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。     

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。     

静脉注射钙镁离子对家兔高空减压血流中气泡生成的影响

观察了静脉注射硫酸镁和葡萄糖酸钙溶液对家兔高空减压时血流中气泡生成的影响。实验采用3×3拉丁方设计，共进行了4组，36次实验。硫酸镁溶液浓度为12.5％，葡萄糖酸钙浓度为7．5％。减压高度12000m，停留时间20min。用多普勒超声检测心前区血流中气泡。结果表明，注射硫酸镁和葡萄糖酸钙后气泡生成量和出现时间无明显变化。提示单纯血液镁、钙离子升高不是静脉气泡生成的易感因素。     

预先吸入不同浓度富氧气体对急性低压缺氧暴露的生理影响

通过人体急性暴露到低氧性缺氧环境和动物高空迅速减压实验，观察了预先吸入模拟分子筛产氧系统不同富氧浓度的气体对应急减压瞬间的生理影响。模拟暴发性缺氧实验结果表明，当预先供氧浓度低于60％，在暴露到暴发性缺氧环境10s内出现缺氧反应，而高于70％供氧浓度时未出现缺或变化；动物高空迅速减压缩果进一步表明，减压前预先吸入氧浓度为70％～100％，在迅速减压瞬间的生理反应是等效的，吸入各种富氧浓度气体与纯氧之间的血氧饱和度及静脉氧分压光明显差别（P＞0.05），但与迅速减压前呼吸空气（21％氧）的结果之间有显著的差别（P＜0．05）。高空迅速减压时氧自体内向外界的反向弥散有两个过程，它与减压瞬间生理效应和有效意识时间有密切关系。此结果为机教分子筛氧气系统的研制与应用提供了生理依据。     

高空迅速减压患者的临床观察及护理

目的探讨飞行人员在高空减压后出现的症状体征及其相应的护理。方法回顾近10年来,我军发生的5起19人次高空迅速减压事件。结果除1名心理障碍严重而停飞外,余18名症状完全消失,予以放飞。结论高空减压后,对飞行人员造成心理和生理影响,减压后处置是否得当是影响病情发展的重要因素。     

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。     

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。     

在低压环境中气泡密度、弥散和高度对气泡成长过程的作用

前言 设想在任何已知的减压后减压病的概率是不同环境与生理因素的一个函数,这些因素之一是血液与其它组织中气泡的大小。作者研究了弥散引起气泡成长过程的数学表达式,并解决了怎样用数字方式检查各种生理参数如何影响血浆中气泡的成长。这种气泡成长模型将充当美国空军高空飞行减压病计算机发展的基本元件之一。减压病计算机将提供预示性的和实时性的危险估计能力。方法 建立这组代表气     

超声测量技术用于兔皮肤内高空减压气泡测量的探讨CSCD

目的：针对高空减压病病因学气泡生成的机制,探讨了用皮肤超声测量技术检测兔皮肤内减压气泡生成的可行性。方法测量者上升前呼吸纯氧排氮15 min后和家兔一起以30～50 m／s的速度上升到8000 m。在停留5 min和10 min时分别对家兔腹部皮肤进行超声测量,每个部位重复测量10次。测量仪器为德国MINHORST GobH公司生产的Collagenoson‐ICU皮肤高频回声断层扫描仪,其发射频率为22 M Hz ,探测孔径2 mm ,探测深度15 mm ,测量分辨率为0．15 mm。结果高空减压后,兔皮肤扫描图像中代表存在气体界面反射的明亮像素增多,减压前后的像素均值差异有统计学意义（ F＝11．162, P＜0．01）;减压后的像素值明显高于减压前（ P＜0．01）。结论本研究初步证明皮肤超声测量可望为减压病气泡生成的客观检测提供一个新的潜在指标。     

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。     

The effect of repeated altitude exposures on the incidence of decompression sickness

