PULMONARY-FUNCTION IN OBESE SUBJECTS WITH A NORMAL FEV(1) FVC RATIO/

Study objective: To determine pulmonary function test (PFT) profile an d respiratory muscle strength (RMS) of a group of obese individuals wh o did not have evidence of obstructive airway disease or other underly ing diseases affecting their respiratory system. Design: Prospective, open. Setting: PFT laboratory, VA Medical Center. Participants: Sixty- three consecutive obese (body mass index greater than 27.8 kg/m(2)) ma le subjects without overt obstructive airway disease (FEV(1)/FVC ratio greater than 80%). Measurements and results: Standard PFTs and maximu m static inspiratory (PImax) and expiratory (PEmax) mouth pressures we re determined. RMS was calculated from the following formula: (PImax+P Emax):2. Two distinct groups were identified, those with normal maximu m voluntary ventilation (MW) (> 80% predicted) and those with low MVV. Both inspiratory and expiratory now rates (FVC, FEV(1), forced expira tory flow at 50% vital capacity [V-50], maximum inspiratory flow rate [MIFR]), lung volumes (vital capacity [VC], inspiratory capacity [IC], expiratory reserve volume), PImax, and RMS were significantly lower, and residual volume/total lung capacity (RV/TLC) ratio was significant ly higher in obese subjects with low MW compared with those in whom MW was normal. MVV correlated significantly with FVC, FEV(1), V-50, MIFR , TLC, VC, IC, RV/TLC, and RMS; the strongest correlation was with MIF R (r = 0.76, p < 0.0001). Conclusions: Standard PFTs allow recognition of a subgroup of obese subjects without overt obstructive airway dise ase who have more severe lung dysfunction, the marker of which is a lo w MVV. Peripheral airway abnormalities may be responsible for these ob servations.