Journal article
Acceleration-induced near-loss of consciousness: the "A-LOC" syndrome
Aviation, space, and environmental medicine, v 74(10), pp 1021-1028
Oct 2003
PMID: 14556561
Featured in Collection : UN Sustainable Development Goals @ Drexel
Abstract
There is an insidious phenomenon that can occur when aircrew are exposed to +Gz stress even at levels that are insufficient to cause +Gz-induced loss of consciousness (G-LOC). Under these circumstances aircrew exhibit an altered state of awareness that was termed Almost Loss of Consciousness (A-LOC) by the U.S. Navy in the late 1980's. A-LOC is a syndrome that includes a wide variety of cognitive, physical, emotional, and physiological symptoms. While A-LOC has been observed in centrifuge studies and reported in flight for over 15 yr, a definitive description of the syndrome does not exist.
Nine subjects were exposed to short +6, 8, and 10 Gz pulses of increasing duration until they experienced G-LOC. Instrumentation included two channels of ECG and near infrared spectroscopy (NIRS) to measure relative cerebral tissue oxygenation (rSo2). Subjects indicated +Gz-induced visual symptoms (light loss, LL) by pressing a switch when LL began and releasing it when total vision was restored. Short-term memory loss was assessed using a simple math task. Data analysis included a description and the time course of the physical, physiological, cognitive, and emotional responses.
There were 66 episodes of A-LOC that were identified out of a total of 161 +Gz pulse exposures. Many incidents of sensory abnormalities, amnesia, confusion, euphoria, difficulty in forming words, and reduced auditory acuity were documented. Often these responses occurred in multiple subjects and at different +Gz levels. One of the most common symptoms was a disconnection between cognition and the ability to act on it. There was a significant reduction in rSo2 over baseline, greater overshoot in rSo2 (increase in oxygenation above baseline after the +Gz exposure), faster fall in rSo2 during +Gz stress, and prolonged recovery time associated with A-LOC as compared with +Gz exposures without symptoms.
Evaluation of the range of symptoms associated with A-LOC can lead to a program to increase pilots' awareness of the phenomenon and further our understanding of the relationship between the outward symptoms and the underlying physiological changes.
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Details
- Title
- Acceleration-induced near-loss of consciousness: the "A-LOC" syndrome
- Creators
- Barry S Shender - Drexel University, Philadelphia, PA, USA. ShenderBS@navair.navy.milEstrella M ForsterLeonid HrebienHan Chool RyooJoseph P Cammarota, Jr
- Publication Details
- Aviation, space, and environmental medicine, v 74(10), pp 1021-1028
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Electrical and Computer Engineering; Pulmonary, Critical Care, and Sleep (Medicine)
- Web of Science ID
- WOS:000185610000001
- Scopus ID
- 2-s2.0-0141679002
- Other Identifier
- 991019168318304721
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- Collaboration types
- Domestic collaboration
- Web of Science research areas
- Public, Environmental & Occupational Health
- Sport Sciences