Medical device and control method thereof

Abstract

To provide a medical device capable of improving comfort at the time of one of inhalation or exhalation, and a control method of the medical device.SOLUTION: A medical device (100) supplies gas of a positive pressure to a respiratory tract of a patient. The medical device has a treatment pressure control part (118) that controls a supply pressure. When it is detected that a flow rate of the gas decreases from a peak flow rate in an inhalation period of the patient by a predetermined value, the treatment pressure control part (118) starts decompression control of the supply pressure of the gas.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a medical device and a control method thereof, and more particularly to a medical device for supplying air to a patient's airway and a control method thereof. [Background technology]

[0002] Known medical devices that supply air to a patient's airway include ventilators used in non-invasive positive pressure ventilation (NPPV) therapy and continuous positive airway pressure devices (hereafter referred to as CPAP devices) used in nasal continuous positive airway pressure (CPAP) therapy. CPAP is a treatment that suppresses the occurrence of apnea and hypopnea by continuously supplying air at an appropriate pressure to the patient's airway through a nasal mask, preventing airway obstruction during sleep.

[0003] Since the flow of positive pressure air supplied by these medical devices and the flow of exhaled air from the patient are in opposite directions, this can cause discomfort when the patient breathes. For this reason, Patent Document 1 describes a CPAP device that aims to reduce discomfort by increasing the supply pressure to therapeutic pressure when the air flow rate changes from negative to positive, and stopping the air supply when the air flow rate changes from positive to negative. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2007-524446 Summary of the Invention [Problem to be solved by the invention]

[0005] The CPAP device described in Patent Document 1 increases the pressure or stops the air supply only when the sign of the air flow rate changes or when the flow rate reaches a threshold. For example, maintaining the therapeutic pressure until the flow rate changes from positive to negative makes it difficult for the patient to exhale, leaving room for further reduction in discomfort experienced by the patient.

[0006] In view of the problems with the prior art, one aspect of the present invention provides a continuous positive airway pressure device and a control method thereof that can improve comfort during at least one of inhalation and exhalation. [Means for solving the problem]

[0007] In one aspect, the present invention provides a continuous positive airway pressure device that supplies positively pressurized air to a patient's airway, the device having a control means for controlling the pressure of the air, the control means starting to control the reduction of the air pressure when it is detected that the air flow rate has decreased by a predetermined percentage from the peak flow rate during the patient's inhalation period. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a continuous actuation positive pressure device and a control method thereof that can improve comfort during at least one of inhalation and exhalation. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing an example of the functional configuration of a continuous positive airway pressure device according to an embodiment. [Figure 2] FIG. 1 is a diagram for explaining an example of supply air pressure control by a continuous positive airway pressure device according to an embodiment. [Figure 3] 1 is a flowchart illustrating the operation of a continuous positive airway pressure device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below based on exemplary embodiments with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the claimed invention. Although the embodiments describe multiple features, not all of them are necessarily essential to the invention, and multiple features may be combined in any desired manner. Furthermore, in the accompanying drawings, the same or similar components are designated by the same reference numerals, and redundant description will be omitted. In addition, while the following describes an embodiment of the present invention in a continuous positive airway pressure device, the present invention can also be implemented in other medical devices (e.g., ventilators) that have the function of supplying air to a patient's airway.

[0011] (Example of continuous positive airway pressure device configuration) FIG. 1 is a block diagram showing an example of the functional configuration of a continuous positive airway pressure device (hereinafter referred to as a CPAP device) according to one embodiment of the present invention.

[0012] The CPAP device 100 includes a main body 101, a mask 125, and a tube 122 connecting the main body 101 and the mask 125. The operation of the CPAP device 100 is realized by a central processing unit (CPU) 112 reading a program stored in a read-only memory (ROM) 113 into a random access memory (RAM) 114 and executing the program. In this manner, a device including the CPU 112, the ROM 113, and the RAM 114 may be considered a computer. Note that functional blocks 117 to 121 described within the CPU 112 are schematic representations of major functions among various functions realized by the CPU 112 executing the program. Therefore, the operations described mainly with the functional blocks 117 to 121 are actually realized by the CPU 112 executing the program. Alternatively, one or more functional blocks may be realized using hardware circuits other than the CPU 112.

