Ventilation mode control method and ventilator

Abstract

The application discloses a ventilation mode control method and a breathing machine in the technical field of respiratory medical equipment, reconstructs pressure distribution in a breathing cycle, adopts a control strategy that inspiratory airway positive pressure is lower than expiratory airway positive pressure, actively reduces pressure to a lower release level to reduce inspiratory load when detecting patient inspiration, and smoothly restores pressure to a higher treatment pressure at the end of expiration to establish support for the next inspiration cycle. The method is realized in the breathing machine through cooperative control of a sensing unit, a processing unit and a pressure generating unit, solves the technical problem that the existing continuous positive airway pressure mode maintains constant high pressure in the whole breathing cycle, causes heavy load and poor comfort during patient inspiration and most of the expiration stage, and improves the overall comfort and long-term use compliance of treatment while ensuring equivalent airway support and treatment effect of the traditional mode.

Description

Technical Field

[0001] This application relates to the field of respiratory medical equipment technology, specifically a ventilation mode control method and a ventilator. Background Technology

[0002] Currently, continuous positive airway pressure (CPAP) ventilation mode is the mainstream method for treating obstructive sleep apnea (OSA) on a ventilator. During OSA treatment, the ventilator continuously delivers airflow to the patient through a nasal mask or face mask, increasing the pressure within the patient's throat, thereby preventing airway collapse and allowing air to enter the respiratory system. In clinical treatment of sleep-disordered breathing, CPAP ventilation mode maintains a relatively constant and high level of positive airway pressure throughout the entire respiratory cycle, including both inspiratory and expiratory phases. Its core mechanism of action is to support the airway with continuous positive pressure, raising the pharyngeal collapse threshold pressure and preventing dynamic collapse of the upper airway during sleep, thus maintaining airway patency. Simultaneously, CPAP can also increase functional residual capacity (FRC), improve alveolar recruitment, and enhance oxygenation efficiency. Currently, CPAP has achieved good therapeutic effects in treating OSA. However, patients have encountered many problems when using CPAP, such as mask discomfort, air leakage, and overall device noise. The biggest problem with CPAP is that the continuous airflow provided to the patient through a nasal or face mask maintains a high, constant pressure throughout both inhalation and exhalation. Because this mode maintains high pressure during exhalation, patients often need to complete the exhalation under positive pressure resistance, which can easily lead to discomfort such as expiratory resistance, chest tightness, or asynchronous exhalation, thus affecting long-term adherence. The discomfort it causes can lead patients to discontinue using the mode.

[0003] To improve comfort, various pressure regulation strategies have been developed clinically. Among the most typical are bilevel positive airway pressure (BPAP) and expiratory pressure release (EPR). These two modes share the characteristic of maintaining a higher inspiratory positive airway pressure (IPAP) during inspiration and actively reducing the expiratory positive airway pressure (EPAP) during expiration, or releasing pressure to a certain extent at the beginning of expiration. Their operating mechanism is based on respiratory phase recognition and pressure switching control. When a flow rate changes from positive to negative or reaches the expiratory trigger threshold, the output pressure is reduced to decrease the external airway pressure that the patient needs to overcome during expiration, thereby reducing expiratory load and discomfort. Although BPAP and EPR alleviate expiratory discomfort to some extent and improve tolerability in some patients, their pressure regulation mainly focuses on the expiratory phase, with less attention paid to the dynamic matching of the inspiratory phase and the overall optimization of respiratory phase coordination. In conventional positive pressure ventilation systems, whether BPAP or EPR, the control strategy typically provides airway pressure higher than or equal to that during the expiratory phase to ensure adequate airway support and maintain upper airway patency during inspiration. However, this pressure configuration may increase inspiratory drive load in some patients, affecting respiratory naturalness and subjective comfort. Therefore, in some patients, simply reducing pressure during expiratory phase can lead to an uneven pressure transition between inspiratory and expiratory phases, and may even affect the stability of airway support. Consequently, ventilation strategies that only reduce therapeutic pressure during the expiratory phase have limitations in terms of overall clinical efficacy and comfort improvement, and are not entirely satisfactory. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides a ventilation mode control method and a ventilator to solve the problems of heavy workload and poor comfort during the inspiratory and most expiratory phases of the aforementioned existing technologies.

