Pain Assessment in Musculoskeletal Pain Patients by Heart Rate Variability

Objectives: Self-report is considered the gold standard of pain measurement. Physiological measures are valuable in situations where self-report measures are more difficult to administer. This investigation assesses pain intensity in patients with musculoskeletal pain before and after the first session of physical therapy by evaluating the visual analog scale [VAS] and verbal rating scale [VRS] and analyzing the heart rate variability [HRV], and examines their relationships.Methods: A short-term electrocardiogram signal, VAS, and VRS of patients experiencing musculoskeletal pain were gathered before and after physical therapy and HRV was analyzed. The normal-to-normal [NN] intervals were obtained from electrocardiogram via Tompkins algorithm, followed by time-domain analyses. Additionally, the power spectrum density was determined via Fast Fourier Transform and frequency-domain analyses were conducted. Differences in each parameter before and after physical therapy were studied with paired t-test or Wilcoxon Signed Rank test. Furthermore, correlations between HRV and self-reported data were analyzed using Spearman [rank] correlation matrix.Results: According to the VAS and VRS, patients' perceptions of pain reduced significantly [P < 0.001] after treatment. The mean, standard deviation [SDNN], square root of the mean squared differences of successive NN intervals [RMSSD], and high frequency [HF] also show significant differences [P < 0.01]. Moreover, the VAS correlated closely with SDNN, RMSSD, low frequency, and HF. The correlation with HF was the most significant [r = 0.624].Conclusions: This study observed that physical therapy is obviously beneficial for patients with musculoskeletal pain. Furthermore, HRV parameters could provide important information regarding pain assessment. These can be helpful in diagnosis of pain intensity.