Body-worn monitor for measuring respiration rate
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 which is selected from the group consisting of an impedance pneumography sensor, an ECG sensor, a PPG sensor, and a motion sensor (e.g., an accelerometer) configured to attach to the patient's torso and measure therefrom a motion signal. The system further comprises (iii) a processing system, configured to operably connect to the first and motion sensors, and to determine a respiration rate value by applying filter parameters obtained from the first sensor signals to the motion sensor signals.
1. A method for determining a respiration rate value from a patient, comprising the following steps:
(a) measuring a first time-dependent signal by detecting a modulated electrical current passing through the patient's torso;
(b) measuring a second time-dependent signal by detecting respiration-induced movements in the patient's torso with at least one motion sensor;
(c) determining if the first and second time-dependent signals are acceptable for further processing based on a motion-related event indicative of patient motion that is not related to the patient's respiration rate value, wherein the motion-related event is determined by processing signals from at least one motion sensor; and
(d) collectively processing both the first and second time-dependent signals to determine a value for respiration rate corresponding to a period when the motion-related event indicates that the first and second time-dependent signals are acceptable for further processing by (i) removing noise components from the first time-dependent signal by filtering the first time-dependent signal with a first non-adaptive filter to provide a first filtered signal; (ii) removing noise components from the second time-dependent signal by filtering the second time-dependent signal with a second non-adaptive filter to provide a second filtered signal; (iii) filtering the second filtered signal with an adaptive filter utilizing filter parameters derived from the first filtered signal to provide a third filtered signal; and determining the respiration rate value from the third filtered signal.