The Science Journal of the American Association for Respiratory Care

2010 OPEN FORUM Abstracts


Steve Burk, Chris Bigham, Jody Lester; Respiratory Care, Boise State University, Boise, ID

BACKGROUND: Guidelines for the prevention of VAP recommend that ETT cuffs be maintained at the minimal occluding volume (MOV). Our literature review found that most in-vitro studies evaluated cuff seal during static conditions and none used MOV as the technique to seal the trachea. In this study we inflated ETT cuffs to MOV and assessed fluid leakage during static (no positive pressure) and dynamic (PPV and CPAP) conditions. METHOD: A stand was built to hold four simulated tracheas (clear vinyl tubes, L =25 cm, ID = 2.5 cm) and four different 8.0 mm ID ETTs: three High Volume-Low Pressure (HVLP) barrel-shaped cuffs (Rusch, Mallinckrodt Hi-Lo, and Hi-Lo Evac) and one tapered cuff (Mallinckrodt TaperGuard Evac). ETTs were connected to a manifold that allowed delivery of either no pressure below the cuff, PPV below the cuff (PIP 30 cmH2O, PEEP 5 cm H2O) or CPAP below the cuff (5 cmH2O). The cuffs were inflated to MOV and ten ml of an artificial saliva product was poured above each cuff. Continuous suction at 20 cmH2O was applied to the two Evac tubes. These tests were conducted: cuff pressure 25 cmH2O + no positive pressure below the cuff; MOV + no PPV; MOV + PPV; MOV + CPAP. Each testing period was five minutes and all tests were repeated three times (on different days). The amount of fluid that bypassed each cuff was measured using a 10 ml graduated cylinder. RESULTS: Inflating cuffs to 25 cmH2O resulted in unsatisfactory cuff seals. When using MOV any leakage occurred via longitudinal folds in the barrel-shaped cuffs. During PPV we visualized air leaking from below the barrel-shaped cuffs (via folds) which caused bubbling but no fluid escaped below any cuffs. Subglottic suction was effective in removing most fluid from above the cuff but cuff of the Hi-LoEvac still allowed some leakage. CONCLUSION: In this bench study, MOV + PPV resulted in no cuff leakage into the artificial trachea regardless of cuff type because of positive pressure below the cuff. The tapered cuff, as designed, developed no cuff folds and was effective in preventing leaking when MOV was used. HVLP cuffs develop longitudinal folds that may allow micro-leakage of fluid from above the cuff into the trachea, especially when there is no positive pressure below the cuff. We found that the number of longitudinal folds increased significantly when the tube was moved up and down (even slightly) in the simulated trachea; future studies should consider the effect of ETT movement. Sponsored Research - None