模拟高海拔氦氧常规潜水减压方案的计算和验证

目的 运用高海拔气压值与海平面气压值之比,计算高海拔氦氧常规潜水的减压方案,并在高低压舱内模拟高海拔氦氧常规潜水验证减压方案的安全性.方法 用高海拔气压值与海平面气压值的比率作为校正因子,对氦氧常规潜水减压表中各有关深度值进行修正后确定4个高海拔氦氧常规潜水减压方案.4名健康男性潜水员在高低压舱内分别暴露于海拔3000、4000和5200 m,进行了模拟30 m/60 min和50 m/60 min的氦氧常规潜水,减压过程中每隔1个停留站深度及返回高海拔压力时对潜水员进行舱内心前区多普勒超声气泡检测及录音.结果 静态、动态多普勒超声气泡检测均未发现血流气泡音,也未发现减压病症状和体征.结论 本研究确定的4个减压方案安全可行.     

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。     

多普勒超声血液气泡检测仪及其在潜水医学上的应用

利用多普勒超声血液气泡检测仪(Doppler ultra-sonic blood bubble detector,以下简称多普勒气泡检测仪)检测血行性气泡,是近十多年来研制成功的一种可对减压病作出客观诊断的新的辅助诊断方法。不论对减压病的早期诊断、预防和加压治疗疗效的观察,还是对减压理论的研究,减压表的制订和验证等,均具有一定的实用价值。     

建立减压病动物模型的研究

目的为深入研究减压病（DCS）提供复现不同种类动物DCS的基本实验方法,掌握不同种类动物DCS发病的共性并明确减压致病的靶器官。方法使11种动物在不同压力、暴露不同时间,以不同加、减压速率将动物减至常压后,心前区Doppler间断监测气泡音,观察动物发病过程,对一些动物进行球结膜显微和病理学检查。结果所用动物减压后心前区监测到Ⅳ级气泡音,75％～100％发生不同程度的DCS,DCS动物血管痉挛,功能障碍,血管内皮肿胀,出血。结论11种动物都能复现出DCS。不同种类动物DCS发病规律相同,血管是减压致病的靶器官。     

以变换识别法提取血液减压气泡信号

监测减压气泡信号可预报早期减压病。传统的多普勒超声检测仪是在心壁、血管壁及心脏瓣膜运动等形成的强大背景噪声下靠耳力辨听气泡音的，既欠客观也难定量。作者深入分析了气泡信号和背景噪声的本质区别，认为背景噪声的主要能量集中在６００Ｈｚ以下，属低频高幅心动噪声；气泡信号则高於此频段，且和血细胞滚动等形成的高频噪声相混叠，但后者幅度远低於气泡信号。基於此认识，提出了用变换识别法提取减压气泡信号的新方案，即利用精密的Ｆ／Ｖ变换器将原始的多普勒频移信号进行变换，使气泡信号呈尖峰波呈现出来，交换后用独特的截频滤波法将低频高幅噪声滤除。又在变换中调节变换输入幅值，利用变换阈限将高频噪声基本除去，这样气泡信号便较清晰地被提取出来。据此研制成的单机经动物和人体减压试验应用，效果较好，实现了实时定量监测目标。类似结果，国内外尚未见报道。     

乙醇治疗急性减压病的实验研究

目的 探讨乙醇治疗急性减压病的病因学及其作用机制.方法 将实验兔32只复制成急性减压病(ADCS)模型,随机分为治疗组和对照组,每组16只.放人动物舱内在5 min内加压至0.6MPa,停留30 min,然后用10 min匀速减至常压(0.1 Mpa)出舱.出舱后每隔5 min定时测定Doppler气泡音.戊巴比妥纳20 mg/kg耳缘静脉麻醉后,手术暴露后腔静脉约10 cm作为观察段.治疗组ADCS模型兔在测定Doppler气泡音后,用25%乙醇溶液3 ml/kg,由耳缘静脉缓慢注射入血管内;对照组则由耳缘静脉缓慢注射10 ml生理盐水.然后经后腔静脉直接观察气泡消长情况,分次解剖,整体观察.结果 对照组16只兔,出舱后30 min相继死亡8只,其余在60～100 min时仍有Ⅰ～Ⅲ级Doppler气泡音,后腔静脉、皮下、肌肉、内脏器官及循环系统可见大量气泡,部分血管完全被气泡阻塞.治疗组无死亡,Doppler气泡音在30～60 min内消失.后腔静脉、皮下、肌肉、内脏器官的血管直径增加一倍以上,血流显著增快.血循环内无气泡或有极少量单个气泡.结论 乙醇疗法是一种快速有效、经济实用的消除急性减压病的新方法.     

