Case report of an aviator with a single episode of altered consciousness due to Hymenoptera hypersensitivity

This case is presented to: a) emphasize the importance of a careful history, including interviewing witnesses and considering a complete differential diagnosis when evaluating aviators with a history of an episode of altered consciousness; and b) demonstrate an appropriate use of literature review, subspecialty consultations, and U.S. Air Force Aeromedical Guidelines to arrive at an aeromedical disposition for an unusual case. A military aviator experienced an episode of syncope/near syncope, initially felt to be caused by a primary seizure or an arrhythmia. Subsequent thorough evaluation included careful history taking, extensive interviewing of witnesses, subspecialty consultations, review of appropriate literature and deliberation by a board of experienced military aeromedical physicians. Cardiac and neurologic diagnoses were considered but careful history and witness interviews revealed that the aviator had sustained an insect sting just minutes before the episode. Evaluation by allergy specialists, including skin testing, identified him as being hypersensitive to Hymenoptera stings. A diagnosis of hypersensitivity reaction to a Hymenoptera sting was determined to be the cause of the altered consciousness episode. Review of the literature revealed that immunotherapy for Hymenoptera sensitivity reduces the risk of future anaphylaxis to only 1-2% after maintenance dose is achieved. Consideration of the risk of future events and the success of rush immunotherapy resulted in a recommendation for a waiver to return the aviator to unrestricted flying duties. The importance of diligent history taking must never be forgotten. In this aviator it led to the correct diagnosis and definitive therapy. In addition, appropriate consideration of the literature and knowledge of outcome rates allowed a return to unrestricted flying for this aviator. If the original diagnosis of seizure or arrhythmia had been accepted, this aviator would have been disqualified without waiver and a valuable flying asset would have been lost.     

Intraventricular conduction disturbances in civilian flying personnel: left anterior hemiblock.

We undertook a retrospective study of the natural history, clinical significance, prognosis, associated conduction disturbances, and pathology, as well as flying fitness qualification of 247 cases of left anterior hemiblock (LAH), detected in a presumably healthy population of 8,915 male individuals engaged in civilian flying activities (prevalence: 2.77%). The cases were divided into three groups according to the electrical axis value of the first electrocardiogram (ECG). The group with the slow mode of appearance of LAH was the most common. If associated with right bundle branch block, LAH usually evolves first. LAH could not be ascribed to any definite pathology; neither was it a forerunner of left bundle branch block nor complete atrioventricular block. Not one episode of syncope nor of sudden incapacitation was reported. As a mere ECG finding, LAH does not modify an aviator's fitness qualification. If another conduction disturbance develops, qualification will depend on the results of complementary studies, non-invasive or invasive, according to any associated conduction disturbance.     

有晕厥史飞行员立位应激下自主神经功能评价

目的：评价加速度引起的意识丧失（G－LOC）或血管迷走性晕厥（VVS）飞行员在立位耐力试验（OTT）条件下自主遥作用。方法：对30例晕厥并阳 性OTT病例组（I组），20例晕厥并阴性OTT病例组（Ⅱ组）和15例年龄，性别，飞行机种，飞行时间相匹配的健康飞行员（对照组）的心率变异（HRV）和OTT的关系进行研究，对所测量OTT前后心率（HR），收缩压（SBP），舒张压（DBP）和HRV指标进行对比分析。结果：3组被试者OTT前平均HR，SBP，DBP比较无显著性差异（P＞0．05），OTT后I组HR明显高于其他两组（P＜0．01），SBP和DBP明显低于其他两组（P＜0．01），HRV指标中I组24h连续RR间期标准差（SDNN），HRV三角指数（HRVI），RR间期平均值（RR）明显小于其他两组（P＜0．01），平均1h 功率谱分析I组低频成分／高频成份比值（LF／HF）明显高于其他两组（P＜0．05），结论：晕厥并阳性OTT飞行员立位应激下交感神经张力增强，副交感神经张力减弱，使自主神经功能失调。     

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.     

Pneumomediastinum in student aviators: 10 cases with return to flying duty

Pneumomediastinum (PnM) is an uncommon phenomenon, though it is one of the most common causes of chest pain in young adults. It may be particularly important among aviators, as it may result in in-flight incapacitation. Spontaneous PnM is a variant usually associated with the Valsalva maneuver, used during high-performance flight. This may increase the risk of PnM recurrence and raises concern regarding the return to flight duties of aviators after an episode of spontaneous PnM. We present 10 student aviators who experienced a single episode of uncomplicated PnM unassociated with flight. All were returned to flying duty following a normal pulmonary evaluation and are still in active duty. Follow-up was conducted for a mean period of 74.7 mo without any adverse consequences. These findings support the return of aviators to flying duty after a single episode of uncomplicated spontaneous PnM.     

