低压舱模拟飞行对于脑力负荷影响的初步探讨

目的:通过低压舱模拟飞行环境下被试人员生理指标的变化,探讨飞行员脑力负荷的变化规律。方法:21名男性志愿者参加低压舱模拟飞行的实验过程,座舱内的压力高度模拟2400米高空压力,持续时间1.5h,重复两次,中间出舱休息0.5h,检测指标为心率变异性(HRV),心理运动测验以及NASA-TLX主观评定量表。结果:研究表明,NASA-TLX量表从主观感受上很好的反映了低压舱模拟飞行后脑力负荷的变化,HRV、心理运动测验也发生了相应的变化。结论:本研究结果提示低压舱模拟飞行所导致的脑力负荷变化是具有一定规律的,生理心理测验可能是测定变化规律的一种间接方法。     

24h睡眠剥夺后作业效率与心率变异性的变化

目的:探索24h睡眠剥夺(Sleep Deprivation,SD)后作业效率和心率变异性的变化.方法:通过观察8名健康男性在24h睡眠剥夺前后的作业效率、主观脑力负荷和心率变异性的变化,寻找与脑力疲劳相关的敏感指标.结果:在24h睡眠剥夺后,NASA-TLX评分呈显著性增加(p＜0.05),75°立位时HF呈显著性减少(p＜0.05),TINN、LF/HF呈显著性增加(p＜0.05).结论:NAsA-TLX量表从主观感受上很好的反映了脑力疲劳后工作绩效下降的变化,HRV的变化主要原因在于24h SD后迷走神经活性降低,交感神经相对加强.     

模拟高原低氧对人的认知能力影响的研究

目的 :研究轻、中度急性缺氧暴露对人的认知能力的影响。方法 :利用低压舱模拟 30 0m(对照高度 )、2 80 0m、36 0 0m、44 0 0m低氧环境 ,考察了 18名健康男性青年受试者在不同高度暴露 1h的感知觉、记忆、注意、思维和心理运动功能的变化情况。结果 :2 80 0m暴露 1h连续识别记忆测验的综合绩效已显著低于对照水平 (P <0 .0 1) ,而36 0 0m暴露 1h后感知觉、记忆、注意、思维和心理运动等各项测验的反应时均延长 ,正确率下降 ,综合绩效显著降低 (P <0 .0 5或P <0 .0 1) ,并随着高度的增加而加重。 44 0 0m暴露 1h各项测验综合绩效进一步降低 (P <0 .0 1)。结论 :各项认知能力受低氧影响符合“高度依赖原则” ,但不同认知能力要素受低氧影响的阈限高度不同。 36 0 0m高度暴露 1h各项测验的综合绩效均显著下降 ,已无法满足工效要求。经过 1h的供氧 ,各项作业绩效基本恢复     

模拟飞行任务负荷对人体姿势控制的影响

目的:研究在机体不同站立姿势下,模拟飞行任务负荷对姿势控制能力的影响,并初步总结其变化规律。方法:从某航空院校学员中随机抽取30名,要求其持续进行4小时的模拟飞行任务负荷,并同时在0 h、1 h、2 h、3 h与4 h时,测试4种不同站立姿势下的静态立位平衡参数,比较不同姿势晃动的变化规律。结果:随着模拟飞行任务的持续,4种站立姿势下,被试的立位平衡能力发生了不同程度的变化,并呈现出一定的变化趋势。其中睁眼站立于脚垫上的姿势晃动程度变化最明显,并有重心前倾的趋势;另外,在暴露于飞行任务负荷下,机体视觉信息通道的关闭有可能激发视觉、前庭、本体与肌肉控制等系统对平衡维持能力的代偿性增强作用,而下肢本体感觉信息的阻碍又同时会损坏视觉、前庭、本体等系统对立位平衡能力的控制作用。结论:模拟飞行任务负荷下,机体的姿势晃动会呈现一定的变化规律,即身体可能会代偿性的向前倾斜,来维持身体的立位平衡状态。同时,视觉通道与下肢本体感觉通道对任务负荷条件下立位平衡功能的代偿能力发挥不同的作用。这种变化规律的初步阐述对我们下一步的立位平衡与飞行疲劳评估的研究打下一定的理论基础。     

