Fig. 1

Schema of the above-cuff leak test. The smaller number at the bottom of the screen of the automated cuff pressure modulation device is the set pressure, and the larger number is the value of the measured pressure. Air (⇢) is delivered from the automated cuff pressure modulation device through the evacuation line to the subglottic evacuation port. Then, the air flow leaks to the upper airway through the gap between the tube and the glottis with an intact upper airway (A). At that time, the measured pressure became smaller than the set pressure. If there was upper airway obstruction, such as laryngeal edema, the air flow did not leak into the upper airway and the set and measured pressures were equal (B)