Objective: To investigate four parameters defining maximal respiratory pressures and to evaluate their correlations and agreements among those parameters for the determination of MIP and MEP. Methods: This was a cross-sectional study involving 49 healthy, well-nourished males and females. The mean age was 23.08 ± 2.5 years. Measurements were carried out using a pressure transducer, and the estimated values for the parameters peak pressure (Ppeak), plateau pressure (Pplateau), mean maximal pressure (Pmean), and pressure according to the area (Parea) were determined with an algorithm developed for the study. To characterize the study sample, we used descriptive statistics, followed by repeated measures ANOVA and Bonferroni post hoc test or by the Friedman test and the Wilcoxon post hoc test, as well as by Pearson's or Spearman's correlation coefficients, depending on the normality of the data. The agreement between the variables was assessed with Bland  Altman plots. Results: There were significant differences among all of the parameters studied for MIP (Ppeak = 95.69 ± 27.89 cmH2O; Parea = 88.53 ± 26.45 cmH2O; Pplateau = 82.48 ± 25.11 cmH2O; Pmean = 89.01 ± 26.41 cmH2O; p < 0.05 for all) and for MEP (Ppeak = 109.98 ± 40.67 cmH2O; Parea = 103.85 ± 36.63 cmH2O; Pplateau = 98.93 ± 32.10 cmH2O; Pmean = 104.43 ± 36.74 cmH2O; p < 0.0083 for all). Poor agreement was found among almost all of the parameters. Higher pressure values resulted in larger differences between the variables. Conclusions: The maximal respiratory pressure parameters evaluated do not seem to be interchangeable, and higher pressure values result in larger differences among the parameters.

Keywords: Respiratory system; Muscle strength; Respiratory function tests.