Influence of 4 interfaces in the assessment of maximal respiratory pressures.

BACKGROUND The measurement of maximal respiratory pressure (MRP) is a procedure widely used in clinical practice to evaluate respiratory muscle strength through the maximal inspiratory pressure (P(Imax)) and maximal expiratory pressure (P(Emax)). Its clinical applications include diagnostic procedures and evaluating responses to interventions. However, there is great variability in the equipment and measurement procedures. Understanding the impacts of the characteristics of different interfaces can augment the repeatability of this method and help to establish widely applicable predictive equations. The aim of this study was to evaluate the influence of 4 different interfaces on a subject's capacity to generate MRP and the impact of these interfaces on the repeatability of these measurements. METHODS Fifty healthy subjects (mean ± SD age 26.36 ± 4.89 y) with normal spirometry were evaluated. MRP was measured by a digital manometer connected to 4 interfaces using different combinations of mouthpieces and tubes. The following variables were analyzed: maximum mean pressure, peak pressure, plateau pressure, and plateau variation. Analysis of variance for repeated measures or a Friedman test was used to compare the 4 interfaces, with P < .008 after Bonferroni adjustment considered significant. RESULTS There was no significant difference between the 4 interfaces with respect to maximum mean pressure, peak pressure, plateau pressure, or plateau variation for P(Imax) (P ≥ .49) or P(Emax) (P ≥ .11), nor did the number of tests performed to fulfill the criteria of repeatability for P(Imax) (P = .69) or P(Emax) (P = .47) differ among the 4 interfaces. CONCLUSIONS P(Imax) and P(Emax) values seem not to be influenced by the different interfaces studied, suggesting that patient comfort and availability of interfaces can be considered.