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目的：探讨人在４种屏气潜水（半坐位颈部以下浸水、半坐位及俯卧位全身包括头面部浸水、及潜泳）时脑血流阻力的改变。方法：利用遥测装置，测量各种屏气潜水条件下人的心率和颈总动脉血流速度，根据各种血流速度参数，计算出反映颈动脉远端血流阻力（可反映脑血流阻力）的两个指标——阻抗指数（ＲＩ）和脉动指数（ＰＩ）。结果与结论：前３种静止性屏气潜水时，阻抗指数和脉动指数逐步降低，屏气时间越长，降低越明显。由于此时颈动脉血流速度增加，因此脑血流将会明显增加。但在潜泳时，两指数均未见显著性改变，此时颈动脉血流速度增加亦不明显，故脑血流不会有明显的增加。这很可能是由于潜泳时四肢剧烈活动，血流向四肢分配较多的缘故。另外，不同体位的全身浸水，脑血流阻力的改变无明显差别，可能此时体液的分布相对均匀，不同体位时的中心血流量差别不大，因而循环调节亦不致有明显差别。颈部以下身体浸水与半坐位全身浸水相比，脑血流阻力的改变亦无明显区别，这可能是由于水温并不低，对头面部的刺激不足以改变脑血流阻力之故。
PURPOSE: To investigate the changes of cerebral blood flow resistance in 4 kinds of breath-hold diversions (water immersion in the half sitting position, whole body in the half sitting position and prone position including head and face immersion and snorkeling). Methods: Human heart rate and carotid artery blood flow velocity were measured by telemetry device under various breath-hold conditions. Based on various blood flow velocity parameters, the blood flow resistance reflecting the distal blood flow of the carotid artery (which can reflect the cerebral blood flow resistance) Of the two indicators - the impedance index (RI) and pulse index (PI). RESULTS AND CONCLUSION: The impedance index and pulsatility index of the first three kinds of resting breath-hold diving decreased gradually. The longer the breath hold time, the more obvious the decrease. Due to the increased carotid blood flow at this time, cerebral blood flow will be significantly increased. However, during the snorkeling, no significant change was observed in both indices. At this time, the increase of carotid artery blood flow velocity was also not obvious, so there was no obvious increase in cerebral blood flow. This is probably due to the intense activity of the limbs during snorkeling and the more blood flow to the extremities. In addition, body position at different positions, cerebral blood flow resistance changes no significant difference may be at this time the distribution of body fluids is relatively uniform, different body position when the central blood flow is not much difference, so the cycle regulation will not be significantly different. There was no significant difference in changes in cerebral blood flow resistance between the body under the neck and body water immersion in the seated half. This may be due to the fact that the water temperature is not low and the stimulation of the head and face is not enough to change the cerebral blood flow resistance.