Background: This study examined the effects of inhaled furosemide on the ventilatory and perceptual response to high-intensity constant-load cycle exercise in chronic obstructive pulmonary disease (COPD).
Methods: In a randomised, double-blind, placebo-controlled, crossover study, 20 patients with COPD (mean (SD) forced expiratory volume in 1 s 45 (15)% predicted) received either nebulised furosemide 40 mg or placebo on two separate days. Thirty minutes after each treatment, patients performed pulmonary function tests and a symptom-limited cycle exercise test at 75% of their maximum incremental work rate. Changes in spirometry, plethysmographic lung volumes, dynamic operating lung volumes, ventilation, breathing pattern, cardiovascular function, dyspnoea intensity and exercise endurance time were compared between treatments.
Results: Compared with placebo, treatment with furosemide resulted in a mean (SD) decrease in dyspnoea intensity at the highest equivalent exercise time (ie, isotime for each patient) of 0.9 (1.0) Borg units (p<0.01) and an increase in exercise endurance time of 1.65 (0.63) min (p<0.05). These improvements were associated with increases in dynamic inspiratory capacity, tidal volume and mean tidal expiratory flow rates at isotime (p<0.01). The eight patients whose exercise endurance time improved by >1 min had greater changes in operating lung volumes (p<0.05), submaximal oxygen pulse (p<0.05) and oxygen uptake (p = 0.05) than those in whom exercise endurance time did not improve.
Conclusion: Alleviation of exertional dyspnoea after single-dose furosemide inhalation in COPD is multifactorial but improvements in dynamic ventilatory mechanics are contributory in some individuals.
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Additional data are published online only at http://thorax.bmj.com/content/vol63/issue7
Presented in part at the ALA/ATS International Conference, San Diego, May 2006 (Amjadi K, Harris-McAllister VL, Webb KA, et al. Mechanisms of exertional dyspnea relief following nebulised furosemide in patients with COPD. Proc Am Thorac Soc 2006;3:A225.)
Funding: This study was funded in part by an Ontario Thoracic Society Block Term Grant. KA received a John Alexander Stewart Research Fellowship from the Department of Medicine, Queen’s University. DJ was supported by an Ontario Graduate Scholarship.
Competing interests: None.
Ethics approval: This study was approved by the local university/hospital research ethics committee.