Comparing peak and sustained values of maximal respiratory pressures in healthy subjects and chronic pulmonary disease patients

BACKGROUND: The measurement of maximal inspiratory and expiratory pressures is useful for the evaluation of pulmonary function. However, the methods to obtain them are not always properly described. OBJECTIVE: To identify the difference between the peak pressure values (Ppeak, the highest pressure reached) and the sustained pressure (Pmaxs, the highest pressure sustained for one second) in MIP and MEP evaluation. METHOD: 55 healthy individuals and 50 patients who were taking part in a pulmonary rehabilitation program, all of them with chronic pulmonary disease, were studied by recording their best maximal inspiratory pressure and maximal expiratory pressure tests. The peak and sustained pressure values were compared and analyzed to determine whether there was a difference between them. RESULTS: The maximum inspiratory pressure records of healthy individuals showed that the maximal peak inspiratory pressure and the maximal inspiratory pressure found were, respectively, 102 ± 33 cmH2O and 92 ± 29 cmH2O (p < 0.001), and those of the patients participating in the pulmonary rehabilitation program were 75 ± 23 cmH2O and 67 ± 22 cmH2O (p < 0.001). The recorded values of maximal expiratory pressure, peak and maximal were 119 ± 42 cmH2O and 110 ± 39 cmH2O (p < 0.001), respectively, for healthy subjects, and 112 ± 40 cmH2O and 103 ± 36 cmH2O (p < 0.001) for the patients. CONCLUSION: There is a significant difference between Ppeak and Pmaxs, that can lead to different interpretations in the evaluation of the respiratory muscle strength. To minimize interpretation errors, the authors suggest the use of devices which record both values (peak and sustained)