[0013] First, the components present in the air flow path will be described. Filter 102 is provided at the air intake port and removes pollen, bacteria, dust, etc. Temperature sensor 103 measures the temperature of the air that has flowed in. The measurement value by temperature sensor 103 is supplied to temperature control unit 119. Humidity sensor 104 measures the humidity of the air that has flowed in. The measurement value by humidity sensor 104 is supplied to temperature control unit 119. Note that although it is assumed here that air is to be supplied to the patient, other gases such as oxygen gas or a mixture of air and oxygen gas may also be supplied. When a gas other than air is to be supplied to the patient, a means for supplying the gas (such as a cylinder) may be connected upstream of filter 102.

[0014] The flow (differential pressure) sensor 105 (hereinafter simply referred to as flow sensor 105) is, for example, a differential pressure type flow sensor, which measures the flow rate of air in the flow path based on the pressure difference between the upstream and downstream sides. Here, a positive measurement value is obtained when the pressure on the upstream side is higher than the pressure on the downstream side, and a negative measurement value is obtained when the pressure on the downstream side is higher than the pressure on the upstream side. Therefore, the measurement value of the flow sensor 105 can also determine the flow direction of air in the flow path. The measurement value of the flow sensor 105 is supplied to the breathing analysis unit 117. Note that the flow sensor 105 may also measure flow velocity. The flow rate is the cross-sectional area of ​​the flow path multiplied by the flow velocity, and since the cross-sectional area of ​​the flow path does not affect the present invention, "flow rate" in the following explanation is equivalent to "flow rate or flow velocity."

[0015] The blower 106 has an impeller and a motor that drives the impeller inside. The treatment pressure control unit 118 controls the rotation speed of the motor through the motor driver 108, thereby adjusting the flow rate and supply pressure (supply air pressure) of air supplied to the patient.

[0016] Pressure sensor 107 is provided downstream of blower 106 in the flow path and measures the pressure in the flow path. The measurement value of pressure sensor 107 is supplied to treatment pressure control unit 118. Treatment pressure control unit 118 controls the supply air pressure assuming that air is being supplied to the patient at the pressure measured by pressure sensor 107.

[0017] Humidifier 109 has a water storage tank and humidifies the air to be supplied to the patient. Here, temperature control unit 119 controls the temperature of heater 110 provided in humidifier 109, thereby controlling the amount of water evaporated from the water storage tank, i.e., the degree of humidification. Temperature sensor 111 measures the temperature of heater 110 and supplies it to temperature control unit 119. If humidification and temperature adjustment are performed separately, humidifier 109 does not need to be provided with heater 110 and temperature sensor 111. Alternatively, air may be blown onto the surface of the water in the water storage tank, or a flow path may be arranged so that the air passes underwater.

[0018] Tube 122 connects main body 101 and mask 125. Tube 122 is stretchable and flexible so that it can easily follow the movement of mask 125. Tube 122 is also provided with heater 123 that adjusts the temperature of air supplied to the patient and temperature sensor 124 that measures the temperature of the air supplied to the patient. The measurement value of temperature sensor 124 is supplied to temperature control unit 119. Note that the temperature of the air supplied to the patient may be adjusted by tube 122 instead of or in addition to heater 123, by controlling the temperature of water vapor evaporated from a water storage tank using heater 110 of humidifier 109.

[0019] The mask 125 is sized and shaped to cover at least one of the patient's nose and mouth, and is attached to the patient by a string or band whose length is adjustable.

[0020] The display unit 115 is, for example, a display provided on the housing of the main body 101, and displays messages regarding the use of the CPAP device 100, various menu screens for setting the CPAP device 100, measurement values ​​of various sensors, etc. The display on the display unit 115 is controlled by the input / output control unit 120.

[0021] Operation unit 116 is a general term for input devices that can be operated by the user, such as buttons and switches provided on the housing of main body 101. If display unit 115 is a touch display, display unit 115 and operation unit 116 are integrated into one unit. An operation on operation unit 116 is detected by input / output control unit 120, and CPU 112 executes an operation according to the detected operation.

