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The fetal oxygen saturation is an important parameter to determine the health status of a fetus, which is until now mostly acquired invasively. The transabdominal, fetal pulse oximetry is a promising approach to measure this non-invasively and continuously. The fetal pulse curve has to be extracted from the mixed signal of mother and fetus to determine its oxygen saturation. For this purpose efficient algorithms are necessary, which have to be evaluated under constant and reproducable test conditions. This paper presents the improved version of a phantom which can generate artificial pulse waves in a synthetic tissue phantom. The tissue phantom consists of several layers that mimic the different optical properties of the fetal and maternal tissue layers. Additionally an artificial vascular system and a dome, which mimics the bending of the belly of a pregnant woman, are incorporated. To obtain data on the pulse waves, several measurement methods are included, to help understand the behavior of the signals gained from the pulse waves. Besides pressure sensors and a transmissive method we integrated a capacitive approach, that makes use of the so called “Pin Oscillator” method. Apart from the enhancements in the tissue phantom and the measurements, we also improved the used blood substitute, which reproduces the different absorption characteristics of fetal and maternal blood. The results show that the phantom can generate pulse waves similar to the natural ones. Furthermore, the phantom represents a reference that can be used to evaluate the algorithms for transabdominal, fetal pulse oximetry.

Monitoring the oxygen saturation of an unborn child is an invasive procedure, so far. Transabdominal fetal pulse oximetry is a promising method under research, used to estimate the oxygen saturation of a fetus noninvasively. Due to the nature of the method, the fetal information needs to be extracted from a mixed signal. To properly evaluate signal processing algorithms, a phantom modeling fetal and maternal blood circuits and tissue layers is necessary. This paper presents an improved hardware concept for an artificial vascular system, utilizing an FPGA based CompactRIO System from National Instruments. The experimental model to simulate the maternal and fetal blood pressure curve consists of two identical hydraulic circuits. Each of these circuits consists of a pre-pressure system and an artificial vascular system. Pulse curves are generated by proportional valves, separating these two systems. The dilation of the fetal and maternal artificial vessels in tissue substitutes is measured by transmissive and reflective photoplethysmography. The measurement results from the pressure sensors and the transmissive optical sensors are visualized to show the functionality of the pulse generating systems. The trigger frequency for the maternal valve was set to 1 per second, the fetal valve was actuated at 0.7 per second for validation. The reflective curve, capturing pulsations of the fetal and maternal circuit, was obtained with a high power LED (905 nm) as light source. The results show that the system generates pulse curves, similar to its physiological equivalent. Further, the acquired reflective optical signal is modulated by the alternating diameter of the tubes of both circuits, allowing for tests of signal processing algorithms.

Objective. Purpose of the study was to evaluate the diagnostic accuracy of fetal pulse oximetry (FPO) and STanalysis of the fetal ECG (STAN) in prediction of fetal acidemia at birth. Methods. A prospective clinical study was conducted at the Department of Obstetrics and Gynaecology, Jessenius Faculty of Medicine, Martin, Slovakia. In total, 63 out of 70 women with non-reassuring CTG patterns in labour were enrolled. Fetal surveillance during the labour continued with simultaneous CTG plus FPO and STAN monitoring. A receiver operating curve (ROC) analysis was performed to ascertain diagnostic accuracy of individual methods. Results. The study confirmed FPO has a significant ability to detect fetal acidemia at birth (UA-pH ≤ 7.2). The optimum diagnostic cut-off value of SpO2 was 33%, with FPO’s diagnostic sensitivity 60%, and specificity 85.2%. The diagnostic accuracies of STAN + CTG and CTG alone were inferior to that of FPO. Conclusions. FPO has an ability to predict fetal birth acidemia (UA-pH ≤ 7.2), and its diagnostic accuracy is superior to STAN + CTG, or CTG alone monitoring. Condensation.FPO has ability to predict fetal birth acidemia (UA - pH≤7.2), and its diagnostic accuracy is superior to STAN + CTG, or CTG alone monitoring.

Objective. The aim of the study was to test the performance and safety of fetal pulse oximetry (FPO) in the management of non-reassuring CTG patterns in labour. Materials. A randomized controlled trial was conducted in 648 women in active labour and pregnancies > 36 weeks with reassuring admission CTG followed by non-reassuring patterns. All women were divided into 2 groups according to the mode of fetal intrapartum monitoring used. In the study group (n=324), women received a combined biophysical fetal monitoring with CTG plus FPO (n=324), while the control group of women had CTG alone monitoring. Main outcome measures were rates of operative deliveries and neonatal outcome. Results. The analysis showed a significant reduction of Caesarean deliveries in the study group receiving a combined fetal monitoring compared to controls (45/324 vs. 67/324; P=0.022). The total operative delivery rate was also lower, but not significantly (92/324 vs. 104/324, P=0.302). No comparative differences were observed in neonatal outcomes, except for 2 controls-group neonates born with pH-UA < 7.1, however completely normal further postnatal course. No such case was encountered in the study group neonates, and no perinatal deaths occurred during the study. Conclusions. A combined biophysical intrapartum fetal monitoring with CTG and fetal pulse oximetry enables safe reduction in Caesarean rate for non-reassuring CTG patterns, however it could not decrease a total operative delivery rate. Condensation: Fetal pulse oximetry safely reduces a Caesarean rate for non-reassuring patterns, but not the overall Caesarean rate.

Plusieurs centres etudient actuellement quel peut etre l'interet de la pulsoxymetrie pour la surveillance intensive du foetus pendant le travail. Nous avons expertise 50 cas cliniquement interessants presentant un cardiotocogramme anormal. Ils ont ete choisis parma 2.000 cas pour lesquels plusieurs cliniques etrangeres ont utilise la pulsoxymetrie en plus de la surveillance courante. Sur la base de notre experience de l'analyse du sang foetal depuis 36 ans, le depouillement de ces 50 cas a donne les resultats suivants: la pulsoxymetrie intervenant sur la base d'un cardiotocogramme anormal et d'une valeur definie comme normale de SpO 2 permet d'identifier les foetus qui ne sont pas menaces et d'eviter un grand nombre d'analyses du sang foetal et d'accouchements assistes (environ la moitie). Dans les cas de SpO 2 reduite et d'enregistrement defaillant (nous donnons les valeurs limites dans notre article), il est recommande d'effectuer en plus un examen du sang foetal pour un examen differentiel, ce qui permet la aussi de reduire le nombre des interventions.