急性缺氧下听觉运动反应的研究

受试者为9名男性青年。在低压舱模拟海拔3000、4000、5000和6000m,分别进行1h实验,共36人次。各高度上停留时作听觉检测,并记录了脑电和主诉。结果表明,在3000m,人的听觉运动反应基本正常;而在5000m、6000m,听觉运动反应的正确率、延时率、遗漏率和反应时等多项指标发生显著变化,工效降低。本研究为急性缺氧防护生理标准和缺氧耐力提供了工效的依据。     

恒定精神负荷下的精神应激水平的变化

目的:以心率变异性指标对恒定精神负荷下的精神应激状况进行评判.方法:通过工效指标、眼动指标和主观问卷表,将30例样本分成疲劳组F、中间状态组M和非疲劳组N三类.分别以20min和5min对1小时的VDT作业进行分段,研究了各样本的工效指标和HRV指标的总体及实时性变化.结果:实验结果表明:1)以工作绩效评价疲劳程度有局限性;2)负荷、应激和疲劳相互关联,又相互区别;3)HRV直接反映的是应激水平,不能直接反映疲劳程度;4)对自主控制的应激反应与受迫型的应激反应必须区别对待:5)样本的个体差异十分显著.结论:单一的HRV指标不能实时测量疲劳程度,但可以实时的指示应激水平的变化;工效指标可以作为疲劳评判的参考指标,但不宜作为疲劳评判的唯一指标;以HR和HRV并结合其它指标来研究精神疲劳,有着强有力的生命力.     

高原移居者记忆与肢体运动能力的改变

目的：采用神经心理测验方法探讨海拔高度及时间对移居者记忆与肢体运动能力的影响及返回平原后的恢复情况。方法：选择即将进入高原的241名健康青年,在其进入高原前、初期、5个月、1年及返回平原时分别采用DDX-200型多功能心理生理能力测试康复仪进行左右手交叉敲击动作频率和数字记忆广度顺背数测验。结果：与进入高原前比较,进入高原5个月至1年,数字记忆广度顺背数测验得分降低,左右手交叉敲击动作频率总次数和正确次数减少,错误次数增多（P〈0．05,或P〈0．01）,进入高原初期,5个月及返回平原5个月与进入高原1年相比,数字记忆广度顺背数测验得分增高,左右手交叉敲击动作频率总次数和正确次数增多,错误次数减少（P〈0．05,或P〈0．01）。移居5个月后4700m组各项测试指标均优于移居5000m以上地区组（P〈0．05,或P〈0．01）。结论：移居高原5个月后记忆力及肢体运动能力降低,特别是移居5000m以上地区,而这些能力在返回平原5个月将得到恢复。     

模拟海拔3600m低氧环境对人的认知灵活性的影响

目的：探讨模拟高原低氧环境对人认知灵活性的影响。方法：低氧舱模拟海拔3600m低氧环境,采用任务转换范式观察低氧模拟各阶段的认知灵活性,同时监测焦虑状态及基本生理指标的变化。23名无高原生活经验、平均年龄25．1岁的男性受试者参加了实验。结果：与低氧暴露1个月后的基础对照相比,低氧阶段的反应时转换损失显著增加;低氧阶段焦虑水平显著高于适应阶段;在适应阶段,焦虑水平与反应时转换损失显著负相关;而在降舱阶段,焦虑水平与反应时转换损失显著正相关。结论：中度低氧暴露影响人的认知灵活性和焦虑状态;低氧暴露前,焦虑可促进个体的认知灵活性;低氧暴露后,焦虑会阻碍个体的认知灵活性。     

