An in-vitro study to evaluate high-volume low-pressure endotracheal tube cuff deflation dynamics

BACKGROUND: High-volume low-pressure (HVLP) endotracheal tube (ETT) cuffs for critically ill patients often deflate during the course of mechanical ventilation. We performed an in-vitro study to comprehensively assess HVLP cuff deflation dynamics and potential preventive measures. METHODS: We evaluated 24-h deflation of 7 HVLP cuffs of cylindrical or tapered shape, and made of polyvinylchloride or polyurethane. Experiments were performed within a thermostated chamber set at 37°C. In the first stage of experiments, the cuff pilot balloon valve was not manipulated. The cuff internal pressure was assessed hourly for 24 hours, via a linear position sensor which monitored cuff deflation displacements. Then, we re-evaluated cuff deflation of the worst-performing ETT cuffs with the cuff pilot balloon valve sealed. Finally, we inflated ETT cuffs within an artificial trachea to evaluate deflation dynamics during mechanical ventilation. RESULTS: Initial tests showed an exponential decrease in cuff internal pressure in 5 out of 7 cuffs. Cuffs of cylindrical shape and made of polyurethane demonstrated the fastest deflation rates (p<0.050 vs. cuffs of conical shape and made of polyvinylchloride). When the cuff pilot balloon valve was not sealed, the internal cuff pressure deflation rate differed significantly among ETTs (p=0.005). Yet, upon sealing the cuff pilot balloon valve and during mechanical ventilation, cuff deflation rates decreased (p