THERMOGENIC EFFECT OF BRONCHODILATORS IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

Background - Patients with chronic obstructive pulmonary disease (COPD ) are frequently malnourished and have increased resting energy expend iture (REE). An increase in the work of breathing is generally conside red to be the main cause of this hypermetabolism, but other factors ma y also be implicated. Bronchodilators may decrease the work of breathi ng by reducing airway obstruction, but beta(2) adrenergic agents have a thermogenic effect. The aim of this study was to determine the effec t of salbutamol and ipratropium bromide administration on REE in patie nts with COPD. Methods - Thirteen patients (10 men) of mean (SD) age 6 8.3 (7.3) years and forced expiratory volume in one second (FEV(1)) 39 .0 (17.0)% predicted were studied on three consecutive days. The REE w as measured by indirect calorimetry at 30, 60, 120, and 180 minutes af ter double blind nebulisation of either salbutamol, ipratropium bromid e, or placebo in random order. Results - FEV(1) increased both after s albutamol and after ipratropium. The difference in the mean response b etween salbutamol and placebo over 180 minutes was + 199 ml (95% CI 104 to + 295). The difference in mean response between ipratropium and placebo was + 78 ml (95% CI + 2 to + 160). REE increased after salbut amol but was not changed after ipratropium. The difference in mean res ponse between salbutamol and placebo was + 4.8% of baseline REE (95% C I + 2.2 to + 7.4). Heart rate increased after salbutamol but not after ipratropium. The difference in the mean response between salbutamol a nd placebo was + 5.5 beats/min (95% CI + 2.6 to + 8.4). Conclusion - S albutamol, but not ipratropium bromide, induces a sustained increase i n the REE of patients with COPD despite a reduction in airway obstruct ion.