The methods and limitations of extracting respiratory rhythm utilizing photoplethysmographic signals

Photoplethysmograph has been a focus for its portable and noninvasive indications of many important physiological phenomenons. From previous researches, it is possible to extract respiratory rhythms from PPG signals. The objective of this paper is to apply and evaluate two methods, envelope and wavelet packet decomposition method, in getting respiratory rate utilizing PPG. The experiments demonstrate that the two methods perform well in the normal and lower respiratory rhythm, however, envelope method requires more signal conditioning, at the same time, wavelet packet decomposition fails in detecting fast rhythm.