Safety and efficiency of metered dose inhaler delivery of salbutamol in the intubated rabbit

OBJECTIVE: To determine the safety and efficiency of metered dose inhaler salbutamol delivered to the intubated rabbit. DESIGN: Prospective, comparative, five-group laboratory investigation. SETTING: Animal laboratory, Department of Nuclear Medicine. SUBJECTS: A total of 30 adult, anesthetized New Zealand White rabbits. INTERVENTIONS: Three groups of rabbits underwent tracheal intubation through a tracheostomy and received 5 puffs of 99mTcO4 salbutamol delivered at the elbow connector (group 1) or via a catheter with its distal tip positioned at the midpoint (group 2) or bevel of the endotracheal tube (group 3). No intervention was provided for the rabbits in the fourth group. A fifth group underwent tracheal intubation through the mouth and received salbutamol (5 puffs) delivered at the bevel of the endotracheal tube. MEASUREMENTS: Delivery efficiency was expressed as the ratio of radioactivity emitted from lungs and trachea to the total radioactivity of the administered dose. Histopathologic injury scores were assigned to each trachea or lung specimen. MAIN RESULTS: Delivery efficiency was 30 times greater in groups 3 and 5 (full catheter) than in group 1 (elbow). The injury scores were similar in all groups. CONCLUSION: We conclude that the increased efficiency obtained by administration of metered dose inhaler salbutamol at the distal tip of endotracheal tube is not necessarily associated with increased epithelial injury.