INTRODUCTION: Repeated altitude exposures in a single day occur during special operations parachute training, hypobaric chamber training, unpressurized flight, and extravehicular space activity. Inconsistent and contradictory information exists regarding the risk of decompression sickness (DCS) during such hypobaric exposures. HYPOTHESIS: We hypothesized that four short exposures to altitude with and without ground intervals would result in a lower incidence of DCS than a single exposure of equal duration. METHODS: The 32 subjects were exposed to 3 different hypobaric exposures--condition A: 2 h continuous exposure (control); condition B: four 30-min exposures with descent/ascent but no ground interval between the exposures; condition C: four 30-min exposures with descent/ascent and 60 min of ground interval breathing air between exposures. All exposures were to 25,000 ft with 100% oxygen breathing. Subjects were observed for symptoms of DCS, and precordial monitoring of venous gas emboli (VGE) was accomplished with a SONOS 1000 echo-imaging system. RESULTS: DCS occurred in 19 subjects during A (mean onset 70+/-29 min), 7 subjects in B (60+/-34 min), and 2 subjects in C (40+/-18 min). There was a significant difference in DCS incidence between B and A (p = 0.0015) and C and A (p = 0.0002), but no significant difference between B and C. There were 28 cases of VGE in A (mean onset 30+/-23 min), 21 in B (41+/-35 min), and 21 in C (41+/-32 min) with a significant onset curve difference between B and A and between C and A, but not between B and C. Exposure A resulted in four cases of serious respiratory/neurological symptoms, while B had one and C had none. All symptoms resolved during recompression to ground level. CONCLUSION: Data indicate that repeated simulated altitude exposures to 25,000 ft significantly reduce DCS and VGE incidence compared with a single continuous altitude exposure.     

Postural control and venous gas bubble formation during hypobaric exposure

BACKGROUND: Earlier studies have shown that acute hypoxia at simulated altitudes up to 18,000 ft affects postural control. The main objective of this study was to investigate whether this is caused by hypoxia or by other effects of reduced barometric pressure. Doppler monitoring was included to rule out venous gas emboli (VGE) as a possible cause of disturbed postural control. A secondary objective was to evaluate two conventional altitude chamber training profiles regarding release of VGE. HYPOTHESIS: Chamber flights up to 18,000 ft affect postural control due to acute hypoxia or other effects of reduced barometric pressure such as bubble formation. VGE probably will not be formed at the altitude chamber flight profiles and procedures selected for this study. METHODS: Repeated registrations of postural control and Doppler monitoring for detection of possible VGE were performed on 12 subjects before, during, and after exposure to two different altitude chamber flight profiles. In chamber flight profile 1 the subjects were first preoxygenated for 45 min and then exposed to a normoxic environment at altitudes of 25,000, 18,000, 14,000, and 8000 ft. Chamber flight profile 2 consisted of an 80 min exposure to 14,000 ft without preoxygenation or supplemental oxygen for the first 60 min. RESULTS: In chamber flight profile 1, where normoxic conditions were achieved during all balance testing, no significant changes in postural control were found. No VGE were observed and no subjective dizziness was reported during this exposure. In chamber flight profile 2, a significant influence on postural control was reported for the eyes-open condition, when breathing air at 14,000 ft. These changes normalized when reaching ground level. VGE were observed in one of the 12 subjects after 75 min at 14,000 ft. Another subject complained of severe dizziness during the initial part of the decompression to 14,000 ft, and was excluded from further experiments. CONCLUSIONS: Changes in postural control at altitudes up to 18,000 ft is probably due to acute hypoxia. VGE may form during acute altitude exposure to 14,000 ft.     

持续高+Gy对豚鼠耳石器的影响

目的观察持续高Ｇ刺激对耳石器的影响。方法应用原位杂交技术观察了１６只豚鼠在＋３Ｇｙ、＋１０Ｇｙ和＋１８Ｇｙ持续刺激１５ｍｉｎ后,前庭囊斑感觉上皮细胞中ｃ－ｆｏｓｍＲＮＡ和ＢＭＰ１ｍＲＮＡ表达量的变化,并观察了高Ｇ刺激后动物的行为变化。结果三种刺激量均引起豚鼠姿势不稳,出现前庭功能不平衡的症状,并引起中耳腔出血;前庭囊斑感觉上皮中ｃ－ｆｏｓ及ＢＭＰ１ｍＲＮＡ的表达量明显增加。结论＋３Ｇｙ以上的高Ｇ刺激可引起豚鼠出现前庭功能不平衡症状,改变前庭囊斑感觉上皮中细胞因子的表达     

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.     

