To dynamically monitor the intracuff pressure of endotracheal tube and study the mechanism of leakage around endotracheal tube cuff to prevent the leakage.

(1) The disposable pressure sensor was used to connect endotracheal tube cuff and monitor and dynamically present the intracuff pressure waveform. The changes in intracuff pressure with breathings, sputum suctions, coughs, and upregulated PEEP were observed and recorded. (2) Different types of endotracheal tubes were inserted into the simulated tracheas (syringes) with intracuff pressure up to 25-30 cmH₂O, Methylene blue diluted with normal saline was used to simulate above cuff secretions and to explore the mechanism of fluid leakage past endotracheal tubes.

The intracuff pressures of patients on mechanical ventilation change periodically with breathing, compared with the cuff pressure during normal breathing [(20.32±2.08) mmHg], the cuff pressure significantly increased during sputum suction [ (27.95±2.72) mmHg] (t=0.14, P<0.01) and cough [(28.68±2.93) mmHg] (t=0.03, P<0.01); when PEEP increased by more than 2 cmH₂O, the cuff pressure increased to (24.12±2.94) mmHg (t=0.01, P<0.01); when the cuff pressure was insufficient, the pressure waveform was flat. The vitro leaking simulation test showed that compared with the No.7 endotracheal tube, the leakage of No.8 endotracheal tube balloon significantly increased (P<0.05), when the outer diameter of the inflated cuff was smaller than the inner diameter of the simulated trachea, the liquid above the cuff leaked through the gap between the cuff and the trachea in a sleeve shape.

The intracuff pressure can be affected by various factors and need individualized settings, and dynamic monitoring and adjustment. An endotracheal tube matching the trachea may reduce the leakage past the cuff.