INTRODUCTION
Bispectral Index (BIS) monitoring is an objective measurement tool for
sedation depth, which is derived from the electroencephalogram (EEG)(1-2). A BIS monitor automatically calculates and
displays the BIS index, a dimensionless number, whose value is comprised
between 0 (isoelectric EEG waves) and 100 (awake)(3).
In non-anesthetized patients, the BIS varies from 90 to 100. On the
other hand, total suppression of cortical electrical activity results in
a BIS of zero (2) .A BIS between 40 and 60 is
associated with a low probability of intraoperative awakening and
awareness (2).
Most studies evaluating the BIS system have been performed in anesthesia
and intensive care units in order to estimate the level of sedation and
anesthesia (3). Only a few small studies have
investigated the BIS index during natural sleep(4-5-6), and their results are inconsistent.
Drug induced sleep endoscopy (DISE) using sedative agents infusion,
guided by a BIS monitor, has been used for decades to directly examine
the upper respiratory tract for detecting airway collapse sites(7-8). According to Traxdorf M*7*5et all for DISE ,BIS leads to a precisely controllable depth of sedation
.The DISE-Target controlled infusion of sedative agent -BIS analysis
procedure is a step towards a required reproducible protocol of sleep
endoscopy capable of standardization. According to Shlemer
JW*8* et all . between the commonly used agents for
DISE dexmedetomidine’s mechanism of action appear most likely to induce
natural sleep pathways compared to propofol and midazolam . Different
sedation levels such as 50-60 (deep sedation) or 65-75 (light sedation)
are recommended for DISE by different researchers(9-10), but it is not exactly known which BIS level
corresponds to which phase of normal sleep.
In this study, we aimed to investigate the BIS values of normal sleep
stages, by investigating BIS values during sleep in patients who
underwent polysomnography in the sleep laboratory.