Determinants of maximum voluntary ventilation in patients with chronic obstructive pulmonary disease

Purpose: The 12 second maximum voluntary ventilation (MVV) has proven to be a useful test of pulmonary function throughout the years. The best studied determinant of MVV is an expiratory variable, the forced expiratory volume in one second (FEV1). Inspiratory variables have the potential to improve the prediction of MVV. We hypothesized that the resting maximum inspiratory flow rate (MIFR) is a determinant of MVV and sought to determine how the MIFR compared with other studied inspiratory variables. Methods: We prospectively evaluated thirty-one volunteers with COPD (28 males and 3 females; age 68.7±5.7 years; FEV1 1.15L±0.44L; (mean±SD) who had at least a 20 pack-year smoking history, a stable clinical course for the 3 months preceding testing and at least two consistent expiratory efforts according to American Thoracic Society guidelines. Results: Using univariate analysis, the MVV was significantly correlated with: the MIFR (r=0.65; p=0.00008), the index of respiratory muscle strength (RMS) (r=0.52; p=0.0027) and the Pimax (r=0.46; p=0.0092) However, as a single variable, the FEV1 remained the best determinant of MVV (r=0.81; p=0.0000). Using stepwise multiple linear regression analysis, the FEV1, MIFR and RMS together were all significant predictors of MVV (R²=0.79; p=0.0000). Conclusions: We conclude that the MIFR is a determinant of MVV in this group of COPD patients. Clinical Implications: The MIFR should be included as one of the variables whenever determination of the indirect MVV is necessary in COPD patients.