Measurement of Critical Closing Pressure (Pcrit) During Drug-Induced Sleep Endoscopy (DISE)

DISE is performed in a semi-dark, silent operating theatre, starting with the patient in supine position. To first induce sleep, an IV bolus of midazolam (1.5 mg) is administered. Then, a flexible fiberoptic nasopharyngoscope (Olympus END-GP, 3.7 mm diameter, Olympus Europe GmbH, Hamburg, Germany) is inserted through one of the nostrils. Either at the start of the examination or while holding the scope at the level of the palate, propofol (2.0-3.0 µg/ml) will be administered via a target-controlled infusion (TCI) pump. Sleep occurrence is confirmed using the additional EEG measurement.

After sleep onset, the CPAP pressure well be increased until no flow limitations are observed. This pressure is called the holding pressure and is used as a base for all the following measurements for that individual OSA patient. After observing sleep stage 2 or 3, the holding pressure is reduced abruptly by 1 cmH2O during expiration for 5 breaths. Then the pressure is set back to the holding pressure for the duration of 1 minute. This procedure is repeated until obstructive sleep apnea is noted.