Inhaled fenoterol-ipratropium bromide in mechanically ventilated patients with chronic obstructive pulmonary disease

In 18 patients with chronic obstructive pulmonary disease intubated and mec hanically ventilated, we prospectively randomized 200 mu g fenoterol-80 pg ipratropium bromide (four puffs) from a metered-dose inhaler (MDI) versus 1 .25 mg fenoterol-500 mu g ipratropium bromide in 5 mi saline from a nebuliz er (NEB). Respiratory mechanics were assessed before and 30 min after the e nd of each delivery by the rapid end-inspiratory airway occlusion technique . We did vary on single breaths the inflation flow ((V) over dot) from 0.2 to 1.2 L.s(-1), at constant inflation volume. The total respiratory resista nce of the respiratory system (Rrs) was partitioned into airway (Rint,rs) a nd tissue (Delta Rrs) resistances. We found that Rrs was equivalently reduc ed, from 16.49 +/- 1.37 to 14.85 +/- 1.88 cm H2O.L-1.s with MDI (p < 0.05) and from 18.04 +/- 1.85 to 15.15 +/- 1.33 cm H2O.L-1.s with NEB (p < 0.01). Whereas the prevailing effect of MDI was to reduce Rint,rs, that of NEB wa s to decrease Delta Rrs. In addition, the (V) over dot resistance of the re spiratory system over the whole range of (V) over dot was significantly aff ected by NEE but not by MDI.