高空减压氮气过饱和安全系数

高空减压氮气过饱和安全系数赵民预防减压病是保证高空飞行及航天安全的重要研究课题。制订合适的座舱压力制度。采取预呼吸措施、筛除减压病易感者、为反复减压规定足够的间隔时间、控制航天员舱外活动（ＥＶＡ）的频度、持续时间及其水平等，皆为有效的预防措施。航天中...     

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。     

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。     

长时间高压暴露减压后影响静脉气泡生成的个体危险因素

即使减压条件相同，减压病的发生也存在明显的个体差异。以往报道的易感因素有年龄、体脂含量、体重指数、性别、吸烟等，但均无明显结论。因此使得相关医务人员无法给从事航空航天、潜水等职业的人员提供有用的医学咨询。许多研究采用的是主观症状（例如关节痛），做为评价减压病发生的指标，故有一定局限性；用多普勒超声检测静脉气泡则更为客观些。作者用多元线性回归与统计方法分析了250例高压减压后的资料，包括减压条件、体质因素和静脉气泡等级。结果表明，影响气泡生成的最主要减压条件是高压暴露的时间和压力值；而个体因素中与静脉气泡生成相关最明显的是年龄，体重指数，但性别与其不相关。作者认为从年龄增加所致的生理变化角度研究对气泡生成的影响，可能有助于揭示减压病易感性的问题。     

在9144m高度吸氧排氮时间与减压病的关系

前言减压病的起因是气压降到使氮气超饱和的水平,导致组织和血液内气泡形成。在减压前通过呼吸纯氧排氮称作预先呼吸或预先吸氧。预先吸氧时间与减压病发生之间的关系Waligora等(1987年)曾描述为直线回归,预先吸氧8 h、4 h,相应的减压病发病率为0％、21％,并推测预吸氧1 h的发病率达40％。这与所测的排氮指数曲线有明显差异,在4 h以内尤甚。本     

减压病易感性预测

在相同的减压条件下,身体情况(如性别、年龄、体脂肪百分比等)相同或相近的一些人,减压病的易感性(susceptibility)常常相差较大。检出减压病易感性较大的人,使之不参加发生减压病可能性较大的飞行工作,对于解决航空、航天活动中减压病的预防有重要意义。1 根据发病的严重程度进行筛选在航空医学中过去常用的预测方法是在低压舱内上升到     

补体水平与低压舱试验

减压病有时发生于例行的低压舱试验中。曾有人报道，减压病的易感性与气泡激活所致补体代谢物C。。和CS。的增加有关。由于减压病可能难以诊断，如果易感者减压后显示有C3。和CS。的改变，那么检测这些代谢物或许对帮助诊断有用。作者在常规低压舱升至25OOOfi（相当于7620m）高度试验前的lh（A），试验后lh（B）和24h（C）取血5ml测量11名男性和2名女性（年龄在19—41岁之间）受试者的补体激活代谢物C。。和CS。。将结果与4名未参加低压舱试验的对照者（3男1女，年龄在30－54岁之间，于同一间隔取血）相比较。单侧方差分析（ANOVA）…     

结合运动的氧气预呼吸对减压病的预防作用

目的 综述国外氧气预呼吸过程中进行体育运动以提高对减压病预防作用的科研工作进展。资料来源与选择 主要资料选自公开发表的氧气预呼吸过程中进行体育运动以提高对减压病预防作用的文献。资料引用 参考文献16篇。资料综合 氧气预呼吸过程中进行体育活动可以减少减压病发生率，这已为低压减压实验及数学模型初步证实，这种作用可能是因为体育运动能使肺通气量、心输出量及组织灌流增加引起排氮效率提高的结果。结论 结合运动的氧气预呼吸可以缩短氧气预呼吸时间而保持预防效果，符合高空飞行及航天员出舱活动的需要，故此方法值得深入研究。     

脊髓型减压病80例临床分析

脊髓型减压病８０例临床分析张树昌随着沿海地区潜水捕捞业的兴起，因违反操作规则不减压潜水而致的脊髓型减压病时有发生。本院近１０年收治脊髓型减压病８０例，现报道如下。一、临床资料（一）一般资料：本组８０例均为男性渔民潜水员，年龄２０～４７岁，潜水工龄１～...     

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。     

安静和运动条件下富氧气体排氮效果的观察

目的探讨人体呼吸不同富氧气体的排氮规律,为促进吸氧排氮效果提供依据。方法7名男性青年采用自身对照,在静坐和运动状态下呼吸60％至纯氧的氧氮混合气。采用开放式排氮测量方法,用氧浓度计测量储气袋中氧气浓度,同步实时测量肺通气量和心输出量,功率脚踏车提供40w运动负荷。结果呼吸60％、70％、80％和90％富氧气体的排氮效果分别相当于呼吸纯氧排氮效果的59．31％、72．81％、76．45％和84．18％。运动对呼吸不同富氧气体排氮作用的影响不同。40w的运动负荷能使呼吸60％、70％富氧气体的排氮作用分别增加45％和12％;但呼吸80％和90％富氧气体时排氮作用增加的很少。结论体力活动所致的呼吸和循环功能增加能促进吸氧排氮的作用,吸氧浓度越低时,运动促进排氮的作用越明显。     

Decompression sickness and bubble formation in females exposed to a simulated 7.8 psia suit environment

The purpose of this study was to measure female susceptibility to decompression sickness (DCS) during simulated extravehicular activity (EVA) at a candidate (7.8 psia) suit pressure. Thirty female volunteer subjects, in groups of three, were exposed to three consecutive daily EVA simulations at 7.8 psia (5,031 m altitude equivalent) continuously for 6 h. During each altitude exposure, the subjects breathed a gas mixture of 50% oxygen/50% nitrogen, and participated in exercise workloads similar to those expected to be experienced by astronauts during a typical EVA scenario. Precordial Doppler bubble monitoring was accomplished after each cycle of exercise workload simulations. During at least 1 of the 3 days (d) of exposure, 43% of the subjects experienced intravenous bubbling. Of the 30 subjects, 17 (57%) did not experience detectable bubbling on any of the 3 d of exposure and 5 (17%) developed decompression sickness (DCS) during the study. Two cases were delayed, occurring after recompression to ground level; and three subjects required hyperbaric oxygen treatment. The results of this study suggest that female subjects may suffer more delayed DCS symptoms, necessitating hyperbaric oxygen treatment, than their male counterparts under the same experimental conditions. Female subjects did not experience intravenous bubbling as frequently as male subjects when exposed to these study conditions.     

