[Interpretation of pulse oximetry and near infrared spectroscopy values sub partu]

Abstract

Pulse oximetry and Near Infrared Spectroscopy (NIRS) are both optical methods which have been made applicable to the fetus during labour in order to improve the assessment of fetal oxygen supply and well being. 317 pulse oximetry measurements showed that postpartum pH, Base Excess, PO2 are significantly negatively resp. pCO2 is positively correlated to the time, during which arterial oxygen saturation (SpO2) is below a critical threshold of 30%. The 1' APGAR-score is also influenced by the duration of SpO2 values below 30%. Near Infrared Spectroscopy semiquantitatively measures cerebral concentration changes of oxygenized, desoxygenized and total hemoglobin as well as that of cytochrome aa3 which is the key enzyme of the intracellular respiratory chain. In an analysis of 1350 contractions during 42 deliveries decelerations type 1 and 2 differed from normal CTG by a significantly deeper drop of oxygenized and total hemoglobin in the brain on top of contractions. Until the following contraction oxygenized and total hemoglobin remained deeper below their original levels in case of decelerations type 2 than in case of normal CTG or type 1 decelerations. Simultaneous registration of pulse oximetry and NIRS revealed an increase of cerebral blood volume in case of low arterial oxygen saturation (SpO2 < 30%) which may be interpreted as "brain sparing effect".