Heart rate variability: an objective measure of mental stress in surgical simulation

Purpose Highly stressful conditions in the operating room are associated with an increased risk of surgical adverse events and worse patient outcomes. Identifying and measuring mental stress in the surgical setting can guide our intervention efforts. The aim of this study was to evaluate the feasibility of heart rate variability (HRV) monitoring as an objective measure of mental stress and its correlation with expertise level in surgical simulation. Methods General surgery residents and faculty participated in a laparoscopic hiatal hernia repair simulation on porcine and synthetic models. Whole-procedure electrocardiographic (ECG) data was recorded, and manual artifact correction was performed. On power spectral density analysis, we computed the low-frequency/high-frequency (LF/HF) ratio, considered a surrogate for stress and mental strain. Mental workload was also subjectively assessed using the NASA-TLX rating scale. Results We recruited 37 participants: 18 novice, 14 intermediate, and 5 expert surgeons. When comparing the first to the second half of the procedure, the LF/HF ratio (stress level) relatively increased in novices (+ 23% for fundoplication, + 19% for crural repair), decreased in intermediates (− 11% and − 8%, respectively), and decreased in experts (− 40%, − 30%) (p = 0.001, p = 0.009). Pairwise comparison showed significant differences in stress level between novices and experts in both simulation models. NASA-TLX revealed higher mental and physical load among novice trainees, while experts reported greater satisfaction with their performance. Conclusions HRV monitoring in surgical simulation is a feasible and effective method to objectively evaluate mental stress and correlate it with the level of surgical expertise. We have shown that the relative change in LF/HF ratio can adequately distinguish between novice and expert surgeons. Our study supports the incorporation of HRV monitoring in surgical simulators to complement objective assessment of technical skills.