The Science Journal of the American Association for Respiratory Care

2008 OPEN FORUM Abstracts


Lawrence B. Cole1, Robert Hase1, Jan Bard1

Background: Respiratory Care Practitioners (RCPs) at Virginia Mason apply positive airway pressure via a flow-inflating bag while deflating the endotracheal tube (ETT) cuff to force secretions pooled above the cuff into the oropharynx. This procedure is intended to help prevent silent aspiration of pooled oropharyngeal secretions, to reduce need for ETT suctioning and decrease incidence of Ventilator-Associated Pneumonia (VAP). We wondered if the procedure itself could contribute to aspiration.

Methods: We constructed a tracheal model consisting of a ridgid plastic tube 1.2 inches in diameter which was then attached to a wood frame fixed at thirty degrees up-angle. The distal end of the plastic tube was adapted to a Total Test Lung (TTL) set to a compliance of 100 cmH2O. A size 7.5 mm HiLow Evac ETT was inserted into the plastic tube's proximal end and secured using a Comfit ETT holder. The ETT cuff was inflated to 25 cmH2O and positioned 5 cm below the plastic tube's proximal opening. We used two test solutions, one water-thin (Sthn) and the other thickened (Sthk) with a ratio of 4 ounces H20 to 3.5 teaspoons dietary thickener, each with one drop of blue food coloring added. 5cc of each mixture in turn was placed above the inflated cuff via the HiLow Evac tube's suction port. We then sought RCP volunteers to participate in the study. Each RCP was blinded from observation of the ETT cuff using a towel drape, performing purge procedures for each solution. Each purge was observed for aspiration, defined as any amount of blue fluid dropping below the ETT cuff.

After gathering data for all RCP volunteers, we also observed the kinetics of both solutions during purge maneuvers facilitated by ventilator leak-compensation flow. We attached our patient model to a Puritan-Bennet 840 set at CPAP with pressure support (PS) levels of 5, 10, 15, 20, and 25 cmH20.

Results: A small but significant percentage (9% for Sthk and 36% Sthn) of aspiration occurs using flow-inflating bag purges. Aspiration was also observed with PS purges, but only at PS levels of 5 and 10 cmH20; no aspiration occured at 15 cmH20 or higher.

Conclusion: Purge maneuvers using flow-inflating bags may directly cause gross aspiration of pooled secretions while purges using PS leak compensation do not appear to cause aspiration for PS set at least 15 cmH20. We did not address whether purge maneuvers are in fact a desirable or effective adjunct to decrease silent aspiration or prevent VAP.