European journal of obstetrics, gynecology, and reproductive biology
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Eur. J. Obstet. Gynecol. Reprod. Biol. · Mar 1997
ReviewPulse oximetry--physiological considerations.
Fetal well-being depends on the level of oxygenation in vital organs such as the heart and brain. In this review, we discuss the physiological parameters which underlie the use of pulse oximetry to evaluate fetal conditions intrapartum. Whilst the measurement of haemoglobin oxygen saturation (SaO2) depends on partial pressure of oxygen (PO2), the relation is alinear, is relatively insensitive to changes in PO2 at the upper physiological range, and it is affected by the Bohr shift. ⋯ In hypoxia for example, oxygen delivery to an organ, e.g. the brain, cannot be assessed without simultaneous measurement of blood flow, which again changes with fetal condition. Lastly, it is not possible to gauge fetal tissue unless some measure of, for example, cytochrome aa3 oxidation is used: tissue oxidation in relation to oxygen delivery can change due to local vascular readjustments and changes in metabolism. We conclude that use of SaO2 to assess fetal well-being is fraught with difficulties, and that much more research is needed before its routine clinical use can be considered.
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Eur. J. Obstet. Gynecol. Reprod. Biol. · Mar 1997
ReviewAccuracy of fetal pulse oximetry and pitfalls in measurements.
Pulse oximetry is a technique for estimating arterial oxygen saturation continuously and non-invasively. Reflectance pulse oximetry might become useful for monitoring the fetus during labour but it is much more susceptible to all kinds of physiological variations than the well-established transmission pulse oximetry for neonatal or adult monitoring. This review focuses on the accuracy of reflectance pulse oximetry. ⋯ A new 735/890 nm sensor (Nellcor Puritan Bennett) demonstrates a promising accuracy (precision around 5%) in two studies. Various other sensors have also been developed, but are not or scarcely evaluated. Without thorough establishment of the reliability of this technique, clinical fetal oxygen saturation data are still of limited value.