Derivation of respiration from electrocardiogram during heart rate variability studies

A method was developed to derive the respiration signal from the ECG signal based on the observation that the body-surface ECG is influenced by electrode motion relative to the heart and that fluctuations in the mean cardiac electrical axis accompany respiration. ECG signals were taken from 9 healthy subjects during rest, paced breathing and exercise. The respiration was derived from the recorded ECG signals. The ECG-derived respiration was compared with the original respiration recorded through an impedance pneumography device. The derived respiration shows an excellent correspondence with the original respiration. Statistical analysis indicates that the ECG-derived respiration has a high correlation with the original respiration in the frequency domain