Oded Luria

Two-dimensional and three-dimensional Doppler assessment of fetal growth restriction with different severity and onset

To investigate the role of three‐dimensional (3D) power Doppler ultrasonography in the assessment of fetal growth‐restriction (FGR) with various degrees of severity and onset, and compare the results with the analysis of two‐dimensional (2D) Doppler.

Effect of vaginal progesterone, administered to prevent preterm birth, on impedance to blood flow in fetal and uterine circulation

To evaluate the effect on the maternal and fetal circulation of progesterone administered to prevent preterm birth.

Relations between fetal head descent and cervical dilatation during individual uterine contractions in the active stage of labor

The relationship between instantaneous changes in fetal head station and cervical dilatation within the individual contraction during the active stage of labor were studied and an index of labor progress was suggested. Cervix dilatation and fetal head station were measured continuously in 30 nullipara women (mean age 27.5, standard deviation 4.8). The continuous measurements enabled the analysis of each variable and the analysis of the relations between these two variables. The relationship between the head station and the cervical dilatation were demonstrated by plotting one against the other during a contraction. This led to the definition of a contraction vector that integrates the interaction between the two variables. The angle of this vector, that indicates this relation, was plotted against mean head station to demonstrate change along the delivery process regardless of time to normalize the progress and allow comparison between different women with different labor durations. This plot showed a sharp change from almost zero into a steep curve at about zero head station. A zero angle indicates that the cervix dilates during a contraction with little effect on head station while a steep angle indicates a significant effect of cervical dilatation on head station during the contraction. The contraction‐vector angle reflects the changing intra‐contraction relationship between head station and cervical dilatation. The angle of this vector may serve as an indicator of labor progress.

Effects of the individual uterine contraction on fetal head descent and cervical dilatation during the active stage of labor

OBJECTIVE To evaluate the effects of individual uterine contractions on instantaneous values of cervical dilatation and head station along the active stage of labor. STUDY DESIGN Cervix dilatation and fetal head station were measured continuously using a labor monitor that is based on ultrasonic triangulation. The relations between the two variables in response to each contraction were analyzed. The relative effect of the contraction on head station and on cervical dilatation was demonstrated by plotting one against the other during the contraction and quantified by two indices: (a) the contraction vector that integrates the maximum effect of uterine contraction on both variables and (b) the efficiency vector that indicates the contribution of each contraction to labor progression. The amplitude and angle of each vector were calculated. Correlation between the waveforms of head station and cervix dilatation during contractions was also calculated. These indices were plotted against cervix dilatation and head station at different stages in labor progress. RESULTS Effects of uterine contractions on cervix dilatation and head station varied during labor. The amplitude of the contraction vector and efficiency vector increased to a maximal value at cervical dilatation of 6 cm. The angle of the contraction vector increased with the progress of labor. Correlation between cervical dilatation and head station was maximal at the engagement zone of the birth canal. High variability was observed between subjects for all indices measured. CONCLUSION The contraction vector and the efficiency vector exhibited distinct behavior during labor. These vectors may serve as indicators for normal and abnormal progress of labor. More data are required to obtain statistical significance.

The role of blood flow distribution in the regulation of cerebral oxygen availability in fetal growth restriction

Fetal growth restriction (FGR) elicits hemodynamic compensatory mechanisms in the fetal circulation. These mechanisms are complex and their effect on the cerebral oxygen availability is not fully understood. To quantify the contribution of each compensatory mechanism to the fetal cerebral oxygen availability, a mathematical model of the fetal circulation was developed. The model was based on cardiac-output distribution in the fetal circulation. The compensatory mechanisms of FGR were simulated and their effects on cerebral oxygen availability were analyzed. The mathematical analysis included the effects of cerebral vasodilation, placental resistance to blood flow, degree of blood shunting by the ductus venosus and the effect of maternal-originated placental insufficiency. The model indicated a unimodal dependency between placental blood flow and cerebral oxygen availability. Optimal cerebral oxygen availability was achieved when the placental blood flow was mildly reduced compared to the normal flow. This optimal ratio was found to increase as the hypoxic state of FGR worsens. The model indicated that cerebral oxygen availability is increasingly dependent on the cardiac output distribution as the fetus gains weight.

Feto-Maternal Interaction: A Mathematical Model Simulating Placental Response in Hypertensive Disorders of Pregnancy

Elevated maternal blood pressure (BP) is common in pregnancies complicated by hypertensive disorders. In response, increased production and accumulation of elastin occurs in the feto-placental blood vessels. This results in increased vascular wall stiffness that increases the resistance to flow. To study the interaction between the stiffness of the fetoplacental blood vessels, fetoplacental blood flow and BP, a mathematical model of the fetoplacental vascular tree was developed. The model describes an elastic structure exposed to external pressure. Model results indicate that increased vascular stiffness in the fetal blood vessels may contribute to optimizing fetoplacental blood flow in hypertensive pregnancies. According to model predictions, uncontrolled lowering of BP following vascular adaptation may adversely affect fetoplacental blood flow.

