Reproducibility of Maximum Respiratory Pressure Assessment: A Systematic Review and Meta-analysis

Background: Accurate assessment of maximum respiratory pressure is vital when tracking disease progression and devising treatment strategies. Previous studies indicate a learning effect when undertaking maximum respiratory pressure measurements. The extent of this learning effect and methodologies undertaken to mitigate this learning effect have not been investigated systematically. Research Question: What is the magnitude of improvements in maximum respiratory pressure in response to respiratory muscle warm-up protocols and repeated measures of maximum respiratory pressure in healthy individuals and clinical populations? Methods: A comprehensive search of electronic databases was undertaken during August 2021 for studies examining the intrarater reliability of maximum inspiratory or expiratory pressure, or both, studies developing a protocol or an intervention to obtain maximum values, and studies analyzing the reliability of repeated maneuvers in a single testing session in healthy individuals and clinical populations. Included articles were analyzed critically using two appraisal tools. Standardized mean differences with 95% CIs were calculated and corrected for the sample size as a measure of the magnitude of change in maximum respiratory pressure outcomes. Results: Of the 1,969 articles retrieved, 32 were included in the meta-analysis. Eighteen studies included healthy individuals and 14 studies included individuals with chronic medical conditions. The overall effect of inspiratory muscle warm-up protocols was higher (effects size [ES], 0.40; 95% CI, 0.17-0.63) in comparison with single testing session studies (ES, 0.20; 95% CI, 0.05-0.35) and studies performing repeated testing sessions of maximum respiratory pressure (ES, 0.14; 95% CI, 0.07-022). Interpretation: Inspiratory muscles warm-up procedures induce higher increases in maximum inspiratory pressure in comparison with single and repeated testing sessions of maximum respiratory pressure in healthy individuals. Warm-up protocols are more effective to obtain the maximum performance of inspiratory muscles in one testing session in comparison with other methods. Trial Registry: PROSPERO; No.: CRD42022304591; URL: https://www.crd.york.ac.uk/prospero/