FETAL PULSE OXIMETRY AND VISUAL ONLINE SIGNAL IDENTIFICATION IN THE 2ND STAGE OF LABOR

OBJECTIVE: To determine the accuracy of reflection pulse oximetry and visual on-line signal identification during the second stage of labor. STUDY DESIGN: The reflection pulse oximetry system used allows visual on-line identification of valid signals by showing the original red a nd infrared signals. With this system oxygen saturation measurements a re averaged over nine heartbeats only. An atraumatic suction probe was used. The measurements of the last 10 minutes before delivery were co mpared with umbilical venous cord blood samples taken soon after deliv ery. RESULTS: The correlation between reflection pulse oximetry readin gs during the last 10 minutes before delivery and umbilical vein oxyge n saturation was significant (r = 0.45; p < 0.0005). Standard regressi on analysis showed R(2) of 0.45. This did not change if weighted by th e rate of valid signals (R(2) = 0.42). If the predelivery loss of vali d signals was less than 5 minutes, the correlation improved (r = 0.47, p < 0.001). Umbilical vein pH did not correlate with pulse oximetry r eadings. CONCLUSION: The reflection pulse oximetry system used allows visual on-line identification of even short periods of valid signals a nd reflects actual oxygen saturation in fetal arterial blood.