解除模拟失重后清醒大鼠血压信号的谱分析

本文旨在观察模拟失重28 d大鼠解除尾部悬吊前、后(2 h内),清醒自由活动状态下动脉收缩压(systolic bloodpressure,SBP)、舒张压(diastolic blood pressure,DBP)和心率(heart rate,HR)的变化.采用自回归模型法对不同时间点的收缩压变异性(SBP variability,SBPV)和心率变异性(HR variability,HRV)进行自谱与互谱分析,并比较自回归法与周期图法的自谱分析结果:由传递函数分析得到反映压力感受器-心率反射敏感性(baroreceptor-heart rate reflex sensitivity,BRS)变化的有关数据.结果显示,用自回归模型法对清醒大鼠血压信号进行短时程谱分析可得到较为平滑、谱峰清楚的谱估计曲线.28 d模拟失重大鼠解除尾部悬吊前、后,SBP、DBP和HR及其主要谱指标,以及高、低频段传递函数的平均增益均无显著性变化,不同时间点的谱指标也无显著差别;但模拟失重组的SBP、DBP和HR却显著高于对照组.上述结果提示,中期模拟失重大鼠恢复正常体位后,其清醒状态的BPV与HR均处于升高状态,但其短时程BPV与HRV谱及BRS均无显著变化,与最近报道的航天员HRV与BRS无显著改变一致.     

学龄前儿童不同距离往返跑后HR和HRV改变的比较*

目的: 筛选一种适用于评估学前儿童速度和心功能的测试方法。方法: 选取某幼儿园30名健康儿童作为实验对象,分别建立“10 m、20 m和30 m往返跑”的运动模型,通过佩戴人体能耗检测仪的方式,监测其运动前后心率和心率变异性(HRV)指标的变化特征,进而通过计算其运动负荷和生理负荷指数,通过HRV时域、频域和庞莱恩散点图参数的变化,判断学前儿童在不同距离往返跑后心脏交感神经和迷走神经的活性与支配功能状态。结果: 儿童10 m、20 m和30 m往返跑依次为中、大和超大强度的范围;HRV指标测试结果显示:与运动前基线值相比较,三种往返跑后的R-R间期标准差(SDNN)均呈现显著性的降低;儿童30 m往返跑后,除了低频与高频的比值(LF/HF)显著升高(P<0.01),其余频域指标以及庞莱恩散点图参数较基线值均有不同程度的降低(P<0.05,0.01);此外,与10 m往返跑后相比较,儿童20 m往返跑后LF呈现显著性的增加(P<0.01),其余HRV指标均无显著性变化,但30 m往返跑后的HRV频域指标和庞莱恩散点图参数均不同程度呈现显著降低(P<0.05,0.01),且LF/HF值超出正常参考值范围。结论: 20 m往返跑后儿童的心交感神经活性和迷走神经活性变化不显著、综合调节能力未下降,心功能安全性较好。     

Hematological change in venous blood of the lower leg during prolonged sitting in a low humidity and hypobaric environment

The present study examined the effects of low humidity and hypobaric conditions on hematological change in venous blood of the lower leg during quiet prolonged sitting. Ten healthy male students participated as the subjects after singing a consent form to participate in this study. Their diet and water intake were controlled from 19:00 on the day before the experiments. The subjects sat for 130 min in a climatic chamber. Four experimental conditions in the chamber were designed from a combination of relative humidity (20% or 60%) and air pressure (sea level or equivalent to an altitude of 2,000 m). Ambient temperature was maintained at 24 degrees C in every condition. Venous blood was sampled from the lower leg before and after exposure to the experimental conditions, and was analyzed for blood viscosity and hematological indices. Also, body weight and leg circumference were measured as indices of total water loss and edema, respectively. Regarding the results of ANOVA, significant interactions between humidity and time were observed in blood viscosity, red blood cell count and hematocrit (each p<0.05). However, there were no significant differences in these indices among the conditions. Significant increases were observed in leg circumference (p<0.01), platelet count (p<0.05) and total protein (p<0.05) after the exposure compared with those before the exposure. There were no noticeable effects of hypobaric conditions in every measurement. In conclusion, prolonged sitting seems to be a more hazardous factor for thrombogenesis low humidity and hypobaric conditions during a long-distance flight.     

