Fetal pulse oximetry and visual on-line signal identification in the second stage of labor.

Abstract

To determine the accuracy of reflection pulse oximetry and visual on-line signal identification during the second stage of labor. The reflection pulse oximetry system used allows visual on-line identification of valid signals by showing the original red and infrared signals. With this system oxygen saturation measurements are averaged over nine heartbeats only. An atraumatic suction probe was used. The measurements of the last 10 minutes before delivery were compared with umbilical venous cord blood samples taken soon after delivery. The correlation between reflection pulse oximetry readings during the last 10 minutes before delivery and umbilical vein oxygen saturation was significant (r = 0.45; p < 0.0005). Standard regression analysis showed R2 of 0.45. This did not change if weighted by the rate of valid signals (R2 = 0.42). If the predelivery loss of valid signals was less than 5 minutes, the correlation improved (r = 0.47, p < 0.001). Umbilical vein pH did not correlate with pulse oximetry readings. The reflection pulse oximetry system used allows visual on-line identification of even short periods of valid signals and reflects actual oxygen saturation in fetal arterial blood.