The Science Journal of the American Association for Respiratory Care

2009 OPEN FORUM Abstracts

INFLUENCE OF BIAS FLOW, ACTUATION TIMING, AND INLINE SPACER ON DRUG DELIVERY DURING ADULT MECHANICAL VENTILATION

Hui-Ling Lin1, James B. Fink2, Yue Zhou3, Yung-Song Cheng3; 1Respiratory Care Program, Chang Gung University, Tao-Yuan, Taiwan; 2Respiratory Therapy, Georgia State University, Atlanta, GA; 3Lovelace Respriatory Research Institute, Albuqureque, NM

Background: The deposition of medication delivered from a pMDI may be influenced by various factors. This in vitro study determined the influence of bias flow, actuation timing, and adapter type on drug delivery efficiency and particle size distribution distal to the ETT. Methods: Actuations (8) from HFA albuterol pMDI (Key Pharmaceuticals) through the AeroVent® chamber (Aero; Monaghan Medical), MiniSpacer® dual-spray nozzle (MI; Cardinal Health Corp), and the unidirectional nozzle built into the “Y” of the heated- wire circuit (Y; Fisher & Paykel Inc) with bias/trigger flows of 0.4 L/min, 2 L/min, and 5 L/min. All devices were placed in the inspiratory limb of the ventilator circuit proximal to the Y. Actuation was synchronized with beginning of inspiration (Synch), and one second before inspiration (1S). An Avea ventilator (Viasys Inc) delivered Vt of 700 mL, rate of 12 breaths/min, 50 L/min of inspiratory flow with descending flow pattern, and 5 cmH2O PEEP. An Impactor (NGI; MSP Corp.) 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 μm), and a factorial ANOVA was performed (p<0.05). Results: The percentage of emitted dose (±SD) deposited distal to the endotracheal tube is shown in the Figure below. Discussion: The AeroVent spacer yielded significantly higher inhaled mass than other devices with no difference with bias flow or timing. Delivery with the MI and Y was more efficient with bias flow of 2 L/min than 5 L/min, and effect of timing was device dependent. The variables examined did not influence particle size distribution. Conclusion: Device design impacts the effect of trigger flow and actuation timing on aerosol delivery, but not MMAD, from a pMDI during mechanical ventilation. We thank the American Respiratory Care Foundation for the grants, and VIASYS Health Inc for the support of the AVEA ventilator. Sponsored Research - None

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