# US 11,109,791 B2 · Diagnosis and monitoring of cardio-respiratory disorders > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,109,791 B2 - Document ID: US11109791B2 - Status: Granted - Kind: B2 - Application number: 15/579,839 - Filed: 2016-06-24 - Published: 2018-06-07 - Granted: 2021-09-07 - Earliest claimed: 2015-06-26 - Assignees: ResMed Pty Ltd - Applicants: ResMed Pty Ltd; University of Technology Sydney - Inventors: Adel Ali Al-Jumaily; Vinh Phuc Tran - Web page: https://patentgrep.com/patent/US11109791B2 ## CPC - A61B 5/0205: Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition - A61B 5/021: Measuring pressure in heart or blood vessels - A61B 5/024: Measuring pulse rate or heart rate - A61B 5/0507: using microwaves or terahertz waves - A61B 5/113: occurring during breathing - A61B 5/6803: {Head-worn items, e.g. helmets, masks, headphones or goggles} - A61B 5/0006: {ECG or EEG signals} - A61B 5/0261: {using optical means, e.g. infrared light} - A61B 5/0816: {Measuring devices for examining respiratory frequency (measuring frequency of electric signals G01R23/00)} - A61B 5/087: Measuring breath flow - A61B 5/0873: {using optical means} - A61B 5/097: Devices for facilitating collection of breath or for directing breath into or through measuring devices - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) ## Abstract Methods and systems estimate cardio-respiratory parameter(s), such as from in-phase and quadrature channels. The channels may represent patient chest movement and may be generated with a sensor, such as a contactless sensor that may sense movement with radio-frequency signals. In the methods/systems, the in-phase and quadrature channels may be processed, such as in a processor(s), using relative demodulation to generate cardio-respiratory parameter estimate(s). Optionally, the processing produces a jerk signal that may be filtered for producing a heart rate estimate, such as from zero-crossings of the filtered signal. Optionally, the processing produces a chest velocity signal that may be filtered for producing a respiratory rate estimate, such as from zero-crossings of the filtered signal. Optionally, a respiratory volume, such as tidal volume, may be estimated from an intrapulmonary pressure signal generated by applying a function to a chest displacement signal where the function relates intrapulmonary pressure and chest displacement. ## Claims ### Claim 1 A method of estimating a heart rate of a patient from an in-phase channel and a quadrature channel, each channel representing chest movement of the patient, the method comprising: in one or more processors, processing the in-phase channel and the quadrature channel by relative demodulation to generate a jerk signal, wherein the relative demodulation comprises numerically differentiating the in-phase channel and the quadrature channel to produce a numeric derivative of the in-phase channel and a numeric derivative of the quadrature channel, and generating a chest velocity signal from the numeric derivative of the in-phase channel and the numeric derivative of the quadrature channel; filtering the jerk signal with a cardiac band-pass filter to produce a cardiac jerk signal; and generating a heart rate estimate from zero-crossings of the cardiac jerk signal. ### Claim 2 (depends on 1) A method according to claim 1, wherein the generating the heart rate estimate comprises: detecting systole phases of heartbeats by determination of the zero-crossings of the cardiac jerk signal; and calculating the heart rate estimate from a number of detected systole phases in a window of the cardiac jerk signal. ### Claim 3 (depends on 1) A method according to claim 1, wherein the generating the heart rate estimate comprises: detecting diastole phases of heartbeats by determination of the zero-crossings of the cardiac jerk signal; and calculating the heart rate estimate from a number of detected diastole phases in a window of the cardiac jerk signal. ### Claim 4 (depends on 1) A method according to claim 1, wherein the jerk signal is a third derivative of chest displacement of the patient. ### Claim 5 (depends on 1) A method according to claim 1, wherein the relative demodulation further comprises: numerically differentiating the chest velocity signal to generate the jerk signal. ### Claim 6 (depends on 1) A method according to claim 1, wherein the generating the chest velocity signal comprises: dividing the numeric derivative of the quadrature channel by the in-phase channel to obtain a first ratio signal; dividing the numeric derivative of the in-phase channel by the quadrature channel to obtain a second ratio signal; and subtracting the second ratio signal from the first ratio signal multiplied by a scaling factor. ### Claim 7 (depends on 6) A method according to claim 6, wherein the scaling factor is a ratio of amplitude gain constants of the in-phase channel and the quadrature channel. ### Claim 8 (depends on 6) A method according to claim 6, further comprising subtracting respective offsets from the in-phase channel and the quadrature channel before the dividing steps. ### Claim 9 (depends on 1) A method according to claim 1, wherein the cardiac band-pass filter comprises a band-pass filter with a pass-band of 0.7 to 1.6 Hz. ### Claim 10 (depends on 9) A method according to claim 9, wherein the band-pass filter is a sixth-order Butterworth filter. ### Claim 11 (depends on 1) A method according to claim 1, wherein the in-phase channel and the