低氧对小鼠学习记忆力及脑中tau蛋白磷酸化的影响

目的：研究不同低氧暴露对小鼠学习记忆及脑中tau蛋白磷酸化的影响。方法：雄性昆明小鼠40只,随机分为4组（n=10）：对照组（control）、8h低氧暴露组（8h）、7d低氧暴露组（7d）和28d低氧暴露组（28d）。将低氧暴露模型组置于模拟高原海拔5500m的低压氧舱,每天低氧暴露8h,避暗和旷场实验检测其活动能力及学习记忆能力：免疫印迹技术检测小鼠海马和皮层中tau蛋白磷酸化水平。结果：随着低氧时间的增加,小鼠短期学习记忆力及活动能力下降程度增大,28d低氧暴露后其下降程度最大;海马中tau蛋白多个位点的磷酸化水平呈现升高趋势,28d时tau蛋白磷酸化程度最高（P〈0．05）;皮层中的磷酸化水平在低氧暴露7d时达到最高,低氧暴露28d时略有降低,但与control组相比仍有明显差异（P〈0．05）。结论：慢性间歇性低氧可导致小鼠学习记忆能力下降,其机制可能与tau蛋白过度磷酸化相关。     

模拟高原环境下高原肺水肿大鼠模型的建立

目的在人工实验舱模拟高原环境下,探讨建立高原肺水肿大鼠模型的条件。方法 Wistar大鼠,雌雄各半,随机分为5组:空白对照组、低氧24 h组、低氧48 h组、低氧72 h组、低氧7 d组,测定大鼠肺组织含水量,肺组织中TNF-α、IL-6含量及病理改变。结果与正常对照组相比,低氧24、48、72 h组大鼠肺组织含水量依次为(81.58±0.86)%、(82.13±0.57)%、(82.21±0.88)%,高于正常对照组(78.72±0.52)%,肺组织中IL-6依次为(329.30±133.58)、(323.92±127.42)、(506.29±197.19)pg/mL,TNF-α依次(221.08±20.26)、(208.05±20.33)、(244.63±51.53)pg/mL,高于正常对照组IL-6(187.26±69.49)pg/mL,TNF-α为(91.81±22.24)pg/mL。低氧7d组肺组织含水量(81.47±0.65)%、肺组织中IL-6(241.33±83.60)pg/mL、TNF-α(109.99±31.98)pg/mL,均显著低于低氧72h组,病理学结果显示72h组肺组织有炎性细胞浸润,肺泡壁有明显的充血和水肿。结论模拟海拔5000 m环境,建立大鼠肺水肿模型的较好的时间为72 h。     

间歇低压低氧预处理对心肌缺血／再灌注损伤及ZFP580表达的影响

目的：探讨间歇性低压低氧（IHH）预处理对大鼠心肌缺血／再灌注（I/R）损伤后血清中心肌酶、心肌梗死的影响及锌指核转录因子ZFP580发挥的作用。方法：32只雄性Wistar大鼠随机分为IHH预处理组和常氧对照组（n=16）。IHH组大鼠置于模拟海拔高度为5000m的低压氧舱中,每天6h,持续42d。两组大鼠经结扎冠状动脉左前降支建立心肌I/R损伤模型后,检测血清中乳酸脱氢酶（LDH）活性及肌酸磷酸肌酶同功酶（CK-MB）浓度,并利用Western blot方法观察各组大鼠心肌组织中ZFP580的表达情况。每组另外8只大鼠经心肌酞菁蓝-TIC染色后比较心肌梗死面积。培养大鼠H9c2心肌细胞,利用慢病毒介导的基因转染实验获得高表达ZFP580的心肌细胞,并进行心肌细胞模拟缺血／再灌注（SI/）损伤实验。利用Annexin V-PE／7-AAD柒色及流式细胞术检测H9c2心肌细胞的凋亡情况。结果：IHH预处理能明显减少心肌I／R损伤后IDH、CK-MB漏出至血清,并明显缩小心肌梗死面积。大鼠经IHH预处理后心肌组织中ZFP580的表达上调,IHH预处理明显上调心肌L／R损伤后心肌组织中ZFP580的表达。高表达ZFP580的H9c2心肌细胞在STIR损伤后细胞凋亡率明显下降。结论：IHH预处理对于心肌I／R损伤具有明显细胞保护作用,其上调的ZFPS80表达具有减少心肌细胞凋亡的作用,ZFP580可能作为心肌细胞内源性抗凋亡分子之一,参与IHH预处理抗心肌I／R损伤的过程。     

