The Science Journal of the American Association for Respiratory Care

2007 OPEN FORUM Abstracts

INFLUENCE OF MDI TIMING ON AEROSOL DELIVERY DURING MECHANICAL VENTILATION WITH BIAS-FLOW

H. Lin1, Y. Zhou2, Y. Cheng2


Background: Mechanical ventilators with bias flow might affect the efficacy of aerosol therapy.
Purpose: To evaluate metered-dose inhalers’ (MDIs) performance during mechanical ventilation with 10 L/m bias flow.

Methods: MDIs were actuated in three different timings during mechanical ventilation: (1) synchronized with an inspiration; (2) one second before inspiration, and (3) 0.3-0.5 second after initiation of inspiration at the point of peak flow (n=3). Eight actuations of HFA albuterol sulfate were delivered through an 8.0 mm endotracheal tube (ETT) by using a MiniSpace® dual-spray (Cardinal Health) placed between the inspiratory limb and the Y-connector of a ventilator circuit. A ventilator (Pulmonetics LTV™, VIASYS) was used at adult settings, tidal volume of 700 mL, respiratory rate 12 breaths/min, inspiratory time 1.0 sec, and PEEP 5 cmH2O. Each MDI was shaken and actuated at a 20-sec interval. To determine total inhaled mass and mass median aerodynamic diameter (MMAD),the drug was collected either on filter paper (Whiteman Ltd.) or on the New Generation Impactor (MSP). Samples were analyzed by using a spectrophotometer at a wavelength of 224 nm. Statistical analyses were performed by one-way ANOVA with an alpha level of 0.05.


Results: There was no significant difference or pattern with MDI actuation timing on inhaled mass (p=0.763) or MMAD (p=0.563). The table below shows mean, standard deviation (SD) and percentage of inhaled drug mass, and MMAD.


Conclusion: Actuation timing of MDIs during mechanical ventilation with 10 L/m bias-flow did not affect total inhaled mass or particle size distribution delivered through the ETT.
Funded by the American Respiratory Care Foundation.

Inhaled Drug Mass and MMAD
Method \ Results Mean ± SD, % MMAD
Synchronized with inspiration 156.4 ± 22.6 µg, 21.7% 1.86 µm
1 second before inspiration 142 ± 24.8 µg, 20% 1.77 µm
Peak inspiration flow 153.89 ± 22.2 µg, 21.4% 1.80 µm



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