Biomedical subjects

L J Connell

Publications and source records attributed to L J Connell.

8 recordsLinked to original sources

PubMed1998

Flight crew fatigue I: objectives and methods.

In 1980, NASA-Ames Research Center, Moffett Field, CA, initiated a program to assess flight crew fatigue, determine its potential operational consequences, and provide practical countermeasure suggestions. To assess the extent of the problem, crewmembers were monitored before, during, and after commercial short-haul (fixed-wing and helicopter aircraft), overnight cargo, and long-haul operations. A total of 197 volunteers were studied on 94 trip patterns with 1299 flight segments and 2046 h of flying time. The present paper outlines the program and describes the common methodology used in these studies, which are then presented in detail in the four subsequent papers. The sixth paper offers a synthesis of this work, reviewing the major causes of flight crew fatigue and making specific suggestions about ways to manage it in different operations.

Aviation↗

PubMed1998

Flight crew fatigue II: short-haul fixed-wing air transport operations.

We monitored 74 crewmembers before, during, and after 3-4-d commercial short-haul trips crossing no more than one time zone per 24 h. The average duty day lasted 10.6 duty hours, with 4.5 flight hours and 5.5 flights. On trips, crewmembers slept less, woke earlier, and reported having more difficulty falling asleep, with lighter, less restful sleep than pretrip. The consumption of caffeine, alcohol, and snacks increased on trip days, as did reports of headaches, congested nose, and back pain. The study suggests the following ways of reducing fatigue during these operations: base the duration of rest periods on duty hours as well as flight hours; avoid scheduling rest periods progressively earlier across a trip; minimize early duty report times; and inform crewmembers about strategic use of caffeine and alternatives to alcohol for relaxing before sleep.

Adult↗

PubMed1998

Flight crew fatigue III: North Sea helicopter air transport operations.

We studied 32 helicopter pilots before, during, and after 4-5 d trips from Aberdeen, Scotland, to service North Sea oil rigs. On duty days, subjects awoke 1.5 h earlier than pretrip or posttrip, after having slept nearly an hour less. Subjective fatigue was greater posttrip than pretrip. By the end of trip days, fatigue was greater and mood more negative than by the end of pretrip days. During trips, daily caffeine consumption increased 42%, reports of headache doubled, reports of back pain increased 12-fold, and reports of burning eyes quadrupled. In the cockpits studied, thermal discomfort and high vibration levels were common. Subjective workload during preflight, taxi, climb, and cruise was related to the crewmembers' ratings of the quality of the aircraft systems. During descent and approach, workload was affected by weather at the landing site. During landing, it was influenced by the quality of the landing site and air traffic control. Beginning duty later, and greater attention to aircraft comfort and maintenance, should reduce fatigue in these operations.

Adult↗

PubMed1998

Flight crew fatigue IV: overnight cargo operations.

We monitored 34 B-727 crewmembers before, during, and after 8-d commercial overnight cargo trips crossing no more than one time zone per 24 h. Daytime sleep episodes were 41% shorter and were rated as poorer than nighttime sleep episodes. When the layover was long enough, crewmembers usually slept again in the evening before going back on night duty. Nevertheless, the total sleep per 24 h on duty days averaged 1.2 h less than pretrip. The circadian temperature rhythm did not adapt completely to night duty, delaying by about 3 h. Self-rated fatigue was highest around the time of the temperature minimum, which occurred near the end of the nighttime duty period. On trip days, crewmembers ate more snacks and there was a marked increase in reports of headaches, congested noses, and burning eyes. Comparisons with daytime short-haul operations confirm that a daytime rest period does not represent the same sleep opportunity as a nighttime rest period of the same duration. We examine regulatory and scheduling options, and personal countermeasure strategies, that could help to reduce sleep loss during overnight cargo operations.

Adult↗

PubMed1998

Flight crew fatigue V: long-haul air transport operations.