The variability of the heart rhythm and the nature of the feedback as a result of operator activity in man]

In a memory task which required sustained attention, the positive or negative emotional state of an operator was created by introduction of two different types of feedback in accordance with the number of correct or wrong solutions. Standard and original indices were used for evaluation of the short-term variability of the heart rate (HRV) during performance. Changes in the HRV were observed only in the periods of performance with the failure type of the feedback. These changes reflected stabilization of heart bit-to-bit intervals. The original index of the fast HRV turned to be the most sensitive for testing HRV changes. Human autonomic reactions of such a kind during operator-like activity are known as a predictor for the functional state of dissatisfaction. This confirms the practical importance of application of the HRV indices for testing the ergonomic properties of the systems which control the operator-computer interaction.     

Proteomic Identification of Novel Differentiation Plasma Protein Markers in Hypobaric Hypoxia-Induced Rat Model

Background

Hypobaric hypoxia causes complex changes in the expression of genes, including stress related genes and corresponding proteins that are necessary to maintain homeostasis. Whereas most prior studies focused on single proteins, newer methods allowing the simultaneous study of many proteins could lead to a better understanding of complex and dynamic changes that occur during the hypobaric hypoxia.

Methods

In this study we investigated the temporal plasma protein alterations of rat induced by hypobaric hypoxia at a simulated altitude of 7620 m (25,000 ft, 282 mm Hg) in a hypobaric chamber. Total plasma proteins collected at different time points (0, 6, 12 and 24 h), separated by two-dimensional electrophoresis (2-DE) and identified using matrix assisted laser desorption ionization time of flight (MALDI-TOF/TOF). Biological processes that were enriched in the plasma proteins during hypobaric hypoxia were identified using Gene Ontology (GO) analysis. According to their properties and obvious alterations during hypobaric hypoxia, changes of plasma concentrations of Ttr, Prdx-2, Gpx -3, Apo A-I, Hp, Apo-E, Fetub and Nme were selected to be validated by Western blot analysis.

Results

Bioinformatics analysis of 25 differentially expressed proteins showed that 23 had corresponding candidates in the database. The expression patterns of the eight selected proteins observed by Western blot were in agreement with 2-DE results, thus confirming the reliability of the proteomic analysis. Most of the proteins identified are related to cellular defense mechanisms involving anti-inflammatory and antioxidant activity. Their presence reflects the consequence of serial cascades initiated by hypobaric hypoxia.

Conclusion/Significance

This study provides information about the plasma proteome changes induced in response to hypobaric hypoxia and thus identification of the candidate proteins which can act as novel biomarkers.     

Daytime blood pressure elevation after nocturnal hypoxia.

