卵圆孔未闭与高空减压病

目的 回顾近年国外有关心脏卵圆孔未闭（PFO）所致减压时静脉气泡右向左分流，在神经型减压病发病中作用的研究进展。资料来源与选择 国外本领域正式发表的研究论文，综述和会议摘要。资料引用，相互引用，独立引用。资料综合 简要概述了PFO的概念，发生情况，研究意义，重点介绍了国外关于PFO在促进神经型减压病发病中的支持和反对观点，并扼要提出了进一步进行此方面研究应注意的问题。结论 PFO是神经型减压病发生的易发因素之一，但其确切作用还有待进一步研究。此工作对预防高空减压病，认识减压气体栓塞在中枢神经系统损伤中的作用有重要意义。     

高空爆炸减压事件对飞行人员心理功能的影响

飞机座舱高空急速减压严重损害飞行人员的机体功能,致发高空减压病。为了探讨经历高空爆炸减压事件并患有高空减压病飞行人员心理功能改变的性质、范围和特点,我们对在一次训练飞行中因座舱爆炸减压发生高空减压病的     

高空迅速减压飞行人员的临床诊治和医学鉴定

目的探讨飞行中高空迅速减压飞行人员的临床诊治经验和医学鉴定方法。方法回顾分析近10年来空军发生的5起19人次高空迅速减压病例资料，暴露高度为8300至10000m。结果①5起高空迅速减压中有3起10人（A组）返航后未经休息、吸氧和高压氧治疗，其中7人发生了Ⅱ型高空减压病，发病率为70％，另2起9人（B组）返航后及时休息、吸氧并送就近医院行高压氧治疗，均未发生高空减压病，两组高空减压病发生率有显著性差异（P〈0．01）。②两组对比分析发现，除了已明确的迅速减压时的高度外，在本组资料中个体敏感性、减压后高空缺氧以及空中和返航后的处置是否得当是影响发病的重要因素。③所有发病者经治疗均重返飞行岗位，但发病后治疗不适当或飞行员出现心理障碍会延长康复时间。结论高空迅速减压可对飞行人员造成显著的心理和生理影响，并且发生高空减压病的危险很大，减压后空中及返航后处置是否得当是影响病情发展的莺要因素。     

体力活动与高空减压病

体力活动与高空减压病赵民体力活动（体育运动，体育锻炼）对减压病易感性影响的问题，在航空航天医学中有重要意义，从４０年代起已有较多工作报道。现对低气压暴露过程中及低气压暴露前体力活动对减压病易感性影响综述如下。低气压暴露过程研究证明，在低气压不缺氧条件...     

美国高空减压病专题讨论会及近年工作简介

介绍了美国高空减压病专题讨论会的主要内容，并对1990年以来在该领域的工作进行了简要的回顾。会议主要讨论了有关①提高体内气泡的检测技术水平；②卵圆孔未闭合在发病过程中的作用；③新的减压病分型标准；④神经系统检查的重要性；⑤预防方法的改进提高；⑥患病飞行员的放飞标准及航天飞行中减压病的预防等内容，反映了国外目前及日后研究的主要方向，对国内高空减压病的基础研究和临床工作具有一定参考价值。     

加拿大空军航空医学训练

加拿大空军传统上采用低压舱进行飞行人员的航空医学训练。尽管这种训练的益处显而易见，但是高空减压病的高发率在加拿大空军还是引起了关注。当前低压舱缺氧训练的最大高度是30000英尺，高空减压病的发病率是千分之七点四八。2003年11月之前的缺氧训练模式有两种：模式1暴露高度为25000英尺，相应的减压病发病率为千分之10．66；     

减压病:用多普勒可测微气泡作个体危险性的Bayes分析

前言有几种个体体质因素是对高空减压病危险性有影响的。本文中作者采用Bayes氏理论来评估低气压情况下减压病的个体危险性因素。方法应用美国国家航空航天局屈肢痛数据库(n=516)的资料,以微气泡Ⅲ级作为阳性,首次检验了用多普勒可测微气泡预测减压病症状的诊断准确性。在参加本试验的一些受试者(n=164)中采用个体体质因素的资料按逻辑斯蒂回归模式估算其先验高空减压病危险性,再利用Bayes氏理论由多普勒检测结果计算个体减压病后     

高空减压病概率模型

目的 研究高空飞行时减压病发病的概率或危险度,建立概率模型。方法 用生存分析方法分析高空减压病的信息。结果 减压病危险度先是增加,到一定时间后,再因吸氧排氮而减少。风险函数可以叙述这种变化特点。高空减压病概率模型的参数用最大的似然法估算。结论 以对数ｌｏｇｉｓｔｉｃ分布为基础的生存模型,预测能力良好。     