[0005] To achieve the above objectives, this application provides the following technical solution: A ventilation mode control method, applied to a ventilator, includes the following steps: Pressure release transition step: When the patient begins to inhale, the output pressure is controlled to smoothly decrease from the expiratory positive airway pressure to the inspiratory positive airway pressure; the condition for determining when the patient begins to inhale is that the patient's inspiratory flow rate reaches the set inspiratory trigger absolute threshold or inspiratory trigger relative threshold. Pressure maintenance procedure: Control the output pressure to maintain the positive inspiratory airway pressure; Treatment pressure transition step: When it is detected that the patient's exhalation is about to end, the output pressure is controlled to smoothly rise from the positive inspiratory airway pressure to the positive expiratory airway pressure; the condition for determining that the patient's exhalation is about to end is that the patient's inspiratory flow rate reaches the set inspiratory trigger absolute threshold or inspiratory trigger relative threshold. Within a single respiratory cycle, the positive airway pressure during exhalation is greater than the positive airway pressure during inhalation.

[0006] Preferably, the smooth descent employs a two-stage descent, with the first stage beginning when the patient is detected to begin inhaling, and the second stage beginning after the inspiratory flow rate is detected to have reached its peak.

[0007] Preferably, the absolute threshold for inhalation triggering is set in the range of 1.5L / min to 8L / min.

[0008] Preferably, the relative threshold for inhalation triggering is set within the range of 10% to 40% of the peak inhalation flow rate of the previous inhalation.

[0009] Preferably, the positive pressure value of the inspiratory airway is not lower than a preset minimum pressure limit, wherein the minimum pressure limit is set as follows: The positive expiratory airway pressure does not exceed a preset maximum pressure limit, which is set to... .

[0010] Preferably, the absolute threshold for triggering exhalation is set in the range of 2L / min to 5L / min.

[0011] Preferably, the relative threshold for triggering exhalation is set within the range of 30% to 85% of the current peak expiratory flow rate.

[0012] Preferably, the duration of the pressure release transition step is 400–800 ms; the duration of the treatment pressure transition step is 800–1500 ms.

[0013] Preferably, the smooth descent or smooth ascent is implemented using a first-order low-pass filter model or an exponential function model.

[0014] Based on the same inventive concept, this application also discloses a ventilator, including a pressure generation unit, a sensing unit, a human-machine interaction unit, and a processing unit. The processing unit is signal-connected to the pressure generation unit, the sensing unit, and the human-machine interaction unit, and includes a processor and a memory. The processor is configured to execute instructions stored in the memory, and to implement the aforementioned ventilation mode control method based on the flow signal monitored in real time by the sensing unit and the user's settings for the expiratory positive airway pressure and / or inspiratory positive airway pressure received by the human-machine interaction unit, using the pressure generation unit to generate airflow delivered to the patient's airway.

