This in vitro experiment utilized a plastic tracheal model specifically recommended by the American National Standards Institute for the testing of ETT cuffs designed for prolonged intubation. Plastic tracheal models avoid the problems of rapid deterioration of freshly excised tracheas and poor correlation between animal species. While our mechanical model allowed strict control of test conditions, the absolute pressures reported may not accurately reflect in vi-Doresults.
Unlike the poorly compliant tracheal model, the human trachea can expand significantly with increases in airway pressure, impacting negatively on ETT cuff seal. When softened by warmth and humidity ETT cuffs are more likely to collapse as airway pressure increases, further jeopardizing tracheal occlusion. Therefore, the absolute in vivo intracuff pressures were likely to be underestimated by our model, but the values obtained in this study are reasonable estimates of in vivo pressures. Apart from its in vivo relevance, the model certainly is accurate enough to establish the relative performance of one cuff design to another under similar conditions, especially when using three cuff designs from a single manufacturer that possess similar physical characteristics.