Purpose: Preoperative inspiratory muscle training reduces the incidence of postoperative pulmonary complications after cardiac surgery, but training protocols vary widely in terms of intensity. Currently, the mechanisms underlying the effectiveness of this practice are not known. The purpose of the present study is to determine whether preoperative high-intensity inspiratory muscle training (HI-IMT) modulates the perioperative systemic inflammatory response in cardiac surgery patients.
Methods: Participants awaiting surgical aortic valve replacement were randomized to 3 to 6 weeks preoperative home-based HI-IMT or same duration low-intensity inspiratory muscle training (LI-IMT). The primary outcome was the preoperative value of the soluble tumor necrosis factor receptor 1 (sTNFR1). Secondary outcomes assessed perioperative evolution of the cytokines: sTNFR1, Tumor necrosis factor-α, Interleukin (IL)-6, IL-8, IL10, IL1β, and their combined z-score; reflecting post-training and postoperative inflammatory response. Perioperative pulmonary function and postoperative clinical outcomes were collected.
Results: Between February 2018 and March 30, 2019 patients were randomized, to HI-IMT or LI-IMT. There were no differences between the groups in terms of baseline characteristics. The median (IQR) training duration was 34 (28-44) days. After training, the median (IQR) predicted maximal inspiratory pressure was higher in the HI-IMT vs LI-IMT group (119 (96-142%) vs 97 (81-107%); p = .04) Levels of the sTNFR1 cytokine increased during training in the HI-IMT group, pre vs post training (Median (IQR) 1073 (920; 1219) vs 1172 (965; 1368) ng/L; p = .03). The 24-h postoperative global inflammatory score was lower in the HI-IMT than in the LI-IMT group (Median (IQR), -0.37 (-0.62, 0.03) vs -0.10 (-0.17, 0.49), p = .04). Global inflammatory scores were not different at other time points. There were no significant differences between the groups in post-operative pulmonary function and postoperative clinical outcome.
Conclusion: High intensity inspiratory muscle training shows immunomodulatory properties. These properties could explain why preoperative inspiratory muscle training can lead to lung protection after cardiac surgery.
Keywords: Immune response; perioperative medicine; prehabilitation; respiratory muscle training.