短时间高强噪声对豚鼠听器的影响

目的 为研究高强噪声对豚鼠听功能的影响。方法２４只豚鼠随机分成对照、１１５ｄＢ（Ａ）暴露和１１８ｄＢ（Ａ）暴露三组,每组８只。观察分析了粉红噪声暴露３ｍｉｎ,豚鼠的鼓膜、毛细胞及听力的变化。结果 耳镜检查两暴露组鼓膜无明显损伤;但两暴露组都出现了明显的暂时性听阈偏移（ｔｅｍｐｏｒａｒｙ ｔｈｒｅｓｈｏｌｄ ｓｈｉｆｔ,ＴＴＳ）;耳蜗铺片观察两暴露组都发现了毛细胞损伤（Ｐ〈０．０１）。两暴露组的ＴＴ     

强次声波对豚鼠前庭功能的影响

目的 观察强次声波对豚鼠前庭功能的影响。方法 将１５只豚鼠置于频率８Ｈｚ、强度为１３５ｄＢ ＳＰＬ的次声声次中连续暴露９０ｍｉｎ。应用正弦摆动试验（ＳＰＴ）记录技术定量评价强次声波暴露前后豚鼠前庭功能的变化。结果 强次声波暴露后不同时间正弦摆动诱发的豚鼠前庭性眼震的最大慢相速度（ＳＰＶ）和频率较次声暴露前有轻微降低趋势,但差异无显著性意义,在观测终期,眼震ＳＰＶ及频率（ＳＰＶ）和频率较次声暴露前有     

Intraocular pressure at a simulated altitude of 9000 m with and without 100% oxygen

INTRODUCTION: Exposure to high altitude may affect intraocular pressure (lOP). This study aimed to determine how IOP was altered by two different inspired oxygen tensions at altitude. METHODS: There were 34 healthy male pilots, ages 26-39 yr (mean 31.9 yr), who were studied at the Air Health Examination and Physiological Training Centre in Eskisehir, Turkey. They were studied at ground level, which is 792 m (2414 ft), and during a training session in a hypobaric chamber at a simulated altitude of 9144 m (30,000 ft). IOP was measured with a Tone-pen XL tonometer before subjects entered the chamber, at altitude while breathing 100% oxygen by mask and after removing the mask, and again 30 min after leaving the chamber. RESULTS: Ground level values for IOP (mean +/- SD) were 12.31 +/* 2.98 mmHg. Levels increased significantly at altitude on oxygen (16.75 +/- 4.14 mmHg) and decreased slightly on breathing ambient air (14.37 +/- 3.44 mmHg). In 30 min after leaving the chamber, IOP was 12.81 +/- 1.74 mmHg, indistinguishable from pre-test values. DISCUSSION: Healthy subjects whose baseline IOP is in the normal range experience only a small, temporary elevation of IOP during passive exposure to high altitude with either normoxia or acute hypoxia.     

高、低压舱致豚鼠耳气压损伤的形态学变化

目的 验证高压氧舱法和低压舱法检测咽鼓管通气功能时，引起实验豚鼠的中耳、内耳病理改变的一致性。方法 健康的杂色豚鼠38只随机分为3个高压氧舱组和3个低压舱组，分别在相应条件下进行模拟上升和下降实验，出舱电耳镜观察豚鼠鼓膜后处死，进行中耳及内耳组织学观察。结果 鼓膜反应及中耳、内耳组织学改变组间无差异。结论 本实验从病理形态学角度证实高压氧舱可以检测咽鼓管通气功能。     

呼吸不同浓度氧气对兔高空暴露的防护作用

目的 观察兔暴露于高空时呼吸不同浓度氧气后的生理变化和组织超微结构改变,探讨分子筛氧源在高空的防护效果。方法 将20只兔随机分为呼吸空气组(A)、呼吸63％富氧气体组(B)、呼吸83％富氧气体组(C)和呼吸纯氧组(D)。各组兔在低压舱内上升到11000m,停留30min,记录心脏区气泡、心电图和客观反应,观察心和脑组织超微结构的变化,肾组织促红细胞生成素(EPO)的表达。结果 空气组心脏区气泡数量明显增加,多数兔出现心律失常;富氧浓度组和纯氧组偶见气泡;随着吸人气氧浓度的增加,脑、心组织超微结构缺氧改变减轻,肾EPOmRNA表达的阳性率降低。结论 呼吸含氧浓度大于80％的富氧气体对高空暴露的机体有明显的防护作用。