Body-worn monitor for measuring respiration rate

Abstract

The invention provides a multi-sensor system that uses an algorithm based on adaptive filtering to monitor a patient's respiratory rate. The system features a first sensor selected from the following group: i) an impedance pneumography sensor featuring at least two electrodes and a processing circuit configured to measure an impedance pneumography signal; ii) an ECG sensor featuring at least two electrodes and an ECG processing circuit configured to measure an ECG signal; and iii) a PPG sensor featuring a light source, photodetector, and PPG processing circuit configured to measure a PPG signal. Each of these sensors measures a time-dependent signal which is sensitive to respiratory rate and, during operation, is processed to determine an initial respiratory rate value. An adaptive digital filter is determined from the initial respiratory rate. The system features a second sensor (e.g. a digital 3-axis accelerometer) that attaches to the patient's torso and measures an ACC signal indicating movement of the chest or abdomen that is also sensitive to respiratory rate. This second signal is processed with the adaptive filter to determine a final value for respiratory rate.

What is claimed is: 
     
         1 . A body-worn system for monitoring respiratory rate from a patient, comprising:
 a housing configured to be mounted on the patient's torso, an accelerometer system contained within the housing and comprising: (i) a first accelerometer configured to generate a first set of time-dependent digital motion waveforms indicative of movement of the chest or abdomen, (ii) an impedance pneumography system configured to generate a time-dependent digital impedance pneumography waveform, and (iii) an ECG system configured to generate a time-dependent digital ECG waveform;   a second accelerometer configured to generate a second set of time-dependent digital motion waveforms indicative of motions of the patient's upper arm;   a third accelerometer configured to generate a third set of time-dependent digital motion waveforms along three orthogonal axes indicative of motions of the patient's lower arm;   a processing system configured to be mounted on the patient's wrist, wherein the processing system comprises a processor and a cable port operably connected to the processor; and   a cable that operably connects to each of the first and second accelerometers, the impedance pneumography system, and the ECG system and comprising a terminal connector which inserts into the cable port and thereby provides a single common transmission line for communication of the first set of time-dependent digital motion waveforms, the second set of time-dependent digital motion waveforms, the time-dependent digital impedance pneumography waveform and the time-dependent digital ECG waveform to the processing component, wherein each of the first set of time-dependent digital motion waveforms, the second set of time-dependent digital motion waveforms, the time-dependent digital impedance pneumography waveform and the time-dependent digital ECG waveform are transmitted as data streams comprising a header portion and a data portion, the header portion indicating the specific signal type of the data and the sensor from which the data originates;   wherein the processing system is configured to receive and process the first set of time-dependent digital motion waveforms, the second set of time-dependent digital motion waveforms, the time-dependent digital impedance pneumography waveform and the time-dependent digital ECG waveform and thereby determine the patient's respiratory rate and the patient's posture, activity level, and degree of motion.