[0022] The respiration analysis unit 117 detects various conditions related to the patient's breathing and the occurrence of predetermined events based on the flow rate measured by the flow sensor 105. The events may be, for example, one or more of obstructive apnea, central apnea, hypopnea, flow limitation (partial obstruction of breathing), snoring, and Cheyne-Stokes respiration (CRS), but are not limited to these. CRS is a characteristic respiratory waveform in which apnea and hyperventilation occur consecutively. When the respiration analysis unit 117 detects the occurrence of a predetermined event, it notifies the therapeutic pressure control unit 118.

[0023] Based on the measurement value of pressure sensor 107, therapeutic pressure control unit 118 controls the operation of blower 106 so that the supply pressure becomes the target value. Furthermore, therapeutic pressure control unit 118 controls the supply pressure based on information detected by respiration analysis unit 117 as to whether the patient is exhaling or inhaling. Specifically, therapeutic pressure control unit 118 controls the supply pressure to the therapeutic pressure if the patient is inhaling, and to the minimum pressure if the patient is exhaling. The therapeutic pressure control unit 118 controls the supply pressure by, for example, controlling the duty ratio of the pulse voltage applied to motor driver 108 to control the rotation speed of the impeller of blower 106. The therapeutic pressure control unit 118 notifies temperature control unit 119 of the current supply pressure.

[0024] The temperature control unit 119 controls the operation of the heater 110 using at least the measurement value of the temperature sensor 111 to control the temperature and humidity of the air supplied to the patient. The temperature control unit 119 may also control the operation of the heaters 110 and 123, taking into account one or more of the measurement values ​​of the temperature sensor 103, the measurement values ​​of the humidity sensor 104, the measurement value of the temperature sensor 124, and the supply air pressure notified by the treatment pressure control unit 118. Even if the temperature of the heater 110 is constant, the humidification effect is lower when the flow rate is high than when the flow rate is low. Therefore, by controlling the temperature of the heater 110 while taking the supply air pressure into consideration, the humidity of the air supplied to the patient can be more appropriately controlled. The temperature and humidity of the air supplied to the patient may be the temperature and humidity notified to the temperature control unit 119 via the input / output control unit 120, i.e., the temperature and humidity set by the user via the operation unit 116.

[0025] The communication control unit 121 executes processes related to communication between the main body 101 and the external system 130. The communication control unit 121 can execute communication with the external system 130 in accordance with, for example, one or more well-known wireless and / or wired communication standards. The external system 130 may be, for example, an in-hospital management system for diagnosis and treatment data or a remote management system for the CPAP device 100.

[0026] (Control method of boost pressure) As described in Patent Document 1, if the boosting operation is performed or the air supply is stopped based only on the timing when the sign of the air flow rate is reversed or the timing when the flow rate reaches a threshold value, the following problems may arise. -Air is supplied at therapeutic pressure until the air flow rate changes from positive to negative, making it difficult to exhale. The supply pressure begins to rise towards the therapeutic pressure when the air flow rate changes from negative to positive, but if the supply pressure rises before the actual start of inhalation, it becomes difficult to inhale. The boost pressure control in this embodiment can alleviate at least one of these problems.

[0027] 2 is a diagram illustrating an example of supply air pressure control performed by CPAP device 100 in this embodiment. The upper part of FIG. 2 shows the change over time in the measurement value (flow rate or flow velocity) of flow sensor 105. The lower part shows the change over time in the supply air pressure controlled by therapeutic pressure control unit 118.

[0028] As described above, the breathing analysis unit 117 detects various breathing conditions of the patient based on changes in the flow rate measured by the flow sensor 105. Here, the breathing analysis unit 117 detects the following breathing conditions of the patient: (1) whether the patient is inhaling or exhaling, (2) the timing of the start of inhalation, and (3) the timing at which the flow rate drops by a certain percentage from the peak flow rate during the inhalation period. The breathing analysis unit 117 may also detect other breathing conditions of the patient. In addition, the breathing analysis unit 117 calculates the predicted time from the start of inhalation until the flow rate reaches its peak.