We monitored 32 flight crewmembers before, during, and after 4-9 d commercial long-haul trips crossing up to 8 time zones per 24 h. The average duty day lasted 9.8 h, and the average layover 24.8 h. Layover sleep episodes averaged 105 min shorter than pretrip sleep episodes. However, in two-thirds of layovers, crewmembers slept twice so that their total sleep per 24 h on trips averaged 49 min less than pretrip. Greater sleep loss was associated with nighttime flights than with daytime flights. The organization of layover sleep depended on prior flight direction, local time, and the circadian cycle. The circadian temperature rhythm did not synchronize to the erratic environmental time cues. Consequently, the circadian low point in alertness and performance sometimes occurred in flight. On trip days, by comparison with pretrip, crewmembers reported higher fatigue and lower activation; drank more caffeine; ate more snacks and fewer meals; and there were marked increases in reports of headaches, congested nose, and back pain. Scheduling strategies and countermeasures to improve layover sleep, cockpit alertness, and performance, are discussed.

Aviation↗

PubMed1993

Age, circadian rhythms, and sleep loss in flight crews.

Age-related changes in trip-induced sleep loss, personality (n = 205), and the pre-duty temperature rhythm (n = 91) were analyzed in crews from various flight operations. Eveningness decreased with age (subjects aged 20-30 were more evening-type than subjects over 40). The minimum of the baseline temperature rhythm occurred earlier with age (earlier in subjects aged 30-50 than in subjects aged 20-30). The amplitude of the baseline temperature rhythm declined with age (greater in subjects aged 20-30 than in subjects over 40). Average daily percentage sleep loss during trips increased with age. Among crewmembers flying longhaul flight operations, subjects aged 50-60 averaged 3.5 times more sleep loss per day than subjects aged 20-30. These studies support previous findings that evening types and subjects with later peaking temperature rhythms adapt better to shift work and time zone changes. Age and circadian type may be important considerations for duty schedules and fatigue countermeasures.

Adaptation, Physiological↗

PubMed1986

Masking of the circadian rhythms of heart rate and core temperature by the rest-activity cycle in man.

Heart rate and core temperature are elevated by physical activity and reduced during rest and/or sleep. These masking effects may confound interpretation of rhythm waveforms, particularly in situations where the rest-activity rhythm has a different period from that of the core temperature rhythm. Such desynchronization often occurs temporarily as an individual adjusts to a new work shift or to a new time zone following rapid transmeridian travel, making it difficult to assess the impact of such schedule changes on the circadian system. The present experiments were designed to estimate the magnitude of these masking effects, by monitoring the heart rate, rectal temperature, and nondominant wrist activity (2-min samples) of 12 male subjects during 6 days of normal routine outside the lab and during 6 days of strict bedrest. Subjects also kept sleep, dietary, and exercise logs throughout the study. Average (20-min) waveforms were computed for each subject and each rhythm, at home and in bedrest. In addition, data were partitioned according to self-reported sleep and wake times and were analyzed separately for each state. Average waveform comparisons indicated that about 45% of the range of the circadian heart rate rhythm during normal routine was attributable to the masking effects of activity during wake, which also produced a 16% elevation in mean heart rate during wake and an 11% increase in mean heart rate overall. (Analysis of variance indicated that mean heart rate during sleep at home was not significantly different from the mean during sleep in bedrest.) On average, about 14% of the range of the circadian temperature rhythm during normal routine was attributable to the effects of activity masking. However, the change in range of the temperature rhythm, from home to bedrest, was very variable between subjects (-41% to +13%). This variability was not accounted for by age or by reported frequency of exercise at home. Normal activity during wake increased the mean temperature during wake by an average of 0.16 degrees C and the overall mean by about 0.12 degrees C. (Analysis of variance indicated that mean temperature during sleep at home was not significantly different from the mean during sleep in bedrest.) A 10-hr "night" (lights-off from 2200 to 0800 hr) was provided during bedrest, within which subjects could select their own sleep times. Times of sleep onset and wake onset were not significantly different between home and bedrest.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1986

International aircrew sleep and wakefulness after multiple time zone flights: a cooperative study.

An international research team has carried out an electroencephalographic study of sleep and wakefulness in flight crews operating long-haul routes across seven or eight time zones. Following baseline recordings, volunteer crews (n = 56) from four airlines spent their first outbound layover at a sleep laboratory. This paper provides an overview of the project's history, its research design, and the standardization of procedures. The overall results are remarkably consistent among the four participating laboratories and strongly support the feasibility of cooperative international sleep research in the operational arena.

Adult↗