[0015] Compared to existing technologies, this solution offers the following advantages: This application proposes a novel therapeutic ventilation mode for ventilators, namely Inspiratory Release Positive Pressure Ventilation (IR-PAP), which improves comfort during CPAP treatment without altering its therapeutic efficacy. The airway pressure is reduced after the start of inspiration and for most of the expiratory phase, only returning to an appropriate therapeutic pressure level near the end of expiration. Reducing the therapeutic pressure during inspiration makes breathing closer to natural breathing, resulting in a more natural inspiratory flow rate and improved patient comfort; restoring the pressure to the therapeutic level at the end of expiration dilates the airway, ensuring the ventilator's therapeutic effect and reducing the occurrence of OSA events. This innovative pressure control strategy employs dynamic modulation throughout the entire respiratory cycle, where the inspiratory IPAP is lower than the expiratory EPAP. This novel pressure distribution mechanism, distinct from conventional IPAP-higher-EPAP control strategies, reconstructs the pressure distribution within the respiratory cycle. It moderately reduces positive airway pressure during inspiration while maintaining relatively high support pressure during expiration. Pressure release primarily occurs throughout the entire inspiration and most of the expiration phase, rather than just during expiration, directly reducing the inspiratory drive load, resulting in a more natural respiratory rhythm and reducing the risk of patient-ventilator asynchrony. Early restoration of therapeutic pressure at the end of expiration establishes a stable airway support baseline for the next inspiratory cycle, avoiding the risk of airway collapse that may result from simple expiratory decompression. This improves comfort while maintaining a more stable therapeutic pressure environment. Furthermore, a smooth transition mechanism achieves pressure switching, maintaining a minimum safe pressure threshold while synergistically optimizing therapeutic efficacy and comfort. It optimizes the pressure distribution within the respiratory phase, making inspiration smoother and reducing perceived respiratory resistance, thereby significantly improving patient subjective comfort and treatment adherence. While enhancing comfort, this mode maintains the same ventilation logic as traditional methods. This approach offers comparable airway support and therapeutic effectiveness to conventional CPAP or BPAP devices. By rationally designing the pressure modulation curve and phase switching mechanism, this protocol reduces the pressure load during the inspiratory phase while maintaining upper airway patency and stability, thereby improving patient tolerance and achieving an optimized balance between comfort and efficacy. This provides a new technical approach for positive pressure ventilation therapy. Attached Figure Description

[0016] Figure 1 A schematic diagram of pressure and flow rate in the existing CPAP ventilation mode; Figure 2 A schematic diagram of pressure and flow rate in a current dual-level BPAP technology; Figure 3 This is a schematic diagram showing the typical pressure and flow rate of the ventilation mode in this application; Figure 4 This is a schematic flowchart of an embodiment of the ventilation mode control method of this application; Figure 5 A schematic diagram of airflow during the inspiratory phase of a respiratory cycle in an example of using a ventilator for a patient; Figure 6 A schematic diagram of airflow during the expiratory phase of a respiratory cycle in an example of using a ventilator for a patient; Among them, 1-pressure, 2-flow rate, IPAP-inspiratory positive airway pressure, EPAP-expiratory positive airway pressure, RT-pressure release transition, TT-therapeutic pressure transition, 3-inspiratory phase, 4-expiratory phase, 5-respiratory cycle, 10-turbine, 20-sensor, 30-humidifier, 40-breathing tubing, 50-breathing airway, 60-lungs, 70-mask, 80-microcontroller, 90-host computer touch screen, 100-exhaust port. Detailed Implementation

[0017] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0018] This embodiment provides a technical solution: This solution first discloses an embodiment of a ventilation mode control method, which is named IR-PAP in this application and is applied to a ventilator, including the following steps: The pressure release transition (RT) step is a process of transitioning from therapeutic expiratory positive airway pressure (EPAP) to release pressure inspiratory positive airway pressure (IPAP): when the patient begins to inhale, the output pressure is smoothly reduced from the EPAP value to the IPAP value. The condition for determining when the patient begins to inhale is that the patient's inspiratory flow rate reaches a set absolute or relative inspiratory trigger threshold. This process typically occurs in the early stage of the inspiratory phase 3 and completes the pressure drop according to a preset controlled slope to avoid respiratory asynchrony, patient discomfort, or airway instability caused by sudden pressure changes. In some embodiments, the duration of the entire pressure drop in the pressure release transition RT can be set to any value between 400 and 800 ms.