美国高空减压病专题讨论会及近年工作简介

介绍了美国高空减压病专题讨论会的主要内容，并对１９９０年以来在该领域的工作进行了简要的回顾。会议主要讨论了有关（１）提高体内气泡的检测技术水平；（２）卵圆孔未闭合在发病过程中的作用；（３）新的减压病分型标准；（４）神经系统检查的重要性；（５）预防方法的改进提高；（６）患病飞行员的放飞标准及航天飞行中减压病的预防等内容，反映了国外目前及日后研究的主要方向，对国内高空减压病的基础研究和临床工作具有一定     

高空低压和缺氧生理学研究进展

1 高空减压病的研究进展 在高空生理学领域,对许多问题已经有了比较系统、深入的认识。但对于高空减压病(altitude decompression sickness,ADS)的研究和认识,特别是在其病因和病理学方面,仍存在明显的不足。其原因,一是二次大战后增压座舱的出现使ADS的发生率大幅度降低,各国相对降低了对其研究的投入。二是ADS的病因病理学比较复杂,不是一个纯医学     

Altitude decompression sickness symptom resolution during descent to ground level

INTRODUCTION: Altitude decompression sickness (DCS) is a health risk associated with the conduct of high altitude airdrop operations, high altitude reconnaissance, future fighter operations, hypobaric chamber training, unpressurized flight, and extravehicular activity (EVA) in space. The treatment for DCS includes the provision of 100% oxygen (O2) at ground level (GLO) and/or hyperbaric oxygen therapy (HBO). In this paper we examine the effect of repressurization to ground level from hypobaric conditions on DCS symptoms. Timely recompression (descent at first recognition of any DCS symptom) may be a safe, effective treatment for the large majority of DCS symptoms. METHODS: Data from altitude chamber exposures recorded in the Air Force Research Laboratory (AFRL) Altitude DCS Database were reviewed to determine the level of recompression required for complete resolution of 1,699 observed symptoms. RESULTS: Of the 1,699 DCS symptoms reviewed, 66 (3.9%) resolved at altitude, 117 (6.9%) resolved at ground level, and 1,433 (84.3%) resolved during descent. Increasing the pressure by 138 mmHg from the altitude of exposure where symptoms occurred resolved roughly 50% of symptoms. Little resolution of symptoms was noted with recompressions of < 50 mmHg. The greatest rate of symptom resolution occurred with recompressions of 50-250 mmHg. CONCLUSION: These findings support the concept that descent and postflight, ground-level oxygen may be sufficient to relieve the majority of altitude DCS symptoms. HBO may be reserved for serious, recurring, delayed, or refractory symptoms. The findings also suggest a need for further study of DCS symptom resolution.     

Inner ear decompression sickness following altitude chamber operation

Decompression sickness (DCS) is a known hazard of altitude chamber operation. The musculoskeletal, dermal, neurological and pulmonary manifestations of DCS are well recognized, but inner ear injury has not been reported. We present the unusual case of a medical corpsman suffering from vestibular DCS after an altitude chamber exposure to 25,000 ft. The patient had a good clinical response to hyperbaric treatment, but there was laboratory evidence of mild residual vestibular damage with full compensation. This case suggests that aviation medical personnel should be more aware of the possible occurrence of inner ear DCS among subjects exposed to altitude.     

Type II decompression sickness in naval hypobaric chambers: A case of mistaken identity?

INTRODUCTION: Historically, U.S. Navy clinicians have used the U.S. Navy Dive Manual for guidance in the diagnosis and treatment of injuries incurred during hyper- or hypobaric operations. Based on this manual, paresthesias are considered to be central nervous system manifestations and thus are classified as Type II (severe) decompression sickness (DCS). Yet given the highly successful response to treatment of peripheral nervous system manifestations of DCS in the literature, both the diving and aviation communities have questioned its classification as "severe" DCS. This record review was undertaken to examine U.S. Naval severe cases of altitude DCS with the goal of identifying dissimilarities between hypobaric facilities in classification and incidence. METHODS: Hypobaric exposures and cases were reviewed from quarterly training reports maintained at the Naval Operational Medicine Institute, Pensacola, FL, between January 1993 and April 2004. Cases were analyzed for age, gender, flight profile, symptom complex, type of DCS, and treatment provided. RESULTS: There were 50,355 hypobaric exposures resulting in 97 cases of altitude DCS. Of the 97 cases of diagnosed DCS, 58 were classified as Type II, while 39 were Type I. Of the 58 cases of Type II DCS, 29 were diagnosed as Type II by the sole finding of non-dermatomal paresthesias. DISCUSSION: Type II DCS, a designation traditionally reserved for severe DCS, is frequently diagnosed by the sole finding of non-dermatomal paresthesias in Naval hypobaric training. A review and revision of the U.S. Naval Aviation classification system for altitude DCS should be undertaken with emphasis on severity not symptomatology.     

