Does Endotracheal Tube Design Affect Cuff Seal, Safety and Subglottic Suction Performance: An in-vitro study?

Introduction: Ideally endotracheal tubes (ETT) should protect the airways without causing pressure induced tissue damage. Traditionally, the addition of a tracheal cuff was heralded as seal against aspiration. This type of ETT utilized a low volume high pressure cuff which caused tracheal damage such as stenosis and malacia. The next development in ETT design was the high volume low pressure cuffs intended to protect the airways while reducing tissue damage. Although reducing damage, the new cuff did not reliably protect the airways. Microaspiration still remains a serious complication of intubation. A taper shaped cuff design was recently introduced to prevent microaspiration without causing tracheal damage. Concerns were raised regarding the contact area and the resultant pressure against the tracheal wall of the taper shaped cuff. Another innovation introduced to prevent microaspiration is subglottic suction present in the tube design. Therefore, the aim of this paper is to evaluate cuff seal performance, cuff safety and intrinsic suction efficiency of current commercially available ETT. Methods: Three separate studies evaluated these areas of interest. Cuff seal performance was evaluated using an approved in vitro test fixture mimicking the human trachea. We investigated the cuff seal performance of 7 endotracheal tubes with different cuff designs and identical tracheal tube size using water as the medium. Three different size tubes from 3 different manufacturers were tested to determine subglottic suction efficiency and cuff sealing performance using the same in vitro test fixture. In a similar fixture a pressure sensitive array was mounted to compare the surface pressure of a standard barrel shaped cuff to the taper shaped cuff. The array design allowed for the pressure profile of the cuff to be mapped where it contacted the cylinder wall. In all tests the cuff pressures were maintained at 25 cm H2O according to manufacturer’s recommendations. Results: The sealing performance varied between the tube manufacturers with TaperGuard (TG) showing the lowest leak at .6 g/5minutes and Kimberly Clark Micro cuff (KCmc) with the highest 59.2 g/5 minutes. In terms of suction efficiency Teleflex ISIS (ISIS) had the best suction performance (.2-5.3ml/sec) at all viscosities and Portex (SACETT) (.3-2.9 ml/min) was the lowest. When comparing surface force the taper shaped cuff was less compared to the barrel shaped cuff. Conclusions: Performance in all areas tested ETTs varied considerably in terms of sealing and suction efficiency. However, the taper shaped cuff demonstrated the least surface pressure and best sealing.