[0019] Pressure maintenance procedure: The output pressure is maintained at the inspiratory positive airway pressure (IPAP). When the pressure drops to the IPAP level via the pressure release transition (RT), this corresponds to the lowest IPAP level within the entire respiratory cycle (5). After pressure release, the system maintains the output pressure at the low IPAP level, covering the latter part of inspiratory phase 3 and most of expiratory phase 4. By setting this low-pressure maintenance phase, fluctuations and discomfort caused by frequent pressure switching are reduced, and a relatively smooth airflow pathway is provided for the patient's exhalation. Since the airflow drive is established during the inspiratory phase, and the external airway pressure load is significantly reduced, the patient's perceived inspiratory resistance is significantly reduced during this phase, thereby significantly improving subjective comfort and the naturalness of breathing.

[0020] The therapeutic pressure transition (TT) step is a process of restoring from the release pressure of inspiratory positive airway pressure (IPAP) to the therapeutic pressure of expiratory positive airway pressure (EPAP): when the patient's expiration is detected to be nearing its end, the output pressure is smoothly increased from the inspiratory positive airway pressure value to the expiratory positive airway pressure value. The condition for determining that the patient's expiration is nearing its end is that the patient's inspiratory flow rate reaches the set inspiratory trigger absolute threshold or inspiratory trigger relative threshold. This process mainly occurs at the end of expiration, and its design goal is to establish the effective airway support pressure required for the next cycle in advance without increasing the expiratory burden. When expiration is nearing its end and the system determines that the next inspiratory cycle is about to begin, the pressure is smoothly increased from inspiratory positive airway pressure (IPAP) to expiratory positive airway pressure (EPAP). A sufficient upper airway support pressure base is established before the next inspiration begins, which can effectively open the airway, prevent airway collapse, reduce the occurrence of OSA events, and effectively ensure treatment. The pressure increase rate during this process is controlled to avoid excessively rapid pressure rise that would cause the patient to experience significant pressure perception, thereby affecting ventilatory comfort. In some implementations, the duration of the therapeutic pressure transition (TT) process can be set to any value between 800 and 1500 ms.

[0021] In this new ventilation mode, the expiratory positive airway pressure (EPAP) is greater than the inspiratory positive airway pressure (IPAP) within a single respiratory cycle (5). Specifically, the higher expiratory positive airway pressure (EPAP) of IR-PAP is used at the end of the expiratory phase and between the beginning of the inspiratory phase, while the lower inspiratory positive airway pressure (IPAP) is used for the remaining inspiratory phase (3) and most of the expiratory phase (4). The pressure profile generated by this new ventilation mode differs from previous conventional ventilation modes.

[0022] This embodiment employs a staged pressure modulation strategy within a complete respiratory cycle (5). When the system detects the patient initiating inspiration, the output pressure decreases from the therapeutic expiratory positive airway pressure (EPAP) to the release pressure inspiratory positive airway pressure (IPAP). In this embodiment, the start of inspiration triggering is defined as the moment when the patient's inspiratory flow rate reaches a preset inspiratory triggering threshold. This inspiratory triggering threshold can be set to any value between 1.5 L / min and 8 L / min; alternatively, it can be set to any percentage between 10% and 40% of the previous inspiratory flow rate peak value. The previous inspiratory flow rate peak value can be determined based on the flow rate peak value of the previous inspiratory cycle, or it can be determined based on the average of multiple previous inspiratory cycle flow rate peak values, to improve the stability and anti-interference capability of the triggering determination.

[0023] During at least a portion of the inspiratory phase and most of the expiratory phase, the system outputs inspiratory positive airway pressure (IPAP) at the pressure release level; while between the end of expiration and the beginning of the next inspiratory phase, the pressure returns to the therapeutic positive airway pressure (EPAP). The end of expiration is defined in this application as the starting point for triggering the therapeutic pressure transition (TT) process. In some embodiments, when the patient's flow rate reaches a preset threshold, it is determined that the end of expiration has begun and the therapeutic pressure transition (TT) process is initiated. The preset threshold can be any value between 2 L / min and 5 L / min, depending on clinical conditions; alternatively, the preset threshold can be set as any percentage between 30% and 85% of the peak expiratory flow rate within the patient's current respiratory cycle.

