The Science Journal of the American Association for Respiratory Care

2008 OPEN FORUM Abstracts

AEROSOL DELIVERY WITH METERED-DOSE INHALER DURING ADULT MECHANICAL VENTILATION: INFLUENCE OF INSPIRATORY FLOW RATE, TIDAL VOLUME, AND ACTUATION ADAPTORS

Hui-Ling L. Lin1, Yue Zhou2, Yung-Song S. Cheng2, James B. Fink3



Background: The deposition of aerosol medications may be influenced by various factors. An in vitro model was used to determine the influence of tidal volume, inspiratory flow, and adaptor type on drug delivery and particle size distribution distal to the ETT.

Methods: HFA albuterol pMDI (Key Pharmaceuticals) was actuated 8 times using an Aerovent® chamber (Monaghan Medical), a MiniSpacer® dual-spray nozzle (Cardinal Health Corp), and unidirectional nozzle built into the "Y" of the heated-wire ventilator circuit (Fisher & Paykel Inc). An AVEA ventilator (VIASYS Inc) with 2L/min bias flow and 5 cmH2O PEEP set to deliver: (1) 700 mL VT, 12 breaths/min, 50 L/min IFR; (2) 700 mL VT, 12 b/min, 70 L/min IFR; (3) 400 mL VT, 15 b/min, 50 L/min IFR; (4) 400 mL VT, 15 breaths/min, 30 L/min IFR; and (5) 250 mL VT, 20 b/min, 30 L/min IFR. An Impactor (NGI; MSP) was placed between the ETT and test lung to determine inhaled mass and mass median aerodynamic diameter (MMAD) (n=3). Samples were analyzed via spectrophotometer (224 nm) and a factorial ANOVA was performed (p<0.05).

Results: The % of emitted dose (±SE) deposited distal to the endotracheal tube is shown in the figure below. Discussion: Aerosol delivery through an AeroVent spacer yielded significantly higher inhaled mass (p < 0.01). Using this model the changes in volume and inspiratory flow did not significantly change inhaled mass or MMAD.

Conclusion: Based on this model, changes in drug delivery do not support changing ventilator flow rate or tidal volumes for administration of albuterol with an HFA pMDI.

We thank American Respiratory Care Foundation for the grants and VIASYS Health Inc for the support of the AVEA ventilator.