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Biomedical subjects

H M Wegmann

Publications and source records attributed to H M Wegmann.

At least 19 recordsLinked to original sources
PubMed1997

Aircrew fatigue in long-haul operations.

The studies were conducted on the transmeridian routes Düsseldorf (DUS)-Atlanta (ATL) and Hamburg (HAM)-Los Angeles (LAX), and on the north-south route Frankfurt (FRA)-Mahe (SEZ). Scheduled flight duration was between 8:50 hours (ATL-DUS) and 11:50 hours (HAM-LAX). In total, 25 rotations (50 flights) have been investigated by pre-, in- and post-flight data collection of sleep, taskload, fatigue and stress by electroencephalogram and electrocardiogram measurements and subjective ratings. Inflight ratings of taskload showed low perceived exertion during the Atlantic flights, and were moderate during the north-south transitions. Fatigue ratings increased with progressing flight duration. Towards the end of long U.S.-westcoast flights performed at day-time, and in all night flights, fatigue was elevated compared to the 'baseline' ratings collected during the day-time DUS-ATL flights. Fatigue was rated as being 'critical' by several pilots, particularly during the return flight SEZ-FRA when fatigue was severely pronounced. From the findings it is concluded that duty schedules, as performed on the route HAM-LAX (because of long duty hours), and particularly on the route FRA-SEZ (because of consecutive night work), may place excessive demands on mental and physiological capacity. With respect to legal aspects, the results are significant and should promote further deliberations for advanced schemes of flight duty time limitations and rest requirements.

Accidents, Aviation↗
PubMed1997

Bright light: a countermeasure for jet lag?

After time-zone flights, the environmental time is shifted abruptly. The sleep-wake cycle and the circadian system cannot follow this sudden phase shift. Therefore, some or several days are necessary to achieve complete adjustment to a new time zone. The effects resulting from the displacement between internal and external time are well known as jet lag. In principle, timed bright light is able to enhance the resynchronization process of the circadian system after advance or delay shifts. In this report, the effects of bright light exposure on circadian phases and amplitudes after real or simulated time zone transitions are reviewed from the accessible literature and are critically discussed. It can be concluded that laboratory studies have not been unequivocally successful to support the hypothesis that bright light alleviates jet lag. The sparse number of field studies do not yet allow a clear judgment on the beneficial effect of bright light treatment on jet lag.

Acclimatization↗
PubMed1997

Two-crew operations: stress and fatigue during long-haul night flights.

BACKGROUND: As part of a research program concerning legal aspects of two-pilot operations on long-haul routes, the purpose of the study was to investigate two-crew extended range operations during a flight roster with two consecutive night flights and a short layover. HYPOTHESIS: Present flight time regulations may not be adequate for two-crew minimum operations. METHODS: The study was conducted in cooperation with a German airline company on the route Frankfurt (FRA)-Mahe (SEZ). There were 11 rotations (22 flights) that were investigated by pre-, in- and post-flight data collection each time from the two pilots. Recordings included sleep, taskload, fatigue and stress by measurement of EEG, ECG, motor activity, and subjective ratings. The average actual flight times were 9:15 h (FRA-SEZ) and 9:53 h (SEZ-FRA). All flights took place at night. The layover duration in Mahe was 13:30 h during day-time. RESULTS: During layover, sleep was shortened by 2 h on average compared with 8-h baseline sleep. The two consecutive night duties resulted in a sleep loss of 9.3 h upon return to home base. Inflight ratings of taskload showed moderate grades, but for fatigue ratings an increasing level was observed. Fatigue was more pronounced during the return flight and several pilots scored their fatigue at a critical level. Motor activity, brainwave activity (occurrences of micro-events) and heart rate indicated drowsiness and a low state of vigilance and alertness during both night flights, but these effects were more pronounced during the second flight. CONCLUSIONS: From the findings it is concluded that a duty roster, as conducted in this study, may impose excessive demands on mental and physiological capacity.

Adult↗
PubMed1995

[Therapy of jet lag].

After transmeridian flights, disturbances of the circadian rhythm and sleep occur due to the desynchronization between the body clock and external zeitgebers. Under normal circumstances, these disturbances are not pathological and disappear within a few days. However, they impair well-being and lead to significant changes in performance and vigilance. These effects are of particular importance for tasks and operations which require enhanced attention and alertness. Some of the acute symptoms of jet-lag can be reduced and shortened by appropriate countermeasures. The application of these therapies is practicable and has been successfully incorporated in clinical measures.

Arousal↗
PubMed1995

Water immersion: analysis of diurnal rhythms of water and electrolyte excretion.

