ECG-derived respirations based on phase-space reconstruction of single-lead ECG: Validations over various physical activities based on parallel recordings of ECG, respiration, and body accelerations

ECG derived respiration (EDR) provides a comfortable measurement of respiration and is recently applied to sleep studies. Nevertheless, the mechanic disturbances due to postural changes or other physical activity during long-term recording is less investigated. In the present study, ECG, impedance-based respiration, and body accelerations were parallel recorded during a series of scheduled postures in 8 healthy subjects and during 24 hours in one subject. In addition, a novel EDR method based on phase space reconstruction of single-lead ECG is also proposed. The area under major portrait radius (MPR) curve is employed to quantify the deviation of phase-space loop which is related to respiration. Coherence analysis between the EDR and the impedance-based respiration demonstrated that the MPR-based EDR had better performance than using R peak or QRS area as the EDR feature in the scheduled postures.