Reflectance Pulse Oximetry - Principles and Obstetric Application in the Zurich System

Transmission and reflectance are the two main modes of pulse oximetry. In obstetrics, due to the absence of a transilluminable fetal part for transmission oximetry, the only feasible option is the reflectance mode, in which sensor and detector are located on the same surface of the body part. However, none of the reflectance pulse oximeters developed for intrapartum use are fully satisfactory, as indicated by the fact that none have entered routine use. We have designed, developed, constructed and tested a reflectance pulse oximeter with the possibility to adjust the electronic circuits and signal processing in order to determine the effects of various parameters on signal amplitude and wave-form and to optimize the sensitivity and spatial arrangement of the optical elements. Following an explanation of the principles of reflectance pulse oximetry, we report our experience with the design, development, construction and field-testing of an in-house reflectance pulse oximetry system for obstetric applicatio

Maternal serum interleukin-1β, -6 and -8 levels and potential determinants in pregnancy and peripartum

Aims: To measure maternal serum interleukins (IL) in pregnancy, delivery and early puerperium, and to identify their potential determinants. Methods: Prospective longitudinal measures of serum IL-1β, IL-6 and IL-8 in 38 healthy pregnant women at antenatal visits, through labor and delivery, with clinical correlates (infection, vaginal hemorrhage and anemia) recorded by questionnaire. Results: Pregnancy IL levels remained consistently low. IL-1β increased shortly before delivery, then returned to pregnant levels, except where blood loss exceeded 500 ml. IL-6 and IL-8 rose at labor onset and exceeded pregnancy levels through postpartum day three. Postpartum IL-6 was higher after non-elective cesarean section than after spontaneous delivery (P < 0.0001), and where blood loss exceeded 500 ml. IL-6 and IL-8 were higher with systemic infection during delivery (P < 0.0001) and on postpartum day one (P < 0.05); IL-8 was higher in anemia (delivery: P < 0.005; postpartum day 1: P < 0.05). Differences due to delivery mode and systemic infection remained significant after correction for other conditions. Conclusions: Labor-dependent inflammation increases all IL levels at delivery. Further studies with larger sample sizes are required to establish reference values differentiating physiology from pathology as an aid to peripartum managemen

Maternal hyperventilation and the fetus

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Transcutaneous measurement of blood Po2 (tcPo2) — Method and application in perinatal medicine

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Determination of the minimum number of cardiac cycles necessary to ensure representative blood flow velocity measurements

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Physiological insights based on fetal tcPo2 monitoring

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Continuous PO2 and PCO2 Monitoring in the Neonate

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Monitoring the intravascular Po2 in newborn infants

Peer Reviewe