[0024] Under the aforementioned pressure configuration, the expiratory positive airway pressure (EPAP) is higher than the inspiratory positive airway pressure (IPAP), thus creating a phase-reconfiguration ventilation mode characterized by therapeutic pressure as the baseline and inspiratory decompression. This mode can maintain therapeutic pressure support at the end of expiration and during key upper airway phases while reducing pressure loads related to inspiration and most of the expiratory phases, thereby balancing therapeutic effectiveness and patient comfort.

[0025] The conversion between expiratory positive airway pressure (EPAP) and inspiratory positive airway pressure (IPAP) is achieved through the coordinated control of two phase transition processes: pressure release transition (RT) and therapeutic pressure transition (TT). The IR-PAP of this application optimizes comfort and respiratory compliance during the inspiratory phase while maintaining sufficient airway expansion pressure, thus achieving a dynamic balance between the effectiveness of pressure therapy and subjective tolerance.

[0026] In the initial inspiratory phase, this embodiment also employs a segmented descent control strategy to optimize inspiratory comfort while ensuring airway stability. This process is divided into two consecutive phases, gradually reducing the pressure from expiratory positive airway pressure (EPAP) to the target inspiratory positive airway pressure (IPAP): the first phase of descent is initiated immediately upon detecting the start of inspiration based on a flow-triggered criterion, completing the initial pressure release; the second phase of descent is initiated after the inspiratory flow rate is detected to have reached its peak, completing the remaining pressure release and ultimately stabilizing the pressure at the IPAP level. This design retains a certain amount of airway support pressure during the initial inspiratory build-up phase, releasing pressure further after sufficient inspiratory flow has been established, thus balancing airway opening stability and inspiratory compliance.

[0027] In this embodiment, the segmented descent control is set in stages according to the principle of adjusting the pressure amplitude in segments with the treatment baseline pressure: the higher the treatment pressure, the greater the allowable release amplitude; when the treatment pressure is low, the release amplitude is limited to avoid insufficient airway support. In this embodiment, only the expiratory positive airway pressure (EPAP) is set, and the segmented descent amplitude and inspiratory positive airway pressure (IPAP) are determined according to different treatment pressure levels, based on the following conditions: To ensure the basic effectiveness and safety margin of ventilation therapy, the expiratory positive airway pressure (EPAP) value shall not exceed a preset maximum pressure limit, which is set as follows: .

[0028] Positive expiratory airway pressure for therapeutic stress First descend Then it dropped again. Total decline ; Positive expiratory airway pressure for therapeutic stress First descend Then it dropped again. Total decline ; Positive expiratory airway pressure for therapeutic stress First descend Then it dropped again. Total decline ; Positive expiratory airway pressure for therapeutic stress First descend Then it dropped again. Total decline .

[0029] Special attention should be paid to the positive expiratory airway pressure during treatment. Since the positive pressure of the inspiratory airway should not be lower than a preset minimum pressure limit, the lower limit is set as follows: The ventilation mode will switch to CPAP mode, which is not within the scope of IR-PAP disclosed in this application. This lower pressure limit is used to prevent excessive decompression during pressure release, thereby avoiding an increased risk of upper airway collapse or decreased ventilation stability. That is, in this embodiment, the expiratory positive airway pressure (EPAP) setting pressure can be... Adjustments can be made within a certain range to meet the individualized treatment needs of different patients.

[0030] In addition to the methods mentioned above, you can also directly set the expiratory positive airway pressure (EPAP) and inspiratory positive airway pressure (IPAP), or set the inspiratory positive airway pressure (IPAP) and let the internal control mechanism determine the expiratory positive airway pressure (EPAP).

