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Anesth Analg 2002;94:125-129
© 2002 International Anesthesia Research Society

TECHNOLOGY, COMPUTING, AND SIMULATION

Bispectral Index Values and Spectral Edge Frequency at Different Stages of Physiologic Sleep

Diederik Nieuwenhuijs, MD*, Emma L. Coleman, BSc{dagger}, Neil J. Douglas, FRCP{dagger}, Gordon B. Drummond, FRCA{ddagger}, and Albert Dahan, MD PhD*

*Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands; {dagger}Scottish National Sleep Laboratory; and {ddagger}Department of Anaesthesia, Critical Care and Pain Medicine, Royal Infirmary, Edinburgh, United Kingdom

Address correspondence and reprint requests to Dr. D. Nieuwenhuijs, Department of Anesthesiology, Leiden University Medical Center (P5-Q) PO Box 9600, 2300 RC Leiden, The Netherlands. Address e-mail to djfn{at}worldonline.nl

Bispectral index (BIS) and spectral edge frequency (SEF) are used as measures of depth of anesthesia and sedation. We tested whether these signals could predict physiologic sleep stages, by taking processed electroencephalogram measurements and recording full polysomnography through a night’s sleep in 10 subjects being investigated for mild sleep apnea/hypopnea syndrome. Computerized polysomnograph signals were analyzed manually according to standard criteria, classifying each 30-s epoch as a specific sleep stage. The BIS and SEF values were taken at the end of each period of sleep when the same stage had lasted for at least 2 min. Before sleep, median values for BIS were 97 ± 12.1 and for SEF 23 ± 4.2 Hz. After sleep initiation, the median BIS values for arousal, light, slow wave, and rapid eye movement sleep were 67 ± 20.2, 50 ± 16.5, 42 ± 11.2, and 48 ± 7.1, respectively, and the median SEF values were 20 ± 4.7, 15 ± 3.6, 10 ± 2.6, and 19 ± 4.1 Hz, respectively. Although both BIS and SEF decreased with increasing sleep depth, the distribution of values at each sleep depth was considerable, with overlap between each sleep stage. Neither BIS nor SEF reliably indicated conventionally determined sleep stages. In addition, the response of the BIS was slow and patients could arouse with low BIS values, which then took some time to increase.

IMPLICATIONS: Although computer processing of the electroencephalogram can provide an adequate index of depth of anesthesia, the same processing cannot reliably convey depth of natural sleep. At each sleep stage, the output signal has a wide range of possible values.






Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press
Copyright © 2002 by the International Anesthesia Research Society.