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。     

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。     

模拟大深度潜艇艇员快速上浮脱险致减压病大鼠模型的建立

目的 建立稳定的模拟大深度潜艇艇员快速上浮脱险致减压病大鼠模型.方法 雄性SD大鼠80只,采用数字表法随机分为4组:正常对照组,高压暴露2、4、8 min组,每组20只.高压暴露各组置于空气加压舱内以2t/8指数速率加压至150 m,分别停留2、4、8 min后,以3m/s匀速减压至常压出舱.观察各组大鼠行为学和肺、脑、脊髓组织病理结果.结果 高压暴露2、4、8 min组大鼠出舱后均出现竖毛、搔抓、行动迟缓、反应性差等行为状态.病理结果显示,大鼠肺泡和肺间质及脊髓组织出血明显,细胞水肿,脑组织未见明显改变.暴露2、4、8 min组大鼠发病率分别为20.0％、55.0％、10.0％,死亡率分别为0、20.0％、85.0％,3个高压暴露组大鼠发病率及死亡率差异均有统计学意义(P＜0.01).由于8 min方案暴露时间过长,制备的大鼠模型出舱后死亡率较高,而2 min方案高压下停留时间不够,制备的大鼠模型发病率较低,高压暴露4 min方案大鼠死亡率低且减压病发病率高.结论 本实验以高压暴露4 min方案成功地建立了大深度潜艇艇员快速上浮脱险致减压病动物模型.     

高空减压气泡的多普勒超声检测

1968年，Spencer等以及Gillis等将多普勒(Doppler)超声血流测定技术加以改进，应用于高压一减压实验动物血管中气泡的检测以来，现已发展为广泛使用的无创性人体心前区气泡检测方法，成为潜水医学、航空航天医学中减压病的有效研究手段之一，并为该领域谱写了新篇章。我国海军医学研究所1975年首先开始应用Doppler超声技术于科研工作，也已获得一定成果。     

Doppler detection of decompression bubbles with computer assisted digitization of ultrasonic signals.

Precordial Doppler ultrasonic monitoring is routinely used for detection of venous gas bubbles resulting from decompression in hypobaric or hyperbaric applications. Bubble scoring codes have been devised in an attempt to quantify the number of audible bubble signals heard over the background sounds of the cardiac cycle. The audio interpretation of these ultrasonic backscatter signals remains the most common method for decompression evaluation. We report on the use of an inexpensive, commercially available audio digitizer in conjunction with a personal computer to digitize Doppler bubble signals for visual and electronic evaluation. This device can be operated simultaneously with Doppler audio monitoring. Precordial and arterial Doppler recordings of gas bubbles were obtained from anesthetized dogs after intravascular infusion or following decompression. Additional evaluations were conducted on Doppler bubble recordings obtained from human decompression studies. The device can be used in real-time or for later signal analysis. Accompanying menu-driven software provides for numerous signal modification options and visual displays. This device can provide a simultaneous visual display of Doppler signals normally only available for audio evaluation.     

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。     

Computed chest tomography in an animal model for decompression sickness: radiologic, physiologic, and pathologic findings

