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Biomedical subjects

J E Whinnery

Publications and source records attributed to J E Whinnery.

12 recordsLinked to original sources
PubMed1979

Concurrent loss of consciousness and sino-atrial block during +Gz stress.

Current USAF fighter aircraft easily exceed human physiologic limits with their rapid onset of head-to-foot acceleration forces (+Gz). Sudden in-flight incapacitation caused by these increased +Gz forces could be disastrous with loss of materiel and human life. The physiologic mechanisms responsible for loss of consciousness (LOC) secondary to high +Gz must be fully understood so that maximum protection against it can be provided. An interesting case of an episode of LOC with concurrent sino-atrial block occurring during a relaxed rapid onset (1 G/s) centrifuge run is presented. The patient was undergoing flight medical evaluation for an episode of syncope, etiology unknown. An unusual characteristic of the patient was his high level of endurance training. The possibility of an excessive increase in vagal tone, developed by endurance training, is discussed as a probable etiology for this patient's prolonged time of incapacitation evidenced after +Gz-induced loss of consciousness.

Acceleration↗
PubMed1979

Reproducibility of +Gz tolerance testing.

The +Gz tolerance of USAF aircrewmen undergoing medical evaluation has been tested at the USAF School of Aerospace Medicine since 1973. For various reasons, the test protocol can usually be carried out only once on these patients. Accurate determination of the +Gz tolerance of aircrewmen who fly high performance fighter aircraft is very important in assuring aero-medical safety, since loss of consciousness as a result of exceeding a pilot's G tolerance may result in loss of life and loss of aircraft. It is, therefore, necessary to estimate the variability associated with each profile of the test so that a more accurate assessment of +Gz tolerance can be made. Multiple repeat medical evaluation test protocols were performed on 17 centrifuge acceleration panel members. The standard deviations in the +Gz measurements for the four centrifuge profiles were GOR(1) = 0.38 Gz, ROR=0.22 Gz, GOR(2)=0.34 Gz, and GOR(S)=0.39 Gz. A statistically significant learning effect, which increases +Gz tolerance, was observed in both experienced and inexperienced subjects. Knowledge of the variability associated with each test profile will allow a more accurate definition of an individual +Gz tolerance when only a single centrifuge test protocol can be performed. In addition, possible future use of this centrifuge protocol in the selection of individuals with above- or below-average +Gz tolerance is facilitated with an accurate assessment of the variability associated with the test.

Aerospace Medicine↗
PubMed1979

Technique for simulating G-induced tunnel vision.

A simple technique is described which helps subjects gain an understanding of the endpoint used to terminate exposure to centrifuge stress during training procedures on the human centrifuge. The technique involves manual induction of increased intraocular pressure which, in turn, causes a decrease in retinal perfusion followed by greyout and tunnel vision.

Aerospace Medicine↗
PubMed1978

Medical evaluation of G-sensitive aircrewmen.

Etiologies for loss of consciousness in an aerospace environment are diverse and may present as a perplexing problem in specific cases. The high, sustained G that current aircraft are capable of producing represent another etiology for inflight loss of consciousness. Protective measures give only partial protection, however, and pilots continue to remain susceptible to the excessively high G forces. Certain protective methods, including M-1 and L-1 straining maneuvers, may actually become a source of loss of consciousness if not performed correctly. The current methods utilized to evaluate loss of consciousness in flight, as demonstrated in the specific case of a student pilot performing an improper straining maneuver, are reviewed. Specific measures that might be instituted to prevent certain of these loss-of-consciousness episodes are recommended. The human centrifuge can be an integral part of aeromedical evaluation when G-related problems are involved and is an extremely valuable training device in determining individual G tolerance and enabling controlled G-stress training. Use of the centrifuge in high-G training could well lead to both human life and aircraft cost savings in addition to assuring full utilization of today's high-performance aircraft.

Adult↗
PubMed1977

The electrocardiographic response to maximal treadmill exercise of asymptomatic men with left bundle branch block.

This study presents the results of maximal treadmill testing and coronary angiography in 31 asymptomatic USAF aircrewmen with acquired left bundle branch block. There were two subgroups: 26 men with normal coronary angiography and five men with significant angiographic coronary angiography and five men with significant angiographic coronary artery disease. The mean amount of maximal ST-segment depression induced by treadmill exercise was --0.5 mv. for both groups and the range in the normal subgroup was --0.3 to --1.0 mv. No significant differences were found between the groups. We concluded that apparently healthy, asymptomatic men with acquired left bundle branch block can have considerable ST-segment depression in response to maximal treadmill testing and that their ST-segment response cannot be used to make diagnostic decisions about them.

Adult↗
PubMed1977

The electrocardiographic response to maximal treadmill exercise of asymptomatic men with right bundle branch block.

This study presents the results of maximal treadmill testing and cardiac catheterization in 40 asymptomatic and apparently healthy men with acquired right bundle-branch block. Eight of the men had significant angiographic coronary artery disease, and six of the eight only had single-vessel disease. The 40 men had normal maximal oxygen consumptions, normal maximal heart rates, and normal maximal blood pressure responses; none of the men had abnormal ST-segment changes in response to maximal treadmill testing. Thus, the sensitivity of exercise testing for coronary artery disease in men with right bundle branch block is uncertain. However, the apparently high specificity of exercise testing demonstrated by this study necessitates further evaluation for coronary artery disease in men with right bundle branch block who develop abnormal ST-segment depression in response to exercise testing.

Adult↗