Nasal cpap acoustic monitoring system and method based on dual fiber differential processing

Abstract

This application provides a transnasal CPAP acoustic monitoring system and method based on dual-fiber differential processing. The system includes a transnasal CPAP interface, an air supply line, a first fiber optic acoustic sensing unit, a second fiber optic acoustic sensing unit, a fiber optic demodulation module, and a differential acoustic processing module. The first fiber optic acoustic sensing unit is located in the high-response region of the transnasal CPAP interface to acquire a mixed signal containing the patient's breath sounds and background noise caused by continuous positive pressure airflow. The second fiber optic acoustic sensing unit is located in the low-response region of the air supply line or the transnasal CPAP interface to acquire a reference signal with background noise as the main component. The differential acoustic processing module performs synchronous demodulation, amplitude normalization, phase compensation, differential noise reduction, adaptive filtering, and spectrum analysis on the two fiber optic signals to stably extract real breath sounds under continuous positive pressure and high flow environment.

Description

Technical Field

[0001] This application relates to the field of respiratory monitoring and treatment equipment technology, and in particular to a transnasal CPAP acoustic monitoring system and method based on dual-fiber differential processing. Background Technology

[0002] Continuous positive airway pressure (CPAP) ventilation is an important treatment for conditions such as obstructive sleep apnea syndrome, chronic obstructive pulmonary disease with respiratory failure, perioperative respiratory support, and neonatal respiratory distress syndrome. During treatment, the CPAP unit continuously delivers horizontal positive pressure airflow to the patient's nose through the air supply tubing and mask interface, maintaining upper airway patency, preventing airway collapse, and improving ventilation.

[0003] Currently used CPAP systems primarily monitor parameters such as delivery pressure, leakage, respiratory rate, tidal volume, and blood oxygen saturation. While these parameters reflect the basic status of ventilation therapy, they are severely inadequate in reflecting the patient's true airway acoustic status. In particular, existing CPAP systems cannot directly reflect the patient's true breath sounds within the airway, including changes in snoring and wheezing, characteristic acoustic changes preceding airway narrowing and apnea, and characteristic airflow sounds caused by minute leaks at the mask edge. These acoustic characteristics are of significant clinical value in assessing the effectiveness of CPAP therapy, providing early warning of airway abnormalities, and optimizing treatment pressure parameters.

[0004] In actual CPAP (Continuous Positive Pressure) ventilation, when the CPAP unit drives the airflow at a certain velocity through the air supply line into the mask, it generates CPAP background noise, including pipe flow noise, turbulence noise, and mask resonance noise, as it passes through the pipes, air inlets, airflow guides, and mask cavity. Simultaneously, the breathing sounds generated by the patient's airflow through the airway, nasal cavity, and oral cavity are superimposed on the aforementioned CPAP background noise within the mask cavity, making it impossible to stably and accurately extract the patient's true breathing sounds in a continuous positive pressure ventilation environment. Summary of the Invention

[0005] To address the aforementioned issues, one objective of this application is to provide a nasal CPAP breath sound monitoring system based on dual-fiber differential acoustics, thereby solving the problem that existing CPAP monitoring schemes cannot stably extract the patient's true breath sound signals in environments with strong background noise caused by continuous positive airflow. A second objective of this application is to provide a nasal continuous positive airway pressure (CPAP) breath sound monitoring method based on dual-fiber differential acoustics, enabling real-time identification and alarm of abnormal respiratory events such as apnea, hypoventilation, interface leakage, and airway obstruction during CPAP treatment.

[0006] To achieve one of the objectives, in a first aspect, this application provides a transnasal CPAP breath sound monitoring system based on dual-fiber differential acoustics, the system comprising: The nasal CPAP interface is configured to seal with the patient's nose and form a positive pressure ventilation chamber; The air supply line, connected to the nasal CPAP interface, is configured to supply a continuous positive pressure airflow into the positive pressure ventilation chamber; The first fiber optic acoustic sensing unit is arranged in the positive pressure ventilation cavity to collect a mixed signal containing the patient's breath sounds and the background noise caused by the continuous positive pressure airflow. The second fiber optic acoustic sensing unit is arranged on the air supply pipeline so that its main acoustic coupling is with the background noise caused by the continuous positive pressure airflow, and is used to collect a reference signal with the background noise as the main component. The fiber optic demodulation module is connected to the first fiber optic acoustic sensing unit and the second fiber optic acoustic sensing unit respectively, and is configured to convert the mixed signal and the reference signal from optical signals into first electrical signals and second electrical signals. The differential acoustic processing module, which is communicatively connected to the fiber optic demodulation module, is configured to perform differential noise reduction processing between the first electrical signal and the second electrical signal to eliminate the background noise from the mixed signal and obtain the patient's true breath sound signal.

[0007] Optionally, both the first fiber optic acoustic sensing unit and the second fiber optic acoustic sensing unit include at least one of a fiber Bragg grating structure, a Fabry-Perot cavity structure, a Mach-Zehnder interferometer structure, and a micro / nano fiber optic structure.

[0008] Optionally, the first fiber optic acoustic sensing unit is disposed on the inner wall of the cavity of the transnasal CPAP interface, and is arranged in a ring or in a partial manner corresponding to the area around the patient's nasal ala and the nasal cavity outlet.

