Jørgensen J S, Schmid E R, König V, Faisst K, Huch A, Huch R
Department of Obstetrics, University Hospital of Zurich, Switzerland.
J Clin Monit. 1995 Jul;11(4):253-6. doi: 10.1007/BF01617520.
During initial clinical tests to calibrate our reflectance pulse oximetry system, we observed serious physiologic limitations to the use of pulse oximetry in the forehead region. We present a case of simultaneous reflectance and transmission mode pulse oximetry monitoring in a child undergoing cardiac surgery for congenital cyanotic heart disease with a large intracardiac shunt. During general anesthesia, when the patient was endotracheally intubated and mechanically ventilated, the transmission mode saturation agreed well with arterial oxygen saturation measurements; but, our reflectance pulse oximeter, with the sensor applied to the forehead, displayed spuriously lower (-18%) oxygen saturations. Before and after anesthesia and surgery, there was fine agreement between reflectance and transmission mode saturation values. We suggest that the difference was caused by vasodilatation and pooling of venous blood due to compromised venous return to the heart, and a combination of arterial and venous pulsations in the forehead region. This means that the reflectance pulse oximeter measured a mixed arterial-venous oxygen saturation.
在对我们的反射式脉搏血氧饱和度测定系统进行初始临床测试以进行校准期间，我们观察到在前额区域使用脉搏血氧饱和度测定法存在严重的生理限制。我们报告了一例在患有大型心内分流的先天性青紫型心脏病患儿接受心脏手术期间同时进行反射式和透射式脉搏血氧饱和度监测的病例。在全身麻醉期间，当患者进行气管插管并机械通气时，透射式血氧饱和度与动脉血氧饱和度测量值吻合良好；但是，我们将传感器应用于前额的反射式脉搏血氧仪显示的血氧饱和度假性降低（-18%）。麻醉和手术前后，反射式和透射式血氧饱和度值吻合良好。我们认为这种差异是由于心脏静脉回流受损导致静脉血管扩张和血液淤积，以及前额区域动脉和静脉搏动共同作用所致。这意味着反射式脉搏血氧仪测量的是混合动静脉血氧饱和度。
