Robust electrocardiogram derived respiration from stress test recordings: validation with respiration recordings

In this work U method is presented for robust estimation of the respiratory frequency from exercise ECG. The method is based on the rotation angles of the heart´s electrical axis as induced by respiration, determined by aligning successive QRS loops to a reference loop using a least squares criterion. The respirarory frequency is estimated by power specfral analysis of the estimated rotation angle series. Special attention has been paid to handling highly non-stationary and noisy exercise ECGs. The ECG and respiratory signals of 14 volunteers and 20 patients were simultaneously recoded during stress resting to evaluate the method. The respiratmy frequency was estimated from exercise ECGs and compared to the frequency obtained from respiratory signals. An error of 6.1% ± f3.7% (0.024±0.017Hz, mean±sd) is achieved, suggesting that the method is useful for analysis of exercise ECGs.