[0009] Optionally, the nasal CPAP interface includes a nasal CPAP mask, which is provided with an air inlet and an exhaust port, and the air inlet is connected to the air supply line.

[0010] Optionally, the second fiber optic acoustic sensing unit is arranged at least at one end of the air supply line near the air inlet of the nasal CPAP interface and at one of the line accessories, such that the second fiber optic acoustic sensing unit is located on the path of the continuous positive pressure airflow and away from the positive pressure ventilation cavity so as not to directly contact the patient's respiratory airflow.

[0011] Optionally, the differential acoustic processing module includes at least one of an adaptive filtering unit, a phase compensation unit, an amplitude normalization unit, a spectrum difference unit, and a short-time Fourier transform unit; The differential noise reduction process includes at least one of the following: adaptive filtering, phase compensation, amplitude normalization, spectral subtraction, and short-time Fourier transform processing of the first and second electrical signals.

[0012] Optionally, the first fiber optic acoustic sensing unit and / or the second fiber optic acoustic sensing unit are respectively encapsulated and fixed at corresponding positions by a medical silicone layer, a polymer elastic layer, or an elastic film.

[0013] Optionally, the system further includes: The breath sound analysis module, which is communicatively connected to the differential acoustic processing module, is configured to identify the respiratory state and abnormal respiratory events based on the patient's actual breath sound signals. The respiratory state includes at least one of snoring, wheezing, and respiratory rate; The abnormal breathing events include at least one of the following: apnea event, hypoventilation event, interface leakage event, and airway obstruction event.

[0014] Optionally, the system further includes: The display and alarm module is communicatively connected to the breathing sound analysis module and is configured to display the breathing status and issue an alarm based on the identified abnormal breathing events.

[0015] To achieve the second objective, in a second aspect, this application provides a transnasal CPAP breath sound monitoring method based on dual-fiber differential acoustics, applied to the system provided in the first aspect of this application, the method comprising: A mixed signal comprising the patient's breath sounds and the background noise caused by the continuous positive pressure airflow is acquired through a first fiber optic acoustic sensing unit; and a reference signal with the background noise as the main component is acquired through a second fiber optic acoustic sensing unit. The mixed signal and the reference signal are converted from optical signals into a first electrical signal and a second electrical signal, respectively, by an optical fiber demodulation module. Using the differential acoustic processing module, the second electrical signal is used as a noise reference to perform differential noise reduction processing on the first electrical signal, thereby eliminating the background noise from the mixed signal to obtain the patient's true breath sound signal; The respiratory sound analysis module identifies the patient's respiratory status and abnormal respiratory events based on the patient's actual respiratory sound signals. The breathing status is displayed through the display and alarm module, and an alarm is issued based on the identified abnormal breathing events.

[0016] Compared with the prior art, this application has the following advantages: The system provided in this application employs a differential dual-channel structure composed of dual fiber optic sensing units. The first fiber optic acoustic sensing unit is arranged within the positive pressure ventilation chamber to simultaneously acquire respiratory sound signals and background noise signals. The second fiber optic acoustic sensing unit is arranged on the air supply line to primarily acquire background noise reference signals. This allows the system to stably extract the patient's true respiratory sound signals through differential noise reduction processing in environments with strong background noise caused by continuous positive pressure airflow, solving the fundamental difficulty in existing solutions where signals and noise coexist in the same physical space and cannot be effectively separated. Furthermore, by spatially separating the signal channel and the noise channel, the reverse acoustic impedance gradient formed by continuous positive pressure airflow significantly attenuates the patient's respiratory sound waves before they propagate back to the second sensing unit. This ensures that the reference signal acquired by the second sensing unit is dominated by background noise, achieving physical isolation of the respiratory sound signal by the reference channel. The structure is simple and highly reliable. In addition, the fiber optic acoustic sensing unit is small in size, flexible, and inherently resistant to electromagnetic interference, making it easy to integrate into the nasal CPAP interface and air supply line.

[0017] The method described above has the same advantages over existing technologies as the system described above, and will not be repeated here. Attached Figure Description

[0018] To more clearly illustrate the technical solution of this application, the drawings used in the description of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of a transnasal CPAP respiratory sound monitoring system based on dual-fiber differential acoustics according to an embodiment of this application; Figure 2 This is an electrical connection diagram of a transnasal CPAP respiratory sound monitoring system based on dual-fiber differential acoustics according to an embodiment of this application; Figure 3 This is a flowchart of the steps of the transnasal CPAP respiratory sound monitoring method based on dual-fiber differential acoustics according to an embodiment of this application.

[0020] Explanation of reference numerals in the attached figures: 1. Face mask; 11. Air inlet; 12. Exhaust port; 13. Headband; 2. Air supply line; 3. First fiber optic acoustic sensor unit; 4. Second fiber optic acoustic sensor unit; 5. Central monitoring station. Detailed Implementation

[0021] The technical solutions of 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, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] It should be noted that before describing the technical solution of this application in detail, the current state of the prior art and its limitations will be further explained in order to facilitate understanding of the improvements made by the technical solution of this application compared with the prior art.

