Evaluation of methods for estimation of respiratory frequency from the ECG

A comparative study of methods for estimating respiratory frequency through electrocardiogram was carried out. Methods were based on beat morphology (QRS area or amplitude) and heart rate variability. In addition a combination of methods was also investigated. For each method, time and frequency correlation between the ECG derived respiration and the real respiration recorded by chest plethysmography were computed as well as the relative error in the respiration rate. Results indicate that combining the spectra of different methods gives overall the best estimation of the respiration rate. This technique obtained a median relative error of 1.07% (mad=22.13) in free breathing signals. Methods based on Area, Amplitude and AMEA had relative errors around 1.10% (17/18). HRV however, had high relative errors in free breathing signals (42.70% (24.26)).