屏气时的颈动脉血流阻力

利用遥测装置，对屏气时心率和颈总动脉血流速度的改变进行了测量，根据各种血流速度参数，计算出反映颈动脉末端血流阻力（可基本反映脑血流阻力）的两个指标─一阻抗指数和脉动指数，对其在４种屏气条件下［立位屏气、卧位屏气、面部温浸水（３５℃）、面部冷浸水（２０℃）］的改变进行了探讨。结果显示：屏气时颈动脉血流速度增加，阻抗指数和脉动指数逐步降低，屏气时间越长，降低越明显。而且，不同于其它３种屏气试验，在冷浸水条件下，于屏气一开始即出现明显降低。提示：屏气时脑血流增加，并且冷水对面部的刺激可诱发潜水反射，促进脑血流的增加。

Carotid Artery Flow Resistance during Breath Holding

Using telemetering device , we observed changes in ECG and blood flow velocity in the common carotid artery with four breath-hold conditions(breath holding in standing and supine position,face immersion in warn (35℃) and cold (20℃) water). Resistance index(RI) and pulsatility index (PI)were then calculated from several parameters of blood flow velocity.These two indices are thought to reflect distal flow resistance of common carotid artery and then , approximately to reflect cerebral blood flow resistance.Blood flow velocity in the common carotid artery increased and RI and Pl decreased during the 4 breath-hold conditions.RI and PI reached lowest level at the end of breadth holding. Moreover,different from other three conditions, the RI and PI displayed marked decrease when face immersion began in cold water.It is suggested that cerebral blood flow may increase during breath-hold,and that cold stimulation on face could cause diving reflex and then accelerate this increase .