PREVALENCE OF AN ELEVATED RESTING ENERGY-EXPENDITURE IN PATIENTS WITHCHRONIC OBSTRUCTIVE PULMONARY-DISEASE IN RELATION TO BODY-COMPOSITIONAND LUNG-FUNCTION

Objective: This study describes the prevalence and characteristics of an elevated resting energy expenditure (REE) in patients with chronic obstructive pulmonary disease (COPD). Design and setting: Patients wer e consecutively admitted to an in-patient pulmonary rehabilitation cen tre. Subjects: The study group consisted of 172 (123 male) clinically stable patients with COPD, age mean (s.d.) 64(10)y). Interventions: RE E was assessed by indirect calorimetry (ventilated hood) and adjusted for the influence of fat-free mass (FFM; measured by bioelectrical imp edance analysis) using the linear regression equations of REE on FFM g enerated in 92 healthy age-matched subjects (58 male, age 67(8)y) for men and women separately. The predicted REE adjusted for FFM (REEFFM) was obtained by using the FFM of each individual patient in the linear regression equation of REE on FFM generated in the healthy control gr oup. Results: 26% of the patients were hypermetabolic (defined as REE > 110% REEFFM), characterized by a lower age (60(10) vs 65(9)y) and a lower total lung capacity (TLC; 122(27) vs 139(28)%pred) compared to n ormometabolic patients (P < 0.001). The prevalence of FFM-depletion wa s equal among normo-and hypermetabolic patients: 36% vs 33% respective ly. Depleted patients expressed however a significantly higher residua l volume/TLC ratio and a lower maximal inspiratory mouth pressure inde pendently of hypermetabolism (P < 0.05). In contrast, on base of the H arris & Benedict (MB) prediction equations, which do not take body com position into account, 54% of the patients were hypermetabolic (REE > 110% REEHB), characterized by a higher age and a lower body mass and F FM (P < 0.05). Conclusions: Hypermetabolism commonly occurs in COPD, c haracterized by less hyperinflation at rest, in contrast to the sugges ted contribution of an elevated oxygen cost of breathing (OCB) to hype rmetabolism in COPD. The higher hyperinflation at rest in FFM-depleted patients independently of hypermetabolism suggests a higher OCB durin g activities, contributing to the elevated total daily energy expendit ure previously reported in COPD. The MB-equations overestimate the pre valence of hypermetabolism and link hypermetabolism incorrectly to agi ng and depletion.