[0031] By employing a segmented pressure release transition RT control strategy and a lower pressure limit protection mechanism, the IR-PAP mode can achieve fine-tuning of the pressure release process during the inspiratory phase while ensuring treatment effectiveness, taking into account both patient comfort and ventilation safety.

[0032] During the two transition phases of pressure release (RT) and treatment pressure transition (TT), to avoid airflow disturbances or human-machine asynchrony caused by sudden pressure changes, the pressure change process can be trajectory-planned using a continuous, differentiable smooth function. Specifically, the pressure transition curve can be smoothly controlled based on a mathematical model of a first-order low-pass filter model or an exponential function model.

[0033] The first-order low-pass filter model is expressed as follows: ,in Indicates time t The output pressure, This represents the target pressure value at the end of the transition. The magnitude of pressure change is represented by the formula. definition, This indicates the pressure value at the start of the transition. and The dimensions are those commonly used in this field. Alternatively, the SI unit Pa can be used. (Exponential term) It is a dimensionless quantity. The time constant is used. The model is passed through... Control the response speed, The smaller the size, the faster the transition; The larger the value, the smoother the transition, and the longer the time constant. It is recommended that the value be any value between 150 and 500ms.

[0034] The exponential function model is expressed as follows: The meaning is the same as above; in this model... It is recommended that the value be between 100 and 700 ms. This model can make the output pressure gradually approach the target pressure according to an exponential law, thereby achieving a more natural and smooth transition.

[0035] The above methods can all ensure that the pressure changes continuously during the transition period, avoiding the shock effect caused by a step response, while using the time constant The parametric design enables fine-tuning of the rise / fall rate and curve morphology. Besides the two models mentioned above, other models such as power function models or parabolic function models can also be used to achieve smooth pressure changes during the transition period. By appropriately selecting or combining these smoothing functions, the pressure release transition (RT) and treatment pressure transition (TT) processes can be made smoother and more natural while ensuring airway support stability, thereby further improving overall ventilatory comfort and respiratory synchrony. The IR-PAP mode of this application has been implemented in the applicant's home ventilator series and has achieved good clinical results in human clinical trials.

[0036] Based on the same inventive concept, this application further discloses a ventilator embodiment, including a pressure generation unit, a sensing unit, a human-machine interaction unit, and a processing unit. The processing unit is signal-connected to the pressure generation unit, the sensing unit, and the human-machine interaction unit, and includes a processor and a memory. The processor is configured to execute instructions stored in the memory, and to implement the aforementioned IR-PAP ventilation mode control method based on the flow signal monitored in real time by the sensing unit and the user's settings for the expiratory positive airway pressure and / or inspiratory positive airway pressure received by the human-machine interaction unit. The pressure generation unit generates an airflow to be delivered to the patient's airway.

[0037] In this embodiment, the pressure generation unit is implemented using a turbine 10 to provide positive air pressure to the patient's airway; the sensing unit is implemented using a sensor 20 to detect the pressure and flow values ​​at the patient's end; the processing unit is implemented using a module composed of a microcontroller 80; and the human-machine interaction unit is implemented using a host computer touchscreen 90 to achieve human-machine interactive adjustment of the IR-PAP ventilation mode setting pressure. The entire ventilator embodiment also includes a humidifier 30, a breathing tubing 40, a mask 70, and an exhaust port 100. The humidifier 30 humidifies the ventilator's output gas to improve patient comfort; the breathing tubing 40 works with the mask 70 to deliver the humidified gas to the patient; when the patient exhales, excess gas is discharged through the exhaust port 100. The microcontroller 80 is electrically connected to the sensor 20 and the turbine 10, and can adaptively adjust the speed of the turbine 10 based on the actual patient pressure signal detected by the sensor 20 to adjust the treatment pressure applied to the patient. The IR-PAP ventilation mode algorithm is deployed in the module composed of the microcontroller 80.