This study was conducted to investigate the early pulmonary effects of acute decompression in an animal model for human decompression sickness by CT and light microscopy. Ten test pigs were exposed to severe decompression stress in a chamber dive. Three pigs were kept at ambient pressure to serve as controls. Decompression stress was monitored by measurement of pulmonary artery pressure and arterial and venous Doppler recording of bubbles of inert gas. Chest CT was performed pre- and postdive and in addition the inflated lungs were examined after resection. Each lung was investigated by light microscopy. Hemodynamic data and bubble recordings reflected severe decompression stress in the ten test pigs. Computed tomography revealed large quantities of ectopic gas, predominantly intravascular, in three of ten pigs. These findings corresponded to maximum bubble counts in the Doppler study. The remaining test pigs showed lower bubble grades and no ectopic gas by CT. Sporadic interstitial edema was demonstrated in all animals – both test and control pigs – by CT of resected lungs and on histologic examination. A severe compression–decompression schedule can liberate large volumes of inert gas which are detectable by CT. Despite this severe decompression stress, which led to venous microembolism, CT and light microscopy did not demonstrate changes in lung structure related to the experimental dive. Increased extravascular lung water found in all animals may be due to infusion therapy. Received: 7 December 1998; Revision received: 2 June 1999; Accepted: 9 June 1999     

The relationship between venous gas bubbles and adverse effects of decompression after air dives.

The presence of gas bubbles in the vascular system is often considered a sign of decompression stress and several studies in the existing literature have addressed the relationship between the amount of bubbles detected by ultrasound Doppler systems and the incidence of decompression sickness. The use of ultrasound imaging has some important advantages to Doppler systems, and here we have looked at the relationship between the amount of intravascular gas bubbles detected by ultrasound echocardiography and the incidence of signs and symptoms of decompression stress after 203 air dives. The results show that venous gas bubbles detected by ultrasound imaging is a highly sensitive, although not specific, predictor of such adverse effects of decompression. Our results agree with the published concordance between Doppler detected bubbles and decompression sickness. We conclude that bubble detection by ultrasonic scanning of the heart can be used as a tool to assess the safety of decompression procedures for air dives.     

A theoretical method for selecting space craft and space suit atmospheres

A theoretical method for selecting space craft and space suit atmospheres assumes that gas bubbles cause decompression sickness and that the risk increases when a critical bubble volume is exceeded. The method is consistent with empirical decompression exposures for humans under conditions of nitrogen equilibrium between the lungs and tissues. Space station atmospheres are selected so that flight crews may decompress immediately from sea level to station pressure without preoxygenation. Bubbles form as a result of this decompression but are less than the critical volume. The bubbles are absorbed during an equilibration period after which immediate transition to suit pressure is possible. Exercise after decompression and incomplete nitrogen equilibrium are shown to increase bubble size, and limit the usefulness of one previously tested stage decompression procedure for the Shuttle. The method might be helpful for evaluating decompression procedures before testing.     

Doppler detection of thresholds for decompression-induced venous gas emboli in the awake rat.

Awake, unrestrained rats with chronic implants of a Doppler probe on the vena cava, were saturated in a small plexiglass chamber at a maximum pressure (P1), rapidly decompressed to a predetermined pressure (P2) and then monitored for the presence of intravascular bubbles. If there were no indication of bubbles within 1 h, the decompression was considered bubble free. For each saturation pressure, an increasing pressure difference (deltaP = P1 - P2) was tried on each exposure until the threshold for bubble detection was found. The relationship deltaP = a P1 + b, where a and b are constants defining the threshold for bubble detection, was experimentally determined at pressures from 3-10 ATA. The depth-dependent linear relationship deltaP = 0.38P, + 1.29 (r = 0.97, P is less than 0.001) was found for first exposures and deltaP = 0.62 P1 + 0.16 (r = 0.99, p is less than 0.001) for repeat exposures. The chronic Doppler preparation allows a more sensitive threshold determination than past methods for small animals and also allows repeat pressure exposures without the effects of a severe decompression stress.     

Growth dynamics and the largest size of gas bubbles emerging in body tissues due to decompression]

Symptoms of decompression sickness (DCS) develop when the total volume of gas bubbles due to decompression reaches the magnitude critical for a body tissue. Number of the bubbles is a function of random nucleation intensity before, during or after decompression and tissue superaeration dynamics, whereas their size is unambiguously dependent on a tissue, decompression phase and bubbling time. A mathematical model of bubble tissue dynamics has been proposed for calculating the dynamics of mathematical expectation of the total gas in tissues and mounting a method for comparative analysis of the maximal DCS probability as a result of implementation of different decompression tables. Unequal intensity of nucleation during spaceflight EVA and its ground simulation w/o spacesuit is the course of inequality of decompression safety of these operations.