空中晕厥与心血管功能障碍的研究进展

论述了空中晕厥发生的心血管机制，介绍了目前模拟空中环境，对战斗机飞行员进行心血管功能检查的几种方法，指出了加强习行员Ｇ耐力训练和研究对防止空中晕厥的重要意义。     

空中晕厥与心血管功能障碍的研究进展

晚近，飞行员空中曼厥亦称G致意识丧失（简称G－LOC）与心血管功能障碍之间的关系已引起人们的普遍重视，其主要理由是：（1）心血管功能障碍与空中暴厥之间互为因果，即心血管功能失调者，G耐力差，易发生空中景厥，而发生空中晕厥者常伴有心血管功能障碍[1,2]。（2）心脏自主神经功能失调是造成飞行员心血管功能障碍的机制之一，而心血管功能障碍又是停飞的重要原因[3,4]。（3）测定心血管功能失调的方法学有了很大的进展，如模拟空中环境下的心率变异性（HRV）、血压变异性（BPV）分析及Q－T离散（Q－Td）分析等[3,5]。（4）加强…     

立位耐力不良飞行员模拟飞行中心理生理反应与心率变异性分析

目的探讨立位耐力不良飞行员模拟空中环境下心脏自主神经功能调节状态和心理生理反应特点，为空中晕厥的诊断提供客观的评价方法。方法对２２名立位耐力不良（不良组）飞行员进行了连续动态心电记录和模拟飞行条件下的心理生理参数测定与心率变异性（ＨＲＶ）分析，并与１５名立位耐力正常的健康飞行员（健康组）做了对比。结果不良组飞行员在模拟仪表飞行中心理生理储备能力明显降低，表现为完成两项任务的质量和处理信息速度的能力较健康组低（Ｐ＜０．０１）；心血管自主神经功能严重失调；心理生理储备值与ＨＲＶ多数指标之间存在明显的相关性。结论结合模拟仪表飞行条件下的心理生理负荷评定和ＨＲＶ分析能较客观地反映立位耐力不良飞行员心血管自主神经功能障碍的发生机制和调节规律，为空中晕厥的诊断提供量化的指标。     

歼击机飞行员空中加速度性晕厥的防护

地面的各种晕厥也许只会给您带来伤痛,但发生在空中的晕厥却意味机毁人亡,会给国家财产和飞行员生命安全带来极大的损失。所以,空中晕厥是飞行训练安全的“拦路虎”。笔者通过对飞行部队的调查,就飞行员空中晕厥的发生原因和防护措施谈几点意见。空中晕厥发生的因素加速度耐力下降飞行员在飞行过程中,由于加速度作用造成大脑血液循环受累和血压下降而引起的突然意识丧失,称为“加速度性意识丧失(G-LOC)”、也称为“加速度性晕厥”。资料显示,美军歼击机飞行员加速度性晕厥的发生率为16.13%,我军歼击机飞行员(歼六以上机型)加速度性晕厥的…     

空中晕厥飞行员精神心理障碍评价及其护理对策

空中晕厥主要见于高性能战斗机在大负荷飞行中，由于血液的惯性作用，使心脏回血不足，脑循环障碍而发生短暂的意识丧失。目前多数学者认为，空中晕厥是飞行员中最重要的心身疾病。本文应用症状自评量表（ＳＣＬ－９０）对空中晕厥飞行员进行评价分析，探讨本病患者精神心理障碍的特征，进一步指导本病的临床护理工作。１　对象与方法１．１　研究对象选择空中晕厥歼击机飞行员２７例为试验组，所选病例为本院住院患者，均为１９９５年２月至１１月期间的连续病例。年龄２５～３９岁（平均３１．２岁）。均经主治医师以上人员确诊。选择同期…     

有空中晕厥史飞行员微循环的特征及其可能的影响

目的 探讨微循环与空中晕厥发生的关系。方法试验对象为39名有空中晕厥文的飞行员并设对照健康组飞行员46人。两组飞行员均作常规主动立位耐力试验，试验前后测量血压、心率和微循环各项指标。结果 两组立位耐力试验后，晕厥组多项指标与对照组差异明显，特别是管拌数目、心率、收缩压、血管长度、拌顶宽度、输入枝、输出枝直径等(P＜0．05)。而多数变化从立位即刻开始至立位后20min持续加深而血压进一步下降。结论 微循环的变化与易发空中晕厥有关系，改善微循环对预防和矫治空中晕厥可能有意义。     

立位耐力试验对空中晕厥的诊断价值

目的评价立位耐力试验对空中晕厥诊断的特异性、敏感性和诊断价值。方法应用自行研制的立位耐力监测系统，对31例空中晕厥病例和61例健康飞行员进行立位耐力试验。结果立位耐力试验阳性晕厥组为12例（38.71%），对照组为5例(8.20%)。立位耐力试验敏感性38.71%,特异性91.80%,诊断价值73.91%。结论立位耐力试验对空中晕厥的敏感性低，特异性高，可作为一种诊断空中晕厥的客观方法。     