[0029] The breathing analysis unit 117 detects, for example, the time when the sign of the measurement value of the flow sensor 105 changes from negative to positive as the start timing of inspiration. The breathing analysis unit 117 may also detect, as the start timing of inspiration, the time when the sign of the measurement value of the flow sensor 105 changes from negative to 0.

[0030] Furthermore, the breathing analysis unit 117 calculates a predicted time from the start of inspiration to the peak flow rate based on, for example, the time from the start of inspiration to the peak flow rate in a predetermined number of recent breaths. As an example, the breathing analysis unit 117 can calculate the predicted time based on the time from the start of inspiration to the peak flow rate in at least one but not more than 30 recent breaths.

[0031] When using the time from the start of inspiration to the peak flow rate in the most recent breath, the breathing analysis unit 117 uses the time from the start of inspiration to the peak flow rate in the most recent breath as the predicted time. However, in this case, the prediction accuracy may be low, so it is preferable to calculate the average time from the start of inspiration to the peak flow rate in the most recent two or more breaths as the predicted time.

[0032] On the other hand, the upper limit of the respiratory rate can be appropriately determined in consideration of the time required to obtain the initial value, etc. However, since the followability to the variation of the respiratory rate per unit time decreases as the number of times increases, it is preferably 15 times or less, and more preferably 8 times or less. When calculating the prediction time using the time from the start of inspiration to the peak of the flow rate in the most recent n or more (n≥2) breaths, the respiration analysis unit 117 may calculate a weighted average value with a higher weight for the most recent predetermined number of times m (m < n) as the prediction time.

[0033] When the respiration analysis unit 117 detects the start timing of inspiration, it notifies the treatment pressure control unit 118 of the prediction time to the peak flow rate. When the treatment pressure control unit 118 is notified of the prediction time from the respiration analysis unit 117, it starts the boost control of the supply air pressure. That is, the treatment pressure control unit 118 starts the control of the blower 106 such that the supply air pressure rises at an increasing rate so as to reach a predetermined treatment pressure after the prediction time (that is, after the prediction time from the start of inspiration) after receiving the notification from the respiration analysis unit 117. The increasing rate may or may not be constant. The treatment pressure may be a fixed value preset by the doctor according to the patient, or a value automatically set by the treatment pressure control unit 118 according to the event detected by the respiration analysis unit 117. The range of the treatment pressure automatically set by the treatment pressure control unit 118 is assumed to be preset by the doctor according to the patient. The treatment pressure or the range of the treatment pressure is set through the operation unit 116 or the external system 130 and stored in the ROM 113.

[0034] Similarly, the lower limit value (minimum pressure) of the supply air pressure is also set by the doctor via the operation unit 116 or the external system 130 and stored in the ROM 113. The minimum pressure can be set in the range of 0 cmH2O or more and less than the therapeutic pressure. The minimum pressure may be set as an absolute value or as a pressure reduction amount from the therapeutic pressure (for example, in units of 1 cmH2O). Setting the minimum pressure higher than 0 cmH2O can prevent a decrease in the therapeutic effect. Setting the minimum pressure higher than 0 cmH2O also has the advantage of allowing the supply air pressure to be increased smoothly during pressure increase control.

[0035] Because sudden changes in supply pressure can cause discomfort to the patient, treatment pressure control unit 118 controls blower 106 so that the supply pressure increases at a constant or substantially constant rate both during pressure increase and pressure decrease. As described above, treatment pressure control unit 118 controls the supply pressure through feedback control using the measurement value of pressure sensor 107.

[0036] In this way, in this embodiment, when the start of inspiration is detected, the supply pressure is increased so that the therapeutic pressure is reached at the peak of inspiration, so the patient is less likely to feel uncomfortable when inhaling and can inhale naturally. Furthermore, because the time required to reach the therapeutic pressure is dynamically predicted based on the most recent multiple breaths, the patient is less likely to feel uncomfortable even if the patient's breathing intervals change.

[0037] Furthermore, the breathing analysis unit 117 determines that the inhalation flow rate has reached its peak when the measurement value of the flow sensor 105 changes from an increase to a decrease. Then, the breathing analysis unit 117 updates the predicted time using the time from when the start of inhalation is detected until the inhalation flow rate reaches its peak.

