口服酒精溶液对豚鼠高空减压气泡生成的影响

目的为建立高空减压病易感性的筛选指标提供实验依据，我们观察了豚鼠口服酒精后高空减压时体内气泡生成的变化。方法30只豚鼠随机分成3组，其中两组分别在口服50％酒精溶液4.0和8．0ml后10.min和20min减压至13000m高度。用超声多普勒装置检测豚鼠心前区气泡音。结果口服8．0ml酒精溶液后减压，气泡生成明显增加（P＜0．01），血浆表面张力明显降低（＜0．01）。结论减压前饮酒能明显促进动物高空减压气泡的生成。     

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。     

吸氧排氮对家兔低气压暴露时气泡产生的影响

目的 探讨不同时间的吸氧排氮方案对高空减压病的预防效果。方法 24只家兔随机分为对照组、吸氧排氮30、60和120min组4组。麻醉后行机械通气,分别吸氧排氮0、30、60和120min后上升至11000m停留30min,用超声多普勒技术检测气泡产生情况。结果 高空减压时气泡首次检出时间随着吸氧排氮时间的增加而延长,吸氧排氮60min和120min组家兔气泡首次检出时间较对照组显著延长(P＜0．01),气泡首次检出时间与吸氧排氮时间呈正相关关系(P＜0．01);累积气泡数随着吸氧排氮时间的增加而减少,吸氧排氮60min和120min组家兔累积气泡数较对照组显著减少(P＜0．01),累积气泡数与吸氧排氮时间呈负相关关系(P＜0．01)。结论 吸氧排氮60min和120min两种方案可以显著减少兔由地面上升到11000m高空减压时气泡的产生。     

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。     

高空减压病发病的最低高度

一般认为，从地面向高空上升时组织体液中处于饱和状态的溶解气体将变为过饱和状态；过饱和超过一定程度，即可有气泡形成，引起减压病的发生。本世纪初，Haldane指出，在一定条件下，减压系数(减压前压力／减压后压力)不超过2时是安全的。故5500m(1／2大气压)一般被认为是高空减压病发病的最低高度。     

血粘度增加对家兔高空减压气泡生成的影响

目的 观察家兔血液粘度增加对高空减压气泡生成的影响。方法 家兔禁水2天,禁水前后测量血液流变学指标。进行高空减压(12000m,停留20min),用多普勒超声法检测心前区气泡生成情况。结果 血液流变学指标的全血粘度和血浆粘度均有升高(P<0.05),红细胞比容无明显变化。结论 血液粘度轻度升高对高空减压气泡的生成无明显的影响。     

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10 000 m. 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作高压氧治疗,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重要因素。     

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     

用三参量模糊分析法识别潜水减压气泡信号的研究

目的 探讨潜水减压多普勒超声气泡信号的模糊识别方法。方法 根据气泡信号的频谱分布特征，构建f-f-△p三参量模糊算法，并通过减压病动物模型进行验证，同时对66例氦氧150m饱和-180m巡回潜水减压的数据进行检测。结果 在减压病动物模型中分别检测到I～Ⅱ级气泡(按Spencer分级标准)，气泡数量6～113个／3s内不等；在饱和潜水减压资料中，检测到1人两次有I级气泡音，气泡数量分别为3个(11s录音)与6个(17s录音)，与人工监听结果基本一致。结论 用三参量模糊分析方法充分借鉴了多年来人工分析所积累的经验，同时利用了计算机辅助分析技术，气泡信号的检测分析较为准确客观。     

空军飞行人员高空减压病7例

高空减压病是比较典型的航空病,一般在高空意外减压而致病,当飞行人员直接暴露于低压缺氧环境时,在组织、体液中溶解的氮气被离析出来,在血管内形成气泡,有可能栓塞血管,严重者危及生命安全。该病在世界航空界及国内时有报道。其诊断主要依据是高空低气压暴露史、典型的临床表现以及相关辅助检查。现就我院收治的二起7例高空减压病进行报道。     

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.     

模拟飞机座舱迅速减压肺损伤动物模型的研究

目的 建立迅速减压肺损伤的动物模型,为研究迅速减压肺损伤提供平台. 方法 健康一级新西兰白兔30只,分为4组,放入迅速减压舱内,舱内压力在0.3 S内由53.3 kPa迅速降低至19.3 kPa,停留3～5 S后,在1 min内迅速将减压舱压力恢复至正常地面大气压力. 结果 随着与气管相联的排气装置排气口直径的减小,各组动物肺脏损伤逐渐加重,肺脏内减压峰值升高(F=129.987,P<0.01). 结论 该迅速减压动物模型能够模拟肺脏内不同的减压峰值,客观地体现胸廓及膈肌在飞机增压座舱发生高空迅速减压时对肺脏的保护作用,为深入研究迅速减压肺损伤以及探讨机体对减压峰值的耐限问题提供了可靠手段.     

Bubble formation of aqueous humor and lens opacity during chamber flight

A transparent miniature decompression chamber was placed on the stage of a large-working zoom-stereo microscope so that the effect of decompression on the frog eye could be microscopically observed and photographed. It was found that chamber flight at a simulated altitude of 66,000 ft (20,117 m) or more caused bubble formation in aqueous humor and lens opacities in some of the experimental animals. On return to ground level, the bubbles either decreased in size or completely disappeared. The cataract could also regress after recompression to 1 atm. Such lens opacities may be termed altitude cataract, instead of asphyxial or anoxic cataract.     

