Drug-induced sleep endoscopy (DISE) is the most important sleep apnea surgery evaluation tool in my 20-plus years of work in sleep apnea surgery. That being said, it is far from a perfect sleep apnea surgery evaluation, and there is some controversy about the best technique. Over the years, questions about the technique have centered around the sedative medication to use and the value of monitoring the depth of sedation when making decisions about sleep apnea surgery.

DISE was developed in the late 1980s to examine the pattern of upper airway obstruction in patients considering sleep apnea surgery. The core principle of DISE is that unconscious sedation allows fiberoptic endoscopy that can visualize the structures that cause airway obstruction, the underlying issue in sleep apnea surgery. DISE is valuable for sleep apnea surgery because the structures that cause airway obstruction may need to be addressed with sleep apnea surgery to achieve good results. In this way, DISE becomes the foundation for making sleep apnea surgery decisions.

What Is the Best DISE Technique?

DISE is much more than just administering sedation to patients who are candidates for sleep apnea surgery. The goal is to use sedation to reproduce breathing patterns similar to natural sleep so that one can understand the causes of blockage of breathing and design a sleep apnea surgery treatment plan for an individual patient. Originally, DISE (then called sleep nasendoscopy) was performed with midazolam as the sedative medication of choice. Midazolam has a reasonably short time to take effect but is slower to wear off, making it acceptable but not ideal for DISE as a sleep apnea surgery tool. Advances came with the adoption of propofol, a medication that has a quick onset of action and offset of action, making it possible to maintain a reasonable level of sedation without oversedating patients for prolonged periods.

A key study that has guided me in the performance of DISE as a sleep apnea surgery evaluation was conducted at the University of Western Australia by a group led by Dr. David Hillman and Dr. Peter Eastwood. This work showed that the throat behaves similarly to natural sleep at the transition from consciousness to unconsciousness (loss of response to calling the patient’s name) with sedation using propofol. This transition to unconsciousness was associated with bispectral index scores (BIS) of 55-70.

So this is exactly what I do in performing DISE for sleep apnea surgery evaluation. Our team goes slowly with propofol sedation and start our exam at that transition to unconsciousness while also using BIS monitoring of the level of sedation. The idea behind BIS monitoring of the depth of sedation is to avoid oversedation, given that sleep is associated with some low level of muscle activation that you would want to maintain during DISE if you are performing the exam to guide sleep apnea surgery decisions.

Does DISE Technique Matter?

A recent publication in the Journal of Clinical Sleep Medicine evaluated some of these DISE technique differences in a systematic review and meta-analysis of published studies. This is perhaps not an ideal way of examining technique differences, but it is reasonable. A true comparison would require study participants to undergo multiple DISE examinations, something that large numbers of patients considering sleep apnea surgery would not normally do. What the published study could do was compare DISE findings across different individuals, trying to adjust for differences among them.

Their study suggested that the sedative medication (midazolam vs. propofol vs. dexmedetomidine) was not clearly associated with DISE findings. In contrast, BIS monitoring was associated with a lesser degree of tongue-related obstruction. The implication is that monitoring (there are multiple sedation monitoring systems that can be used) reduces oversedation that might lead to more collapse of the tongue and greater associated airway obstruction. Because sleep is associated with some muscle activation that you would want to maintain during DISE, this suggests that monitoring provides a more-accurate assessment of the pattern of obstruction during DISE and therefore may lead to improved sleep apnea surgery choices.

What Else Do I Do during DISE?

During DISE, I do a number of other things that I believe are important to my sleep apnea surgery decisions:

First, we examine these sleep apnea surgery patients with them on their side and then on their back. Studies have shown that about half of all patients with obstructive sleep apnea have what is called positional sleep apnea, meaning that their sleep apnea is at least twice as bad on their back as on their sides. Many patients sleep only on their sides because of this improvement in sleep apnea that can occur, and when choosing the right sleep apnea surgery, it is important to evaluate patients in their natural sleep position. Our research has confirmed that body position also changes the pattern of obstruction, potentially altering the type of sleep apnea surgery that might be best for a patient. Performing DISE in multiple body positions adds time to the evaluation, but this has important advantages in choices about sleep apnea surgery.

Secondly, we also advance the lower jaw (mandible) during DISE when the patient is on their back (it is difficult to do this when they are on their side). Even though my patients are undergoing DISE as they consider sleep apnea surgery, it is important to collect information related to all treatment options. The purpose of this is to achieve a rough approximation of the impact of a mandibular advancement device (the most common type of oral appliance). The findings of this portion of the DISE exam can lead to recommendations to consider an oral appliance, whether alone or in combination with sleep apnea surgery. While all of my DISE patients have obstructive sleep apnea and are considering sleep apnea surgery because they have been unable to tolerate positive airway pressure (such as CPAP), some of them have not had a trial of an oral appliance or have tolerated it but not achieved resolution of their sleep apnea. Understanding the full array of options — not limited to sleep apnea surgery — is essential.

Finally, over the past few years, we have been administering positive airway pressure therapy during the DISE exam, sometimes called DISE-PAP. The purpose of DISE-PAP is to see how a patient responds to positive airway pressure. There is limited evidence that sleep apnea surgery (specifically the Inspire Upper Airway Stimulation system) may have better outcomes in patients whose throat opens during DISE at lesser positive airway pressure levels. Our research sponsored by the National Institutes of Health is examining whether findings during DISE-PAP are associated with outcomes of other types of sleep apnea surgery.