Delivery of salbutamol pressurized metered-dose inhaler administered via small-volume spacer devices in intubated, spontaneously breathing rabbits

Little is known about the ability of small-volume valved spacer devices to deliver a significant amount of an aerosolized drug to the lungs of babies. This study compared the in vitro delivery of salbutamol administered via A erochamber-Infant (145 mL), Babyhaler (350 mL), and metallic NES-spacer (25 0 mL), as well as the in vivo delivery using an animal model. The lung depo sition study of technetium-99m-labeled salbutamol was conducted in six anes thetized, intubated (3.0-mm endotracheal tube simulating oropharyngeal depo sition), spontaneously breathing New Zealand White rabbits, a model for 3-k g babies. Each rabbit was studied on three separate occasions, once with ea ch spacer device. The amount of radioactivity deposited in the spacer devic e, the endotracheal tube, the lungs, or the body was measured by a gamma ca mera and expressed as a percentage of the emitted labeled dose. The emitted dose and particle size distribution of salbutamol,ia the three spacer devi ces were measured using unit dose sampling tubes and an eight-stage Anderso n cascade impactor, respectively. The results were compared by ANOVA or Stu dent-Newman-Keuls Lest when indicated. In vitro, the NES-spacer and Babyhal er were equivalent for delivering particles < 5.8 mum in diameter (NES-spac er = Babyhaler > Aerochamber-Infant; p < 0.05). In vivo, the lung and body deposition was low with all spacer devices (range: 0.52-5.40% of the delive red dose) but greater with the NES-spacer than with the Aerochamber-Infant or the Babyhaler (5.40 +/- 2.40%, 2.91 +/- 0.86%, 0.52 +/- 0.46%, respectiv ely p = 0.002). These results suggest the metal-valved spacer device may be preferable for delivering pressurized aerosols to spontaneously breathing infants.