The biorhythmological structure of water-electrolyte metabolism was studied in humans during 7-day "dry" immersion. Results were processed with a set of mathematical methods in order to identify a parameter which would allow to obtain scientifically valid, reliable data without violation of any ethic constraints inherent to investigations with healthy test-subjects. Even this period of immersion gravely impacted functioning of kidney as an executive organ in the system of water-electrolyte homeostasis. Data of this study point to applicability of Cosinor analysis for quantitative assessment of fluctuation patterns in parameters of close to harmonical circadian rhythms, and variation analysis and normalized mean for rhythms of arbitrary forms.

Adult↗
PubMed1993

Pre-adaptation to shiftwork in space.

Astronauts are often required to work in shift schedules. To test pre-mission adaptation strategies and effects on the circadian system, a study was performed using microgravity simulation by head-down bedrest. Eight male subjects were studied over 4 control days, and 7 days each for pre-mission adaptation, bedrest, and readjustment. The circadian system was assessed by monitoring ECG and temperature, and by collecting urine for determination of hormones and electrolytes. Rhythms did not achieve complete adjustment within the adaptation period when the sleep-wake cycle was shortened by 1 h/day, but resynchronization continued during bedrest. After the bedrest period when the time shift was reversed by a 7-h delay within 2 days, resynchronization was achieved satisfactorily only within 7 days. From the results it is concluded that a sleep-wake cycle advance as used in this study is insufficient to keep the circadian system in pace. Under operational conditions the circadian system of astronauts may become longer and more destabilized than under controlled laboratory conditions.

Adaptation, Physiological↗
PubMed1993

Response of the circadian system to 6 degrees head-down tilt bed rest.

The influence of simulated microgravity and reduced zeitgebers on the circadian system was examined in eight subjects. The 12-d study included a 3-d period for baseline measurements, 7 d of 6 degrees head-down bed rest, and 2 d for recovery. The sleep-wake cycle was kept constant during the study. The state of the circadian system was assessed from continuous measurements of temperature and ECG, and collections of urine at 3-h intervals for the determination of hormone and electrolyte excretions. Results indicate that only minor changes occurred in rhythm acrophases, whereas daily means for several physiological functions and their circadian amplitudes were significantly altered during the bed-rest phase. These studies using head-down tilt confirm previous findings with horizontal bed rest and indicate that rhythm disturbances can occur without change in the sleep-wake cycle. To the degree that bed-rest studies simulate manned spaceflights, results indicate that variations in circadian cycles can occur even during short-term missions and must be taken into account when interpreting subsequently obtained physiological data.

Adult↗
PubMed1991

Influence of melatonin treatment on human circadian rhythmicity before and after a simulated 9-hr time shift.

The hormone melatonin is currently proposed by some investigators to be an efficient means for decreasing the impairing effects of jet lag. Eight healthy male subjects, aged 20 to 32, underwent a 9-hr advance shift in the isolation facility of our institute during two periods each of 15 days' duration. In a double-blind, crossover design, subjects took either melatonin or placebo at 1800 hr local time for 3 days before the time shift and at 1400 hr for 4 days afterwards. The time shift was simulated on days 7 and 8 by shortening the sleep period by 6 hr and the following wake period by 3 hr. Body temperature was recorded every 90 min, and urine was collected at 3-hr intervals all day and night. Melatonin treatment enhanced the resynchronization speed of some, but not all, hormone and electrolyte excretion rates for several days after the time shift. The adaptation speed of the temperature rhythm significantly increased during one postshift day. In addition, the circadian temperature rhythm had a significantly higher amplitude under melatonin treatment than under placebo after the time displacement. For the placebo group, the rhythm of 6-hydroxymelatoninsulfate excretion exhibited an advance shift in five subjects, whereas the other three showed a delay shift, and adjustment did not achieve more than one-half of the expected value within 8 days. A significantly different adjustment could be observed in the melatonin-treated group: Seven subjects underwent an advance shift of the expected 9 hr within an average of 8 days. The results suggest that melatonin treatment can accelerate resynchronization of the melatonin excretion rhythm after eastward time zone transitions. The improvement is not, however, sufficiently great that we can recommend melatonin for the alleviation of jet lag.

Adult↗
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↗
PubMed1989

Transition between advance and delay responses to eastbound transmeridian flights.

