Development of the system and electrode for simultaneous measurements of regional blood flow, oxygen pressure and activity

为了监测麻醉和重症监护下中枢神经系统的功能，研制了一种同时测量局部血流量、氧分压和电活动的导管电极。在聚全氟乙烯硬膜外导管顶端放置3个铂-铱电极，外径为0.8 mm，内径为0.5 mm。其中一个被用来通过反转其极性来测量区域液滴流量和氧气压力。另两个电极用于记录电活动。根据电解产生的氢气的清除量计算局部血流量。我们的初步实验表明，局部脊髓血流量与局部硬膜外血流量(REBF)呈线性相关，以响应动脉二氧化碳分压和平均动脉压的变化。将电极置入硬膜外后间隙，在神经麻醉(NLA)下记录rEBF、血氧分压和脊髓诱发电位(ESCP)。NLA期间吸入2%氟烷后，rEBF增加。节段性ESCP也可同时被记录到，它由一个开始的正尖峰(P1)，然后是一个尖锐的负(N1)波和一个缓慢的正(P2)波组成。氧分压测量的重复性不足以获得可靠的数值。结果表明，虽然氧分压测量方法尚需进一步研究，但应用导管电极系统可以在不穿透硬脑膜的情况下监测上述三项参数的脊髓功能。

In order to monitor the functions of central nerve system under anesthesia and intensive care, a catheter electrode with simultaneous measurement system of regional blood flow, oxygen pressure and electrcal activity was developed. Three platinum-iridium electrodes were arranged at the tip of the polyperfluoroethylene epidural catheter with outer and inner diameters of 0.8 and 0.5 mm, respectively. One of them was used for measurements of both regional bloof flow and oxgen pressure by inversion of its polarity. The other two electrodes were used for recording of electrical activity. Regional blood flow was calculated from the clearance of hydrogen generated by electrolysis. Our preliminary experiment has demonstrated that regional spinal cord blood flow has a linear correlationship with regional epidural blood flow (rEBF) in response to changes in arterial carbon dioxide tension and mean arterial pressure. The catheter electrode was inserted into the posterior epidural space, and rEBF, oxygen pressure and evoked spinal cord potential (ESCP) were measured and recorded under neuroleptanesthesia (NLA). An increase of rEBF was observed when 2% halothane was administrated during NLA. The segmental ESCP which consists of an initial positive spike (P1) followed by a sharp negative- (N1) and a slow positive (P2) wave could also be recorded simultaneously. Reproducibility of measurement of oxygen pressure was not enough to obtain reliable values. From the results, although further studies were needed for improvement of oxygen pressure measure, it is indicated that the function of spinal cord in terms of above three parameters could be monitored without puncture of dura by application of the catheter electrode system.