Study objectives: Some subjects with COPD have an elevated resting energy expenditure (REE) which may be related to an increased work of breathing at rest. The purpose of this study was to examine the effect of lung volume reduction surgery (LVRS) on REE and body weight.
Design: Ten subjects with COPD were recruited (mean age +/- SD = 61.4 +/- 6.1 years). At baseline (which was following preoperative pulmonary rehabilitation) and four months following LVRS (combined with postoperative pulmonary rehabilitation), each subject had tests of lung function, REE via indirect calorimetry using a canopy system, six minute walk distance (6MWD) and quality of life (QoL) using the St George's Hospital Respiratory Questionnaire (SGRQ).
Measurements: The FEV1 (% predicted) increased from 27.7 +/- 5.8% (mean +/- SD) at baseline to 33.9 +/- 7.8% following LVRS (P < 0.05). REE (% predicted) was 110 +/- 9.8% at baseline and decreased to 106 +/- 6.7% following LVRS (P = 0.04). Body mass index (BMI) following LVRS was unchanged (P = 0.67). No correlation between the change in BMI and change in REE was shown (r2 = 0.3, P = 0.1). There was a significant improvement in QoL following LVRS (P < 0.001). 6MWD also significantly increased from 354 +/- 83 m to 412 +/- 82 m following LVRS (P = 0.001).
Conclusion: Whilst there was an increase in lung function and a reduction in REE following LVRS, there was no corresponding change to body weight. The improvement in REE following LVRS may be related to an improvement in work of breathing.