[0023] In CPAP ventilation therapy, real-time monitoring of the patient's breath sounds has significant clinical value. Information contained in the breath sounds, such as changes in snoring intensity, wheezing frequency shifts, acoustic characteristic changes before and after apnea, and high-frequency acoustic characteristics of air leakage at the edge of mask 1, can provide crucial information for clinicians to assess the effectiveness of CPAP treatment, optimize treatment pressure levels, and provide early warning of potential airway hazards. During operation, the CPAP device's built-in motor and fan continuously drive airflow through the air supply line 2 to the mask 1 at a certain pressure. As the airflow passes through bends in the line, abrupt changes in the cross-section of the mask 1's air inlet, the cavity expansion section, and the exhaust port 12, CPAP noise, including airflow turbulence noise, line flow noise, and mask 1 resonance noise, is inevitably generated. This CPAP noise is the inherent background noise that the system itself inevitably generates to maintain a continuous positive pressure ventilation environment. This background noise and the patient's actual breath sounds superimpose in both time and frequency, making it difficult to separate them using simple bandpass filtering in both the time and frequency domains, thus interfering with breath sound recognition.

[0024] In related technologies, the most common approach is to place a single electronic microphone in the CPAP mask 1 or the air supply line 2 to collect respiratory sounds. However, this single microphone simultaneously receives the patient's respiratory sounds and background noise, both originating from the same sound source area, thus making it impossible to effectively separate the true respiratory sound components from the microphone's output signal. Another approach is to use a microphone placed outside the mask 1 to collect ambient noise in the ward (such as conversations, equipment operation sounds, etc.) to help identify respiratory sound signals. However, external ambient noise is not the background noise generated by the CPAP system itself, and the external microphone cannot obtain an effective reference signal for the background noise, still failing to eliminate the interference of airflow turbulence noise, pipeline flow noise, and mask 1 resonance noise on the true respiratory sound signal.

[0025] Among related technologies, fiber optic acoustic sensors have advantages such as small size, flexibility, strong resistance to electromagnetic interference, and intrinsic safety, making them suitable for acoustic signal acquisition in medical-grade wearable structures. However, if a single fiber optic acoustic sensor is placed inside the cavity of the CPAP mask 1, the sensor will simultaneously sense both the patient's breath sound signal and the background noise signal. These two types of signals have significant overlap in their spectra and both originate from inside the cavity of the mask 1, making them impossible to separate using conventional frequency domain filtering or threshold detection. Therefore, the single fiber optic sensor solution still cannot achieve the core objective of stably extracting realistic breath sounds in a continuous positive pressure ventilation environment.

[0026] Based on the above analysis, there is an urgent need for a respiratory sound monitoring system that can be applied in a nasal CPAP continuous positive pressure ventilation environment, capable of stably extracting the patient's real respiratory sound signal under strong background noise conditions, and realizing real-time identification and alarm of respiratory status and abnormal respiratory events based on the real respiratory sound signal.

[0027] In order to overcome or at least partially solve the above problems, one or more embodiments of this application will be further described below with reference to specific embodiments.

[0028] Reference Figure 1 and Figure 2 As shown, Figure 1 and Figure 2 The diagrams show the structural composition and electrical connection of a nasal continuous positive airway pressure (CPAP) respiratory sound monitoring system based on dual-fiber differential acoustics, as provided in this embodiment. The system includes a nasal CPAP interface, an air supply line 2, a first fiber optic acoustic sensing unit 3, a second fiber optic acoustic sensing unit 4, a fiber optic demodulation module, and a differential acoustic processing module. Optionally, the system further includes a respiratory sound analysis module and a display and alarm module.

[0029] The nasal CPAP interface is configured to seal tightly against the patient's nose, forming a relatively closed positive pressure ventilation chamber inside. One end of the air supply line 2 is connected to the CPAP main unit, and the other end is connected to the air inlet of the nasal CPAP interface, delivering the continuous positive pressure airflow generated by the CPAP main unit to the positive pressure ventilation chamber through the air supply line 2 to maintain the patient's airway open. The nasal CPAP interface is also equipped with an exhaust port 12 to expel the patient's exhaled air and excess airflow to the external environment.

[0030] As an optional implementation, the nasal CPAP interface can take the form of a nasal CPAP mask 1. The nasal CPAP mask 1 (hereinafter referred to as mask 1) is provided with an air inlet 11 and an exhaust port 12. The air inlet 11 is typically a circular or elliptical pipe connector, and the air supply line 2 extending from the CPAP host is sleeved or snapped onto it. Exemplarily, the mask 1 can be made of medical-grade silicone or thermoplastic elastomer material and is fixed to the patient's face by a headband 13 or an adhesive area. The mask 1 can also typically include sealing components or other structures. A positive pressure ventilation cavity is formed inside the mask 1, and a first fiber optic acoustic sensing unit 3 is arranged on the inner wall of this positive pressure ventilation cavity, corresponding to the area of ​​the nasal cavity outlet. The air supply line 2 can be a section of a CPAP pipeline, with one end connected to the CPAP host and the other end communicating with the inside of the mask 1 through the air inlet 11.

[0031] The first fiber optic acoustic sensing unit 3 is disposed within the positive pressure ventilation chamber, for example, on the inner wall of the chamber near the patient's nasal cavity outlet. The first fiber optic acoustic sensing unit 3 receives the sound pressure fluctuations of the respiratory sounds generated by the patient's inhalation and exhalation through the nasal cavity, thereby outputting a respiratory sound signal. Simultaneously, it receives the background noise sound pressure fluctuations generated within the chamber by the positive pressure airflow continuously supplied by the CPAP host through the air supply line 2. Therefore, the mixed signal output by the first fiber optic acoustic sensing unit 3 includes both the patient's respiratory sound signal and the background noise signal.

