Assessment of fetal scalp oxygen saturation determination in the sheep by transmission pulse oximetry

Nijland, Mark J.; Shankar, Uday; Iyer, Vijay K.; Ross, Michael G.

doi:10.1067/mob.2000.107736

Cited by 14 publications

(8 citation statements)

References 13 publications

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“…Five pregnant ewes (132-144 days gestation) were evaluated in this study. The animals were han- First, the pregnant ewe was anesthetized with halothane [187]. The carotid artery was catheterized for maternal arterial blood sampling and blood pressure monitoring.…”

Section: Animal Protocolmentioning

confidence: 99%

Diffuse optical tomography and spectroscopy of breast cancer and fetal brain

Choe

2005

Medical Physics

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Diffuse optical techniques utilize light in the near infrared spectral range to measure tissue physiology noninvasively. Based on these measurements, either average bulk optical properties or threedimensional spatial maps of tissue properties such as total hemoglobin concentration, blood oxygen saturation and scattering can be obtained using model-based reconstruction algorithms. In this thesis, diffuse optical techniques were applied for in vivo breast cancer imaging and transabdominal fetal brain oxygenation monitoring. For clinical in vivo breast cancer imaging, diffuse optical tomography technique and related instrumentation were developed. The clinical diffuse optical tomography instrument utilized near infrared light sources of multiple wavelengths, and multiple source-detector positions in a parallel plate geometry. Transmission continuous-wave measurements by a lens-coupled CCD camera and remission frequency-domain measurements by fiber-coupled detector channels were performed simultaneously. Human subject measurements were carried out in the prone position. The breast was softly compressed and the space adjacent to the breast was filled with a matching fluid with similar optical properties to that of the breast. A nonlinear conjugate gradient inverse algorithm with a priori spectral constraints was utilized to reconstruct threedimensional endogeneous optical and physiological breast properties. Bulk physiological properties were quantified for 52 healthy subjects in the parallel-plate transmission geometry. Threedimensional images of the breast were reconstructed for 21 subjects with breast carcinomas. Tumor contrast with respect to normal tissue was found in total hemoglobin concentration and scattering coefficient. An optical index combining total hemoglobin concentration and scattering coefficient shows the tumor contrast to be 2-3 times larger compared to the healthy tissue. Tumor contrast and tumor volume changes during neoadjuvant chemotherapy were tracked for one subject and compared to the dynamic contrast-enhanced magnetic resonance imaging ͑MRI͒. Our measurement revealed tumor shrinkage during the course of chemotherapy, in reasonable agreement with magnetic resonance images of the same subject. Finally, the feasibility of measuring blood flow of breast tumors using optical methods was demonstrated for seven subjects. In a qualitatively different set of experiments, the feasibility of transabdominal fetal brain oxygenation monitoring was demonstrated on pregnant ewes with induced transient fetal hypoxia. Preliminary noninvasive clinical measurements before and after human Cesarean sections were discussed, identifying future directions. Overall, this research has translated diffuse optical tomography techniques into a clinical research environment.

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Section: Animal Protocolmentioning

confidence: 99%

Diffuse optical tomography and spectroscopy of breast cancer and fetal brain

Choe

2005

Medical Physics

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“…Fetal pulse oximetry is a promising new technique which measures fetal oxygenation directly, without reference to the FHR pattern. It has the advantage of continuous monitoring, and its efficacy is equal to that of fetal blood analysis [5,10].…”

Section: Discussionmentioning

confidence: 99%

Intrapartum Surveillance of IUGR Fetuses with Cardiotocography and Fetal Pulse Oximetry

