title: Bronchodilation improves endurance but not muscular efficiency in chronic obstructive pulmonary disease.
abstract: We hypothesized that bronchodilator treatment not only improves hyperinflation and endurance capacity but also muscular efficiency in stable chronic obstructive pulmonary disease (COPD). We aimed to demonstrate that tiotropium and salmeterol improve muscular efficiency compared with placebo. Twenty-five COPD patients were studied, including 20 males of mean (standard deviation) age 62 years (7 years) with baseline forced expiratory volume in 1 second of 41% (10%) predicted, and maximal workload of 101 Watt (36 Watt). Subjects were randomized for 6-week treatment with tiotropium 18 μg once daily, salmeterol 50 μg twice daily, or placebo using a double-blind, crossover design. Muscular efficiency and endurance time were measured during cycling at 50% of maximal work load. Resting energy expenditure was measured using a ventilated hood. Muscular efficiency after tiotropium, salmeterol, and placebo treatment was 14.6%, 14.4%, and 14.4%, respectively (P > 0.05), and resting energy expenditure was 1485 kcal/24 hours, 1709 kcal/24 hours, and 1472 kcal/24 hours (P > 0.05), respectively. Endurance time after tiotropium treatment was significantly higher than that after placebo (27.0 minutes versus 19.3 minutes [P = 0.02]), whereas endurance time after salmeterol treatment was not higher than that after placebo (23.3 minutes [P = 0.22]). In this small study, we were not able to demonstrate that bronchodilator therapy improved muscular efficiency. Apparently, reduced costs of breathing relative to total energy expenditure were too small to be detected.
authors.affiliation: University Medical Center, Groningen, The Netherlands. h.van.der.vaart@long.umcg.nl
authors.forename: Hester
authors.initials: H
authors.lastname: van der Vaart
authors.forename: Dirkje S
authors.initials: DS
authors.lastname: Postma
authors.forename: René
authors.initials: R
authors.lastname: Grevink
authors.forename: Willem
authors.initials: W
authors.lastname: Roemer
authors.forename: Nick
authors.initials: N
authors.lastname: ten Hacken
mesh_terms: D000368:Aged; D000420:Albuterol / Q000031:analogs & derivatives* / Q000627:therapeutic use; D001993:Bronchodilator Agents / Q000627:therapeutic use*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004734:Energy Metabolism / Q000187:drug effects; D005080:Exercise Test; D017079:Exercise Tolerance / Q000187:drug effects*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000187:drug effects* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000503:physiopathology; D009426:Netherlands; D010807:Physical Endurance / Q000187:drug effects*; D010991:Plethysmography; D029424:Pulmonary Disease, Chronic Obstructive / Q000188:drug therapy* / Q000503:physiopathology; D000068299:Salmeterol Xinafoate; D012602:Scopolamine Derivatives / Q000627:therapeutic use*; D013997:Time Factors; D000069447:Tiotropium Bromide; D016896:Treatment Outcome; D014797:Vital Capacity
chemical_list: D001993:Bronchodilator Agents; D012602:Scopolamine Derivatives; D000068299:Salmeterol Xinafoate; D000420:Albuterol; D000069447:Tiotropium Bromide