Changes in metabolic rate in patients with severe emphysema after lung volume reduction surgery.

Background. Resting metabolic rate (RMR) increases in severe emphysema. Lung volume-reduction surgery (LVRS) proved effective therapy in palliating symptoms and improving lung function, but the mechanism underlying the improvement is not yet elucidated. We hypothesized that the improvement after surgery may be related to a RMR saving due to more effective act of breathing. The aim of our study is to evaluate changes in RMR after LVRS and explain possible correlations with symptoms amelioration. Methods. In 14 patients, mean age 63.8±10.2, body mass index (BMI) 24.3±4.4kg/m2, who underwent LVRS, RMR was measured using a whole body respiratory chamber. Anthropometric measurements, nutritional status, respiratory parameters, ergometric tests and quality of life scales were also assessed. The baseline values were compared with a homogeneous non-emphysematous population of 10 subjects (65.5±7.9, BMI 26.8±3.3kg/m2). Height, weight, skinfold thickness, forced expiratory volume 1 second (FEV1), residual volume, 6-minute walking and quality of life measurements were also assessed. Basal transversal and 6-month longitudinal comparisons were performed according to the more appropriate statistical tests. Results. At the baseline the emphysematous patients showed a more elevated fat free mass RMR (128.4±10.8 Vs 116.7±11.6 kJ/kg/die, p=0.007) than the control group. At 6 months forced expiratory flow in one second (FEV1) (0.90 Vs 1.29L, p=0001), residual volume (RV) (4.98 Vs 3.43L, p=0.0001), and quality of life scores (p=0.0001) significantly improved. Accordingly, RMR was significantly decreased for absolute (4.339±0.6, p=0.05) and fat free mass (117.3±11.8, p=0.01) values and reached the predicted values calculated from the Harris-Benedict equation. RMR saving was significantly related with RV decrement (p=0.001). Conclusions. RMR improves with lung function and symptoms after LVRS, thus outlining a more elevated cost of breath