Dassel A C, Graaff R, Meijer A, Zijlstra W G, Aarnoudse J G
Department of Obstetrics and Gynaecology, University Hospital Groningen, The Netherlands.
J Clin Monit. 1996 Nov;12(6):421-8. doi: 10.1007/BF02199702.
Transmission pulse oximetry (TPO) is not a practical method of intrapartum fetal monitoring of arterial oxygen saturation. Reflectance pulse oximetry (RPO) requires a sensor applied to the skin of the fetal head and may be a useful technique. During labor, various degrees of pressure will be exerted on the RPO sensor. Previous studies have shown that moderate pressure on the sensor can improve the RPO signal. At increasing pressure, however, blood flow underneath the sensor will be occluded. This study examines the influence of pressure applied to the RPO sensor on the signal from the forehead of healthy newborns as a model for the fetal situation.
After institutional approval, 12 healthy newborns were studied. The RPO probe was placed at the forehead. Pressure on the probe was increased stepwise from 0 to 80 mmHg, and the effect on the ratio between the relative changes of the red and infrared light intensities (R/IR, inversely related to oxygen saturation) and pulse sizes was evaluated. Additionally, the effect of firm pressure (> 150 mmHg) on the probe was evaluated.
R/IR values remained virtually unchanged when pressure onto the probe was increased from 0 to 80 mmHg, although the standard deviation slightly decreased. The pulse size increased as pressure on the probe increased. During firm pressure on the probe (> 150 mmHg), plethysmographic signals remained detectable, but R/IR values markedly increased.
In newborns, mild to moderate pressure on the probe has little influence on the RPO signal at the forehead. Even during firm pressure, RPO can be used to obtain pulsatile signals, that presumably derive from tissue underneath the skull, such as the cerebral circulation.
透射式脉搏血氧饱和度仪（TPO）并非产时胎儿动脉血氧饱和度监测的实用方法。反射式脉搏血氧饱和度仪（RPO）需要将传感器应用于胎儿头部皮肤，可能是一种有用的技术。分娩过程中，RPO传感器会受到不同程度的压力。先前的研究表明，对传感器施加适度压力可改善RPO信号。然而，随着压力增加，传感器下方的血流会被阻断。本研究以健康新生儿前额作为胎儿情况的模型，考察施加于RPO传感器的压力对信号的影响。
经机构批准后，对12名健康新生儿进行研究。将RPO探头置于前额。探头压力从0逐步增加至80 mmHg，并评估其对红光和红外光强度相对变化之比（R/IR，与血氧饱和度呈反比）及脉搏大小的影响。此外，还评估了对探头施加稳固压力（> 150 mmHg）的影响。
当探头压力从0增加至80 mmHg时，R/IR值基本保持不变，尽管标准差略有下降。脉搏大小随探头压力增加而增大。在对探头施加稳固压力（> 150 mmHg）期间，体积描记信号仍可检测到，但R/IR值显著增加。
在新生儿中，对探头施加轻度至中度压力对前额的RPO信号影响不大。即使在稳固压力下，RPO仍可用于获取搏动信号，这些信号可能源自颅骨下方的组织，如脑循环。
