Investigation of the Feasibility of Postoperative Pain Assessment Using Frequency Analysis of Photoplethysmogram Variability

Quantifying of pain is necessary for optimal dose of opioid. In pain quantification, there have been many attempts to analyze the photoplethysmography (PPG) waveform as a promising maker of autonomic function. In this paper, we investigate the feasibility of PPG amplitude variability (PPGV) as a novel marker of pain quantification. We derived 8 parameters related to the PPG amplitude and amplitude variability: ACA_baseline, ACA_dia, PPGAV_sys, PPGAV_dia, PPGAV_sys/ACA_baseline, PPGAV_sys/ACA_dia, PPGAV_dia/ACA_baseline and PPGAV_dia/ACA_dia, and calculated frequency domain variables, TP, VLF, LF, HF, nLF, nHF and LF/HF, that have been used for heart rate variability analysis. Every parameter was derived in clinical dataset obtained before and after surgery, and a significant difference was statistically verified using paired t-test. Consequently, a significant difference (p < 0.05) was found in every derived variable except for most variables in ACA_baseline, ACA_dia, PPGAV_sys, PPGV_dia, in nHF of PPGAV_sys/ACA_baseline, in nHF, LF/HF of PPGAV_sys/ACA_dia, in nLF, nHF of PPGAV_dia/ACA_dia, and in nLF, nHF of PPGAV_dia/ACA_baseline. This result suggests that the possibility of frequency domain analysis of PPGV as a novel indicator of surgical pain quantification.