[0038] During the patient's inhalation, the lungs 60 actively expand, and air is drawn into the lungs through the respiratory airway 50; during the patient's exhalation, the lungs 60 contract, and the air in the lungs is exhaled through the respiratory airway 50 and discharged through the exhaust port 100. Throughout the entire respiratory cycle 5, the turbine 10 continuously provides positive pressure airflow of different pressure levels to the patient through the breathing tubing 40 and the mask 70 to achieve pressure support for the patient's breathing process.

[0039] In the description of this application, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0040] The above description is only a preferred embodiment of the present solution, but the scope of protection claimed by the present solution is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and inventive concept of this application, should be included within the scope of protection of this application.

Claims

1. A ventilation mode control method, applied to a ventilator, characterized in that, Includes the following steps: Pressure release transition step: When the patient begins to inhale, the output pressure is controlled to smoothly decrease from the expiratory positive airway pressure to the inspiratory positive airway pressure; the condition for determining when the patient begins to inhale is that the patient's inspiratory flow rate reaches the set inspiratory trigger absolute threshold or inspiratory trigger relative threshold. Pressure maintenance procedure: Control the output pressure to maintain the positive inspiratory airway pressure; Treatment pressure transition step: When it is detected that the patient's exhalation is about to end, the output pressure is controlled to smoothly rise from the positive inspiratory airway pressure to the positive expiratory airway pressure; the condition for determining that the patient's exhalation is about to end is that the patient's inspiratory flow rate reaches the set inspiratory trigger absolute threshold or inspiratory trigger relative threshold. Within a single respiratory cycle, the positive airway pressure during exhalation is greater than the positive airway pressure during inhalation.

2. The ventilation mode control method according to claim 1, characterized in that: The smooth descent employs a two-stage descent: the first stage begins when the patient is detected to begin inhaling, and the second stage begins when the inspiratory flow rate is detected to have reached its peak.

3. The ventilation mode control method according to claim 1, characterized in that: The absolute threshold for inhalation triggering is set in the range of 1.5L / min to 8L / min.

4. The ventilation mode control method according to claim 1, characterized in that: The relative threshold setting range for the inhalation trigger is 10% to 40% of the peak inhalation flow rate of the previous inhalation.

5. The ventilation mode control method according to claim 1, characterized in that: The positive pressure value of the inspiratory airway is not lower than the preset minimum pressure limit, which is set to 5 cmH2O, and the positive pressure value of the expiratory airway is not higher than the preset maximum pressure limit, which is set to 20 cmH2O.

6. The ventilation mode control method according to claim 1, characterized in that: The absolute threshold for triggering exhalation is set in the range of 2L / min to 5L / min.

7. The ventilation mode control method according to claim 1, characterized in that: The relative threshold setting range for exhalation trigger is 30% to 85% of the current peak expiratory flow rate.

8. The ventilation mode control method according to claim 1, characterized in that: The duration of the pressure release transition step is 400–800 ms; the duration of the treatment pressure transition step is 800–1500 ms.

9. The ventilation mode control method according to claim 1, characterized in that: The smooth descent or smooth ascent is achieved using a first-order low-pass filter model or an exponential function model.

10. A ventilator, characterized in that: The device includes a pressure generation unit, a sensing unit, a human-machine interface unit, and a processing unit. The processing unit is signal-connected to the pressure generation unit, the sensing unit, and the human-machine interface unit. It includes a processor and a memory. The processor is configured to execute instructions stored in the memory to implement the ventilation mode control method as described in any one of claims 1 to 9, based on the flow signal monitored in real time by the sensing unit and the user's settings for the expiratory positive airway pressure and / or the inspiratory positive airway pressure received by the human-machine interface unit, thereby generating an airflow to be delivered to the patient's airway using the pressure generation unit.

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