetermined threshold is set, and if the index calculated in the third step falls below or exceeds the threshold, the reliability of the calculated respiratory rate is determined to be low, and a signal to that effect is output. In this case, multiple indicators may be calculated in the second step, and each indicator may be judged against a predetermined threshold. For example, if the threshold for variability in respiratory intervals is A and the threshold for the amplitude decrease is B, the reliability may be determined to be low if either (third quartile - first quartile) / median of the respiratory interval > A or amplitude value 10 seconds ago - most recent amplitude value > B is met.

[0047] The respiratory rate calculated in the above steps, the indicator value related to the reliability of the respiratory rate, and the result of the reliability assessment can be communicated to the user by transmitting them via a communication line or displaying them on the device screen.

[0048] The respiratory rate calculation unit can determine that the reliability of the calculated respiratory rate is low if the length of time and / or frequency of periods during which no breathing was detected during the respiratory rate calculation period is greater than a predetermined value. The period during which no breathing was detected can be calculated using either the period during which the detected respiratory interval falls outside the normal respiratory interval range (e.g., 1 second to 10 seconds) or the period during which the amplitude of the respiratory waveform falls below a certain value.

[0049] If the respiratory rate calculation unit calculates that the length of time during which no breathing was detected, or the sum of the lengths of time during which no breathing was detected over a certain period, is greater than a threshold value, and the amplitude of the respiratory waveform during the period in which breathing was detected is greater than or equal to a predetermined threshold, then apnea may have occurred.

[0050] On the other hand, if the length of time during which no breathing was detected is greater than a predetermined threshold that is greater than the threshold for detecting the occurrence of apnea, there is a possibility that the patient connection was improperly fitted.

[0051] Figure 5 shows a second example of the calculation flow within the respiratory rate calculation unit 4 of the respiratory rate measuring device of the present invention. The difference from the first example shown in Figure 4 is that, as data for calculating the reliability index, the reliability index is calculated not only from the information obtained from the exhalation / inhalation detection results, but also by directly extracting amplitude values ​​from the detected respiratory waveform information. As a method for extracting amplitude values ​​from respiratory waveform information, generally known methods such as the method of finding the envelope or the method of finding the variance can be used. As a method for calculating the reliability index, in addition to the index shown in the first example, the range of fluctuation of the amplitude value over a certain period and the rate of fluctuation can be used as indicators.

[0052] By using the reliability index calculation method of the present invention, amplitude values ​​can be calculated even in situations where the start point of exhalation / inhalation cannot be detected. In particular, even when the amplitude fluctuates significantly during sleep apnea, a reliability index based on amplitude can be appropriately calculated.

[0053] Figure 6 shows a comparison between the ground truth data (visually counted respiratory rate from respiratory waveforms acquired by polysomnography and plotted every minute) and the detected values ​​calculated by the respiratory rate measuring device of the present invention, when the period for evaluating the variability of respiratory intervals is changed to a) 20 seconds, b) 1 minute, and c) 5 minutes, in an example of the calculation flow inside the respiratory rate calculation unit 4 of the respiratory rate measuring device of the present invention. The graph shows the ground truth data and detected values ​​(data judged to have low reliability are excluded from the plot) when the measurement starts immediately after the subject performs high-intensity exercise such as muscle training, and transitions from a resting state to a sleep state.

[0054] In the case where a) 20 seconds was used as the period for evaluating variability in respiratory intervals, it closely tracked the situation where the respiratory rate changed drastically immediately after exercise. However, in situations where breathing decreased during sleep, the number of breaths used to evaluate variability decreased, and the number of cases where accurate detection was not possible increased. This is considered to be the lower limit of the period for evaluating variability. In the case where b) 1 minute was used, breathing immediately after exercise was detected relatively well, and breathing during sleep was also detected appropriately. In the case where c) 5 minutes was used, while sleep breathing was detected with extremely high accuracy, in the region where the respiratory rate fluctuated greatly immediately after exercise, the reliability was judged as low due to the large variability, and it was hardly detected at all. This is considered to be the upper limit of the period for evaluating variability.

[0055] In cases where the time for evaluating variability was set to the intermediate values ​​mentioned above, d) 30 seconds and e) 3 minutes, there was no significant difference compared to case b) 1 minute, suggesting that 30 seconds to 3 minutes is the range in which the most favorable results are obtained. Based on these results, it is considered appropriate to use a period of 5 minutes to 20 seconds, and more preferably 3 minutes to 30 seconds, as the evaluation period for variability, as this matches the physiological response speed of humans. [Industrial applicability]

[0056] The respiratory rate measuring device of the present invention is a device that can evaluate and display the reliability of the measured respiratory rate value, and can be used as a medical device for detecting patient respiration, displaying the respiratory rate of oxygen supply devices used by patients with respiratory diseases, etc. [Explanation of Symbols]

[0057] 1. User (patient) 2. Patient connection section 3. Conversion section 4.Respiration rate calculator 5. Signal Output Section 6. Screen display section 7. Communication output section 8. Oxygen supply source 9. Oxygen supply means 10. Respiratory rate measurement device integrated with oxygen supply source

Claims

1. A respiratory rate measuring device comprising: a patient connection unit for acquiring biometric information from a user for detecting respiration; a conversion unit for converting the biometric information detected by the patient connection unit into an electrical signal; a respiratory rate calculation unit for processing the converted electrical signal and calculating the respiratory rate; and a signal output unit for outputting the calculated respiratory rate by at least one of the following means: voice, screen display, or communication signal, wherein the respiratory rate calculation unit calculates respiratory ancillary information including, in addition to the respiratory rate, the respiratory interval for each breath and / or the amplitude of the detected respiratory waveform in the respiration detected based on the electrical signal; and, as an index relating to the reliability of the respiratory rate, calculates information representing the fluctuation of the respiratory interval for each breath and / or the amplitude of the respiratory waveform detected within a specific period preceding the timing at which the respiratory rate calculation unit calculates the respiratory rate; and, based on the respiratory ancillary information, calculates an index relating to the reliability of the calculated respiratory rate and outputs it through the signal output unit.

