The Science Journal of the American Association for Respiratory Care

2004 OPEN FORUM Abstracts

ALBUTEROL DELIVERY USING THE DHD CIRCUVENT.

Terrence O. Brady, RRT; Dean R. Hess, PhD, RRT, FAARC. Massachusetts General Hospital and Harvard Medical School, Boston MA.

Background:
Inhaled albuterol is commonly administered to mechanically ventilated patients. The CircuVent (DHD Healthcare) allows for delivery of aerosolized medications without removing the heat-and-moisture exchanger from the circuit.

Hypothesis:
Albuterol delivery through an endotracheal tube is affected by use of the CircuVent.

Methods:
A Draeger Evita 4 ventilator was set to deliver a tidal volume of 0.5 L, respiratory rate 12/min, flow of 30 L/min, and inspiratory time 1 s. The circuit was attached to an endotracheal tube (Mallinckrodt, 8 mm inner diameter), the distal end of which was attached to a Puritan-Bennett D/Flex filter. The filter was attached to a test lung with a compliance of 50 mL/cm H2O. A Monaghan AeroVent spacer was placed into the ventilator circuit and a pressurized metered-dose inhaler was actuated into the spacer synchronized with the initiation of inhalation (4 actuations separated by ≥ 30 s). Albuterol was washed from the filter with 0.1 N NaOH and assessed for albuterol by spectrophotometry at 243 nm. Albuterol was delivered with and without the CircuVent in line, with a humidified circuit (35 C, 100% RH) and with a dry circuit. The CircuVent was set in the HME bypass position. Each set of conditions was repeated in triplicate.

Results:
Albuterol delivery was significantly less with use of the CircuVent (P < 0.001). Albuterol delivery was also significantly reduced with a wet circuit (P < 0.001). The most efficient delivery was with a dry circuit and without the CircuVent. Use of the CircuVent with a dry circuit (the usual configuration) resulted in a reduction in delivered albuterol by about 40%.

Conclusions:
Albuterol delivery by metered dose inhaler during mechanical ventilation was decreased by use of the CircuVent. If the CircuVent is used, it may be necessary to increase the dose to achieve an equivalent therapeutic dose – our data suggests that the dose should be doubled. These data should be subjected to clinical study.





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