Assessing the Reliability of the Dynamic-Index of Inspiratory Muscle Strength in Cardiac Surgery Candidates

Introduction: Inspiratory muscle strength (IMS) is a crucial predictor of the development of pulmonary complications after cardiac surgery. The strength index (S-index), a novel non- invasive tool, dynamically assesses inspiratory muscles and is associated with lower risks for heart patients than static tests. This study aims to investigate the reliability of the S-index in patients scheduled for cardiac surgery. Materials and Methods: This study included 20 preoperative cardiac surgery candidates (11 men and 9 women; mean age, 56±13 years). The S-index, peak inspiratory flow (PIF) and vital capacity (VC) were evaluated using a power breath K5 Electronic respiratory device. An examiner conducted these measurements at two distinct intervals, one hour apart. Each index’s average and best values were evaluated for reliability using the intra-class correlation coefficient (ICC). Results: The study revealed excellent (ICC>0.9) and good (ICC>0.8) intra-examiner reliability for the best and average values of the S-index and PIF, respectively. Also, the results of the present study showed excellent intra-examiner reliability for the best and average values of the VC (ICC>0.9) Conclusion: The ICC results of the present study showed that the S-index can be used to determine the dynamic strength of the inspiratory muscles with acceptable repeatability in cardiac surgery candidates. One of its advantages is the ability to determine the appropriate load for inspiratory muscle training (IMT) exercises during the hospitalization phase of these patients dynamically without breath-holding.