Drug induced sleep endoscopy: its role in evaluation of the upper airway obstruction and patient selection for surgical and non-surgical treatment.

Sleep related breathing disorders cause obstruction of the upper airway which can be alleviated by continuous positive airway pressure (CPAP) therapy, oral devices or surgical intervention. Non-surgical treatment modalities are not always accepted by patients and in order to attain successful surgical outcomes, evaluation of the upper airway is necessary to carefully select the patients who would benefit from surgery. There are numerous techniques available to assess the upper airway obstruction and these include imaging, acoustic analysis, pressure transducer recording and endoscopic evaluation. It is essential to note that the nocturnal obstructive upper airway has limited muscle control compared to the tone of the upper airway lumen during wakefulness. Thus, if one were to attempt to identify the anatomical segments contributing to upper airway obstruction in sleep related breathing disorders; it must be borne in mind that evaluation of the airway must be performed if possible when the patient is awake and asleep albeit during drug induced sleep. This fact as such limits the use of imaging techniques for the purpose. Drug induced sleep endoscopy (DISE) was pioneered at Royal National Throat, Nose and Ear Hospital, London in 1990 and initially introduced as sleep nasendoscopy. The nomenclature and the technique has been modified by various Institutions but the core value of this evaluation technique remains similar and extremely useful for identifying the anatomical segment responsible for obstructing the upper airway during sleep in patients with sleep related breathing disorders. There have been numerous controversies that have surrounded this technique but over the last two decades most of these have been addressed and it now remains in the forefront of methods of evaluating the upper airway obstruction. A variety of sedative agents and different grading systems have been described and efforts to unify various aspects of the technique have been made. This article will look at its usefulness and advantages and will discuss some important contributions made to the field of evaluation of the upper airway using DISE.