Sickle cell trait and the aviator

Sickle cell trait (SCT) for years has been a controversial disorder within the aerospace medicine community. Some authorities consider SCT to be an entirely benign condition without particular significance, at least to moderate altitudes. Others are in disagreement and consider it a serious enough threat that flying duties should be precluded for all individuals with this disorder. These issues are addressed by reviewing SCT, its relationship to altitude, and its risk to aviation. The author concludes that flying organizations must establish their own policy on flying status for individuals with SCT based upon mission peculiarities and the assessment of risk inherent in that mission.     

Unexpected syncope and death during intense physical training: evolving role of molecular genetics

Special operations forces (SOF) undergo an unparalleled degree of physical training. The medical officer responsible for these personnel must often deal with episodes of syncope that cannot be readily explained. In the past, loss of consciousness during heavy physical exertion was attributed to inadequate fluid intake resulting in dehydration or abnormalities in temperature regulation. However, many of those diagnoses, in retrospect were probably incorrect. The occurrence of exercise-related syncope in multiple members of the same family suggested that there could be a genetic basis for the unexpected loss of consciousness during exercise. Intensive clinical examinations of these patients, coupled with current advances in molecular genetics, have shown this to be the case. We review some of the more common genetic abnormalities associated with exertion-related syncope. These syndromes should be considered by the medical officer presented with a patient having syncope of indeterminate cause.     

飞行人员晕厥诊治特点与航空医学鉴定--附36例临床分析

目的：总结飞行人员晕厥诊治和航空医学鉴定特点,为其诊治及航空医学鉴定提供参考。方法回顾性分析1998年10月—2015年10月入住空军总医院空勤科的36例军事飞行人员晕厥临床资料并复习相关文献。结果30～39岁年龄组的飞行人员发生晕厥较多,共19例,占52.8%;36例中血管迷走性晕厥23例,占63.9%,发生率最高;19例飞行合格,7例暂时飞行不合格,10例飞行不合格;飞行人员晕厥在不同机种间发病率差异无统计学意义。结论飞行人员晕厥包括地面晕厥和空中晕厥,诊治有其特殊性;按照现行飞行人员体格检查标准,借鉴美国相关标准,结合诱因是否明确、飞行机种、飞行经验、职别、个人意向及部队需求予以医学鉴定。     

Psychiatric considerations in military aerospace medicine

Military aerospace medicine requires a psychiatric selection and certification process that determines not only the absence of significant mental disorders, but also the presence of positive qualities in the realms of motivation, ability and stability: not all normal people are fit to fly. Other issues of aerospace psychiatry involve maintenance of mental resilience and hardiness during a flying career, aeromedical decisions about when to remove from flight duties and when to return, criteria for waivers for psychiatric conditions, use of medications for treatment of psychiatric symptoms, questions of substance abuse, and research in such areas as genetics. This report reviews the basis for military aerospace psychiatry, primarily as practiced in the United States Air Force (USAF), and presents some of its underlying principles as they apply to clinical situations.     

Head-up tilt test for recurrent syncope in pilots

Syncope is defined as a sudden temporary loss of consciousness and postural tone that is associated with spontaneous recovery. Vasovagal or neurocardiogenic syncope is a common and usually benign cause of syncope. The mechanism may be cardioinhibitory, vasodepressor, or both. Diagnosis is usually made by a typical patient history with a definite trigger. Although vasovagal syncope is considered a benign condition, its occurrence in an aviator is worrisome, especially if recurrent and without a definite trigger. The head-up tilt test (HUTT) is used as a vasovagal syncope challenge test. A drop in BP and asystole during HUTT suggest a tendency to recurrent vasovagal syncope. We describe two military aviators with recurrent episodes of vasovagal syncope, one with definite triggers and one without. Both had positive HUTTs. The aviator with trigger-defined vasovagal syncope was disqualified from high-performance platforms due to his positive HUTT. The second case was disqualified from all platforms, irrespective of his HUTT result, because a definite trigger was not definable for all his syncopal episodes.     

Cases from the aerospace medicine residents' teaching file. Case report of an aviator with focal myocarditis mimicking myocardial infarction with normal coronaries

A military aviator was initially diagnosed with myocardial infarction following a viral syndrome. Confusion about recurrence of chest pain versus gastritis led to his continued cardiac patient status until this was clarified diagnostically. He was presumed to have had coronary vasospasm, and was treated with a calcium channel blocker. Absent his strong desire to return to flying duties, he may have continued in that diagnostic pathway indefinitely. After thorough aeromedical evaluation, resolved focal viral myocarditis was felt to be the most likely diagnosis and he was returned to military flying duties.     