[0038] Furthermore, the respiration analysis unit 117 detects the timing when the measurement value of the flow sensor 105 drops from the peak flow rate by a predetermined value as the start timing of pressure reduction control. The predetermined value may be a fixed value or a percentage of the peak flow rate. In the case of a percentage of the peak flow rate, it is preferably 25% or more and 90% or less, and more preferably 30% or more and 50% or less. Figure 2 shows an example of detecting the timing when the measurement value of the flow sensor 105 drops 33% from the peak flow rate (peak flow rate * 0.67).

[0039] When breathing analysis unit 117 detects the timing to start decompression control, it notifies therapeutic pressure control unit 118. In response to this notification, therapeutic pressure control unit 118 reduces the supply pressure (starts decompression control of the supply pressure). In decompression control of the supply pressure, therapeutic pressure control unit 118 does not stop blower 106, but controls blower 106 so that the supply pressure decreases at a constant rate (decompression rate) predetermined in a program stored in ROM 113. Therapeutic pressure control unit 118 stops decompression when the supply pressure reaches a predetermined minimum pressure.

[0040] The treatment pressure control unit 118 controls the blower 106 so that the supply pressure decreases at a predetermined decompression rate from the decompression start timing. Here, the decompression rate can be determined as a value that reaches the minimum pressure within a decompression period of a length predetermined in a program stored in the ROM 113 from the decompression start timing. The decompression period is preferably 400 ms or more and 1000 ms or less. If it is shorter than 400 ms, the pressure will decrease too quickly, reducing the therapeutic effect. If it is longer than 1000 ms, the pressure will decrease too slowly, making it more difficult to exhale.

[0041] In this manner, in this embodiment, when it is determined that the inhalation flow rate has reached its peak, the supply pressure is reduced at a predetermined constant rate (pressure reduction rate) at the timing when the flow rate has decreased by a predetermined value from the peak flow rate. This allows for natural pressure reduction that is synchronized with the transition from inhalation to exhalation of the patient, making it less likely that the patient will feel uncomfortable.

[0042] Furthermore, the supply pressure is reduced at a constant pressure reduction rate before the sign of the measurement value of flow sensor 105 changes from positive to negative (or from positive to zero). Therefore, it is possible to alleviate the difficulty in exhaling compared to control that stops the blower when the sign of the measurement value changes from positive to negative (or from positive to zero). Furthermore, if the minimum pressure is set to be greater than 0 cmH2O, it is possible to suppress a decrease in the therapeutic effect, and furthermore, it is possible to smoothly increase the supply pressure during pressure increase control.

[0043] If the measurement value of the flow sensor 105 has multiple peaks during the intake period (the period when the measurement value of the flow sensor 105 is positive), using the first peak to calculate the predicted time will enable supply pressure control that makes intake easier.On the other hand, the pressure reduction start timing is determined using the first peak after the predicted time.

[0044] The above-described control for increasing the supply pressure or the control for decreasing the supply pressure may be performed either alone or both.

[0045] The above-mentioned control operation of the supply air pressure will be further explained using the flowchart shown in FIG.

[0046] In S301, the breathing analysis unit 117 determines whether or not the timing for starting inhalation has been detected. If the breathing analysis unit 117 determines that the timing for starting inhalation has been detected, it notifies the therapeutic pressure control unit 118 of the predicted time until the peak flow rate is reached and proceeds to S303; if not, it proceeds to S319. If the timing for starting inhalation has not been detected, in S319 the therapeutic pressure control unit 118 controls the blower 106 to maintain the supply air pressure at the minimum pressure, and returns the process to S301.

[0047] In S303, therapeutic pressure control unit 118 starts increasing control of the supply pressure. As described above, therapeutic pressure control unit 118 controls blower 106 so that the supply pressure increases at an increase rate that will result in a predetermined therapeutic pressure after a predicted time has elapsed since receiving notification from breathing analysis unit 117 (i.e., the predicted time has elapsed since the start of inhalation).

[0048] In S305, the therapeutic pressure control unit 118 determines whether the supply air pressure has reached the therapeutic pressure, and if it has reached the therapeutic pressure, the process proceeds to S307, and if not, the process proceeds to S309.