The effectiveness of ground level oxygen treatment for altitude decompression sickness in human research subjects

BACKGROUND: Current therapy for altitude decompression sickness (DCS) includes hyperbaric oxygen therapy and ground-level oxygen (GLO). The purpose of this paper is to describe the Air Force Research Laboratory experience in the extensive use of GLO for the treatment of altitude DCS in research subjects. METHODS: Data were collected from 2001 altitude chamber subject-exposures. These data, describing DCS symptoms, circulating intracardiac venous gas emboli, and treatment procedures used were collected for each subject exposure and stored in an altitude DCS database. RESULTS: In the database of 2001 subject exposures, 801 subjects (40.0%) were diagnosed with altitude DCS. Subjects reporting DCS symptoms were immediately recompressed to ground level. Of the 749 subjects who received 2 h GLO, 739 (98.7%) resolved completely and required no further treatment. CONCLUSIONS: Although not an operational study, these data provide indirect support for the current USAF guidelines for the treatment of altitude DCS with GLO.     

Advantages of a low-oxygen environment in space cabins

The advantages of having a low-oxygen environment in space cabins are discussed. The major advantage is a sharply reduced fire hazard, which is a major threat in manned space flights. At 1 atm, for example, 15% O2 (9,000 ft altitude equivalent) would not support most fires and could accommodate the crew with respect to hypoxia, decompression sickness (DCS), and other requirements. Chronic exposure to such a hypoxic environment (altitude acclimatization) could improve major areas of crew health and safety including alleviating deconditioning effects, decreasing susceptibility to DCS, and improving tolerance to severe hypoxia.     

Decompression sickness risk model: development and validation by 150 prospective hypobaric exposures

INTRODUCTION: High altitude exposure has an inherent risk of altitude decompression sickness (DCS). A predictive DCS model was needed to reduce operational risk. To be operationally acceptable, such a theoretical model would need to be validated in the laboratory using human subjects. METHODS: The Air Force Research Laboratory (AFRL) has conducted numerous studies on human subjects exposed to simulated altitudes in hypobaric chambers. The database from those studies was used to develop a statistical altitude DCS model. In addition, a bubble growth model was developed using a finite difference method to solve for bubble radius as a function of time. The bubble growth model, integrated with the statistical model, constitutes the AFRL DCS Risk Assessment Model. Validation of the model was accomplished by comparing computer predictions of DCS risk with results from subsequent prospective human subject exposures. There were five exposure profiles, not previously found in the database, covering a wide parameter of ranges of altitude (18,000-35,000 ft), exposure time (180-360 min), prebreathe time (0-90 min), and activity level (rest-strenuous) that were used. The subjects were monitored for DCS symptoms and venous gas emboli. RESULTS: There were 30 subjects who were exposed to each of the 5 altitude profiles. The DCS incidence onset curves predicted by the model were not significantly different from the experimental values for all scenarios tested and were generally within +/- 5% of the actual values. CONCLUSION: A predictive altitude DCS model was successfully developed and validated.     

The influence of prior exercise at anaerobic threshold on decompression sickness.

This study was conducted to examine the effects of exercise prior to decompression on the incidence of altitude decompression sickness (DCS). In a balanced, two-period, crossover trial, 39 healthy individuals (29 males, 10 females) of mean (S.D.) age 32.5 (7.7) years and body mass index 23.7 (3.4) were each exposed twice, without denitrogenation, to an altitude of 6,400 m (21,000 ft) in a hypobaric chamber. Under the experimental condition, subjects exercised at their predetermined anaerobic threshold levels for 30 min each day for 3 d prior to altitude exposure; the other condition was a non-exercise control. Under both conditions, subjects performed exercise simulating space extravehicular activities at altitude for a period of 3 h, while breathing 100% oxygen. There were nine preferences (untied responses) for DCS, four under control and five under experimental conditions; all were Type I, pain-only bends. No carryover effect between exposures was detected, and the test for treatment differences showed p = 0.56 (95% confidence interval = 0.34-0.58) for symptoms. No significant difference in DCS preferences was found after subjects exercised up to their anaerobic threshold levels during the days prior to decompression.     

