Biomedical subjects

A Samel

Publications and source records attributed to A Samel.

24 records · Page 2Linked to original sources

PubMed1991

Sleep patterns in aircrew operating on the polar route between Germany and east Asia.

The study was performed as the second part of an investigation to assess sleep behavior and circadian rhythmicity in aircrew operating regular passenger flights between Germany and East Asia via Anchorage (ANC). Continuous records of sleep and ratings of sleep quality were obtained by sleep logs from 101 B747-cockpit crewmembers, starting at least 3 d before commencing flight duty, continuing during days on duty (the duration depending on the flight schedule) and finishing 4 d after return, at the earliest. Regardless of the specific duty roster, sleep deficit occurred mainly after the first flight leg to ANC, presumably due to the 10-h time zone difference and the short layover time. During the layover in the Far East, the sleep deficit diminished partly because of additional naps. Sleep was often disturbed and scattered over days and nights. Another pronounced sleep deficit occurred after the first return flight from South Korea or Japan to ANC. Compared to the outgoing layover period in ANC, the number and duration of naps increased during this layover and, additionally, on the first 2 d after returning home. Poorer sleep quality ratings were associated with accumulated sleep deficit and increased napping, but significant decrements in sleep quality were seen only during two out of the six different duty rosters. All six of the polar route duty rosters may lead to significant sleep disturbances. During some flight schedules the sleep deficit is large enough to raise operational implications.

Adult↗

PubMed1988

Sleep and circadian rhythms of an airline pilot operating on the polar route: a case study.

This study was planned and performed as a first step to assess sleep behaviour and circadian rhythmicity in aircrews operating on regular passenger flights between Germany and Japan via Anchorage, AK. Sleep patterns as well as continuous recordings of ECG and temperature were obtained from a B747 captain during a period of 13 d, including a preceding control day, 8 d on duty and 4 d at home base after return. Sleep behaviour and circadian rhythms changed dramatically due to adverse effects from the duty roster on the polar route. Sleep periods became fragmented into several sleep periods per day in a very irregular manner. Total sleep duration was shortened and sleep deficits occurred between flights. After return to the home base, sleep distribution remained divided into two intervals per day. The circadian system was considerably disrupted on route. Effects associated with irregular duty and sleep patterns intensified desynchronization. Readjustment was extremely slow resulting in a phase-displacement of at least 10 h even after being home for 4 d. Altogether, the results give reason for serious concerns and for the conclusion to strongly recommend more extensive studies on this route.

Aerospace Medicine↗

PubMed1986

Sleep, sleepiness, and circadian rhythmicity in aircrews operating on transatlantic routes.

This study was performed on B-747 aircrews operating on regular passenger flights between Frankfurt and the U.S. west coast (9 h time difference). In an initial phase, sleep behavior was surveyed by daily logs in 38 crewmembers. The results for the layover period indicate congruent sleep patterns with shifts in sleep onset distinctly less than 9 h. In comparison with preflight control data, sleep duration was significantly prolonged and, on average, no sleep deficits were experienced before commencing the return flight. The main part of the study consisted of polygraphic sleep recordings and multiple sleep latency tests (MSLT) applied to four complete cockpit crews (12 members total) in a baseline period, during layover, and after return to homebase. In addition, body temperature and ECG were continuously recorded. During layover, mean bed times were shifted by 4.5 h at maximum. Sleep was disturbed by early and prolonged awakenings which led to a reduction of sleep efficiency. In contrast, no sleep deficits nor increases in daytime sleepiness occurred. Night duty associated with the return flight caused sleep deprivation which conversely resulted in good sleep during the first night back in Germany. However, during the second night after return, impaired sleep was observed, at least in part caused by the rhythm disturbances. As predicted by our resynchronization model, ECG and rectal temperature recordings gave evidence for a desynchronization of the circadian system and an internal dissociation of different body functions.

