The factors influence compatibility of pulse-pulse intervals with R-R intervals

Cardiac autonomic dysfunction assessed by power spectral analysis of electrocardigographic (ECG) R-R intervals (RRI) is a useful method in clinical research. The compatibility of pulse-pulse intervals (PPI) acquired by photoplethysmography (PPG) with RRI is equivocal. In this study, we would like to investigate factors influence the compatibility. We recruited 25 young and health subjects divided into two groups: normal subjects (Group1, BMI < 24, n=15) and overweight subjects (Group2, BMI >/= 24, n=10). ECG and PPG were measured for 5 minutes. Used cross-approximate entropy (CAE) and Fast Fourier transform (FFT) to obtained compatibility between RRI and PPI. The CAE value in Group1 were significantly lower than in Group2 (1.71 ± 0.12 vs. 1.83 ± 0.11, P = 0.011). A positive linear relationship between CAE value and risk factors of metabolic syndrome. No significantly difference between LFP/HFP ratio of RRI (LHRRRI) and LFP/HFP ratio of PPI (LHRPPI) in Group1 (1.42 ± 0.19 vs. 1.38 ± 0.17, P = 0.064), LHRRRI significantly higher than LHRPPI in Group2 (2.18 ± 0.37 vs. 1.93 ± 0.30, P = 0.005). It should be careful that using PPI to assess autonomic function in the obese subjects or the patients with metabolic syndrome.