Background: The optimal method of delivering
bronchodilators in mechanically ventilated patients is unclear. The
purpose of this study was to compare the pulmonary bioavailability of
albuterol delivered by the nebulizer, the metered-dose inhaler
(MDI) and spacer, and the right-angle MDI adaptor in ventilated
patients using urinary analysis of drug levels.
Methods: Mechanically ventilated patients who had not
received a bronchodilator in the previous 48 h and who had normal
renal function were randomized to receive the following: (1) five puffs
(450 μg) of albuterol delivered by the MDI with a small volume
spacer; (2) five puffs of albuterol delivered by the MDI port on a
right-angle adaptor; or (3) 2.5 mg albuterol delivered by a nebulizer.
Urine was collected 6 h after the administration of the drug, and
the amounts of albuterol and its sulfate conjugate were determined in
the urine by a chromatographic assay.
patients were studied, 10 in each group: their mean age and serum
creatinine level were 62 years and 1.3 mg/dL, respectively. With the
MDI and spacer, (mean ± SD) 169 ± 129 μg albuterol (38%) was
recovered in the urine; with the nebulizer, 409 ± 515 μg albuterol
(16%) was recovered in the urine; and with the MDI port on the
right-angle adaptor, 41 ± 61 μg albuterol (9%) was recovered in
the urine (p = 0.02 between groups). The level of albuterol in the
urine was below the level of detection in four patients in whom the
drug was delivered using the right-angle MDI adaptor.
Conclusion: The three delivery systems varied markedly in
their efficiency of drug delivery to the lung. As previous studies have
confirmed, this study has demonstrated that using an MDI and spacer is
an efficient method for delivering inhaled bronchodilators to the lung.
The pulmonary bioavailability was poor with the right-angle MDI port.
This port should not be used to deliver bronchodilators in mechanically