Adult↗

PubMed1985

Comparison of cAMP with other radioprotectors against chronic damage to the rat parotid gland.

Radiation damage to the parotid gland is protectable by cAMP during the first week after irradiation (acute phase), though appreciable recovery occurred later with or without such protection. Further damage developed later (chronic phase, 60-90 days), and cAMP was still protective against this damage with a dose modification factor of 1.86 for gland weight. A summary of the protective factors, acute and chronic, for WR-2721, isoproterenol, and cAMP is included. Chronic damage is about 1.5 times as great as acute, and protection against acute and chronic damage is about equal for all three compounds.

Amifostine↗

PubMedDate not supplied

Bright light as a chronobiological countermeasure for shiftwork in space.

Work-rest schedules during long duration space missions involve several factors which could disrupt sleep and circadian temporal organisation: (1) displacement of sleep due to two-shift operations; (2) planned or unplanned schedule changes due to operational requirements; (3) social and light zeitgebers different from those on earth; (4) changes in the gravitational exposure. Timed bright light treatment has the potential to accelerating adaptation to schedule changes. Four male subjects were exposed to two sessions of 11 d of simulated microgravity (6 degrees head down tilt bedrest) with 6-h extensions of the wake period on 2 days (12-h phase delay). In a blind crossover design, subjects were exposed to bright light (>3500 lux) for 5 h on each of the 2 shift days and the following day, at times either expected to accelerate the adjustment to the phase delay (experimental condition) or to have no phase shifting effect (control condition). Sleep was recorded polygraphically, the circadian system was monitored by recordings of heart rate and body temperature, and by collection of urine (electrolyte and hormone excretion). Only the rhythms of 6-hydroxymelatoninsulphate and potassium excretions showed significantly enhanced adjustment under the experimental condition. Different rhythms adapted to the 12-h delay at different rates, comparable to those observed after time zone shifts. Sleep was shorter in simulated weightlessness than in normal ambulatory age-matched subjects, consistent with the shorter sleep durations characteristic of space flight. These results confirm the disruptive effects of wake-rest schedule shifts on sleep and circadian rhythms. Contrary to our initial hypothesis, 5-h exposures to bright light finishing at the time of the circadian temperature minimum were not more effective at accelerating adjustment to a 12-h schedule delay than exposures coinciding with the temperature maximum. We conclude that, while bright light may accelerate adjustment to work-rest schedule delays, any such effect seems to be largely independent from the timing of the light exposure.

Adaptation, Physiological↗

PubMedDate not supplied

Nocturnal aircraft noise effects.

Noise protection associated with the construction and extension of airports in the Federal Republic of Germany has been regulated by the law for protection against aircraft noise since 1971. This legislation is due for revision because of different aspects. One aspect is the growth of air traffic which has led many airports to the limits of their capacity and in search of new ways of adaptation to the increasing demand for flight services. Another aspect is the increasing concern of the population about noise effects which has to be addressed by better protection against the effects of aircraft noise. The framework conditions of policy in terms of society as a whole, its health and economic environment need to be put into effect by political action. Science can contribute to this goal by performing noise effects research and by providing recommendations to the political body. However, it remains controversial, what measures are necessary or adequate to assure effective protection of the population against aircraft noise. This is particularly true for the protection of rest and sleep at night. The problem of finding a common basis for adequate recommendations is associated with (1) the low number of primary studies, which also exhibited highly variable results and assessments, (2) the handling of acoustic or psycho-acoustic dimensions for quantifying psychological or physiological reactions, and (3) the conception of how far preventive measures have to go to prove effective. With this in mind, the DLR Institute for Aerospace Medicine is conducting a large-scale, multi-stage study for investigating the acute effects of nocturnal aircraft noise on human sleep. This enterprise is implemented in the framework of the HGF/DLR project "Quiet Air Traffic" for developing sustainable assessment criteria for human-specific effects of aircraft noise at night.

Aerospace Medicine↗