Analysis of Photoplethysmography-Based Surgical Pain Severity Assessment Markers

We investigated the use of photoplethysmography (PPG) features to assess the severity of both intraoperative and postoperative pain. PPG data was collected from 386 patients undergoing routine surgery. We extracted 180 pain assessment features based on PPG waveform characteristics identified in previous studies. Pain assessment involves a two-step process. First, we evaluated the presence of pain using the extracted features. If significant pain was detected, we then conducted a severity analysis. Pain severity was categorized into three groups: no pain, moderate, and severe. Intraoperative and postoperative pain labeling were based on clinical judgment and numerical rating scale criteria, respectively. For intraoperative pain presence, we performed statistical tests to identify significant changes in features before and after both intubation and skin incision. Postoperative pain presence analysis compared preoperative and postoperative periods. Statistical analysis revealed 106 and 124 features significant for intraoperative and postoperative pain presence, respectively. Among the pain-related features, 27 related to PPG amplitude, area, and slope were significant for all severity comparisons (no pain vs. moderate, no pain vs. severe, and moderate vs. severe) during intraoperative assessment. Postoperative severity assessment identified 12 significant features related to PPG amplitude, area, and pulse interval. These results suggest the potential of PPG-based features for assessing pain severity.