Chest
Volume 115, Issue 6, June 1999, Pages 1653-1657
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Clinical Investigations in Critical Care
A Comparison of Bronchodilator Therapy Delivered by Nebulization and Metered-Dose Inhaler in Mechanically Ventilated Patients

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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.

Results

Thirty 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 ventilated patients.

Section snippets

Materials and Methods

This study was conducted in the Medical and Surgical ICUs at St. Vincent Hospital, a community teaching hospital in central Massachusetts. It was approved by the hospital's institutional review board. As all three delivery methods were concurrently being used in our ICUs, and they were dependent on the respiratory therapist's preferences, this protocol did not deviate from our standard of care, and the institutional review board therefore waived the need for informed consent. Mechanically

Results

Thirty patients were studied, with 10 randomized to each group. The patients’ clinical characteristics and ventilator settings are listed in Table 1. The amounts of albuterol recovered in the urine were 169 ± 129 μg (38%) using the MDI and spacer, 409 ± 515 μg (16%) using the nebulizer, and 41 ± 61 μg (9%) using the in-line MDI. The percentage of drug excreted differed significantly among all three groups (p = 0.02). The level of albuterol in the urine was below the level of detection in four

Discussion

In this study, we have confirmed that an MDI and spacer is an efficient method for delivering therapeutic aerosols in mechanically ventilated patients. Although the total dose of the drug delivered to the lung was greatest with the nebulizer, it was less efficient than the MDI and spacer. The MDI port on the right-angle adaptor resulted in significantly less delivery, with undetectable levels of the drug in a number of patients. Our study, therefore, emphasizes the improved delivery of aerosol

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The results of this study were presented in part at the 28th Educational and Scientific Symposium of the Society of Critical Care Medicine, San Francisco, CA, January 23 to 27, 1999.

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