Immediate Respiratory Warm-Up Effect on Dynamic Inspiratory Muscle Strength in Cardiac Surgery Candidates

Introduction: The strength of inspiratory muscles is one of the essential factors in preventing postoperative pulmonary complications (POPC). One of the new tools to safely measure the strength of the inspiratory muscles in heart patients dynamically and without breath holding is the strength-index (S-index). This study aims to evaluate the immediate effects of a respiratory warm-up (RWU) session on the S-index and other lung parameters in cardiac surgery candidates, a subject with limited existing research. Materials and Methods: This study was conducted as a randomized controlled trial. Forty participants scheduled for heart surgeries were randomly assigned to either the study (RWU between two tests) or control (without RWU) groups. RWU consists of threshold loading inspiratory muscle training (TL-IMT) exercises at 30% of the S-index with 30 breathing cycles. Respiratory tests, including S-index, peak inspiratory flow (PIF) and vital capacity (VC), were assessed twice using an electronic respiratory device. Results: Covariance analysis showed no significant difference in the average and best values of the S-index, PIF or VC indices at the second tests, between two groups (P 0.05), or in the independent t test and Mann-Whitney U test for the “rate of changes,” between two tests (P 0.05). Finally, intra-group changes, assessed with paired sample t test between two tests, were mostly non-significant for these indices (P 0.05), except for the best VC in the study group (P=0.03). Conclusion: The study results suggest that a RWU session does not significantly impact cardiac surgery candidates’ S-index or other respiratory parameters. Thus, incorporating RWU before S-index testing may not be necessary.