1
Introduction
Drug-induced sleep endoscopy (DISE) was introduced by Croft and Pringle in 1991 and over time has increased in popularity and is applied worldwide. The evaluation requires pharmacologic induction of sedation and flexible fiber-optic endoscopy to visualize upper airway obstruction and/or snoring. As opposed to most surgical evaluation techniques, DISE not only uniquely offers a dynamic evaluation of the upper airway during conditions that ideally mimic natural sleep, but also enables visualization of specific structures that contribute to upper airway obstruction.
2
Indications
Home sleep apnea testing or polysomnography (PSG) must be performed before DISE. Assessment of the site(s) of obstruction is paramount to surgical success, and possibly by applying a jaw thrust during DISE, one may predict the likelihood that a mandibular advancement device (MAD) would be effective. Hence DISE is employed as a diagnostic tool for patients with habitual snoring, as well as those with obstructive sleep apnea (OSA) when surgery or MAD therapy is being considered as a treatment option by the patient and physician. Furthermore DISE can be applied to improve understanding of the anatomic basis for surgical, MAD, or continuous positive airway pressure (CPAP) failure and to evaluate additional conservative medical or surgical treatment alternatives. DISE is not necessary if CPAP, weight loss, or positional therapy is being considered, as visualization of the level of obstruction is not mandatory for these treatment modalities.
4
Technique
There are no standardized protocols concerning DISE technique. The procedure can be carried out in the operating or endoscopy room, and the sedation can be administrated by either an anesthesiologist or nurse anesthetist. Pulse oximetry, heart rate, and blood pressure are closely monitored throughout the procedure, and it must be possible to administer oxygen if needed. Patients should remain nil per os before the procedure to reduce the risk of regurgitation and aspiration. Administration of atropine or other anticholinergic agents 30 minutes before starting the procedure can be considered to reduce salivation.
A topical anesthetic, with or without a decongestant, can be administered to one or both nostrils at least 20 minutes before starting the procedure, being careful not to overanesthetize the pharynx, as the risk of aspiration and coughing increases, in addition to a potential interaction with the upper airway and breathing control.
Commonly, the procedure is commenced with the patient in a supine position on an operating table or in a bed. The position should attempt to mimic sleeping habits at home (e.g. one or two pillows, with or without dentures). To gain added value, the body position should be easily changeable, should one want to visualize potential consequences of another position. The lights should be dimmed and the room quiet to minimize awaking stimuli. It is practical to be able to view the film of the flexible endoscopy on a screen and record it. With the addition of a microphone, acoustic and visual signals can be recorded simultaneously.
5
Anesthesia
Drugs commonly used for DISE are propofol and/or midazolam. Some use propofol only; others use midazolam only. Others start with midazolam and continue with propofol.
Propofol has a rapid onset of action; is metabolized quickly, giving a fast recovery phase; and has a low incidence of postoperative nausea, vomiting, and headache. Propofol has the benefit of possessing a rapid onset of action and recovery period, with minimal side effects. In addition, it allows for standardization and reproducibility between different operators.
A computerized target-controlled infusion system for propofol can be helpful, as well as a bispectral index score system for monitoring the depth of sedation, respectively; neither are compulsory.
Anesthetic depth is of key importance. The target depth of sedation is the transition from consciousness to unconsciousness (loss of response to verbal stimulation). Because individuals have different susceptibilities to propofol, the required dosage can vary widely. Detailed suggestions for drug dosages are reported in the European position paper on DISE ( Table 6.1 ).