The risk of altitude decompression sickness at 12,000 m and the effect of ascent rate

INTRODUCTION: Loss of aircraft cabin pressurization can result in very rapid decompression rates. The literature contains reports of increased or unchanged levels of altitude decompression sickness (DCS) resulting from increasing the rate of decompression. We conducted two prospective exposure profiles to quantify the DCS risk at 12,192 m (40,000 ft), and to determine if there was a greater DCS hazard associated with a much higher rate of decompression than typically used during past DCS studies. METHODS: The 63 human subjects participated in 80 altitude chamber decompression exposures to a simulated altitude of 12,192 m (2.72 psia; 18.75 kPa) for 90 min, following preoxygenation with 100% oxygen for 90 min. Half of the subject-exposures involved an 8-min decompression (1,524 mpm; 5,000 fpm) and the other half experienced a 30-s decompression (mean of 24,384 mpm; 80,000 fpm). Throughout each ascent and exposure, subjects were seated at rest and breathed 100% oxygen. At altitude, they were monitored for precordial venous gas emboli (VGE) and DCS symptoms. RESULTS: The higher decompression rate yielded 55.0% DCS and 72.5% VGE and the lower rate produced 47.5% DCS and 65.0% VGE. Chi square and log rank tests based on the Kaplan-Meier analyses indicated no difference in the incidence or onset rate of DCS or VGE observed during the two profiles. CONCLUSION: Decompression rate to altitude up to 24,384 mpm was found not to have an effect on DCS risk at altitude. However, research is needed to define the DCS risk with decompression rates greater than 24,384 mpm. It was also found that the onset time to DCS symptoms decreases as altitude increases.     

Decompression sickness latency as a function of altitude to 25,000 feet

INTRODUCTION: Current Air Force Instructions (AFIs) allow flight of unrestricted duration in unpressurized aircraft up to 25,000 ft. Supplemental oxygen is required to prevent hypoxia, but decompression sickness (DCS) is not adequately considered in current oxygen use guidelines. Recent information from the Air Force Research Laboratory (AFRL) DCS database, combined with a projected increase in exposure to these altitudes under proposed USAF missions, suggests that DCS may be operationally significant in certain circumstances. METHODS: The AFRL Altitude Decompression Sickness Risk Assessment Computer (ADRAC) model was used to develop a family of curves representing DCS latency (time to symptom onset) as a function of altitude for the case of zero preoxygenation and mild exercise. The DCS database was then searched for serious DCS cases among subjects under the same conditions (n = 175). An upper limit for DCS incidence that avoided serious DCS symptoms was selected and exposure time limits were determined. Preoxygenation requirements necessary to remain below the selected DCS incidence limit were also evaluated using ADRAC and provide an alternative to time limits. RESULTS AND DISCUSSION: The 20% DCS curve met the above criteria. Based on this, continued unlimited exposure time is recommended for 21,000 ft and below. The 20% DCS risk curve for zero-prebreathe exposures to 25,000 ft, 24,000 ft, 23,000 ft, and 22,000 ft are reached at 45 min, 70 min, 120 min, and 200 min, respectively. Consistent with existing AFIs, flying unpressurized above 25,000 ft is not recommended. These times should be reduced for crewmembers engaged in heavy physical activity at altitude. CONCLUSIONS: This article proposes time limits for unpressurized flight above 21,000 ft to reduce DCS risk.     

Moderate exercise after altitude exposure fails to induce decompression sickness

INTRODUCTION: The objective of this study was to determine the effect of exercise after altitude exposure (post-exposure exercise) on subsequent altitude decompression sickness (DCS) incidence. Existing USAF prohibition of exercise following altitude chamber training exposures and interest from operational personnel prompted our evaluation of post-exposure exercise as a DCS-inducing stressor. METHODS: After a 1-h resting preoxygenation, 67 subjects were exposed to 30,000 ft for 2-h while performing mild, upper body exercise. The subjects were monitored for venous gas emboli (VGE) with an echo-imaging system and observed for signs and symptoms of DCS. Subjects without DCS (n = 31) or with DCS which resolved during recompression (n = 29) were randomly assigned to post-exposure rest (control, n = 29) or moderate exercise (50% of peak oxygen uptake, dual-cycle ergometry; n = 31) and both groups were monitored for delayed or recurring DCS. RESULTS: The altitude exposure resulted in 48.3% DCS in the 60 volunteers serving as test or control subjects. Of 31 subjects assigned to the post-exposure exercise group, 15 had developed DCS which resolved during descent. No cases of DCS were observed or reported during or following post-exposure exercise. CONCLUSION: The results show that moderate exercise after exposure did not result in either delayed-onset or recurring DCS.