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

为监测麻醉和重症监护下中枢神经系统的功能，研制了一种导管电极，可同时测量局部血流量、氧分压和电活动。三个铂铱电极被布置在聚全氟乙烯硬膜外导管的尖端，外径和内径分别为0.8和0.5 mm。其中一个通过极性反转用于测量区域性的气流和氧压。另外两个电极用于记录电活动。通过电解产生的氢的清除率计算局部血流量。我们的初步实验表明，脊髓局部血流量与硬膜外局部血流量（rEBF）对动脉二氧化碳分压和平均动脉压变化的反应呈线性相关。将导管电极插入硬膜外后间隙，在安定麻醉（NLA）下测量并记录rEBF、氧分压和脊髓诱发电位（ESCP）。NLA时给予2%氟烷可使rEBF增加。节段性ESCP也可同时记录到，它由一个起始的正棘波（P1）、一个尖的负波（N1）和一个慢的正波（P2）组成。氧压测量的重现性不足以获得可靠的值。结果表明，尽管氧分压测量方法的改进还需进一步研究，但应用导管电极系统可以在不穿刺硬脑膜的情况下监测脊髓的上述三个参数的功能。

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.