[0049] In S307, the treatment pressure control unit 118 ends the control of increasing the supply pressure, and continues to control the blower 106 so as to maintain the supply pressure at the treatment pressure.

[0050] In S309, the breathing analysis unit 117 determines whether or not a peak of the inhalation flow rate has been detected after detecting the start of inhalation, and if it is determined that it has been detected, proceeds to S311, and if not, returns to S305.

[0051] In S311, the breathing analysis unit 117 updates the predicted time from the start of inspiration until the inspiration flow rate reaches its peak.

[0052] In S313, the breathing analysis unit 117 determines whether or not the timing to start decompression has been detected, and if so, notifies the therapeutic pressure control unit 118 and proceeds to S315. On the other hand, if it is not determined that the timing to start decompression has been detected, the breathing analysis unit 117 repeatedly executes S313. Note that if the supply pressure has not reached the therapeutic pressure, the therapeutic pressure control unit 118 continues to control the pressure increase until the supply pressure reaches the therapeutic pressure while the breathing analysis unit 117 is executing S311 and S313, and once the supply pressure reaches the therapeutic pressure, stops the pressure increase control and maintains the supply pressure at the therapeutic pressure.

[0053] In S315, therapeutic pressure control unit 118 starts reducing the supply pressure. That is, therapeutic pressure control unit 118 controls blower 106 so that the supply pressure decreases at a constant rate (decompression rate) predetermined in a program stored in ROM 113. Note that even if the supply pressure has not reached the therapeutic pressure when S315 is executed, therapeutic pressure control unit 118 starts reducing the supply pressure.

[0054] In S317, the treatment pressure control unit 118 determines whether the supply air pressure has reached the minimum pressure, and if it is determined that it has reached the minimum pressure, the process proceeds to S319, and if it is not determined that it has reached the minimum pressure, S317 is repeatedly executed.

[0055] In S319, the treatment pressure control unit 118 ends the control of reducing the supply pressure, controls the blower 106 so that the supply pressure maintains the minimum pressure, and returns the process to S301.

[0056] As described above, according to this embodiment, the supply air pressure is reduced at a constant pressure reduction rate before the sign of the measurement value of flow sensor 105 changes from positive to negative (or from positive to zero). Therefore, compared to control that stops blower 106 when the sign of the measurement value changes from positive to negative (or from positive to zero), it is possible to alleviate the difficulty in exhaling. Furthermore, when the minimum pressure is set to be greater than 0 cmH2O, it is possible to suppress a decrease in the therapeutic effect, and further, it is possible to smoothly increase the supply air pressure during pressure increase control.

[0057] Furthermore, when the start of inspiration is detected, the supply pressure is increased to reach the therapeutic pressure at the timing when the inhalation flow rate is predicted to reach its peak. This allows for a natural increase in pressure in sync with the patient's inhalation, minimizing discomfort to the patient.