[0032] The second fiber optic acoustic sensor unit 4 is arranged on the air supply line 2, in the airflow path between the CPAP main unit and the mask 1 cavity. It collects background noise including sound waves transmitted by the motor vibration in the CPAP main unit through the airflow, turbulence noise generated by the airflow on the line wall, and acoustic resonance noise of the line and mask 1 itself. It should be noted that the second fiber optic acoustic sensor unit 4 is spatially positioned to avoid the air outlet of the patient's nasal cavity and is located on the CPAP airflow path, spatially separated from the first fiber optic acoustic sensor unit 3. Since the continuous positive pressure airflow is a continuous positive pressure supply from the CPAP main unit to the mask 1, a unidirectional positive pressure gradient is formed from the machine end, the line, the mask 1, and the patient's airway. Therefore, the second fiber optic acoustic sensing unit 4 is positioned in the CPAP airflow path, allowing the background noise from the continuous positive pressure airflow to be directly coupled to the second fiber optic acoustic sensing unit 4 along the airflow direction. The airflow noise, motor vibration noise, and pipeline resonance noise of the CPAP machine do not undergo significant directional attenuation along the airflow direction in the pipeline, and thus can be collected by the second fiber optic acoustic sensing unit 4. However, for the patient's exhaled airflow to reach the location of the second fiber optic acoustic sensing unit 4, it must first pass through the mask 1 cavity, and then enter the air supply pipeline 2 through the air inlet 11 against the direction of the continuous positive pressure airflow. Only a very small amount of acoustic energy from the reverse-propagating breath sound can penetrate into the air supply pipeline 2 area. Therefore, the reverse acoustic impedance gradient formed by the continuous positive pressure airflow can be used to physically attenuate the patient's breath sound to a negligible level before it reaches the second fiber optic acoustic sensing unit 4. Consequently, the sound level of the patient's breath sound at the second sensing unit is much lower than the sound level of the background noise at the second fiber optic acoustic sensing unit 4. Therefore, in the output signal of the second fiber acoustic sensing unit 4, the breathing sound component is extremely weak compared to the CPAP noise component, and can even be considered negligible. This makes its reference signal mainly composed of background noise, which can serve as a reliable reference signal to characterize the background noise characteristics, thus initially realizing the physical isolation of the breathing sound signal by the reference channel.

[0033] It should also be noted that although both fiber optic acoustic sensing units receive background noise from the same noise source group, the spectrum, amplitude, and phase of the background noise are not exactly the same at the two locations because they are located at different acoustic nodes in the airflow path, but they are highly correlated. Differential noise cancellation can be achieved between the two highly correlated noise components using adaptive filtering techniques.

[0034] Specifically, differential noise reduction is performed using a differential acoustic processing module. First, a fiber optic demodulation module converts the acoustic-optical changes collected by the first fiber optic acoustic sensing unit 3 and the second fiber optic acoustic sensing unit 4 into electrical signals usable by the subsequent differential acoustic processing module. The fiber optic demodulation module typically includes an optical transmitting unit, an optical receiving unit, and a photoelectric conversion unit. The optical transmitting unit generates probe light that is emitted to the two fiber optic acoustic sensing units, and the optical receiving unit receives the optical signals returned by the two fiber optic acoustic sensing units, which have been altered by sound pressure vibration. The photoelectric conversion unit converts the optical signals transmitted by the optical receiving unit into corresponding electrical signals, and works with an analog-to-digital converter to complete photoelectric conversion and digitization.

[0035] It is understood that the demodulation principle employed by the fiber optic demodulation module depends on the type of fiber optic sensing structure used by the first fiber optic acoustic sensing unit 3 and the second fiber optic acoustic sensing unit 4, and this application does not limit this. As an improvement to this embodiment, the first fiber optic acoustic sensing unit 3 and the second fiber optic acoustic sensing unit 4 adopt the same type of fiber optic sensing structure, so the same fiber optic demodulation module can be used to synchronously demodulate the two fiber optic acoustic sensing units. Of course, the first fiber optic acoustic sensing unit 3 and the second fiber optic acoustic sensing unit 4 can also adopt different types of fiber optic sensing structures, and be configured with corresponding fiber optic demodulation modules separately.

[0036] Then, the differential acoustic processing module uses the second electrical signal corresponding to the reference signal as the reference input of the adaptive filter and the first electrical signal corresponding to the mixed signal as the main input to perform differential noise reduction processing on the reference signal and the mixed signal. This includes, but is not limited to, adaptive filtering, phase compensation, amplitude normalization, spectral difference, short-time Fourier transform, and time-frequency domain feature extraction, in order to remove background noise and extract real breath sounds.

