Metaproterenol was selected as the inhalant bronchodilator for both modes of administration. For the MDI-spacer part of the study, each subject activated one puff of metaproterenol MDI (0.65 mg/ puff) into a fully expanded cylindrical collapsible spacer device (InspirEase, Key Pharmaceuticals, Miami, FL). This device contains a reed that whistles when inspiratory flow exceeds 18 L/min. Subjects were instructed to slowly inhale from this device until the reservoir was completely collapsed.
The subject then exhaled back into this device until it was fully inflated and again reinspired the contents of the spacer. Five minutes after the inhalation of the first puff, a second puff of metaproterenol was activated into this device and inhaled in an identical manner as the first puff. The hand-held wet nebulizer treatments were administered with a disposable medication nebulizer fTravenol, catalogue No. 2C7161, Travenol Corporation, Edison, NJ) containing 15 mg of metaproterenol (0.3 ml of 5 percent solution) mixed with 3 ml of normal saline solution and driven with compressed air at a flow of 6 L/min. The patient breathed quietly via the mouthpiece of the HHN until all of the medication solution was nebulized.