[0058] (Other embodiments) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program.The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0059] <Summary of the embodiment> (Item 1) A medical device for delivering gas at positive pressure to a patient's airway, comprising: a control means for controlling the supply pressure of the gas; the control means starts reducing control of the supply pressure when it is detected that the flow rate of the gas has decreased by a predetermined value from the peak flow rate during the patient's inhalation period. A medical device characterized by: According to this item, the supply pressure is reduced before the end of the inhalation period, making it possible to ease the difficulty of exhaling. (Item 2) 2. The medical device according to item 1, wherein the control means controls the supply pressure so that the supply pressure is reduced at a predetermined pressure reduction rate during the pressure reduction control. According to this item, the supply pressure control is not stopped and the supply pressure is gradually reduced, making it possible to alleviate the difficulty in exhaling. (Item 3) 3. The medical device according to item 1 or 2, wherein when the supply pressure reaches a predetermined minimum pressure greater than 0, the control means controls the supply pressure so as to maintain the minimum pressure. According to this item, it is possible to suppress a decrease in the therapeutic effect, and further to smoothly increase the supply air pressure during pressure increase control. (Item 4) 4. The medical device according to any one of items 1 to 3, wherein the predetermined value is 25% or more and 90% or less of the peak flow rate. According to this item, pressure reduction control can be started at a more appropriate timing. (Item 5) 4. The medical device according to any one of items 1 to 3, wherein the predetermined value is 30% or more and 50% or less of the peak flow rate. According to this item, the pressure reduction control can be started at a more appropriate timing. (Item 6) 6. The medical device according to any one of items 1 to 5, wherein, when there are multiple peak flow rates during the patient's inhalation period, the control means starts the pressure reduction control when it detects that the first peak flow rate has decreased by the predetermined value from the start of the inhalation period after the time at which the peak flow rate is predicted to be reached. According to this item, even if there are multiple peak flow rates during the patient's inhalation period, pressure reduction control can be started at an appropriate timing. (Item 7) the control means starts increasing control of the supply pressure when it is determined that the patient has started inhaling based on the flow rate of the gas; 7. The medical device according to any one of items 1 to 6, wherein the control means controls the supply pressure in the boost control so that the supply pressure reaches a predetermined therapeutic pressure at a time predicted to reach a peak flow rate during the patient's inhalation period. According to this item, the supply pressure is increased to reach the therapeutic pressure at the time when the flow rate during inspiration is expected to reach its peak, thereby achieving a natural increase in pressure that is synchronized with the patient's inspiratory movement and is less likely to cause discomfort to the patient. (Item 8) A medical device for delivering gas at positive pressure to a patient's airway, comprising: a control means for controlling the supply pressure of the gas; the control means starts increasing control of the supply pressure when it is determined that the patient has started inhaling based on the flow rate of the gas; The medical device is characterized in that, in the pressure increase control, the control means controls the supply pressure so that a predetermined therapeutic pressure is reached at a time when a peak flow rate during the patient's inhalation period is predicted to be reached. According to this item, the supply pressure is increased to reach the therapeutic pressure at the time when the flow rate during inspiration is expected to reach its peak, thereby achieving a natural increase in pressure that is synchronized with the patient's inspiratory movement and is less likely to cause discomfort to the patient. (Item 9) 9. The medical device according to item 7 or 8, wherein the predicted time is calculated based on the time from the start of inspiration to the peak flow rate in a predetermined number of recent breaths. This item allows the supply pressure to be controlled so that the therapeutic pressure is reached at the appropriate time. (Item 10) 9. The medical device according to item 7 or 8, wherein when there are multiple peak flow rates during the patient's inhalation period, the predicted time is calculated based on the time from the start of inhalation to the first peak flow rate. According to this item, the supply pressure can be controlled so that the therapeutic pressure is reached at the appropriate time even when there are multiple peak flow rates during the inhalation period. (Item 11) 9. The medical device according to item 7 or 8, wherein the predicted time is the average or weighted average of the time from the start of inspiration to reaching the peak flow rate in the most recent multiple breaths. According to this item, the supply pressure can be controlled so that the therapeutic pressure is reached at a more appropriate time. (Item 12) Item 12. The medical device according to item 11, wherein the most recent multiple times are between 2 and 8 times. According to this item, the supply pressure can be controlled so that the therapeutic pressure is reached at an appropriate time. (Item 13) 13. The medical device according to any one of items 1 to 12, characterized in that the medical device is a ventilator or a continuous positive airway pressure device. (Item 14) 1. A method for controlling a medical device that supplies gas at positive pressure to a patient's airway, comprising: detecting a decrease in the gas flow rate by a predetermined value from a peak flow rate during inspiration of the patient; In response to detecting that the flow rate of the gas has decreased by the predetermined value from the peak flow rate during the patient's inhalation period, starting a pressure reduction control of the supply pressure of the gas; A method for controlling a medical device, comprising: According to this item, the supply pressure is reduced before the end of the inhalation period, making it possible to ease the difficulty of exhaling. (Item 15) 1. A method for controlling a medical device that supplies gas at positive pressure to a patient's airway, comprising: detecting that the patient has started inhaling based on the gas flow rate; When it is detected that the patient has started inhaling, controlling the gas supply pressure to reach a predetermined therapeutic pressure at a time when a peak flow rate during the patient's inhalation period is predicted to be reached; A method for controlling a medical device, comprising: According to this item, the supply pressure is increased to reach the therapeutic pressure at the time when the flow rate during inspiration is expected to reach its peak, thereby achieving a natural increase in pressure that is synchronized with the patient's inspiratory movement and is less likely to cause discomfort to the patient. (Item 16) A program for causing a computer included in a medical device that supplies positive pressure gas to a patient's airway to function as the control means included in the medical device described in any one of items 1 to 13. According to this item, a program for realizing a medical device having the above-mentioned effects is provided.

