Quantification of Immediate Surgical Stress After Major and Minor Thoracic Surgeries Through HRV: A Secondary Post Hoc Analysis of a Randomized Controlled Trial

Purpose

Heart rate variability (HRV) reflects autonomic nervous system activity and is sensitive to physiological stress induced by surgery. This study is a secondary, post hoc analysis of a randomized controlled trial aimed at evaluating changes in HRV following major and minor thoracic surgery, and investigating whether postoperative respiratory physiotherapy can modulate these changes. In a prospective, randomized design, two physiotherapy interventions, including positive expiratory pressure (PEP) and inspiratory muscle training (IMT), were compared to assess their effects on HRV.

Methods

Electrocardiogram recordings were analyzed from 75 patients undergoing either minor pulmonary (PM) or pulmonary resection (PR) surgery. HRV data were collected preoperatively and during the first two postoperative days, immediately following physiotherapy sessions. Patients were assigned to one of two intervention groups (PEP or IMT). Time‐, frequency‐, and nonlinear‐domain HRV parameters were analyzed longitudinally and compared between surgical and intervention groups.

Results

Most HRV parameters exhibited a postoperative reduction, with more pronounced changes observed in the PR surgery group. In particular, the root mean square of successive RR interval differences (RMSSD) and high‐frequency (HF) power, which are commonly associated with parasympathetic modulation, showed marked decreases. Recovery toward baseline values varied across surgical groups, interventions, and HRV parameters; however, no clear signs of recovery were observed in the PR surgery group during the observation period. No statistically significant differences were detected between the PEP and IMT interventions ( p ≥ 0.05), with the exception of short‐term detrended fluctuation analysis (DFA α ₁ ) in the PM surgery group ( p = 0.04).

Conclusion

HRV parameters reflected surgery‐induced autonomic alterations, with more pronounced and persistent changes observed in patients undergoing PR compared with PM surgery. No clear recovery toward baseline was detected during the 2‐day postoperative follow‐up, suggesting prolonged autonomic disturbances after thoracic surgery.

Trial Registration: ClinicalTrials.gov: NCT02931617