A Critical Appraisal of Endotracheal Tube Function

Introduction: Primary functions of endotracheal tubes (ETT) are ventilation and protection of the airway. Although there have been minor innovations in ETT cuff technology over the years, inflatable cuffs allow aspiration of fluids and may cause ischemic tissue damage if over-inflated. Testing data required by the Food and Drug Administration (FDA) does not provide complete information regarding their performance.


Methods: Using in vitro and human cadaveric models, common brands of ETT (barrel cuff and tapered cuff) were evaluated. Leakage tests (FDA protocol) were performed using a range of acrylic tubes compatible with human airway sizes and a range of different size adult ETT. The impact of movement or angulation of tapered cuff ETT in the airway was assessed. Measurements were repeated in fresh-frozen excised human cadaver airways.

Volume-pressure (V-P) curves were established for a range of balloon cuff ETT. Increments of 1cc air were added to the cuff and cuff pressures were monitored with a calibrated hand-held manometer. A cuff pressure of 20-30cm H2O was considered optimal.


Results: Consistent leakage of both types of ETT was observed across all sizes of ETT and airways. Decreased leakage was noted with the tapered cuff design and in excised human airways. Increased leakage was noted with movement or angulation of the tapered cuff ETT.

In both types of ETT, a steep V-P curve was noted with a narrow inflation “safe-zone”. The safe zone of 20-30cm H2O was exceeded with as little as 0.2-0.3cc increment.


Conclusions: Current testing data required by the FDA for approval of ETT does not provide a complete picture of their function. Balloon cuff ETT do not prevent leakage with risk of aspiration. Other protective measures are needed. Balloon cuff pressure should be closely monitored with a manometer to maintain optimal cuff pressure.