By: 27 January 2015
New anaesthesic technique helps show cause of obstruction in sleep apnoea

A simplified anaesthesic technique may enable more widespread use of preoperative testing to demonstrate the cause of airway obstruction in patients with severe sleep apnoea, suggests a study in Anesthesia & Analgesia.

Joshua Atkins, Jeff Mandel and colleagues at the University of Pennsylvania have developed a new ‘ramp control’ anaesthetic technique for putting patients to sleep briefly – just enough to show the obstructive anatomy responsible for sleep apnoea. The simplified technique requires no special expertise and limits drops in blood oxygen level during testing.

Simplified approach to testing before surgery

The researchers evaluated their anaesthetic technique in 97 patients participating in a study of robot-assisted surgery for severe sleep apnoea. Visualising the site of the obstruction in the upper airway is an important part of planning for apnoea surgery. This can be done using drug-induced sleep endoscopy (DISE), in which stepwise doses of anaesthetic doses are given to put the patient to sleep and reproduce the airway obstruction causing apnoea.

However, it’s challenging to achieve just the right anaesthetic dosage – enough to cause typical sleep-related obstruction without causing either prolonged unconsciousness or a big drop in blood oxygen saturation. The standard technique for DISE is time-consuming and not well suited for widespread clinical use.

In the new ramp control approach, a computerised algorithm is used to calculate the two-dose sequence of anaesthetic administration likely to produce sedation in each individual patient. By contrast, the standard stepwise approach to DISE uses a sequence of up to nine doses.

The ramp-control DISE approach allowed doctors to see and photograph the obstructive anatomy in all 97 patients studied. The median time to put the patient to sleep and demonstrate the cause of obstruction was just under four minutes.

Just as important, the necessary level of sedation was achieved without an undue drop in oxygen saturation levels. The median lowest oxygen saturation level during DISE was about 91%, compared with an 81% value recorded in standard sleep studies. (Normal oxygen saturation is between 95 and 100%.)

By simplifying the steps to anaesthesia administration, the researchers believe their simplified approach will help to make DISE more widely available for evaluation of patients being considered for sleep apnoea surgery. However, more research will be needed to determine how well the new technique can be generalised to everyday clinical practice at busy surgical centres.

Atkins, J.H. (2014) Anesthesia & Analgesia 119(4), 805–810