Standard sleep scoring criteria may be unreliable when applied to critically ill patients. We sought to quantify typical and atypical polysomnographic findings in critically ill patients and to begin development and reliability testing of methodology to characterize the atypical polysomnographic tracings that confound standard sleep scoring criteria.
Prospective convenience sample.
Two academic, tertiary care medical centers.
Thirty-seven critically ill, mechanically ventilated, medical ICU patients.
Mechanically ventilated subjects were monitored by continuous polysomnography. After noting frequent atypical polysomnographic findings (i.e., lack of stage N2 markers, the presence of polymorphic delta, burst suppression, or isoelectric electroencephalography), attempts to use standard sleep scoring criteria alone were abandoned. Atypical polysomnographic findings were characterized and used to develop a modified scoring system. Polysomnographic data were scored manually via this revised scoring scheme. Of 7 medical ICU patients enrolled, 6 experienced atypical sleep, which accounted for 85% of all recorded data, with 5.1% normal sleep and 9.4% wake. Coupling observed patient arousal levels with polysomnographic characteristics revealed that standard polysomnographic staging criteria did not reliably determine the presence or absence of sleep. Rapid eye movement occurred in only five patients (14%). The revised scoring system incorporating frequently seen atypical characteristics yielded very high interrater reliability (weighted κ = 0.80; bootstrapped 95% CI, [0.48, 0.89]).
Analysis of polysomnographic data revealed profound deficiencies in standard scoring criteria due to a predominance of atypical polysomnographic findings in ventilated patients. The revised scoring scheme proved reliable in sleep staging and may serve as a building block in future work.
1Departmentof Medicine, Division of Allergy, Pulmonary, and Critical Care, Vanderbilt University Medical Center, Nashville, TN.
2Division of Sleep Disorders, Vanderbilt University Medical Center, Nashville, TN.
3Department of Anesthesiology, Division of Critical Care, Vanderbilt University Medical Center, Nashville, TN.
4VA Department of Anesthesia, Nashville, TN.
5Division of Pulmonary, Critical Care, and Occupational Medicine, University of Iowa, Iowa City, IA.
6Department of Biostatistics, Vanderbilt University Medical Center, Nashville, TN.
7Division of General Health, Vanderbilt University Medical Center, Nashville, TN.
8Center for Health Services Research, Vanderbilt University Medical Center, Nashville, TN.
9VA Tennessee Health Care System, Geriatric Research Education and Clinical Center (GRECC), Nashville, TN.
10Department of Neurology, Vanderbilt University Medical Center, Nashville, TN.
This work was performed in Vanderbilt University Medical Center and University of Chicago.
Dr. Watson received support from the National Institutes of Health (MO1 RR-00095) and the Vanderbilt CTSA grant UL1 RR024975-01 from NCRR/NIH. Dr. Gehlbach received support from the National Institutes of Health (K2 HL088020), the Brain Research Foundation, the Institute for Translational Medicine (CTSA grant number UL1 RR024999), and the Department of Medicine at the University of Chicago. Dr. Pandharipande is supported by a VA Career Development Award (CSRD). Dr. Bernard is supported by NIH/NCRR UL1RR024975-0S5. Dr. Malow is supported by the Vanderbilt CTSA grant UL1 RR024975-01 from NCRR/NIH. Dr. Ely is supported by the National Institutes of Health (R01AG027472 and R01AG05117) and the VA Clinical Science Research and Developmental (VA Merit Review Award). Dr. Watson has received an unrestricted research grant for an investigator-initiated study from Aspect Medical Systems, Inc. and honorarium from Hospira Inc. Dr. Pandharipande has received a research grant from Hospira Inc. and honoraria from Hospira Inc. and Orion Pharma. Dr. Ely has received grants from Aspect Medical Systems, Eli Lily, and honoraria from Hospira, Abbott, and Masimo.The remaining authors have disclosed that they do not have any potential conflicts of interest.
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