[0037] Thus, this application employs a differential dual-channel structure composed of dual fiber optic sensing units. The first fiber optic acoustic sensing unit 3 is arranged within the positive pressure ventilation chamber to simultaneously acquire respiratory sound signals and background noise signals. The second fiber optic acoustic sensing unit 4 is arranged on the air supply line 2, primarily acquiring the background noise reference signal. This allows the application to stably extract the patient's true respiratory sound signal through differential noise reduction processing in an environment with strong background noise caused by continuous positive pressure airflow, solving the fundamental difficulty in existing solutions where signal and noise coexist in the same physical space and cannot be effectively separated. Furthermore, by spatially separating the signal channel and the noise channel, the reverse acoustic impedance gradient formed by continuous positive pressure airflow significantly attenuates the patient's respiratory sound waves before they propagate back to the second sensing unit. This ensures that the reference signal acquired by the second sensing unit is dominated by background noise, achieving physical isolation of the respiratory sound signal by the reference channel. The structure is simple and highly reliable. In addition, the fiber optic acoustic sensing unit is small in size, flexible and bendable, and inherently resistant to electromagnetic interference, making it easy to integrate into the nasal CPAP interface and air supply line 2. It also supports simultaneous monitoring of respiratory sounds in strong electromagnetic environments such as magnetic resonance imaging.

[0038] Optionally, the differential acoustic processing module includes at least one of an adaptive filtering unit, a phase compensation unit, an amplitude normalization unit, a spectral difference unit, and a short-time Fourier transform unit. Differential noise reduction processing includes processing steps such as adaptive filtering, phase compensation, amplitude normalization, spectral subtraction, and short-time Fourier transform. These processing steps can be used individually or in any combination depending on the specific application scenario, without a specific execution order. The adaptive filtering algorithm includes, but is not limited to, the least mean square algorithm, the recursive least squares algorithm, or the normalized least mean square algorithm.

[0039] The following provides a typical workflow for differential noise reduction, which includes the following five steps: (1) Bandpass filtering preprocessing: Bandpass filtering is performed on the first and second electrical signals respectively to remove non-correlated information that is obviously outside the breathing audio band in the two channels, thereby reducing the computational burden of subsequent processing.

[0040] (2) Amplitude normalization: The amplitude of the two preprocessed signals is normalized. Due to the different positions of the two fiber optic acoustic sensing units, the gains of the two channels are not matched. By normalizing the amplitude with the root mean square value of each signal as a reference, the above-mentioned channel gain mismatch can be compensated, so that the average amplitude of the background noise in the two signals is on the same order of magnitude, ensuring the stable convergence of the subsequent adaptive filtering algorithm.

[0041] (3) Phase compensation processing: Perform cross-correlation calculation on the two normalized signals, obtain the relative phase delay of the background noise components in the two signals, and perform corresponding time delay compensation on one of the signals to align the background noise components in the two signals on the time axis.

[0042] (4) Adaptive filtering: The phase-aligned second electrical signal is used as the reference input of the adaptive filter, and the first electrical signal is used as the main input. The normalized least mean square adaptive filtering algorithm is adopted so that the filter output gradually approximates the background noise component in the main input. The error signal obtained by subtracting the background noise component from the main input is the estimated value of the patient's true breath sound signal.

[0043] (5) Short-time Fourier Transform-Spectral Subtraction Processing: A short-time Fourier transform is performed on the patient's actual breath sound signal to convert the time-domain signal to the time-spectral domain. Spectral subtraction is then performed on the time-spectrum to further suppress the non-steady-state residual noise that the adaptive filtering could not completely eliminate.

[0044] The aforementioned adaptive filtering algorithm, phase compensation processing, amplitude normalization processing, spectrum subtraction processing, and short-time Fourier transform processing are all mature technologies in the field of digital signal processing. Those skilled in the art can select appropriate algorithms or combinations thereof according to actual application scenarios to implement the differential noise reduction function of this application. Therefore, this application will not elaborate on the specific principles of each known technology.

[0045] Thus, the differential acoustic processing module reduces the background noise component represented in the mixed signal by using adaptive filtering, amplitude normalization, phase compensation, and spectral differentiation based on the correlation between the two signals. This enables the system to effectively extract real respiratory sound signals with clinical analysis value even under CPAP conditions with extremely low signal-to-noise ratios, making it suitable for CPAP treatment, sleep monitoring, ICU, and perioperative respiratory monitoring scenarios.

[0046] Preferably, the first fiber optic acoustic sensing unit 3 is arranged in the high-response area of ​​the mask 1 for respiratory sounds. It is preferably positioned corresponding to the periphery of the patient's nasal ala, the nasal cavity outlet, or the arc-shaped high-vibration area of ​​the inner wall of the mask 1. As a further explanation of this embodiment, the first fiber optic acoustic sensing unit 3 can be arranged in a ring along the periphery of the nasal cavity outlet on the inner wall of the cavity. Alternatively, the first fiber optic acoustic sensing unit 3 can be arranged in a localized area on the inner wall of the cavity corresponding to one or both nasal cavity outlets. Therefore, the first fiber optic acoustic sensing unit 3 is located close to the patient's nasal cavity outlet, and the sound propagation distance from the sound source to the first fiber optic acoustic sensing unit 3 is extremely short, thus enabling efficient coupling of the patient's respiratory sound signal.