quadrature channel are generated by a contactless motion sensor. ### Claim 12 (depends on 11) A method according to claim 11, wherein the contactless motion sensor is a radio-frequency sensor that generates the in-phase channel and the quadrature channel by processing of signals representing transmitted radio-frequency waves and received reflected ones of the transmitted radio-frequency waves. ### Claim 13 (depends on 1) A method according to claim 1, wherein the one or more processors controls a display to output the heart rate estimate. ### Claim 14 (depends on 1) A method according to claim 1, wherein the one or more processors controls a change to a control parameter of a treatment device in response to the heart rate estimate. ### Claim 15 (depends on 1) A method according to claim 1, wherein the jerk signal is a second derivative of the chest velocity signal. ### Claim 16 (depends on 15) A method according to claim 15, wherein the jerk signal describes changes in acceleration. ### Claim 17 Apparatus for estimating heart rate of a patient, the apparatus comprising: a contactless motion sensor configured to generate an in-phase channel and a quadrature channel, wherein the in-phase channel and the quadrature channel each represent chest movement of the patient when the contactless motion sensor is generally directed toward a chest of the patient; and a processor configured to analyse the in-phase channel and the quadrature channel to generate a heart rate estimate, the analysis comprising: processing the in-phase channel and the quadrature channel by relative demodulation to generate a jerk signal, wherein the relative demodulation comprises numerically differentiating the in-phase channel and the quadrature channel to produce a numeric derivative of the in-phase channel and a numeric derivative of the quadrature channel, and generating a chest velocity signal from the numeric derivative of the in-phase channel and the numeric derivative of the quadrature channel; filtering the jerk signal with a cardiac band-pass filter to produce a cardiac jerk signal; and generating a heart rate estimate from zero-crossings of the cardiac jerk signal. ### Claim 18 (depends on 17) Apparatus according to claim 17, wherein the processor is co-located with the contactless motion sensor. ### Claim 19 (depends on 17) Apparatus according to claim 17, further comprising communications circuitry configured to transfer data to an external computing device via a connection. ### Claim 20 (depends on 19) Apparatus according to claim 19, wherein the processor is a processor of the external computing device. ### Claim 21 (depends on 17) Apparatus according to claim 17, wherein the contactless motion sensor is a radio-frequency sensor that generates the in-phase channel and the quadrature channel by processing of signals representing transmitted radio-frequency waves and received reflected ones of the transmitted radio-frequency waves. ### Claim 22 (depends on 17) Apparatus according to claim 17, wherein the jerk signal is a second derivative of the chest velocity signal. ### Claim 23 (depends on 22) Apparatus according to claim 22, wherein the jerk signal describes changes in acceleration. ### Claim 24 A method of estimating a respiratory rate of a patient from an in-phase channel and a quadrature channel, each channel representing chest movement of the patient, the method comprising: in one or more processors, processing the in-phase channel and the quadrature channel by relative demodulation to generate a chest velocity signal, wherein the relative demodulation comprises numerically differentiating the in-phase channel and the quadrature channel to produce a numeric derivative of the in-phase channel and a numeric derivative of the quadrature channel, and generating the chest velocity signal from the numeric derivative of the in-phase channel and the numeric derivative of the quadrature channel; filtering the chest velocity signal with a respiratory band-pass filter to produce a respiratory velocity signal; and generating a respiratory rate estimate from zero-crossings of the respiratory velocity signal. ### Claim 25 (depends on 24) A method according to claim 24, wherein the generating the respiratory rate estimate comprises: detecting inspiration phases of respiration by determination of the zero-crossings of the respiratory velocity signal; and calculating the respiratory rate estimate from a number of detected inspiration phases in a window of the respiratory velocity signal. ### Claim 26 (depends on 24) A method according to claim 24, wherein the generating the respiratory rate estimate comprises: detecting expiration phases of respiration by determination of the zero-crossings of the respiratory velocity signal; and calculating the respiratory rate estimate from a number of detected expiration phases in a window of the respiratory velocity signal. ### Claim 27 (depends on 24) A method according to claim 24, wherein the chest velocity signal is a first derivative of chest displacement of the patient. ### Claim 28 (depends on 24) A method according to claim 24, wherein the generating the chest velocity signal comprises: dividing the numeric derivative of the quadrature channel by the in-phase channel to obtain a first ratio signal; dividing the numeric derivative of the in-phase channel by the quadrature channel to obtain a second ratio signal; and subtracting the second ratio signal from the first ratio signal multiplied by a scaling