Study objectives: To characterize the metabolic status of weight-stable and clinically stable individuals with advanced emphysema.
Patients: Seventy-nine patients with severe emphysema (FEV1, 29 ± 13% of predicted [mean ± SD]) evaluated for enrollment in the National Emphysema Treatment Trial and 20 age-matched healthy subjects were studied.
Setting: Pulmonary function laboratory of university-affiliated teaching hospital.
Interventions: Data collection.
Measurements and results: We measured lung function, body composition, serum leptin levels, serum tumor necrosis factor receptors (sTNF-Rs), resting oxygen consumption (RV̇o2) normalized to weight in kilograms (RV̇o2/kg), and RV̇o2 normalized to fat-free mass (FFM) [RV̇o2/FFM]. The patient group and healthy group had similar age, body mass index (BMI), and body composition. RV̇o2/kg, RV̇o2/FFM, and sTNF-R levels were higher in patients compared to healthy subjects. There were no differences in serum leptin levels between emphysematous and healthy subjects, and there was no correlation between leptin and sTNF-R and RV̇o2/kg. Furthermore, both groups had similar gender-related differences in FFM, percentage of body fat, and serum leptin levels. Patients with lower BMI showed the greatest differences from control subjects in RV̇o2/kg.
Conclusion: In weight-stable subjects with advanced emphysema, RV̇o2/kg and RV̇o2/FFM were higher compared to healthy subjects, especially in those with BMI in the lower end of the normal range. RV̇o2/kg and RV̇o2/FFM did not correlate with leptin or sTNF-R levels. These data show that a higher metabolic rate is found in patients with emphysema who are clinically and weight stable. Thus, hypermetabolism is a feature of the disease and not sufficient to lead to weight loss.