[0047] Preferably, the second fiber optic acoustic sensing unit 4 can be disposed at the far end of the air supply pipeline 2 near the air inlet 11. When the second fiber optic acoustic sensing unit 4 is disposed in the air supply pipeline 2 near the air inlet 11 of the mask 1, it does not directly contact the continuous positive pressure airflow in the positive pressure ventilation cavity, and is located at the entrance of the continuous positive pressure airflow into the mask 1, and can receive the background noise signal that mainly covers the continuous positive pressure airflow noise, pipeline flow noise and mask 1 resonance noise. The second fiber optic acoustic sensing unit 4 can also be disposed on the pipeline accessories of the air supply pipeline 2. The pipeline accessories are functional additional components in the air supply pipeline 2, and typically include at least one of pipeline joints, exhaust components, humidifier connection sections and pre-formed pipeline elbows, which can be highly responsive to positive pressure airflow noise and pipeline flow noise.

[0048] In some optional embodiments, the second fiber optic acoustic sensing unit 4 can also be arranged in the weak respiratory sound response area of ​​the mask 1. For example, it can be located near the airflow guiding area, air inlet 11, exhaust port 12, or tubing connection of the mask 1. The airflow guiding area corresponds to the space inside the nasal CPAP interface located between the air inlet 11 and the positive pressure ventilation chamber, used to guide the continuous positive pressure airflow to turn or divert. In this arrangement, the second fiber optic acoustic sensing unit 4 is at the airflow turning point, where the aerodynamic turbulence noise intensity is greatest and the respiratory airflow is relatively small. The gas distribution chamber is a secondary chamber inside the nasal CPAP interface used to distribute the continuous positive pressure airflow to both nasal cavities of the patient. In this arrangement, the background noise after pressure equalization in the distribution chamber has a balanced frequency domain distribution, providing a noise reference with more complete spectral coverage for differential noise reduction processing. Arranging the second fiber optic acoustic sensing unit 4 near the exhaust port 12 of the mask 1 allows it to specifically sense the local high-frequency aerodynamic noise generated by the exhaust airflow, suitable for targeted reference acquisition of background noise in specific frequency bands.

[0049] Therefore, the second fiber optic acoustic sensing unit 4 and the first fiber optic acoustic sensing unit 3 are spatially arranged to form a differential dual-channel configuration. The signal channel and the reference channel are highly correlated with CPAP noise but differ significantly in their sensitivity to breath sounds. The reference channel is physically isolated from the patient's breath sounds, thus ensuring that the breath sound signal in the reference signal is attenuated to a negligible level. Simultaneously, the background noise sources of both have a short sound propagation distance, ensuring that the background noise in the reference signal has a high signal-to-noise ratio and low propagation distortion, providing a high-quality noise reference for subsequent differential noise reduction processing.

[0050] Due to its small size, flexibility, and inherent resistance to electromagnetic interference, the fiber optic acoustic sensing unit is ideal. Furthermore, the face mask 1, as the most widely used non-invasive interface in CPAP treatment, enjoys good clinical acceptance and mature manufacturing processes. Integrating the fiber optic sensing unit into the face mask 1 facilitates engineering implementation. In some exemplary embodiments, the first fiber optic acoustic sensing unit 3 can be embedded in the inner wall or interlayer of the face mask 1 without affecting its seal, wearing comfort, or original airflow path. Moreover, the fiber diameter of the fiber optic sensing unit is very small, and its encapsulation in the face mask 1 adds almost no volume / weight, minimizing comfort during CPAP treatment. In some exemplary embodiments, the second fiber optic acoustic sensing unit 4 can be embedded in the outer wall of the air supply line 2.

[0051] In specific engineering implementation, the first fiber optic acoustic sensing unit 3 and / or the second fiber optic acoustic sensing unit 4 can be encapsulated with medical-grade encapsulation material and installed at the corresponding position of the transnasal CPAP interface using an appropriate fixing method (such as adhesive fixation). The encapsulation material can be a medical-grade silicone layer, a polymer elastic layer, or an elastic film. In some embodiments, the fiber optic acoustic sensing unit can be directly fixed to the corresponding position after the encapsulation material has been cured. The fiber optic encapsulation layer should be as thin and flexible as possible to ensure acoustic response sensitivity without affecting the sealing and wearing comfort of the mask 1. Exemplarily, the encapsulated fiber optic sensing unit can be fixed to the inner wall of the mask 1 or in the interlayer between the inner and outer walls. When fixed to the inner wall, the fiber optic sensing unit is directly exposed to the acoustic field environment within the positive pressure ventilation cavity, resulting in the highest acoustic coupling efficiency; when fixed in the interlayer, the fiber optic sensing unit is embedded inside the wall surface, without altering the inner and outer surface morphology of the mask 1, minimizing the impact on sealing and patient comfort. Similarly, when the second fiber optic acoustic sensing unit 4 is fixed to the air supply line 2, it can be connected to the wall of the air supply line 2 through the same encapsulation and fixing method.

[0052] As a preferred embodiment, the first fiber optic acoustic sensing unit 3 and the second fiber optic acoustic sensing unit 4 can be independently selected from various fiber optic acoustic sensing structures. For example, the first fiber optic acoustic sensing unit 3 may include a fiber Bragg grating, a Fabry-Perot cavity structure, a Mach-Zehnder interferometer structure, a micro / nano fiber structure, etc. As a further preferred embodiment, the second fiber optic acoustic sensing unit 4 adopts the same type of fiber optic sensing structure as the first fiber optic acoustic sensing unit 3. The sensitivity-frequency response curves, dynamic range, and phase characteristics of the two fiber optic acoustic sensing units tend to be consistent, which helps to reduce system errors introduced by differences in sensing unit characteristics during subsequent differential noise reduction processing. Simultaneously, it facilitates synchronous demodulation within the same fiber optic demodulation module, reducing system hardware complexity.

