Background: Maximum inspiratory pressure (MIP) is an important and noninvasive index of diaphragm strength and an independent predictor of all-cause mortality. The ability of adults over a wide age range and multiple race/ethnicities to perform MIP tests has previously not been evaluated.
Methods: The Multi-Ethnic Study of Atherosclerosis recruited white, African American, Hispanic, and Chinese American participants, ages 45-84 years, and free of clinical cardiovascular disease in 6 United States cities. MIP was measured using standard techniques among 3,849 Multi-Ethnic Study of Atherosclerosis participants. The MIP quality goal was 5 maneuvers, with the 2 largest values matching within 10 cm H2O. Correlates of MIP quality and values were assessed in logistic and linear regression models.
Results: The 3,849 participants with MIP measures were 51% female, 35% white, 26% African American, 23% Hispanic, and 16% Chinese American. Mean+/-SD MIP was 73+/-26 cm H2O for women and 97+/-29 cm H2O for men. The quality goal was achieved by 83% of the cohort and was associated with female sex, older age, race/ethnicity, study site, low ratio of forced expiratory volume in the first second to forced vital capacity (FEV1/FVC), and wheeze with dyspnea. The multivariate correlates of MIP were male sex, younger age, higher body mass index, shorter height, higher FVC, higher systolic blood pressure (in women) and health status (in men). There were no clinically important race/ethnic differences in MIP values.
Conclusions: Race-specific reference equations for MIP are unnecessary in the United States. More than 80% of adults can be successfully coached for 5 maneuvers, with repeatability within 10 cm H2O.