Journal of sleep research
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Journal of sleep research · Jun 2000
The relationship between frequency of rapid eye movements in REM sleep and SWS rebound.
Previous studies have shown a decrease in rapid eye movement (REM) frequency during desynchronized sleep in recovery nights following total or partial sleep deprivation. This effect has been ascribed to an increase in sleep need or sleep depth consequent to sleep length manipulations. The aims of this study were to assess REM frequency variations in the recovery night after two consecutive nights of selective slow-wave sleep (SWS) deprivation, and to evaluate the relationships between REM frequency and SWS amount and auditory arousal thresholds (AAT), as an independent index of sleep depth. ⋯ In addition, REM frequency decreased significantly compared with baseline. This effect cannot be attributed to a variation in prior sleep duration, since there was no sleep loss during the selective SWS deprivation nights. Stepwise regression also showed that the decrease in REM frequency is not correlated with the increase in AAT, the traditional index of sleep depth, but is correlated with SWS rebound.
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Journal of sleep research · Sep 1998
Clinical TrialEvening administration of melatonin and bright light: interactions on the EEG during sleep and wakefulness.
Both the pineal hormone melatonin and light exposure are considered to play a major role in the circadian regulation of sleep. In a placebo- controlled balanced cross-over design, we investigated the acute effects of exogenous melatonin (5 mg p.o. at 20.40 hours) with or without a 3-h bright light exposure (5000 lux from 21.00 hours-24.00 hours) on subjective sleepiness, internal sleep structure and EEG power density during sleep and wakefulness in healthy young men. The acute effects of melatonin, bright light and their interaction were measured on the first day (treatment day), possible circadian phase shifts were assessed on the post-treatment day. ⋯ Self rated sleep quality was better after melatonin administration whereas the awakening process was rated as more difficult after bright light. On the post-treatment day after evening bright light, the rise in sleepiness and the onset of sleep were delayed, independent of whether melatonin was co-administered or not. Thus, although acute bright light and melatonin administration affected subjective sleepiness, internal sleep structure and EEG power density during sleep and wakefulness in a additive manner, the phase shifting effect of a single evening bright light exposure could not be blocked by exogenous melatonin.
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Journal of sleep research · Jun 1998
Clinical TrialDelayed sleep phase syndrome: A placebo-controlled cross-over study on the effects of melatonin administered five hours before the individual dim light melatonin onset.
In a double-blind placebo-controlled cross-over study, 30 patients with Delayed Sleep Phase Syndrome (DSPS) were included, of whom 25 finished the study. Melatonin 5 mg was administered during two weeks in a double-blind setting and two weeks in an open setting successively or interrupted by two week of placebo. The study's impact was assessed by measurements of the 24-h curves of endogenous melatonin production and rectal temperature (n = 14), polysomnography (n = 22), actigraphy (n = 13), sleep log (n = 22), and subjective sleep quality (n = 25). ⋯ During melatonin treatment patients felt significantly more refreshed in the morning. These results show that analysis of DLMO of patients suffering from DSPS is important both for diagnosis and therapy. These results are discussed in terms of the biochemistry of the pineal.
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It is generally assumed that inspiration will enhance both superior and inferior vena cava (SVC and IVC) blood flows due to the decrease in right atrial pressure produced by the fall in intrathoracic pressure. However, inspiration can also increase abdominal pressure due to the descent of the diaphragm. Using a model of abdominal vascular zone conditions, analogous to pulmonary vascular zone conditions, the abdominal venous compartment can be viewed as either a capacitor (zone III abdomen) or as a collapsible Starling resistor (zone II abdomen). ⋯ Combined generalized increases in abdominal pressure and focal forces over the liver can be shown to be an essential element in the pathogenesis of a Kussmaul's sign. Increases in abdominal pressures produced by active diaphragmatic descent can increase the total IVC venous return by enhancing the splanchnic IVC flow under relatively hypervolaemic conditions, but decrease the total IVC venous return by impeding the non-splanchnic IVC flow under hypovolaemic conditions. Results are presented which suggest that the concept of abdominal vascular zone conditions is useful to understand overall directions of changes in total and regional venous return during normal and obstructed breathing and may provide useful analysis of the haemodynamic events which occur in obstructive sleep apnoea.