头高斜位试验结合心率变异分析对飞行员晕厥的对比研究

最近关于飞行员空中晕厥发生机制与评价方法的研究有了很大进展［１］，倾斜台试验（ＴＴＴ），无论采用头高斜位（ＨＵＴ）或头低斜位法（ＨＤＴ）均被认为是诊断和评价不明原因晕厥的最好方法和“金标准”［２］，心率变异（ＨＲＶ）分析作为评价心血管自主神经功能的无创性定量分析方法，不但能对心肌梗塞、糖尿病及充血性心力衰竭患者的短期疗效和长期预后作出独立的客观评价，而且也能为体位变化或空中微重力及失重环境下的心血管机能变化提供重要信息［３］。ＴＴＴ结合ＨＲＶ分析被认为是研究不明原因晕厥的一个新的重要进展，国外已…     

空中晕厥的检查与鉴定的探讨

飞行员在空中发生晕厥,不仅影响飞行,且可直接危及飞行安全.因此研究空中晕厥的诊断检查与医务鉴定有重要意义.我科自1982年以来共收治检查空中晕厥男性飞行员75名,其中体检结论飞行合格者20名占26.7%,停飞者55名占73.3%.现将75名空中发生晕厥者的调查分析情况与医务鉴定改进意见分述于下.一、研究方法 采用前瞻性调查研究方法,对来院受检的空中晕厥者进行统一项目的检查登记.二、结果和资料分析(一)空中晕厥有关因素调查     

应用下体负压试验对空中加速度性晕厥病因的探讨——附20例报告

下体负压检查技术，有类似飞行时受加速度作用、导致血液动力学政变的生理反应。Stevens和Lamb等发现晕厥和不晕厥者对下体负压反应有区别。Faola等观察到血浆肾素-血管紧张素活性反应与所施负压的大小相关。我们于1982年在海军医学研究所下体负压舱和航生医学研究所心脑电生理遥测的配合下，对20例空中晕厥飞行员在下体负压下观察了临床症状反应、心血管和脑电生理改变。     

Pilots with vasovagal syncope: fit to fly?

Two pilots who had experienced vasovagal syncope were grounded by the aeromedical service. Pilot A had experienced three episodes of syncope in medical settings, none during flight. Pilot B had experienced four episodes of syncope in emotional/medical settings, one during flight. Whether a pilot who experienced one or more episodes of vasovagal syncope is declared fit to fly now depends on the number of episodes experienced. We propose that pilots should be assessed individually. Certainty of the diagnosis of vasovagal syncope, the chance and predictability of recurrences during flight, and the possibility of effective therapy should be assessed. Chance of recurrence during flight is low when the triggering factor is known and avoidable. Pilots with syncopal episodes in predictable (e.g., medical) situations, with clear prodromal symptoms and/or effective therapy, should be declared fit to fly. A symptom-free period and/or restriction to fly 'as or with a co-pilot' can be considered.     

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。     

Regional cerebral perfusion in cardiovascular reflex syncope

Little is known about the regional cerebral perfusion in subjects with presyncope or syncope, and the impact that autonomic nervous dysfunction has on it. Seven subjects with cardiovascular vasodepressor reflex syncope were studied. A baseline test was performed with the patients standing in the 70° upright position, while the passive head-up tilt table test with and without isoprenaline infusion was employed for provocation. Regional cerebral perfusion was assessed by means of single-photon emission tomography with technetium-99m labelled V-oxo-1,2-N,N ₁-ethylenedylbis-l-cysteine diethylester (baseline, and during blood pressure decline in the provocation test) and the autonomic nervous function by means of spectral analysis of heart rate variability (baseline, and before blood pressure decline in the provocation test). Every subject showed an abrupt decline in blood pressure in the provocation test (five with presyncope and two with syncope). The systolic and diastolic blood pressures decreased significantly (P<0.001) between the baseline and the provovation study time points (radiopharmaceutical injection and lowest systolic blood pressure). Mean cerebral perfusion as average count densities decreased upon provocation as compared with baseline (190±63 vs 307±90 couts/voxel, respectively,P=0.0013). Hypoperfusion was most pronounced in the frontal lobe. These results suggest that cerebral perfusion decreases markedly during presyncope or syncope with systemic blood pressure decline in subject with cardiovascular vasodepressor syncope. Furthermore, the autonomic nervous function remains unchanged before the systemic blood pressure decline.     

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。     

Aircrew selection: a prospective study

The medical reasons for rejection among 3,000 consecutive applicants for flight training were evaluated, and the effectiveness of the screening process determined by reviewing subsequent medical wastage occurring during flight training. Of the 46 cadets who left the course because of medical reasons, 8 withheld information which would have led to their rejection on the original screening examination (epilepsy 1, recurrent syncope 1, migraine headache 2, Crohn's disease 1, asthma 1, chronic knee pain 1, and chronic recurrent headaches 1). There were also two errors in medical processing. The other 36 cases could not have been predicted by current screening procedures. We conclude that the major deficiency in our screening process is the concealment or withholding of information by candidates for flight training.     