factor. ### Claim 29 (depends on 28) A method according to claim 28, wherein the scaling factor is a ratio of amplitude gain constants of the in-phase channel and the quadrature channel. ### Claim 30 (depends on 28) A method according to claim 28, further comprising subtracting respective offsets from the in-phase channel and the quadrature channel before the dividing steps. ### Claim 31 (depends on 24) A method according to claim 24, wherein the respiratory band-pass filter comprises a band-pass filter with a pass-band of 0.2 to 0.5 Hz. ### Claim 32 (depends on 31) A method according to claim 31, wherein the band-pass filter is a sixth-order Butterworth filter. ### Claim 33 (depends on 24) A method according to claim 24, wherein the in-phase channel and the quadrature channel are generated by a contactless motion sensor. ### Claim 34 (depends on 33) A method according to claim 33, wherein the contactless motion sensor is a radio-frequency sensor that generates the in-phase channel and quadrature channel by processing of signals representing transmitted radio-frequency waves and received reflected ones of the transmitted radio-frequency waves. ### Claim 35 (depends on 24) A method according to claim 24, wherein the one or more processors controls a display to output the respiratory rate estimate. ### Claim 36 (depends on 24) A method according to claim 24, wherein the one or more processors controls a change to a control parameter of a treatment device in response to the respiratory rate estimate. ### Claim 37 Apparatus for estimating respiratory rate of a patient, the apparatus comprising: a contactless motion sensor configured to generate an in-phase channel and a quadrature channel, each channel representing chest movement of the patient when the contactless motion sensor is generally directed toward a chest of the patient; and a processor configured to analyse the in-phase channel and the quadrature channel to generate a respiratory rate estimate, the analysis comprising: processing the in-phase channel and the quadrature channel by relative demodulation to generate a chest velocity signal, wherein the relative demodulation comprises numerically differentiating the in-phase channel and the quadrature channel to produce a numeric derivative of the in-phase channel and a numeric derivative of the quadrature channel, and generating the chest velocity signal from the numeric derivative of the in-phase channel and the numeric derivative of the quadrature channel; filtering the chest velocity signal with a respiratory band-pass filter to produce a respiratory velocity signal; and generating a respiratory rate estimate from zero-crossings of the respiratory velocity signal. ### Claim 38 (depends on 37) Apparatus according to claim 37, wherein the processor is co-located with the contactless motion sensor. ### Claim 39 (depends on 37) Apparatus according to claim 37, further comprising communications circuitry configured to transfer data to an external computing device via a connection. ### Claim 40 (depends on 39) Apparatus according to claim 39, wherein the processor is a processor of the external computing device. ### Claim 41 (depends on 37) Apparatus according to claim 37, wherein the contactless motion sensor is a radio-frequency sensor that generates the in-phase channel and the quadrature channel by processing of signals representing transmitted radio-frequency waves and received reflected ones of the transmitted radio-frequency waves. ### Claim 42 A patient monitoring system comprising: means for generating an in-phase channel and a quadrature channel, each channel representing chest movement of a patient; and means for analysing the in-phase channel and the quadrature channel to generate a heart rate estimate of the patient, the analysing comprising: processing the in-phase channel and the quadrature channel by relative demodulation to generate a jerk signal, wherein the relative demodulation comprises numerically differentiating the in-phase channel and the quadrature channel to produce a numeric derivative of the in-phase channel and a numeric derivative of the quadrature channel, and generating a chest velocity signal from the numeric derivative of the in-phase channel and the numeric derivative of the quadrature channel; filtering the jerk signal with a cardiac band-pass filter to produce a cardiac jerk signal; and generating a heart rate estimate from zero-crossings of the cardiac jerk signal. ### Claim 43 A patient monitoring system comprising: means for generating an in-phase channel and a quadrature channel, each channel representing chest movement of a patient; and means for analysing the in-phase channel and the quadrature channel to generate a respiratory rate estimate of the patient, the analysing comprising: processing the in-phase channel and the quadrature channel by relative demodulation to generate a chest velocity signal, wherein the relative demodulation comprises numerically differentiating the in-phase channel and the quadrature channel to produce a numeric derivative of the in-phase channel and a numeric derivative of the quadrature channel, and generating the chest velocity signal from the numeric derivative of the in-phase channel and the numeric derivative of the quadrature channel; filtering the chest velocity signal with a respiratory band-pass filter to produce a respiratory velocity signal; and generating a respiratory rate estimate from zero-crossings of the respiratory velocity signal.