The Science Journal of the American Association for Respiratory Care

2007 OPEN FORUM Abstracts

THE EFFECT OF MDI POSITION ON AEROSOL BRONCHODILATOR DELIVERY IN SIMULATED MECHANICALLY VENTILATED PATIENTS.

A. Ari1, H. Areabi1

Background: Successful aerosolized bronchodilator therapy in mechanically ventilated patients depends on achieving adequate drug deposition in the lung. Although MDIs are widely used in mechanically ventilated patients, the effect of MDI placement in a ventilator circuit on the drug delivery is not known. Therefore, the objective of this study was to determine the effect of the MDI position in both heated and unheated ventilator circuit on inhaled drug deposition in simulated mechanically ventilated patients.

Methods: An in-vitro lung model to stimulate mechanically ventilated patients was constructed, using a dual chamber test lung (Michigan Instruments). Ventilator setting used for the study is as follows: Minute Ventilation 7.5 L/min, tidal volume 500ml, frequency 15/min and ramp flow pattern. Using a spectrophotometric technique, aerosol drug delivery was measured at 3 different positions: 1) between the endotracheal tube (ETT) and “Y”; 2) 6 in from “Y” on the inspiratory limb ; 3) 6 inches from the ventilator (n=3). Each position was tested 3 times (n=3) using the MDI (Proair HFA) with a spacer device (Aerovent, Monoghan Inc.).The amount of drug depositing in the filter distal to the ETT was expressed as means and standard deviation of percentages of dose emitted from the MDI. Results were compared with a 2 x 3 factorial design (Heat x Position) with repeated measures analysis of variance with Bonferronni analysis with p<0.05 significant

Results: Table shows mean (standard deviation) percent of dose delivered in a heated and unheated ventilator circuit. There were significant differences between dry and wet ventilator circuit as well as across the positions tested.

Conclusion: The position of the MDI and spacer significantly impacts the quantity of drug delivered past the ETT in this model of mechanically ventilated patients. Bronchodilator delivery via an MDI during mechanical ventilation can be more effective when the MDI and a spacer placed 6 inches from the Y adapter on the inspiratory limb of ventilator circuit.

MDI Position Between ETT & Y 6 in from Y 6 in from Vent
Vent Circuit DryWetDry WetDry Wet
Mean (SD) % 22.1 (1.5)7.6 (1.3) 27.8 (3.3) 17 (1.0) 7.9 (1.5) 2.5 (0.8)



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