Respiratory rate detection using decomposition of ECG
A method and system for determining a respiratory rate of a user using an electrocardiogram (ECG) segment of the user are disclosed. The method comprises decomposing the ECG segment into a plurality of functions and evaluating the plurality of functions to choose one of the plurality of functions based on a respiratory band power. The method includes determining the respiratory rate using the one of the plurality of functions and a domain detection.
1. A system for determining a respiratory rate, the system comprising:
a wireless sensor device that includes at least one electrode, a processor, a transmitter and a memory device coupled to the processor, the memory device stores executable instructions that, when executed by the processor, causes the processor to:
measure an electrocardiogram (ECG) segment via the at least one electrode;
decompose the ECG segment into a plurality of Intrinsic Mode Functions (IMFs), wherein the ECG segment is decomposed into the plurality of IMFs using Ensemble Empirical Mode Decomposition (EEMD);
evaluate the plurality of IMFs by choosing one of the plurality of IMFs that contributes a maximal percentage of a total respiratory band power of the plurality of IMFs;
calculate the respiratory rate using the one of the plurality of IMFs and a domain detection;
store the calculated respiratory rate in the memory device; and
transmit the stored respiratory rate at a periodic rate, thereby providing continuous remote monitoring of the calculated respiratory rate.
2. The system of claim 1 , wherein to evaluate further comprises causing the processor to:
evaluate spectral content of each of the plurality of IMFs by obtaining a Power Spectral Density (PSD) for each of the plurality of IMFs;
obtain the respiratory band power for each of the plurality of IMFs; and
provide the one of the plurality of IMFs as a surrogate respiration waveform.
3. The system of claim 2 , wherein to determine further comprises causing the processor to:
determine the respiratory rate using breath-to-breath peak detection in time-domain and respiratory frequency peak in the PSD of the surrogate respiration waveform.
4. The system of claim 1 , wherein the ECG segment is measured at a 125 Hz sampling frequency (F s ) and at a length of 40 seconds.
5. The system of claim 2 , wherein the PSD is obtained using Welch periodogram.
6. The system of claim 1 , wherein the application further causes the processor to:
process the ECG segment using both a low pass digital filter with cutoff frequency (F c ) of 10 Hz and a down sampling with F s of 25 Hz.
7. The system of claim 2 , wherein the respiratory band power obtained for each of the plurality of IMFs is an area under the PSD between frequencies 0.11 Hz to 0.45 Hz.
8. The system of claim 3 , wherein the breath-to-breath peak detection in time-domain includes an algorithm that identifies peak events by computing a first derivative of the surrogate respiration waveform and finds zero crossing events with positive to negative sign changes.