Respiratory rate measurement using a combination of respiration signals
A method and system for measuring respiratory rate are disclosed. In a first aspect, the method comprises measuring at least one respiration signal and filtering the respiration signal using a lowpass filter. The method includes peak-picking the respiration signal to determine the respiratory rate and determining a quality metric of the respiratory rate. In a second aspect, the system comprises a wireless sensor device coupled to a user via at least one electrode, wherein the wireless sensor device includes a processor and a memory device coupled to the processor, wherein the memory device stores an application which, when executed by the processor, causes the processor to carry out the steps of the method.
1. A method for measuring respiratory rate using a wireless sensor device, the method comprising:
measuring at least one respiration signal wherein measuring at least one respiration signal is measuring a plurality of respiration signals to determine a plurality of respiration rates (RR 1 . . . N ), further comprising:
determining a quality metric (Q 1 . . . N ) for each of the plurality of respiration rates; and
combining the plurality of respiration rates by weighting the quality metric for each of the plurality of respiration rates based on a quality process to calculate a weighted respiration rate (RR weighted );
filtering the respiration signal using a lowpass filter;
peak-picking the respiration signal to determine the respiratory rate by using a standard deviation of the filtered respiration signal over a changing threshold; and
determining a quality metric of the respiratory rate by using previously learned weights of features of the respiratory rate, wherein the features of the respiratory rate include a coefficient of variation of a difference in minima times (c t ), a coefficient of variation of peak-to-peak values (c p ), a mean peak-to-peak value (m p ), and a ratio of a number of picked extrema to a total number of all local extrema (r ext ).
2. The method of claim 1 , wherein the at least one respiration signal is derived using any of a chest-mounted accelerometer, a QRS-area of an EKG signal, a QRS-amplitude of the EKG signal, and a respiratory sinus arrhythmia (RSA).
3. The method of claim 1 , wherein the quality metric is weighted using previously learned weights and transformed using an exponential to get the quality metric to a value between 0 and 1.
4. The method of claim 1 , wherein the quality metric is derived within a predetermined time period.
5. The method of claim 4 , wherein the predetermined time period is 45 seconds.
6. The method of claim 1 , further comprising:
performing a smoothing of the respiratory rate to reduce effects of missed and extraneous peaks using a trimmed mean.
7. The method of claim 1 , wherein the weighted respiration rate (RR weighted ) comprises:
RR weighted =RR 1 ( Q 1 /( Q 1 +Q 2 + . . . +Q N ))+RR 2 *( Q 2 /( Q 1 +Q 2 + . . . +Q N ))RR N *( Q N /( Q 1 +Q 2 + . . . +Q N )).