Sustained maximal inspiratory pressure as a measure to inspiratory muscle function

Abstract

Introduction: Measures of sustained maximal inspiratory pressure (SMIP) has been used to access inspiratory work generated through time, however procedures of this test can vary and its validity should be considered. Aims and Objectives: The aim of this study was evaluate the relationship between the integrated area under the pressure-time curve from SMIP (SMIP_area) and inspiratory muscle work. Methods: Fifteen healthy participants (18 to 59 years), both sex, normal BMI and normal pulmonary function according to spirometry test were evaluated. Inspiratory muscle function was evaluated as Maximal Inspiratory Pressure (MIP), SMIP using a digital manometer (UFMG, Brasil) and inspiratory muscle endurance test with constant load using a tapered flow resistive load electronic device (POWERbreathe KH1, London-UK). Variables considered were: mean maximal pressure from de MIP test, SMIP_area from SMIP test and total external inspiratory work (Insp_work) from endurance test. Statistical analysis was performed by Shapiro-Wilk to evaluate normality of data, Pearson correlation test and linear regression analysis to evaluate relation between SMIP_area and Insp_work and validity of the SMIP test. Results: The data was presented as median (quartile 1-quartile 3). SMIP_area was 451.03 (396.76-587.31) pressure time units (PTUs), and the median Insp_work was 211 (127-302) J. A regression coefficient (R 2 ) of 0.78 was observed (r=0.88; p Conclusion: The results show that the SMIP_area could be used to predict the Insp_work, mainly in cases when the device to measure the inspiratory work capacity is unavailable.