In response to eastbound transmeridian flights, which result in zeitgeber phase advance shifts, adaptation of the circadian system to the new time zone by phase delays and advances are observed. The delay response to an advance zeitgeber shift has been called an antidromic response. For the shift at which the transition from an advance to an antidromic response occurs, the term critical shift is introduced. For the study of critical shifts, a flight experiment across nine time zones and numerical simulations of a van der Pol equation have been evaluated. The interest is focussed on the determination of a range for critical abrupt shifts. An abrupt shift means that the ensemble of zeitgebers including geophysical zeitgebers and the rest-activity cycle is shifted immediately in the new time zone. The range of critical advance shifts has been estimated to reach from +7 to +10 hr. In the literature, results were reported which would imply a much wider range. The discussion of these observations shows that the actual shifts were presumably not abrupt in the quoted experiments. The consequences of critical shifts for jet lag symptoms are investigated. If reduced circadian amplitudes and long times taken for the resynchronization contribute to the feeling of jet lag, the symptoms will be worst for shifts close to the critical one, as numerical simulations revealed. Manipulations of such shifts with the aim to alleviate jet lag are discussed.

Adaptation, Physiological↗
PubMed1988

Assessment of Space Station design and operation through Bioastronautics.

The paper reviews the main elements and major issues affecting human productivity and discusses some selected factors which might not be sufficiently identified and/or considered from the Bioastronautics point of view at the present stage of planning Space Station design and operation.

Aerospace Medicine↗
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↗
PubMed1987

Resynchronization of the circadian system following a 9-hr advance or a delay zeitgeber shift: real flights and simulations by a Van-der-Pol oscillator.

After a flight from Germany to California, eight subjects stayed there for 3 weeks and then were flown back to Germany. After both the westbound and the eastbound flights, body temperature was measured for 2 weeks in the new time zone. Data obtained every 3 hr throughout the day and night were analyzed by the complex demodulation technique to visualize phase adjustments and the nonstationary amplitude of the measured circadian rhythms. The response to the zeitgeber delay was very similar in all subjects and consisted of a phase adjustment of 6 hr in the first 2 days following the flight and a subsequent slow completion of the resynchronization with a rate of 0.5 to 1 hr per day. After the eastbound flight the resynchronization was generally slower, and the circadian amplitudes were more reduced than after the zeitgeber delay. In addition, the advance shift led to different patterns of phase adjustment for the individuals. Shortening and lengthening of circadian periods as well as phase jumps by about 12 hr were observed. Simulations with a Van-der-Pol oscillator forced by a rectangular zeitgeber function clearly reflected the divergence in resynchronization between eastbound and westbound flights. The different resynchronization patterns found after the 9-hr zeitgeber advance, including the corresponding duration of readjustment, could also be well simulated.

Adaptation, Physiological↗
PubMed1986

International cooperative study of aircrew layover sleep: operational summary.

The findings of this cooperative study of layover sleep have direct implications for flight operations. In the consensus view of the principal investigators, these can be divided into their relevance for eastward or westward flight. Eastward flight produced more sleep disruption than westward. Different sleep and scheduling strategies are recommended for each flight direction, and the importance of individual crewmember factors is discussed in relation to age and circadian type. Despite the limitations of this study with regard to trip simplicity and the baseline data, the results for each airline are highly consistent and should be applicable to a wide range of long-haul crewmembers and carriers.

Adult↗
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

Models to predict operational loads of flight schedules.

Several concepts have been presented in the literature which have the potential to predict the operational load on aircrews during long-distance flights. They are briefly described and applied to a flight duty pattern actually scheduled for an airline route. For each model relative and absolute difficulty grades for the different segments of the pattern are evaluated and compared. Relative ranking results in an excellent agreement between the various models. Absolute classification into "normal," "heavy," and "definitely severe" segments reveals less conformity. From our observations on this route, it is concluded that the index of Mohler's model reflects the most realistic load estimates. Finally, a new approach is introduced which considers duty period, night flying, number of transits, preceding layover time, and preceding time-zone transitions as those elements constituting a computable and essential part of the operational load.

Aerospace Medicine↗
PubMed1983

Flight, flight duty, and rest times: a comparison between the regulations of different countries.

Flight time, flight duty limitations, and rest requirements are compared between the regulations from nine different countries. Twelve factors are identified which played a role in formulating restrictions and criteria. Duration of flight duty and crew augmentation are the factors considered by most countries; time of day, night flight, night sleep, and time zones are the factors least considered. Conformity exists in the necessity to prescribe maximum permissible flight or duty times and minimum rest requirements on a daily basis. Agreement was also observed in grading the standards according to more or less fatiguing conditions. Six out of nine regulations define night hours, but fail to agree upon beginning, end, and duration of night. All countries but one limit flying hours on a monthly and yearly basis, although the limits diverge. A brief outline of the German provisions is presented as an example for a compact and practicable regulation.

Australia↗