2. The respiratory rate measuring device according to claim 1, characterized in that the length of the specific period is set to 20 seconds or more and 5 minutes or less.

3. The respiratory rate measuring device according to claim 1, characterized in that the length of the specific period is set to 30 seconds or more and 3 minutes or less.

4. The respiratory rate measuring device according to any one of claims 1 to 3, characterized in that the respiratory rate calculation unit calculates the variability of the respiratory interval for each detected breath as an indicator related to the reliability of the respiratory rate, determines that the reliability of the respiratory rate calculation value is low when the variability value exceeds a predetermined threshold, and outputs the result of the determination together with the respiratory rate measurement device.

5. The respiratory rate measuring device according to claim 4, characterized in that the respiratory rate calculation unit calculates the variance, standard deviation, or interquartile range of the respiratory interval for each breath, or a value obtained by dividing these values ​​by the mean or median of the respiratory interval, as a variability value of the respiratory interval for each breath.

6. The respiratory rate measuring device according to claim 4, characterized in that the respiratory rate calculation unit outputs, as a variation value of the respiratory interval for each breath, the absolute value of the difference between the i-1th respiratory interval t(i-1) of the detected consecutive breaths and the respiratory interval t(i) of the ith breath, averaged over a plurality of i values, or the square root of the mean square of the difference over a plurality of i values.

7. The respiratory rate measuring device according to any one of claims 1 to 3, characterized in that the respiratory rate calculation unit includes either the amplitude value of the detected respiratory waveform or the amplitude increase / decrease range as an indicator related to the reliability of the respiratory rate, and determines that the reliability of the respiratory rate calculation value is low if the amplitude increase / decrease range or the amplitude variation exceeds a threshold, or if the amplitude value falls below a threshold, and outputs the result of the determination together with the respiratory rate measurement device.

8. The respiratory rate measuring device according to claim 7, characterized in that the respiratory rate calculation unit calculates the difference between the average or median of the amplitude values ​​over a certain period in the past and the average or median of the amplitude values ​​over a certain period most recent than the aforementioned period, or the ratio thereof, as the amplitude increase / decrease range.

9. The respiratory rate measuring device according to claim 7, characterized in that the respiratory rate calculation unit outputs one of the variance, standard deviation, or interquartile range of the amplitude value calculated for each detected respiratory rate as the variation in amplitude for each detected respiratory rate.

10. The respiratory rate measuring device according to claim 1, characterized in that the respiratory rate calculation unit determines that the reliability of the respiratory rate calculation value is low if the length of time and / or frequency of time during which no respiration is detected during the respiratory rate calculation period is greater than a predetermined value.

11. The respiratory rate measuring device according to claim 10, characterized in that the respiratory rate calculation unit calculates the period during which no respiration was detected using either a period during which the detected respiratory interval was outside a predetermined range of values ​​as the range of a normal respiratory interval, or a period during which the amplitude of the respiratory waveform was below a certain value.

12. The respiratory rate measuring device according to claim 11, characterized in that the respiratory rate calculation unit calculates a value greater than a predetermined threshold for the length of time during which no breathing was detected, or the total length of time during which no breathing was detected over a certain period, and outputs a signal indicating the possibility of apnea occurring when the amplitude of the respiratory waveform during the period in which breathing was detected is greater than or equal to a predetermined threshold.

13. The respiratory rate measuring device according to claim 11, characterized in that the respiratory rate calculation unit outputs a signal indicating the possibility of a malfunction in the patient connection unit when the value of the length of the period during which no breathing was detected is greater than a predetermined threshold value which is greater than the threshold value for detecting the occurrence of apnea.

14. An oxygen supply device equipped with a respiratory rate measuring device according to claim 1, characterized in that it includes an oxygen supply source that supplies oxygen to the user's mouth or nose, and the patient connection part also serves as an oxygen supply means.

15. A respiratory rate measurement system comprising a respiratory rate measurement device, an external server, and an external terminal as described in claim 1, connected by a communication network, storing the patient's respiratory rate measured and calculated by the respiratory rate measurement device, an index related to the reliability of the respiratory rate, and / or the result of the reliability determination on the external server, and making the data related to the patient's respiratory rate viewable via an external terminal installed by a doctor or medical institution.

16. An oxygen supply device comprising: an oxygen concentrator that concentrates and generates oxygen from the air using a pressure swing method; a patient connection unit that delivers concentrated oxygen gas to the user and is equipped with a detection means for detecting changes in gas pressure associated with the user's breathing; a respiratory rate measurement unit that is equipped with a conversion unit for converting the pressure change value detected by the patient connection unit into an electrical signal; a respiratory rate calculation unit for processing the converted electrical signal and calculating the respiratory rate; and a signal output unit that outputs the calculated respiratory rate by at least one of the means of voice, screen display, or communication signal, wherein the respiratory rate measurement unit calculates respiratory ancillary information including the respiratory interval for each breath and / or the amplitude of the detected respiratory waveform in addition to the respiratory rate calculated by the respiratory rate calculation unit based on the electrical signal; and calculates information representing the fluctuation of the detected respiratory interval and / or the amplitude of the respiratory waveform for each breath during a specific period preceding the timing at which the respiratory rate calculation unit calculates the respiratory rate, as an index relating to the reliability of the respiratory rate; and calculates an index relating to the reliability of the calculated respiratory rate based on the respiratory ancillary information and outputs it through the signal output unit.

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