[0060] The present invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Therefore, the following claims are appended to clarify the scope of the invention. [Explanation of symbols]

[0061] 101...main body, 112...CPU, 117...respiratory analysis unit, 118...treatment pressure control unit, 119...temperature control unit, 106...blower, 108...motor driver, 122...tube, 125...mask

Claims

1. A medical device for delivering gas at positive pressure to a patient's airway, comprising: a control means for controlling the supply pressure of the gas; the control means starts reducing control of the supply pressure when it is detected that the flow rate of the gas has decreased by a predetermined value from the peak flow rate during the patient's inhalation period. A medical device characterized by:

2. 2. The medical device according to claim 1, wherein the control means controls the supply pressure so that the supply pressure is reduced at a predetermined pressure reduction rate during the pressure reduction control.

3. 2. The medical device according to claim 1, wherein the control means controls the supply pressure so as to maintain the minimum pressure when the supply pressure reaches a predetermined minimum pressure greater than 0.

4. 2. The medical device according to claim 1, wherein the predetermined value is between 25% and 90% of the peak flow rate.

5. 2. The medical device according to claim 1, wherein the predetermined value is between 30% and 50% of the peak flow rate.

6. The medical device according to claim 1, characterized in that, when there are multiple peak flow rates during the patient's inhalation period, the control means starts the pressure reduction control when it detects that the first peak flow rate has decreased by the predetermined value from the start of the inhalation period after the time at which the peak flow rate is predicted to be reached.

7. the control means starts increasing control of the supply pressure when it is determined that the patient has started inhaling based on the flow rate of the gas; 2. The medical device according to claim 1, wherein the control means controls the supply pressure so that the predetermined therapeutic pressure is reached at a time when the patient's inhalation period is predicted to reach a peak flow rate during the inhalation period.

8. A medical device for delivering gas at positive pressure to a patient's airway, comprising: a control means for controlling the supply pressure of the gas; the control means starts increasing control of the supply pressure when it is determined that the patient has started inhaling based on the flow rate of the gas; The medical device is characterized in that, in the pressure increase control, the control means controls the supply pressure so that a predetermined therapeutic pressure is reached at a time when a peak flow rate during the patient's inhalation period is predicted to be reached.

9. The medical device according to claim 8, wherein the predicted time is calculated based on the time from the start of inspiration to the peak flow rate in a predetermined number of recent breaths.

10. The medical device of claim 8, wherein when there are multiple peak flow rates during the patient's inhalation period, the predicted time is calculated based on the time from the start of inhalation to the first peak flow rate.

11. The medical device according to claim 8, characterized in that the predicted time is the average or weighted average of the time from the start of inspiration to reaching the peak flow rate in the most recent multiple breaths.

12. The medical device according to claim 11, wherein the most recent multiple times is between two and eight times.

13. 2. The medical device according to claim 1, wherein the medical device is a ventilator or a continuous positive airway pressure device.

14. 1. A method for controlling a medical device that supplies gas at positive pressure to a patient's airway, comprising: detecting a decrease in the gas flow rate by a predetermined value from a peak flow rate during inspiration of the patient; and starting a reduction control of the gas supply pressure in response to detecting that the gas flow rate has decreased by the predetermined value from the peak flow rate during the patient's inhalation period.

15. 1. A method for controlling a medical device that supplies gas at positive pressure to a patient's airway, comprising: detecting that the patient has started inhaling based on the gas flow rate; When it is detected that the patient has started inhaling, controlling the gas supply pressure to reach a predetermined therapeutic pressure at a time when a peak flow rate during the patient's inhalation period is predicted to be reached; A method for controlling a medical device, comprising:

16. A program for causing a computer included in a medical device that supplies positive pressure gas to a patient's airway to function as the control means included in the medical device according to any one of claims 1 to 13.

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