Albuterol delivery by metered-dose inhaler in a mechanically ventilated pediatric lung model.
OBJECTIVE
To assess albuterol delivery by metered-dose inhaler in a mechanically ventilated pediatric lung model and to determine the influence of the following variables on albuterol delivery: endotracheal tube diameter; type of spacer; humidification; and pulmonary mechanics.


METHODS
Prospective, in vitro, laboratory study.


METHODS
Research laboratory.


METHODS
A model, consisting of a volume-cycled ventilator, pediatric breathing circuit, 4.0- or 6.0-mm endotracheal tube, and lung simulator, was assembled. Ventilator settings were: tidal volume 250 mL; FIO2 0.5; inspiration/expiration ratio 1:3; respiratory rate 25 breaths/min; positive end-expiratory pressure 3 cm H2O; temperature 35 degrees C; and a decelerating flow pattern, using dry and humidified air. Lung simulator compliance and resistance values were consistent with those values reported for healthy childeren (20 mL/cm H2O and 40 cm H20/L/sec) and children with pulmonary disease (10 mL/cm H2O and 60 cm H2O/L/sec). Pulmonary mechanics were verified with a pulmonary function diagnostic system. Ten metered-dose inhaler canisters were used to administer 2000 micrograms of albuterol, using either a collapsible or a rigid spacer. A circuit filter placed immediately proximal to the test lung collected drug exiting the endotracheal tube. The filter was rinsed with water and albuterol concentrations were determined by high-performance liquid chromatography. Each variable was tested in triplicate.


RESULTS
Albuterol delivery was significantly (p < or = .05) greater for the 6.0-mm endotracheal tube, rigid spacer, dry air, and pulmonary disease mechanics by multifactor analysis of variance. Drug delivery in humidified air with pulmonary disease mechanics using the rigid chamber was 2.5 =/- 0.27% and 6.3 =/- 0.99% for the 4.0- and 6.0-mm endotracheal tubes, respectively.


CONCLUSIONS
These in vitro results suggest that pulmonary disease mechanics and a 6.0-mm endotracheal tube improve albuterol delivery. Future clinical investigations in intubated pediatric patients with pulmonary disease are needed to address the clinical significance of these results.
Garner
S S
SS
Department of Pharmaceutical Sciences, Medical University of South Carolina, Charleston 29425-0810, USA.
Wiest
D B
DB
Bradley
J W
JW
Lesher
B A
BA
Habib
D M
DM
D000420:Albuterol / Q000008:administration & dosage*; D001249:Asthma / Q000188:drug therapy* / Q000503:physiopathology; D001993:Bronchodilator Agents / Q000008:administration & dosage*; D002648:Child; D004195:Disease Models, Animal; D016503:Drug Delivery Systems / Q000295:instrumentation*; D004353:Drug Evaluation, Preclinical; D006801:Humans; D009330:Nebulizers and Vaporizers; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000295:instrumentation / Q000379:methods*; D015656:Respiratory Mechanics
D001993:Bronchodilator Agents; D000420:Albuterol