Prediction for the maximum inspiratory pressure value from the thoracic expansion measurement in Indonesian healthy young adults

BACKGROUND: The diaphragm is the primary muscle responsible for breathing. Weakness in the diaphragm will result in breathing difficulties. The micro-RPM (respiratory pressure meter) is a non-invasive testing device to measure respiratory muscle strength, which is not always feasible, while thoracic expansion measurements are easy to do. AIM: This study constructs a prediction formula for a maximal inspiratory pressure (MIP) value from thoracic expansion measurements. METHODS: This study was quantitative with a cross-sectional design. Participants were healthy adults aged 20–40 years, with normal Mini-Mental State Examinations, body mass index, spirometry, and moderate activity levels. The tests performed were MIP and thoracic expansion measurements at three levels: axilla (L1), the fourth intercostal space (L2), and at processus xiphoideus (L3). The data were analyzed using an unpaired t-test and multivariate. RESULTS: The mean MIP for males (81.51 ± 13.90 cmH(2)O) was significantly greater than females (63.17 ± 15.89 cmH(2)O) (P = 0.0001). These findings were not different with the Chinese, Indian, Mangalorean, and Malaysian populations because they are all of Asian ethnicity. Thoracic expansion L2 (r = 0.463, P = 0.0001) and L3 (r = 0.502, P = 0.0001) were moderately correlated with MIP, whereas thoracic expansion L2, L3 combined with gender had a weak effect on MIP. The prediction formula was: MIP = 56.802 + 2.387 + L2 + 13.904 + Gender * and MIP = 53.289+ 3.561 + L3 + 9.504 + Gender *, * 0 = female; 1 = male. CONCLUSIONS: A prediction formula for MIP can be made using the thoracic expansion variable with gender as a determinant factor. A quick and easy measurement of thoracic expansion can be used as a mean of screening respiratory muscle strength in patient care.