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EP-4438094-B1 - RESPIRATORY RATE MONITORING FOR RESPIRATORY FLOW THERAPY SYSTEMS

EP4438094B1EP 4438094 B1EP4438094 B1EP 4438094B1EP-4438094-B1

Inventors

  • WILLIAMS, RHYS MATTHEW JAMES
  • CANTRELL, Charles Grady
  • RUSSELL, David Martin
  • RYAN, Brett James
  • EDWARDS, Bryn Alan
  • GULLEY, Anton Kim

Dates

Publication Date
20260513
Application Date
20181122

Claims (13)

  1. A respiratory system configured to deliver a respiratory therapy to a patient, the system also configured to provide information related to the patient's breathing, the system comprising: a respiratory device comprising a controller, wherein the controller is configured to: receive a signal of a parameter of a flow of gases indicative of the patient's respiration; perform a frequency analysis of the signal; identify a plurality of local maxima of the signal resulting from the frequency analysis; and output data indicative of a frequency with a highest magnitude among the plurality of local maxima as an estimated respiratory rate, and wherein the controller further determines a signal quality of the estimated respiratory rate, and wherein the system comprises a non-sealed system that is configured to deliver a nasal high flow therapy.
  2. The system of claim 1, wherein the controller is further configured to filter a magnitude of each waveform associated with each local maxima.
  3. The system of claim 2, wherein the outputted frequency is a frequency of the highest filtered magnitude.
  4. The system of any one of claims 1-3, wherein the controller is configured to identify between two and five local maxima.
  5. The system of any one of claims 1-4, wherein at each iteration of a frequency analysis algorithm, each local maximum is estimated to be caused by the same waveform as a previous local maximum if its frequency is within a certain distance of the previous local maximum.
  6. The system of claim 5, wherein if a local maximum is estimated to be caused by the same waveform as a previous local maximum, a filtered value for the magnitude of the local maximum is determined using the magnitude of the local maximum and a filtered magnitude of the previous local maxima.
  7. The system of any one of claims 1-6, wherein if a frequency of a local maximum is not within a certain distance of a frequency of any previous local maximum, the local maximum is determined to be caused by a new waveform.
  8. The system of Claim 7, wherein if a local maximum is estimated to be caused by a new waveform, a filtered value for a magnitude of the local maximum begins from zero, the filtered value for the magnitude of the local maximum being determined using the magnitude of the local maximum and an assumed previous magnitude of zero.
  9. The system of any one of Claims 1-8, wherein the frequency analysis comprises a discrete Fourier transform algorithm.
  10. The system of any one of claims 1-9, wherein the frequency analysis comprises evaluating a magnitude of frequencies within a typical breathing frequency range.
  11. The system of any one of claims 1-10, wherein the controller is further configured to apply an exponential decay to the signal prior to or as part of the frequency analysis, and wherein the exponential decay is configured to prioritise the most recent data samples of the signal for the frequency analysis.
  12. The system of any one of claims 1-11, wherein the parameter is flow rate, pressure, motor speed, power to motor, flow resistance, carbon dioxide data, humidity, variants thereof, or any combinations thereof.
  13. The system of any one of claims 1-12, wherein the system further comprises a display operatively connected to the controller and which is configured to display information related to the estimated respiratory rate.

Description

FIELD OF THE DISCLOSURE The present disclosure relates to methods and systems for monitoring the respiratory rate of a patient receiving a respiratory flow therapy. In particular, the present disclosure relates to monitoring the respiratory rate of a patient receiving a nasal high flow therapy. BACKGROUND Breathing assistance apparatuses are used in various environments such as hospital, medical facility, residential care, or home environments to deliver a flow of gases to users or patients. A breathing assistance or respiratory therapy apparatus (collectively, "respiratory apparatus" or "respiratory devices") may be used to deliver supplementary oxygen or other gases with a flow of gases, and/or a humidification apparatus to deliver heated and humidified gases. A respiratory apparatus may allow adjustment and control over characteristics of the gases flow, including flow rate, temperature, gases concentration, humidity, pressure, etc. Sensors, such as flow sensors and/or pressure sensors are used to measure characteristics of the gases flow. WO2017/059530 discloses a respiratory system configured to deliver a respiratory therapy to a patient. SUMMARY Respiratory rates of a patient using a respiratory device can be useful information. Respiratory rate data of the patient can inform clinicians about a patient's health, use of the respiratory devices and/or progress in the patient's respiratory functions. Respiratory rate data can also be used to improve the functionality of the respiratory device itself. Inspiration and expiration by a patient using a respiratory device can affect the gases flow in the device. This is because when the patient inhales through a patient interface, such as a mask or nasal cannula, the resistance to the gases flow in the patient interface decreases; when the patient exhales, the resistance to the gases flow in the patient interface increases. In a sealed system, this inhalation and exhalation is relatively easy to measure. However, in an unsealed system, such as a nasal high flow system, patient inhalation and exhalation is much more difficult to determine because of the open nature of the system. In a sealed respiratory system, respiratory devices can control one of the gases flow rate or pressure, leaving the other one of the gases flow rate or the pressure to exhibit observable variations as the patient breathes in and out. In these sealed systems, the start of an inspiration or expiration can serve as a triggering event for the device to alter the pressure and/or flow rate of the gases. These respiratory devices can determine a patient's respiratory rate by monitoring fluctuations in a signal, such as the flow rate or pressure, in the time domain. For example, a peak detection mechanism can determine from the signal when a breath occurs. When the signal is the flow rate, the peaks can indicate inspiration. The respiratory rate can be obtained by determining how frequent a triggering event, such as inspiration or expiration, occurs. Fluctuations of the signal in the time domain can be hard to observe in a respiratory device employing an unsealed patient interface, such as in a nasal high flow system. The device in the unsealed respiratory system can be constantly adjusting the speed of its flow generator motor to maintain a target flow rate. Variations from the target flow rate due to the patient's breathing are often relatively small due to the blower automatically compensating its output flow rate. The unsealed or non-sealed respiratory system can also have lower impedance of the gases flow than a sealed system. The low impedance can be due to leaks from the patient's nares, which are not sealed, and/or the patient's ability to optionally breathe through his or her mouth. In addition, the high flow rate in a nasal high flow system can result in a turbulent flow. The turbulent flow can increase noise in the signal, which can complicate the time-domain signal analysis, such as identification of the triggering events. The combination of small signal variations and increased noise in the signal of the gases flow can make it difficult to determine a breath period or frequency based on analyzing the signal in the time domain. Determining a breath period or frequency based on analyzing the signal in the time domain can also lead to incorrectly measuring the respiratory rate by detecting a breath when there is no breath. It is easy to mistake an irregularity in a time domain signal as a respiratory triggering event. Sealed systems can be designed to give quick readings of a respiratory rate to allow for detection of both sudden changes in and phase information of the respiratory rate to allow for breath synchronization. The quick reading design can compromise accuracy of the respiratory rate measurement. The present disclosure discloses processes for determining respiratory rates of a patient receiving a respiratory therapy from a respiratory system by performing frequency analysis