下体负压对家兔血液动力学的影响

观察了家兔在-20、-40、-60mmHg下体负压下心输出量、心搏量、心率、血压以及心电图、脑电图、视网膜电图的变化。实验结果表明:心搏量与心输出量明显减少,在-60mmHg下作用10分钟两者可下降到负压前对照值的15％。心率大多数加快,以代偿心输出量的下降。如出现持续性心率过缓和心律不齐,标志代偿失调。收缩压、舒张压、平均动脉压、脉压均呈规律性下降。根据血压反应可将动物分为耐力良好、尚好、较差三种类型。心电图变化主要表现为冠脉供血不足,心肌缺氧特征,并伴有高尖状P波。脑电图出现缺氧性慢波、波幅降低。视网膜电图的b波波幅逐渐下降,持续期缩短,80％以上有b负波,这些变化可能与脑部及视网膜供血不足有关。

EFFECTSS OF LOWER BODY NEGATIVE PRESSURE ON THE HEMODYNAMICS IN RABBITS

This study was carried out in healthy rabbits. Anirm.ls were exposed to incremental(-20,-40,-60mmHg) lower body negative pressure(LBNP) and several of variables such as cardiac output(CO), stroke volume-CSV ), heart rateCHR) ,blood presrure(BP) , electrocardiograrn(ECG),electro-en-cephalogramCEEG)and electroretmogram(ERG) were measured in animals when they were in LBNP condition. The results of the experiments showed that LBNP was a strong arid effective stressor for cardiovascular system.SV and CO decreased violently,thus at-60rnmHg after a 10 minute exposure,both of them decreased to 15% of the preexperimental control value. HR increased in most cases to compensate the drop of CO. The continuous bradycardia and arrhythmia usually indicated discompensatjon of the heart. Systolic blood pressure CBPs), diastolic blood pressureCBPd), mean arterial pressureCMAP),pulse pressure(PP)decreased regularly .According to the response of BP animals might be divided into three types : high tolerance, good tolerance and low tolerance. Changes in ECG were indicative of defect of blood suppl}' of coronary circulation and cardiac anoxia.EEGs obtained from the rabbits showed anoxic slow waves,the amplitudes of which decreased significantly .Changes in ERGs induced by LBNP were the stepwise decreases of amplitudes of b waves as the grade of negative pressure increased.Durations of b waves were shortened and b negative waves revealed in 80% cases. All of these changes in EEGs and ERGs might be related with defect of blood supply and anoxia in brain tissues and retina.