[0053] In another technical solution, the system includes a breath sound analysis module and a display and alarm module. The breath sound analysis module is communicatively connected to the differential acoustic processing module and is configured to identify respiratory status and abnormal respiratory events based on the patient's actual breath sound signals. Both the respiratory status and abnormal respiratory events can be characterized from the breath sound features extracted from the actual breath sound signals.

[0054] Respiratory status refers to the acoustically detectable physiological characteristics exhibited by a patient during their current breathing process, including but not limited to snoring, wheezing, and respiratory rate. For example, snoring is characterized by quasi-periodic broadband noise pulses synchronized with the respiratory cycle in the time-domain features of respiratory sounds, with a low spectral center of gravity. Wheezing is characterized by high-frequency, continuous, narrow-band sounds occurring during the inspiratory phase, indicating a narrowing of the upper airway. Respiratory rate is extracted through the periodic fluctuations of the respiratory sound time-domain features.

[0055] Abnormal respiratory events refer to pathological or abnormal events that require clinical attention or trigger alarms, including apnea events, hypoventilation events, interface leak events, and airway obstruction events. For example, an apnea event is characterized by a persistently low temporal characteristic of breath sounds below a preset threshold for a preset time. A hypoventilation event is characterized by a decrease in the maximum value of the breath sound temporal characteristic relative to the patient's historical baseline exceeding a preset percentage and persisting for a preset time. An interface leak event is characterized by a persistent broadband energy increase in the high-frequency range of breath sounds, independent of the respiratory cycle, and the temporal persistence of this energy increase is consistent with the acoustic characteristics of turbulent jets caused by a small opening at the edge of mask 1. An airway obstruction event is characterized by a sudden change in the energy distribution of a specific frequency band in the breath sound spectrum, usually accompanied by a sharp increase in energy in the wheezing frequency band.

[0056] Therefore, multi-dimensional acoustic feature analysis and event recognition based on real respiratory sound signals with high signal-to-noise ratio avoids errors in respiratory sound feature extraction and event misjudgment caused by background noise interference in existing technologies, and significantly improves the detection sensitivity and specificity of abnormal events such as apnea, hypoventilation, air leakage and airway obstruction.

[0057] Correspondingly, the display and alarm module visually displays the respiratory status information output by the respiratory sound analysis module. For example, it can display the current respiratory sound waveform as a real-time waveform graph, the frequency-time distribution of the respiratory sounds as a time-spectrum waterfall graph, the current respiratory frequency as a numerical value or bar chart, and whether snoring or wheezing is detected as a status indicator light or text label. Simultaneously, the display and alarm module issues an alarm when the respiratory sound analysis module identifies an abnormal respiratory event, including but not limited to at least one of the following: audible alarm (buzzer or voice prompt), visual alarm (flashing indicator light or pop-up prompt), and pushing alarm information to the central monitoring station 5 or a mobile terminal via a wireless communication interface.

[0058] It should also be noted that the functions of the "differential acoustic processing module", "breath sound analysis module" and "display and alarm module" in this application can be implemented by an independent embedded controller or a software module running on the monitor or central monitoring station 5. This application does not limit the specific hardware implementation of the above modules.

[0059] Correspondingly, regarding the second aspect, please refer to Figure 3 As shown, Figure 3 This is a flowchart illustrating the steps of a transnasal CPAP breath sound monitoring method based on dual-fiber differential acoustics. This application also provides a transnasal continuous positive airway pressure (CPAP) breath sound monitoring method based on dual-fiber differential acoustics, applicable to any of the above system embodiments, comprising the following steps: S1. Acquire a mixed signal containing patient breath sounds and background noise caused by continuous positive pressure airflow through the first fiber optic acoustic sensing unit 3; and acquire a reference signal with background noise as the main component through the second fiber optic acoustic sensing unit 4. S2. The mixed signal and the reference signal are converted from optical signals into first electrical signals and second electrical signals respectively through the fiber optic demodulation module; S3. Using the differential acoustic processing module, the first electrical signal is differentially denoised using the second electrical signal as a noise reference to eliminate background noise from the mixed signal and obtain the patient's true breath sound signal. S4. Identify respiratory status and abnormal respiratory events based on the patient's actual respiratory sound signals through the breath sound analysis module; S5. Display the breathing status through the display and alarm module, and issue an alarm based on the identified abnormal breathing events.

[0060] It should be noted that, for the method embodiments, the embodiments of this application are not limited to the described order of actions, because according to the embodiments of this application, some steps may be performed in other orders or simultaneously.

[0061] The above method embodiments are basically similar to the system embodiments, so the description is relatively simple. For relevant details, please refer to the description of the system embodiments.

[0062] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0063] It should also be noted that, in this document, the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are 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, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations, nor should they be construed as indicating or implying relative importance. Moreover, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device.

[0064] The foregoing has provided a detailed description of the transnasal CPAP acoustic monitoring system and method based on dual-fiber differential processing provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand this application, and the content of this specification should not be construed as a limitation of this application. Furthermore, those skilled in the art will recognize that various modifications may be made to the specific implementation methods and application scope based on this application. It is neither necessary nor possible to exhaustively list all implementation methods here, but obvious variations or modifications derived therefrom are still within the protection scope of this application.

