Psychometric properties of volitional tests used to measure respiratory muscle strength and endurance: A systematic review

Introduction It is essential that diagnostic tests for evaluating respiratory muscles have proven reliability and validity. This study aims to synthesize studies that evaluated the psychometric properties of volitional tests used to measure respiratory muscle strength and endurance. Methods A systematic literature search was conducted in MEDLINE/PubMed, LILACS, Cochrane Central Register of Controlled Trials, Scopus and SciELO. Primary studies that evaluated the reliability and validity of volitional tests to measure respiratory muscle strength and endurance were included. The quality of the included studies was assessed using the Critical Appraisal Tool (CAT). Results Twenty-eight studies were included in this review, describing the psychometric properties of eight different approaches to measuring respiratory muscle strength and endurance. Respiratory muscle strength and endurance were assessed using static maximal inspiratory pressure, static maximal expiratory pressure, dynamic maximal inspiratory pressure, sustained maximal inspiratory pressure, nasal inspiratory pressure, manual respiratory muscle measurements, and maximal incremental inspiratory muscle performance. Overall, the studies included were of good methodological quality. Data related to validity and reliability showed excellent results for the maximum inspiratory pressure and maximum expiratory pressure, with maximum ICC values of 0.979 (CI 0.947-0.991) and 0.989 (CI 0.022-0.001), respectively. Other tests evaluated did not present high reliability and validity. Conclusion This review concluded that volitional tests vary in reliability for measures of respiratory muscle strength and endurance. The more traditional ones, such as maximum inspiratory pressure and maximum expiratory pressure, presented higher validity and reliability values compared to the other tests.