Gender not a factor for altitude decompression sickness risk

INTRODUCTION: Early, retrospective reports of the incidence of altitude decompression sickness (DCS) during altitude chamber training exposures indicated that women were more susceptible than men. We hypothesized that a controlled, prospective study would show no significant difference. METHODS: We conducted 25 altitude chamber decompression exposure profiles. A total of 291 human subjects, 197 men and 94 women, underwent 961 exposures to simulated altitude for up to 8 h, using zero to 4 h of preoxygenation. Throughout the exposures, subjects breathed 100% oxygen, rested or performed mild or strenuous exercise, and were monitored for precordial venous gas emboli (VGE) and DCS symptoms. RESULTS: No significant differences in DCS incidence were observed between men (49.5%) and women (45.3%). However, VGE occurred at significantly higher rates among men than women under the same exposure conditions, 69.3% and 55.0% respectively. Women using hormonal contraception showed significantly greater susceptibility to DCS than those not using hormonal contraception during the latter two weeks of the menstrual cycle. Significantly higher DCS incidence was observed in the heaviest men, in women with the highest body fat, and in subjects with the highest body mass indices and lowest levels of fitness. CONCLUSION: No differences in altitude DCS incidence were observed between the sexes under our test conditions, although men developed VGE more often than women. Age and height showed no significant influence on DCS incidence, but persons of either sex with higher body mass index and lower physical fitness developed DCS more frequently.     

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.     

Operation Everest II: Altitude decompression sickness during repeated altitude exposure

The incidence of altitude decompression sickness (ADS) was studied in 23 altitude scientists during repeated altitude exposure to 15,000-29,000 ft (4572-8839 m) in a decompression chamber. Prior to each altitude exposure, a 30-60-mm pre-breathing period with 100% oxygen took place. Ascent was made to an altitude at a rate of 2000 ft X min-1. The altitudes studied ranged from 15,000-29,000 ft (4572-8839 m). Symptoms reported appear consistent with previous reports. Incidence of ADS at 26,000-29,000 ft (7925-8839 m) was 29.7%, during 274 chamber flights and 1264.6 h of altitude time. Incidence appeared related to frequency of exposure, severity of altitude, and physical activity. Incidence was not related to age, duration of exposure, or body index (weight/height 2). This high incidence of ADS reported in this study is similar to that reported by NASA.     

Compatible atmospheres for a space suit, space station, and shuttle based on physiological principles

Fundamental physiological principles have been invoked to design compatible environments for a space suit, space station, and the space craft used to transport the astronauts from Earth. These principles include the long-term memory of tissues for a bubble-provoking decompression, the intermittent nature of blood flow in the tight connective tissues(s) responsible for the bends whose incidence in aviators has been shown to be related to bubble volume by the Weibull distribution. In the overall design an astronaut breathing a mixture of 30% O2 in N2 for 4-5 h in a space craft at 11.9 psia can transfer to a space station filled with the same mix at 8.7 psia and, after a further 4-5 h, go EVA at any time without any oxygen prebreathing at any stage. The probable incidence of decompression sickness has been estimated as less than 0.5% using the present suit operating at 4.3 psia but the risk could be reduced to zero if the suit pressure were increased to 6.5 psia.     

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.     

Intracardial bubbles during decompression to altitude in relation to decompression sickness in man.

Doppler ultrasound was used in five subjects to detect intracardial gas bubbles during decompressions to altitude. At a simulated altitude of 8,000 m, neither intracardial bubbles nor symptoms of decompression sickness occurred. At 9,000 m, bubbles were registered in two subjects, one of which had questionable bends. At 11,500 m, bubbles were registered in all but one subject and two had bends. The three subjects who had not gotten bends were exposed to an air-breathing period of 30 min or, in one case, even 45 min at 2 ATA, for extra nitrogen loading, followed by decompression to 11,500 m. These subjects had heavy showers of bubbles followed by bends. In all cases with decompression sickness during the decompressions to altitude, intracardial bubbles were registered prior to the appearance of symptoms. The technique may be used in studies of decompression sickness without provoking actual symptoms, thus making the studies safer.     

Relationship of menstrual history to altitude chamber decompression sickness

Records at the USAF School of Aerospace Medicine, Division of Hyperbaric Medicine, were reviewed to determine the relationship between the incidence of altitude chamber decompression sickness (DCS) in females and menstrual history. The study period spans 11 years, from January 1978 to December 1988. There were 81 records suitable for study. A significant inverse linear correlation was noted between the number of days since the start of last menstrual period and the incidence of DCS. This relationship was noted with both Type I and Type II DCS. Lack of information on the population at risk precluded an analysis of the effects of birth control pills on this phenomenon. The underlying mechanism for the correlation between menstrual cycle and susceptibility to development of DCS is unknown. We conclude that women are at higher risk of developing altitude related decompression sickness during menses, with the risk decreasing linearly as the time since last menstrual period increases.