The purpose of this study was to investigate whether nocturnal hypoxia causes daytime blood pressure (BP) elevation. We hypothesized that overnight exposure to hypoxia leads the next morning to elevation in BP that outlasts the hypoxia stimulus. We studied the effect on BP of two consecutive night exposures to hypobaric hypoxia in 10 healthy normotensive subjects. During the hypoxia nights, subjects slept for 8 h in a hypobaric chamber at a simulated altitude of 4,000 m (barometric pressure = 462 mmHg). Arterial O(2) saturation and electrocardiogram were monitored throughout the night. For 30 min before the nocturnal simulated ascent and for 4 h after return to baseline altitude the next morning, BP was measured every 5 min while the subject was awake. The same measurements were made before and after 2 normoxic nights of sleep in the hypobaric chamber at ambient barometric pressure (745 mmHg). Principal components analysis was applied to evaluate patterns of BP response after the second night of hypoxia and normoxia. A distinct pattern of diastolic BP (DBP) elevation was observed after the hypoxia night in 9 of the 10 subjects but in none after the normoxia night. This pattern showed a mean increase of 4 mmHg in DBP compared with the presleep-awake baseline in the first 60 min and a return to baseline by 90 min. We conclude that nocturnal hypoxia leads to a carryover elevation of daytime DBP.     

Autonomic cardiovascular and respiratory control during prolonged spaceflights aboard the International Space Station.

Impaired autonomic control represents a cardiovascular risk factor during long-term spaceflight. Little has been reported on blood pressure (BP), heart rate (HR), and heart rate variability (HRV) during and after prolonged spaceflight. We tested the hypothesis that cardiovascular control remains stable during prolonged spaceflight. Electrocardiography, photoplethysmography, and respiratory frequency (RF) were assessed in eight male cosmonauts (age 41-50 yr, body-mass index of 22-28 kg/m2) during long-term missions (flight lengths of 162-196 days). Recordings were made 60 and 30 days before the flight, every 4 wk during flight, and on days 3 and 6 postflight during spontaneous and controlled respiration. Orthostatic testing was performed pre- and postflight. RF and BP decreased during spaceflight (P < 0.05). Mean HR and HRV in the low- and high-frequency bands did not change during spaceflight. However, the individual responses were different and correlated with preflight values. Pulse-wave transit time decreased during spaceflight (P < 0.05). HRV reached during controlled respiration (6 breaths/min) decreased in six and increased in one cosmonaut during flight. The most pronounced changes in HR, BP, and HRV occurred after landing. The decreases in BP and RF combined with stable HR and HRV during flight suggest functional adaptation rather than pathological changes. Pulse-wave transit time shortening in our study is surprising and may reflect cardiac output redistribution in space. The decrease in HRV during controlled respiration (6 breaths/min) indicates reduced parasympathetic reserve, which may contribute to postflight disturbances.     

Effects of acute hypobaric hypoxia and exhaustive exercise on AMP-activated protein kinase phosphorylation in rat skeletal muscle

The present study was aimed to explore the changes of phosphorylated AMP-activated protein kinase (pAMPK) level in skeletal muscle after exposure to acute hypobaric hypoxia and exhaustive exercise. Thirty-two male Sprague-Dawley (SD) rats were randomly divided into sea level and high altitude groups. The rats in high altitude group were submitted to simulated 5 000 m of high altitude in a hypobaric chamber for 24 h, and sea level group was maintained at normal conditions. All the rats were subjected to exhaustive swimming exercise. The exhaustion time was recorded. Before and after the exercise, blood lactate and glycogen content in skeletal muscle were determined; AMPK and pAMPK levels in skeletal muscle were detected by Western blot. The results showed that the exhaustion time was significantly decreased after exposure to high altitude. At the moment of exhaustion, high altitude group had lower blood lactate concentration and higher surplus glycogen content in gastrocnemius compared with sea level group. Exhaustive exercise significantly increased the pAMPK/AMPK ratio in rat skeletal muscles from both sea level and high altitude groups. However, high altitude group showed lower pAMPK/AMPK ratio after exhaustion compared to sea level group. These results suggest that, after exposure to acute hypobaric hypoxia, the decrement in exercise capacity may not be due to running out of glycogen, accumulation of lactate or disturbance in energy status in skeletal muscle.