Reactivity of blood vessels in response to prostaglandin E2 in placentas from pregnancies complicated by fetal growth restriction

The authors aimed to study the contractility responses of normal and fetal growth restriction (FGR) placentas to prostaglandin E2 (PGE2) and to correlate the results to subsequent placental histological analysis.

Patient-specific modeling for the assessment of circulatory adaptation in fetal growth restriction

Fetal growth restriction (FGR) is one of the major contributors to adverse perinatal outcome. However, the diagnostic tools currently used for estimating the fetal hemodynamic status are still limited. In this study we developed a methodology for estimating fetal hemodynamic parameters. The method is based on a mathematical model of the fetal circulation, an optimization algorithm and measurements of power-Doppler ultrasound. The model estimates parameters of the fetal circulation that are not possible for direct measurement. The method was tested on a cohort of 20 normal and 22 growth-restricted fetuses. In each fetus, power-Doppler velocity waveforms were measured in large number of sites of the fetal circulation. Three-dimensional volume-flow measurements were performed in the placenta to evaluate its resistance to blood flow. Model predictions indicated significant changes in the circulation of FGR fetuses compared to normal fetuses. In the FGR group, the model predicted significant reduction in fetal cardiac output and decreased cardiac output distribution towards the placenta. In FGR fetuses that showed adverse outcome, the model indicated significant increase in cardiac output distribution towards the brain and in the degree of blood shunted by the ductus venosus, indicating severe brainsparing state in these fetuses. We conclude that patientspecific modeling may be useful in personalizing and optimizing the treatment options in pregnancies complicated by fetal growth-restriction.

Inverse solution of the fetal-circulation model based on ultrasound Doppler measurements

Fetal growth restriction (FGR) is one of the major contributors to adverse perinatal outcome. However, the diagnostic tools currently used for estimating the fetal hemo-dynamic status are still limited. In this study we developed a methodology for estimating fetal hemodynamic parameters. The method is based on a mathematical model of the fetal circulation, an optimization algorithm and measurements of power-Doppler ultrasound. The model estimates parameters of the fetal circulation that are not possible for direct measurement. The method was tested on a cohort of 20 normal and 22 growth-restricted fetuses. In each fetus, power-Doppler velocity waveforms were measured in large number of sites of the fetal circulation. Three-dimensional volume-flow measurements were performed in the placenta to evaluate its resistance to blood flow. Model predictions indicated significant changes in the circulation of FGR fetuses compared to normal fetuses. In the FGR group, the model predicted significant reduction in fetal cardiac output and decreased cardiac output distribution towards the placenta. In FGR fetuses that showed adverse outcome, the model indicated significant increase in cardiac output distribution towards the brain and in the degree of blood shunted by the ductus venosus, indicating severe brain-sparing state in these fetuses. We conclude that patient-specific modeling may be useful in personalizing and optimizing the treatment options in pregnancies complicated by fetal growth-restriction.

Acoustic Parameters for Optimizing Lung Volume During High- Frequency Oscillatory Ventilation in Infants with Respiratory Distress Syndrome: A Feasibility Study~!2009-08-16~!2009-11-25~!2010-03-05~!

During high-frequency oscillatory ventilation (HFOV), the primary variable affecting lung volume is the mean airway pressure (MAP). To effectively maintain lung recruitment and optimal gas exchange without overstretching (or collapsing) the lung, MAP should be set between the lower and upper inflection points of the pressure-volume curve of the lung. At present, there is no efficacious means that allows the neonatologist to determine the MAP (optimal MAP) which attains optimal lung expansion and avoids overdistension. Thus, MAP is usually adjusted by trial and error or by clinical experience of the user. In this study, we investigated the acoustic properties of the neonate lung in six newborns undergoing high frequency oscillatory ventilation, to assess its usefulness as a means for determining optimal mean airway pressure. We found that the shape of the acoustic reflection-pressure curve was similar to the shape of the known pressure-volume curve. In all subjects, the estimated range of MAP was in congruence with the pressure chosen by the neonatologist. The acoustic measurements indicated of an increase in lung volume following administration of exogenous surfactant. Hysteresis in the amplitude of acoustic reflection was measured as expected. Our results indicate that the acoustic technique provides useful information about the state of lung recruitment during HFOV and may be helpful in identifying the adequate MAP for optimal lung expansion without overdistension.