Sleep in Critically III Chemically Paralyzed Patients Requiring Mechanical Ventilation: Polysomnography and Scoring
All subjects were monitored continuously for 24 h using polysomnography recorded on an eight-channel, portable EEG device (Neurotrac II model M1283A; Telefactor; Philadelphia, PA) interfaced with a monitor (model M1094B; Hewlett-Packard; Andover, MA). Gold cup electrode placement was performed according to the international 10/20 system in the following montage: O1-F7, O2-F8, T3-Cz, C3-A2, C4-A1, four electrooculogram (EOG) electrodes were applied for determining vertical and horizontal eye movement, and two chin electrodes were placed. Electrode application was performed by one trained nurse (L.M.) and the author (K.A.H.). Electrode impedance was maintained at < 10,000 ohms. there
Data were archived on an external hard drive for later analysis with customized software on a standard personal computer. Sleep recordings were scored manually in 30-s epochs by a registered polysomnography sleep technician (blinded to patient group) using standard Rechtschaffen and Kales criteria. Epochs with delta frequency that did not meet the 75-^V criteria or stage 1 or 2 requirements were scored as nonclassifiable. To account for an expected decrease in amplitude of delta waves associated with aging, a modified delta (mDelta) criteria was also used and consisted of a frequency criterion of < 4 Hz and an amplitude criterion of > 50 |j,V (peak to peak).
TST was defined as the sum of total time spent in all sleep stages during the total time monitored (sleep period). The percentage of time spent in each stage of sleep during the TST was calculated. This was further separated into daytime and nighttime sleep periods. The daytime period was defined as 6 am until 10 pm, and the nighttime period was defined 10 pm to 6 am. The number of arousals per TST and awakenings per TST were compared between each group to evaluate sleep fragmentation. Arousals were defined as an abrupt change in the EEG frequency to a, 0, or frequencies > 12 Hz lasting > 3 s. Awakenings were defined as changes in the EEG compatible with wakefulness that lasted > 15 s of an epoch preceded and followed by an epoch of sleep. Recordings were conducted continuously over 24 h to allow assessment of circadian variation. Day and night cycles were simulated by turning patient room lights off at 10 pm. The staff were instructed to record the time and length of all activities, vital signs, medications, nursing care, procedures, and medical examinations on a bedside log sheet. The number of interventions was compared between the three groups.
Category: Respiratory Symptoms
Tags: ICU, mechanical ventilation, polysomnography, sleep