Excessive daytime sleepiness in a trainee military pilot

A 21-yr-old army trainee pilot was noted by his colleagues to be frequently falling asleep in his class and was reported to medical authorities. Despite a number of investigations and review by two sleep specialists, a formal diagnosis could not be made. During his medical review board three questions were posed: does the trainee have excessive daytime sleepiness (EDS), or is his sleepiness a variation of normal; if he is excessively sleepy, what is the most likely diagnosis; and should the trainee be allowed to continue to undertake pilot training based on most likely diagnosis and/or his history. The most likely diagnosis was considered to be idiopathic hypersomnia, a relatively uncommon condition which is a diagnosis of exclusion. The condition was considered incompatible with flight duties in a pilot under training due to the potential for compromise of performance, mission completion, and flight safety. Stimulant medications may control symptoms, but are incompatible with flying duties in the Australian Defense Force. This case illustrates the difficulties in determining aeromedical disposition in borderline cases of EDS where a clear diagnosis cannot be made.     

Incidence and outcomes of total hip arthroplasty among U.S. Army aviators

Among Army aviators, the incidence of total hip arthroplasty (THA) is unknown. This study analyzes the incidence and aeromedical disposition of THA among Army aviators. The U.S. Army Epidemiology Data Register was queried for a 10-year period from calendar year 1987 to 1996. The aviators selected for this study cohort were all qualified and on active flight status before undergoing THA. Data collected included age, gender, diagnoses, and aeromedical dispositions. There were 214,003 aviator-years of observation. Eleven aviators underwent 14 THAs. The overall incidence of THA was 0.05 per 1,000 aviator-years of observation. Of the 11 aviators who underwent THA during the study period, 4 received aeromedical suspension from flying duties (36%). THA is a rare medical event among Army aircrew members. Most are able to return to full flying duties with a waiver. Aircrew members younger than 50 years with THA are more likely to be suspended from aviation duties.     

A case of G-LOC in a propeller aircraft

The occurrence of +Gz-induced loss of consciousness (G-LOC) is well recognized in high-performance aircraft. A case of G-LOC is described involving a co-pilot on a flying instructor's course in a propeller-driven aircraft, the CT-4. The cause of G-LOC is attributed to a combination of a lack of recent G exposure, not commanding the aircraft, fatigue, and a possibly less-than-optimal straining manoeuvre. This case reinforces the problems of G-LOC in any aircraft capable of performing aerobatics.     

Aeromedical management of U.S. air force aviators who attempt suicide.

BACKGROUND: Little has been published about the aeromedical management and disposition of aviators who attempt suicide, and almost no such information about military aviators exists in the open literature. The few available data are scattered and frequently anecdotal. METHODS: The authors reviewed all case reports of fliers evaluated at the USAF School of Aerospace Medicine's Aeromedical Consultation Service (ACS) between 1981-96 for possible return to flying duties after a suicide attempt, and prepared a representative case report. RESULTS: Between 1981 and 1996, the ACS evaluated 14 trained aviators (pilots and other aircrew members, excluding flight surgeons) who had attempted suicide. Of these, 11 (79%) ultimately received a recommendation for return to flying duties. CONCLUSIONS: In most instances the underlying stressors included failed intimate interpersonal relationships, administrative or legal problems, psychiatric disorders, death of spouse, or job conflicts. Evidence of abuse of alcoholor other substances was found in 54% of an earlier, larger data set of attempters. Some data on aircrew suicide completion were available and are reported. The top medical priorities after such attempts should be to diagnose what is wrong, and to treat it. In spite of the common assumption that a suicide attempt inevitably ends a military flying career, some attempters can return to safe and effective flying duty after appropriate psychotherapy. If the flier regains physical and mental health and maintains them for at least 6 mo after treatment, then that flier may be evaluated by an outside aeromedical psychiatric consultant such as the ACS (to avoid transference issues between flier and therapist) for possible return to flying duties. Waiver action should be based on the underlying psychiatric diagnosis, not the suicidal attempt itself. Follow-up may be accomplished through periodic mental health evaluations in conjunction with routine physical examination procedures. Issues involving substance abuse and security clearances must be handled through the appropriate channels.     