Hypovolemic intolerance to lower body negative pressure in female runners.

PURPOSE: An attenuated baroreflex response and orthostatic intolerance have been reported in endurance-trained male athletes; however, it is still unknown whether this occurs also in females. The purpose of the present study was to examine whether endurance exercise-trained women had a predisposition to orthostatic compromise, and if so, what causative factor(s) may induce orthostatic intolerance. METHODS: We studied cardiovascular and hormonal responses to graded lower body negative pressure (LBNP) (0 to -60 mm Hg) in 26 middle-distance female runners (18.6 +/- 0.1 yr) as the exercise-trained (ET) subjects and 23 age-matched untrained (UT) control subjects. On the basis of the occurrence of syncope episodes during LBNP, ET and UT subjects were further allocated to two groups; ET with presyncope (ET+syncope) and without presyncope (ET-syncope) and UT with presyncope (UT+syncope) and without presyncope (UT-syncope). RESULTS: Occurrence of presyncope episodes during LBNP was higher in ET (65.4%, P < 0.05) than that for UT (34.8%). Leg compliance was higher (P < 0.05) in ET than in UT. LBNP reduced stroke volume (SV) more (P < 0.05), increased heart rate (HR) higher (P < 0.05), and increased forearm vascular resistance (FVR) more in ET+syncope as compared with the other groups. Response of vasoactive hormones to LBNP was higher in ET+syncope (P < 0.05) than that of the other groups except for norepinephrine (NE); high in both ET+syncope and UT+syncope. The relationship between SV and NE, an index of sympathetic neuronal response, had no training-related changes during LBNP. CONCLUSION: We conclude that exercise-trained females have a high incidence of orthostatic intolerance during LBNP, with a greater reduction of SV independent of changes in baroreflex and neurohumoral function. A lower incidence of LBNP intolerance in UT may be accounted for by a lower reduction of SV during LBNP. An increase in leg compliance in the exercise-trained females may play an important role in inducing pronounced reduction of SV and hence the intolerance to LBNP.     

Blood-injection-injury phobia in a commercial aviator: a case report.

A small percentage of the population suffers from blood-injection-injury phobia. These individuals can have vasodepressor syncope related to episodes when their phobia is triggered by a stimulus such as the sight of blood or receiving an injection. A case is presented in which a commercial aviator had a vasodepressor syncopal event during flight. She is referred for evaluation. A discussion of the diagnosis, disease, treatment, and follow-up recommendations are included.     

Considerations in prescribing preflight aerobic exercise for astronauts

Many human responses to the weightless environment have been documented from actual spaceflights. These include physiological effects on the nervous system, cardiovascular system and fluid balance, and the musculoskeletal system, as well as psychological effects. Simulations on Earth have added to our knowledge about the physiology of weightlessness. Early data on orthostatic intolerance after real and simulated spaceflight led some scientists to discourage a high level of aerobic fitness for astronauts. They believed it was detrimental to orthostatic tolerance on return to Earth. However, most of the data available today do not support this contention. Furthermore, aerobic fitness is beneficial to cardiovascular function and mental performance. Therefore, it may be important in performing extra-vehicular activities during flight. Some astronauts claim exercise enhances their feeling of well-being and self image. And, although the cardiovascular system and exercise performance may recover more slowly after flight to preflight levels when fitness level prior to flight is high, the musculoskeletal system may recover more rapidly. Research is needed to determine optimal levels of aerobic training for performing tasks in flight, maintaining health and well-being during flight, and assuring satisfactory recovery on return to Earth.     

Algorithm for evaluation and disposition of a single episode of loss of consciousness

The presentation of a solitary episode of loss of consciousness in aviators presents a challenge to the aerospace physician, who has certain vital obligations to fulfill: to find the cause of loss of consciousness; to find the likely pathology; and to make a decision about fitness for flying duties. Evaluation of loss of consciousness focuses on three systems: the cardiovascular system; the central nervous system; and the mental functioning. If an abnormality is found in any of the three systems, specific evaluation and treatment is warranted. However, if no pathophysiology is found, aeromedical disposition of such a case is determined by three questions. Is it a case of syncope? If it is indeed syncope, is it vaso-vagal syncope (VVS) or something more sinister? If it is VVS, is it likely to recur in flight? VVS may be a one-time occurrence due to sudden cessation of blood supply to the brain and is the most common cause of loss of consciousness. Correct diagnosis of VVS, while a daunting task, can be made possible by proper attention to history, clinical examination, and relevant clinical investigations. Once diagnosed, a single episode of VVS is considered compatible with flying duties. Two cases of loss of consciousness in different settings have been presented to highlight the dilemmas faced by an aerospace physician. An algorithm for evaluation of cases with a solitary episode of loss of consciousness is also suggested.