INTRODUCTION: Delivery of bronchodilators with a metered-dose inhaler (MDI) and a spacer device in mechanically ventilated patients has become a widespread practice. However, except for the short-acting beta2-agonist salbutamol, the duration of action of other bronchodilators, including long-acting beta2-agonists, delivered with this technique is not well established. The purpose of this study was to examine the duration of bronchodilation induced by the long-acting beta2-agonist salmeterol administered with an MDI and a spacer in a group of mechanically ventilated patients with exacerbation of chronic obstructive pulmonary disease (COPD). METHODS: Ten mechanically ventilated patients with acute exacerbation of COPD received four puffs of salmeterol (25 microg/puff). Salmeterol was administered with an MDI adapted to the inspiratory limb of the ventilator circuit using an aerosol cloud enhance spacer. Static and dynamic airway pressures, minimum (Rint) and maximum (Rrs) inspiratory resistance, and the difference between Rrs and Rint (DeltaR) were measured before and at 15, 30, and 60 minutes as well as at 2, 3, 4, 6, 8, 10, and 12 hours after salmeterol administration. The overall effects of salmeterol on respiratory system mechanics and heart rate during the 12-hour study period were analyzed by nonparametric Wilcoxon signed rank test. RESULTS: Salmeterol caused a significant decrease in dynamic and static airway pressures, Rint, and Rrs. These changes were evident at 30 minutes and remained significant for 8 hours after salmeterol administration. The duration of bronchodilation varied significantly among patients, lasting in some patients more than 10 hours and wearing off in others in less than 6 hours. CONCLUSIONS: It is concluded that four puffs of salmeterol delivered with an MDI and a spacer device induces significant bronchodilation in mechanically ventilated patients with COPD exacerbation, the duration of which is highly variable, precluding definite conclusions in regard to optimum dosing schedules.