Blood glucose awareness training helps return insulin-treated aviators to the cockpit

Insulin-treated diabetes mellitus has traditionally been considered disqualifying for aviation duties, the major concern being the risk of hypoglycemia. This phenomenon may lead to impaired judgment and even loss of consciousness, potentially leading to a mishap. Blood glucose awareness training has been advanced as a strategy to avoid hypoglycemia by teaching individuals to use the appearance of autonomic and neuroglycopenic symptoms as indicators of decreasing blood glucose levels. We present two military aviators with newly diagnosed type 1 diabetes mellitus who were returned to flying duty in a multicrew aircraft. Blood glucose awareness training was used as a tool for the education of these aviators regarding the early signs of hypoglycemia in order to avoid development of more significant hypoglycemia. These cases attest to the importance of blood glucose awareness training in the return of diabetic patients to the cockpit.     

Visual symptoms and G-induced loss of consciousness in 594 Chinese Air Force aircrew--a questionnaire survey

A questionnaire survey was performed for the first time to assess the prevalence of visual symptoms and G-induced loss of consciousness (G-LOC) due to +Gz exposure in the Chinese Air Force (CAF) to determine the effectiveness of current G tolerance training. Responses were received from 594 individuals. Among them, 302 reported at least one episode of some sort of symptoms related to +Gz, including 110 (18.5%) with visual blurring, 231 (38.9%) with greyout, 111 (18.7%) with blackout, and 49 (8.2%) with G-LOC. Incidences were most common in aircrew with 250-1,000 flying hours (53.6%) and were more prevalent in those with fewer on type flying hours (p < 0.001). The most common situation was reported between +5 and 5.9 Gz. The results indicate a fairly high prevalence of visual symptoms and G-LOC among Chinese Air Force aircrew. There remains considerable scope for +Gz education, particularly in the early centrifuge training and selection of rational physical exercises.     

The aeromedical implications of atrial fibrillation

A retrospective study was undertaken to determine the incidence of spontaneous atrial fibrillation (AF) in a group of asymptomatic pilots. The electrocardiograms of 13,037 aircrew members accumulated between 1964 and 1986 were reviewed and those coded for AF were extracted. In each case an attempt was made to investigate factors relating to the onset, course, and prognosis of the AF. Eight subjects (mean age 50.1 years) were found to have AF. Of this group, two had a single isolated episode of AF for which a specific precipitating factor was implicated, three had recurrent paroxysmal AF of which one progressed to chronic persistent AF, and three had chronic persistent AF from the outset. The mean follow-up period for the eight subjects was 13.6 years. The two pilots who had isolated attacks of AF have thus far had no subsequent episodes of AF. Five of the remaining six have been completely well, while one required treatment for an embolus to his left leg. Concerning the aeromedical implications, we believe that pilots demonstrating single isolated episodes of AF in the presence of a normal heart, and in whom recovery is complete, should be allowed to return to full aviation duties on a waiver clause. Patients with chronic AF, lone AF, or paroxysmal AF should be excluded from all flying duties.     

Operational G-induced loss of consciousness: something old; something new

Loss of consciousness (LOC) during exposure to +Gz occurs in aircrew flying high-performance aircraft. This phenomenon is responsible for several USAF aircraft losses with accompanying loss of life. It has been recognized as a potential flying problem since 1938. Acceleration-induced LOC results in 15-to 20-s periods of aircrew total incapacitation, amnesia, and clonic spasms. It can occur at relatively low G levels and without symptoms of loss of light (blackout). Operational anti-G equipment and methods are not completely effective in preventing LOC. Considering the present status of G protection, a deficiency in the anti-G straining maneuver is considered to be the primary cause of G-induced LOC. This deficiency usually can be corrected with proper centrifuge training. Our present understanding of G protection suggests that the elimination of LOC as a serious problem for USAF high-performance aircraft operations must include the supination of aircrew to a minimum seat back angle of 60 degrees to 65 degrees.     

The healthy motivation to fly: no psychiatric diagnosis

Aircrew mission effectiveness may uniquely be influenced by subtle psychological factors not ordinarily brought to the attention of psychiatrists. Pilots tend to be bright, articulate, and anxious to resume their aviation duties when grounded. However, these patients are usually well defended, and rarely psychologically attuned or introspective. Greater insight into what constitutes the normal, healthy motivation to fly will help those who make judgments regarding the return of grounded aviators to flying duty. A review of associated birth order, personality theory, industrial and business psychology, aerospace, and psychoanalytic literature is presented. Highlighted are the difficulties inherent in examining the motivation of a healthy, well-defended population. Our conclusion: an examiner's countertransferential feelings are the best available tool for measurement of healthy motivation.