High-efficiency delivery of salbutamol with a metered-dose inhaler in narrow tracheal tubes and catheters

We sought to determine the percent delivery by metered-dose inhaler (MDI) of a preparation of salbutamol (albuterol) to the distal end of either pediatric-size tracheal tubes or a narrow-gauge catheter. A bench model consisting of a swivel actuator; 3.0-6.0-mm ID tracheal tubes all 16 cm in length or a 19-G (standard wire gauge) catheter; mesh filters; and a continuous flow of dry air was used. Six actuations of salbutamol (100 micrograms each) were delivered during each experiment, and each experiment was repeated nine times. The delivery efficiency (DE) was the ratio of the net increase in weight of the filter, positioned at the distal end of the tracheal tube, to the net weight increase of the entire apparatus. We found that the DE (mean +/- SD) of salbutamol at the end of the tracheal tube was significantly less with a 3.0-mm ID tube (2.5 +/- 7.0%) than it was with a 4.0-mm (10.8 +/- 8.3%), 5.0-mm (10.7 +/- 7.2%), or 6.0-mm (12.3 +/- 8.4%) tube (P less than 0.05). To improve the DE of salbutamol aerosol, a 19-G catheter (0.7 mm ID) was inserted through the elbow connector and passed down the tracheal tube until the tip of the catheter approximated the distal tip of the tube. The DE of salbutamol in tracheal tubes (less than or equal to 12.3%) increased dramatically (97%; P less than 0.001) when a 19-G catheter was used. We conclude that the DE of salbutamol by MDI through 3.0-6.0-mm ID tracheal tubes is low but may be dramatically increased by actuating the canister into a 19-G distally placed catheter. Because of the increased efficiency of delivery, caution must be exercised when using a distally placed catheter to deliver MDI aerosols to patients.