New method for evaluating maximal respiratory pressures: Concurrent validity, test-retest, and inter-rater reliability

Background: Maximal respiratory pressures (MRP) obtained at functional residual capacity (FRC) may reflect the real respiratory muscle pressure. Objectives: To evaluate concurrent validity, test-retest, and inter-rater reliability of MRP performed with a new instrument in healthy individuals, and to compare values obtained at different volumes in healthy individuals and individuals with COPD. Methods: MRP of 100 healthy individuals were obtained using the TrueForce and the MicroRPM (R) at residual volume (RV) and total lung capacity (TLC) to evaluate concurrent validity. MRP were obtained at FRC using the TrueForce to evaluate reliability. Comparisons of inspiratory pressure values (FRC compared to RV) and expiratory pressure values (FRC compared to TLC) were performed with 100 healthy individuals and 15 individuals with COPD. Results: The intraclass correlation coefficient (ICC) was 0.77 and 0.86 for concurrent validity for inspiratory and expiratory pressures, respectively. Test- retest reliability showed an ICC of 0.87 for inspiratory pressure, and 0.78 for expiratory pressure; inter-rater reliability showed an ICC of 0.91 for inspiratory pressure, and 0.84 for expiratory pressure. Measurements performed at RV and TLC were higher when compared to FRC [mean difference (95%CI)= -8.30 (- 11.82, -4.78) cmH(2)O; -37.29 (-42.63, -31.96) cmH(2)O] in healthy individuals, and -11.09 (- 15.83, -6.35) cmH(2)O; -57.14 (-71.05, -43.05) cmH(2)O in COPD, for inspiratory and expiratory pressures, respectively. Conclusion: MRP performed with the TrueForce presented good concurrent validity, good testretest reliability, excellent inter-rater reliability for inspiratory pressure and good inter-rater reliability for expiratory pressure. MRP were lower when obtained at FRC for healthy individuals and with COPD. (C) 2021 Associacao Brasileira de Pesquisa e Pos-Graduacao em Fisioterapia. Published by Elsevier Espana, S.L.U. All rights reserved.