Siristatidis¹,

Salamalekis²,

Vitoratos³

et al. 2003

Neonatology

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Objective: To investigate the efficacy and safety of intrapartum fetal pulse oximetry, as a predictor of metabolic acidosis at birth of fetuses with intrauterine growth retardation (IUGR). Study Design: We studied 18 IUGR fetuses (group I) and a control group of 30 appropriate for gestational age (AGA) fetuses (group II) during labor. Both groups had abnormal fetal heart rate tracings and were monitored simultaneously throughout labor with cardiotocography and fetal pulse oximetry. Apgar scores, pH and base excess of fetal blood obtained from the umbilical artery after delivery were compared in both groups. Setting: The Fetal Surveillance Unit of the 2nd Department of Obstetrics and Gynecology, Aretaieion Hospital, Medical School, Athens University. Results: In IUGR fetuses, when their oxygen saturation value (FSPO₂) was less than 34%, cord artery pH was 7.10 ± 0.04, base excess –13 ± –1 mmol/l and Apgar scores ≤5 at the 5th min, and when FSPO₂ was over 35%, artery pH was 7.29 ± 0.08, base excess –8 ± –2 mmol/l and Apgar scores ≧7 at the 5th minute. In cases of drops of FSPO₂below 30% for more than 2 min, labor was completed operatively and cord pH was 7.00 ± 0.04, base excess –15 ± –2 mmol/l and Apgar scores ≤5 at the 5th minute. In AGA fetuses, when FSPO₂ was over 30%, artery pH was over 7.20, base excess <–11 mmol/l and Apgar scores ≧9 at the 5th minute; in contrast, when FSPO₂ was <30% for 2 min, a cesarean section was performed and cord pH was ≤7.02, base excess ≧–13 mmol/l and Apgar scores ≤4 at the 5th minute. Conclusions: In IUGR fetuses, FSPO₂ values less than 34% represent an acidotic status, while values of ≧35% are well tolerated. Fetal pulse oximetry proved reliable, according to umbilical cord blood measurements and Apgar scores, reducing cesarean deliveries in cases of nonreassuring cardiotocographic patterns in IUGR fetuses.

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“…A midline abdominal incision exposed the uterus and a hysterotomy was performed to expose the fetal head. 26 The fetal head was exteriorized from the amniotic sac. The left fetal brachial artery was catheterized for obtaining arterial blood samples and the right brachial artery was catheterized to monitor fetal blood pressure.…”

Section: Animal Preparationmentioning

confidence: 99%

Effect of errors in baseline optical properties on accuracy of transabdominal near-infrared spectroscopy in fetal sheep brain during hypoxic stress

et al. 2005

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A continuous-wave (cw) near-infrared spectroscopy (NIRS) instrument has been developed to noninvasively quantify fetal cerebral blood oxygen saturation (StO2). A linear Green's function formulism was used to analytically solve the photon diffusion equation and extract the time-varying fetal tissue oxy- and deoxy-hemoglobin concentrations from the NIR measurements. Here we explored the accuracy with which this instrument can be expected to perform over a range of fetal hypoxic states. We investigated the dependence of this accuracy on the accuracy of the reference optical properties chosen based on the literature. The fetal oxygenation of a pregnant ewe model was altered via maternal aortic occlusion. The NIR cw instrument was placed on the maternal abdomen directly above the fetal head, continuously acquiring diffuse optical measurements. Blood was sampled periodically from the fetus to obtain fetal arterial saturation (SaO2) measurements from blood gas analysis. The NIR StO2 values were compared with the fetal SaO2 measurements. Variations in the NIR results due to uncertainty in the reference optical properties were relatively small within the fetal SaO2 range of 30 to 80%. Under hypoxic conditions, however, the variability of the NIR StO2 calculations with changes in the assumed reference properties became more significant.

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Assessment of fetal scalp oxygen saturation determination in the sheep by transmission pulse oximetry

Cited by 14 publications

References 13 publications

Diffuse optical tomography and spectroscopy of breast cancer and fetal brain

Diffuse optical tomography and spectroscopy of breast cancer and fetal brain

Intrapartum Surveillance of IUGR Fetuses with Cardiotocography and Fetal Pulse Oximetry

Effect of errors in baseline optical properties on accuracy of transabdominal near-infrared spectroscopy in fetal sheep brain during hypoxic stress

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