The beneficial effect of inhaled bronchodilators may be mediated, in part, through a reduction in static and dynamic hyperinflation in this disease. This study compared the effect of long acting beta agonist and anticholinergic bronchodilators on lung volumes.
This double-blinded, single-dose, crossover trial compared the effects of single inhaled doses of the long acting beta agonist, formoterol (18 mcg) and the anticholinergic, ipratropium (72 mcg) to placebo on lung volumes in 22 patients with COPD. Spirometry and static lung volumes were determined at baseline and one hour, and exercise testing at approximately 1 ½ hour following drug inhalation.
The mean age was 65 ± 11 years and the FEV1 was 41 ± 14% of predicted. Both formoterol and ipratropium increased the FEV1 (0.36L and 0.27L, resp.) compared to placebo (0.13L). In addition, both bronchodilators were associated with similar reductions in the functional residual capacity (- 0.50L and – 0.49L, resp.) and residual volume (- 0.60L and – 0.65L, resp.) and increases in inspiratory capacity (0.31L and 0.23L, resp.). Ipratropium was also associated with a small increase in exercise endurance and a decrease in Borg-rated exertional dyspnea. The rate of decrease in IC from pre-exercise to isotime near the end of constant workload exercise testing was similar with all three test drugs (−0.38L, - 0.42L, and – 0.38L for formoterol, ipratropium and placebo, resp.). However, since the postbronchodilator, pre-exercise IC’s were higher, the end-of-exercise IC’s remained higher, compared to placebo.CONCLUSIONS: Both formoterol and ipratropium led to similar decreases in static lung volumes. Neither bronchodilator affected the rate of dynamic hyperinflation during exercise, but lower operational lung volumes near the end of exercise reflected lower pre-exercise static volumes.
Both classes of bronchodilators appear to have similar effects on static and dynamic lung volumes in COPD.
N.R. Kanathur, None.