Claims

1. A transnasal CPAP breath sound monitoring system based on dual-fiber differential acoustics, characterized in that the system... include: The nasal CPAP interface is configured to seal with the patient's nose and form a positive pressure ventilation chamber; The air supply line, connected to the nasal CPAP interface, is configured to supply a continuous positive pressure airflow into the positive pressure ventilation chamber; The first fiber optic acoustic sensing unit is arranged in the positive pressure ventilation cavity to collect a mixed signal containing the patient's breath sounds and the background noise caused by the continuous positive pressure airflow. The second fiber optic acoustic sensing unit is arranged on the air supply pipeline so that its main acoustic coupling is with the background noise caused by the continuous positive pressure airflow, and is used to collect a reference signal with the background noise as the main component. The fiber optic demodulation module is connected to the first fiber optic acoustic sensing unit and the second fiber optic acoustic sensing unit respectively, and is configured to convert the mixed signal and the reference signal from optical signals into first electrical signals and second electrical signals. The differential acoustic processing module, which is communicatively connected to the fiber optic demodulation module, is configured to perform differential noise reduction processing between the first electrical signal and the second electrical signal to eliminate the background noise from the mixed signal and obtain the patient's true breath sound signal.

2. The transnasal CPAP breath sound monitoring system based on dual-fiber differential acoustics according to claim 1, characterized in that, Both the first fiber optic acoustic sensing unit and the second fiber optic acoustic sensing unit include at least one of the following: fiber Bragg grating structure, Fabry-Perot cavity structure, Mach-Zehnder interferometer structure, and micro / nano fiber optic structure.

3. The transnasal CPAP breath sound monitoring system based on dual-fiber differential acoustics according to claim 1, characterized in that, The first fiber optic acoustic sensing unit is disposed on the inner wall of the cavity of the transnasal CPAP interface, and is arranged in a ring or in a localized manner corresponding to the area around the patient's nasal ala and the nasal cavity outlet.

4. The transnasal CPAP breath sound monitoring system based on dual-fiber differential acoustics according to claim 1, characterized in that, The nasal CPAP interface includes a nasal CPAP mask, which is provided with an air inlet and an exhaust port. The air inlet is connected to the air supply line.

5. The transnasal CPAP breath sound monitoring system based on dual-fiber differential acoustics according to claim 1, characterized in that, The second fiber optic acoustic sensing unit is arranged at least at one end of the air supply line near the air inlet of the nasal CPAP interface and at one of the line accessories, such that the second fiber optic acoustic sensing unit is located on the path of the continuous positive pressure airflow and away from the positive pressure ventilation cavity so as not to directly contact the patient's respiratory airflow.

6. The transnasal CPAP breath sound monitoring system based on dual-fiber differential acoustics according to claim 1, characterized in that, The differential acoustic processing module includes at least one of an adaptive filtering unit, a phase compensation unit, an amplitude normalization unit, a spectrum difference unit, and a short-time Fourier transform unit. The differential noise reduction process includes at least one of the following: adaptive filtering, phase compensation, amplitude normalization, spectral subtraction, and short-time Fourier transform processing of the first and second electrical signals.

7. The transnasal CPAP breath sound monitoring system based on dual-fiber differential acoustics according to claim 1, characterized in that, The first fiber optic acoustic sensing unit and / or the second fiber optic acoustic sensing unit are respectively encapsulated and fixed at their respective positions by a medical silicone layer, a polymer elastic layer, or an elastic film.

8. The transnasal CPAP breath sound monitoring system based on dual-fiber differential acoustics according to claim 1, characterized in that, The system also includes: The breath sound analysis module, which is communicatively connected to the differential acoustic processing module, is configured to identify the respiratory state and abnormal respiratory events based on the patient's actual breath sound signals. The respiratory state includes at least one of snoring, wheezing, and respiratory rate; The abnormal breathing events include at least one of the following: apnea event, hypoventilation event, interface leakage event, and airway obstruction event.

9. A transnasal CPAP breath sound monitoring system based on dual-fiber differential acoustics according to claim 8, characterized in that, The system also includes: The display and alarm module is communicatively connected to the breathing sound analysis module and is configured to display the breathing status and issue an alarm based on the identified abnormal breathing events.

10. A method for monitoring nasal CPAP breath sounds based on dual-fiber differential acoustics, characterized in that, The method, applied to the system as described in any one of claims 1 to 9, comprises: A mixed signal comprising the patient's breath sounds and the background noise caused by the continuous positive pressure airflow is acquired through a first fiber optic acoustic sensing unit; and a reference signal with the background noise as the main component is acquired through a second fiber optic acoustic sensing unit. The mixed signal and the reference signal are converted from optical signals into a first electrical signal and a second electrical signal, respectively, by an optical fiber demodulation module. Using the differential acoustic processing module, the second electrical signal is used as a noise reference to perform differential noise reduction processing on the first electrical signal, thereby eliminating the background noise from the mixed signal to obtain the patient's true breath sound signal; The respiratory sound analysis module identifies the patient's respiratory status and abnormal respiratory events based on the patient's actual respiratory sound signals. The breathing status is displayed through the display and alarm module, and an alarm is issued based on the identified abnormal breathing events.

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