Heart Rate Variability (HRV) of two short-term photoplethysmogram (PPG)

Heart rate variability (HRV) is often analyzed using short-term studies: 5-min and 2-min heart rate datasets. The correlation between the two data segments in HRV analysis has not been well understood. This paper reports a statistical comparison of the results of HRV spectral analysis for the 5-minute versus 2-minute short-term studies using photoplethysmogram (PPG). Twenty repeat measurements were performed to obtain the comparison data, the power spectral density (PSD) was analyzed for data segments and divided into three frequency components: Ln_VLF, Ln_LF, and Ln_HF. For statistical comparison, we used Pearson’s correlation coefficient (ρb) and a paired t-test. The ρb was 0.3827 (p = 0.0958) for Ln_VLF, 0.6518 (p = 0.0018) for Ln_LF, 0.9250 (p < 0.0001) for Ln_HF, 0.8807 (p < 0.0001) for the R ratio (Ln_LF/Ln_HF), and 0.9592 (p < 0.0001) for the standard deviation (SD). In a paired t-test for the R ratio, the t-statistic, SD, and two-tailed probability were 0.602, 0.07797, and P=0.5541, respectively. Our findings suggest that 2-minute recordings may be appropriate for screening the HRV parameters that reflect the autonomic nervous system (ANS) function and that the 2-minute HRV remains useful, although there is some difference between the HRV parameters of the 2-minute and 5-min HRV.