Respiration derived from the electrocardiogram: a quantitative comparison of three different methods

Three methods were developed to derive the respiration from the electrocardiogram (ECG). The basis for deriving the respiration from the ECG relies on the fact that during respiration, the heart´s position in the thoracic cavity changes. Consequently, the angle of the mean cardiac vector also changes during respiration. Two orthogonal leads of ECG and a measure of respiration were taken from 9 healthy subjects during rest, paced breathing, and exercise. To determine the optimum method, the ECG derived respiration was compared to the measured respiration using cross-correlation and coherence. The results indicate that one method provides more accurate results than the other two