In vitro evaluation of endotracheal tubes with intrinsic suction

Endotracheal tube (ETT) intubation impairs mucus clearance, which can lead to respiratory compromise. We compared three ETTs that have intrinsic capacity to aspirate secretions pooling above the cuff.

We evaluated the ability of three ETTs with suction, Hi-Lo Evac, Teleflex ISIS, and Portex Blue Line SACETT, to aspirate saliva and mucus simulants at continuous or intermittent vacuum pressures. We also evaluated the potential for a flexible tracheal membrane to obstruct the ETT suction port with applied vacuum. We measured the dimensions of the suction tubing at critical points to calculate differences in flow.

In a rigid tracheal model, the ISIS aspirated saliva simulant more quickly with continuous low pressure suction than Evac (P = .0006) and SACETT (P < .0001) as well as with intermittent high pressure suction (P < .0001). For mucus simulant, the ISIS aspirated stimulant better than the other ETTs at high intermittent suction (P < .0001); the Evac was more effective than the SACETT (P = .0019). For low and continuous suction, suction ports in all ETTs occluded with mucus, except for ISIS, at the highest continuous suction tested. In a trachea model with a flexible posterior membrane, this membrane either partially or completely occluded the suction port of all tubes at high continuous or intermittent suction. The ISIS was more prone to obstruction by the flexible membrane than the Evac. We found large differences in suction tubing cross-sectional area between the ISIS and the other tubes, and flow calculations using the Hagen-Poiseuille equation can explain the observed differences in volumes aspirated and tendency toward lumen obstruction.

The ISIS transmits suction pressure to the tube orifice more powerfully than the Evac and SACETT. This feature makes the ISIS less prone to obstruction by mucus but more likely to obstruct by tissue suction.