Hyperbaric oxygen pre-breathe modifies the outcome of decompression sickness.

Deep sea divers, aviators and astronauts are at risk of decompression sickness when the ambient pressure reductions exceed a critical threshold. Venous bubbles associated with decompression sickness have the potential to react with the vascular membrane and adjacent blood products, eliciting an inflammatory cascade. Preventive measures usually involve careful decompression procedures to avoid or reduce bubble formation. De-nitrogenation with 100% oxygen pre-breathing as a preventive measure has been well established at least in altitude decompression exposures. The objective of this study was to determine the physiological and biochemical effects of Hyperbaric Oxygen Pre-breathe (HBOP) upon decompression from a hyperbaric exposure. Male Sprague-Dawley rats were randomly assigned to one of eight groups. Two experimental groups received HBOP at 1 and 18 hours prior to decompression, as compared with ground level oxygen or non-treated groups that still experienced decompression stress, and the associated non-decompressed controls. The results showed decreased extravascular lung water (pulmonary edema), bronchoalveolar lavage and pleural protein and arterial, broncho-alveolar lavage, and urine leukotriene E4 (LKE4) levels in both the 1Hr and 18Hr HBOP decompressed rats compared to non-oxygenated decompressed rats, as well as a decreased overall expression of signs of decompression sickness. This study indicates that HBOP-treated rats exhibit fewer signs and complications of decompression sickness compared with non-treated or ground level oxygen treated rats.     

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.     

Explosive decompression of subjects up to a 20,000-m altitude using a two-pressure flying suit.

The RSAF two-pressure flying suit system to protect the pilot at high altitude has been tested from different medical safety aspects. To secure adequate alveolar oxygen pressure, the suit admits up to 70 mm Hg (9.3 kPa) positive pressure breathing by counter-pressure against the thorax and by a 3.2 times higher pressure in the anti-G suit. After 1 h of oxygen breathing, subjects were exposed to explosive decompression from an altitude of 9,000 m to 17,500 or 20,000 m in 0.5 s in a hypobaric chamber. No symptoms of decompression sickness or of alveolar rupture with gas embolism to the central nervous system were seen. Pulmonary X-rays after the test did not reveal any signs of lung rupture with extrapulmonary gas leakage. With the precordial Doppler ultrasound technique, intracardial gas bubbles (silent bubbles) could be detected only in one subject after explosive decompression to a 20,000-m altitude in the 10 experiments.     

Transport aircraft crew and decompression hazards: study of a positive pressure schedule

The protection of the transport aircraft crew against cabin decompression hazards at high altitude (Z less than 45,000 ft) (13,700 m) is achieved by positive pressure breathing (PPB). Currently, many PPB schedules are used. Our research was performed to propose a PPB schedule, using the hypothesis of a decompression at high altitude, including a stay at the flight level and an emergency descent at the rate of 15,000 ft.min-1. The measures were arterial oxygen saturation, heart rate, speech capabilities, and psychomotor performance. The tests were conducted up to 45,000 ft. They show that the best protection at 45,000 ft is afforded when the PPB is included between 2 and 2.5 kPa (15 to 18.75 mm Hg).     

Decompression and occurrence of cataract in enucleated eyes of experimental animals

Chamber flight at a simulated altitude of 58,000 ft (17,680 m) or more caused marked lens opacities in enucleated eyes of the experimental animals. After descent to ground level, the opacity could subsequently be regressed despite complete deprivation of blood supply to the eye. The present finding suggests that decompression might play an important role in inducing such a cataract.     

Pulmonary decompression sickness at altitude: early symptoms and circulating gas emboli

INTRODUCTION: Pulmonary altitude decompression sickness (DCS) is a rare condition. 'Chokes' which are characterized by the triad of substernal pain, cough, and dyspnea, are considered to be associated with severe accumulation of gas bubbles in the pulmonary capillaries and may rapidly develop into a life-threatening medical emergency. This study was aimed at characterizing early symptomatology and the appearance of venous gas emboli (VGE). METHODS: Symptoms of simulated-altitude DCS and VGE (with echo-imaging ultrasound) were analyzed in 468 subjects who participated in 22 high altitude hypobaric chamber research protocols from 1983 to 2001 at Brooks Air Force Base, TX. RESULTS: Of 2525 subject-exposures to simulated altitude, 1030 (41%) had symptoms of DCS. Only 29 of those included DCS-related pulmonary symptoms. Of these, only 3 subjects had all three pulmonary symptoms of chokes; 9 subjects had two of the pulmonary symptoms; and 17 subjects had only one. Of the 29 subject-exposures with pulmonary symptoms, 27 had VGE and 21 had severe VGE. The mean onset times of VGE and symptoms in the 29 subject-exposures were 42 +/- 30 min and 109 +/- 61 min, respectively. In 15 subjects, the symptoms disappeared during recompression to ground level followed by 2 h of oxygen breathing. In the remaining 14 cases, the symptoms disappeared with immediate hyperbaric oxygen treatment. CONCLUSIONS: Pulmonary altitude DCS or chokes is confirmed to be a rare condition. Our data showed that when diagnosed early, recompression to ground level pressure and/or hyperbaric oxygen treatment was 100% successful in resolving the symptoms.     

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。