The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform

S.-w. Kim - One of the best experts on this subject based on the ideXlab platform.

  • is an abnormal doppler umbilical artery waveform ratio a risk factor for poor perinatal outcome in the non small for gestational age fetus
    American Journal of Perinatology, 2008
    Co-Authors: B H Yoon, Hee Chul Syn, P R Lee, W J Kim, S.-w. Kim
    Abstract:

    To determine if abnormal umbilical artery Velocimetry is associated with a higher rate of perinatal morbidity in pregnancies in which the outcome is not manifested by a small for gestational age (SGA) fetus, perinatal outcome was compared according to the results of Doppler umbilical artery Velocimetry. Doppler study was performed in 328 singleton pregnancies with non-SGA fetuses within 7 days of delivery. The prevalence of abnormal Doppler studies was 10%. Patients with abnormal umbilical artery Velocimetry had a significantly higher rate of complications, including cesarean section for fetal distress, preterm delivery, low Apgar scores, congenital anomalies, admission to the neonatal intensive care unit, and perinatal death, than patients with a normal umbilical artery Velocimetry. Ten perinatal deaths were associated with major congenital anomalies. Moreover, in the absence of congenital anomalies patients with abnormal Doppler results also had a significantly higher incidence of adverse perinatal outcome compared with patients with normal umbilical artery Velocimetry. Our data suggest that even the non-SGA fetus with an abnormal Doppler umbilical artery waveform ratio is at increased risk for poor perinatal outcome.

  • Relationship between the fetal biophysical profile score, umbilical artery Doppler Velocimetry, and fetal blood acid-base status determined by cordocentesis
    American Journal of Obstetrics and Gynecology, 1993
    Co-Authors: Bo Hyun Yoon, Hee Chul Syn, Roberto Romero, Cheng Rae Roh, Seung Hyup Kim, Joel Ager, David B. Cotton, S.-w. Kim
    Abstract:

    Objective: Fetal hypoxia-acidosis is part of the terminal pathway leading to intrauterine fetal death. A central premise of antepartum surveillance is that identification and timely delivery of the hypoxic or acidotic fetus will prevent intrauterine death and decrease long-term neurologic damage. The optimal method to identify fetal hypoxia-acidosis has not been determined. We attempted to compare the performance of the biophysical profile score and umbilical artery Doppler Velocimetry in the identification of fetal acidemia, hypoxemia, and hypercarbia as determined by pH and gas analysis of fetal blood obtained by cordocentesis. Study Design: Fetal biophysical profile and umbilical artery Doppler Velocimetry studies were performed before cordocentesis in 24 patients (26 to 40 weeks). Umbilical vein pH and blood gas values were determined in all cases. The pulsatility index of the umbilical artery was obtained with pulsed Doppler equipment. Receiver-operator characteristic curve analysis and stepwise multiple logistic regression were performed to examine the relationship between biophysical profile score, umbilical artery Doppler Velocimetry, and acid-base status. Results: The prevalence of fetal acidemia (pH 2 SD below the mean for gestational age) was 41.7% (10/24). There was a significant relationship between the change in umbilical artery pulsatility index and fetal acidemia (χ 2 = 26.6, p 2 = 22.9, p 2 = 1.0, p > 0.1), and between the biophysical profile score and fetal acidemia (χ 2 = 11.1, p 2 = 9.0, p 2 = 2.3, p > 0.1). Stepwise multiple logistic regression demonstrated that umbilical artery Doppler Velocimetry was a better explanatory variable for acidemia and hypercarbia than the biophysical profile score. Conclusion: A strong relationship between the degree of fetal acidemia and hypercarbia and the results of umbilical artery Doppler Velocimetry and biophysical profile was found. However, umbilical artery Doppler Velocimetry was a better explanatory variable for these outcomes than the biophysical profile score.

S. Ablett - One of the best experts on this subject based on the ideXlab platform.

  • Chemically resolved NMR Velocimetry
    Chemical Engineering Science, 1997
    Co-Authors: Benedict Newling, S. J. Gibbs, Laurance D. Hall, D.e. Haycock, William J. Frith, S. Ablett
    Abstract:

    Abstract Nuclear magnetic resonance imaging has been widely applied in industry as a noninvasive tool for the study of optically opaque fluids. The pulsed field gradient variant of this technique is sensitive to fluid displacement, allowing the measurement of fluid velocities in three spatial dimensions (Velocimetry). It is also possible to include chemical sensitivity in the measurement. This article reviews the alternative protocols which might be implemented for chemically resolved nuclear magnetic resonance Velocimetry, and illustrates two approaches. Results are presented which show separate velocity maps for oil and water in an oil-in-water emulsion flowing through a straight, rigid pipe and also through an abrupt expansion/contraction pipe system.

  • Chemically resolved NMR Velocimetry
    IEE Colloquium on Advances in Sensors for Fluid Flow Measurement, 1996
    Co-Authors: Benedict Newling, Laurance D. Hall, D.e. Haycock, William J. Frith, S.j. Gibes, S. Ablett
    Abstract:

    Of particular relevance to process engineering is the potential sensitivity of NMR imaging to fluid displacement, which allows measurement of fluid velocities (in the range mm/s to m/s), even in opaque fluids, in three spatial dimensions (NMR Velocimetry). The chemical sensitivity of the NMR technique has often been overlooked in NMR Velocimetry implementations, but we present one protocol for the simultaneous measurement of fluid velocity for the separate components of a flowing mixture of chemical compounds. The fluid flow in the expansion/contraction pipe system is found to be fully characterised in three spatial dimensions. Thus, chemically resolved NMR Velocimetry allows a five-dimensional (three spatial, one temporal and one chemical shift) measurement to be made, non-invasively and in optically opaque liquids.

Svend Kreiner - One of the best experts on this subject based on the ideXlab platform.

  • a critical appraisal of the use of umbilical artery doppler ultrasound in high risk pregnancies use of meta analyses in evidence based obstetrics
    Ultrasound in Obstetrics & Gynecology, 2001
    Co-Authors: Hanne Brix Westergaard, Jens Langhoffroos, Goran Lingman, Karel Marsal, Svend Kreiner
    Abstract:

    Objectives To reanalyze randomized controlled trials on the use of umbilical artery Doppler Velocimetry in high-risk pregnancies and determine which high-risk pregnancies benefit from the use of Doppler Velocimetry, Methods Searching Medline, the Cochrane Library and Embase we found 13 randomized controlled trials on the use of Doppler Velocimetry in high-risk pregnancies. Of these, six included pregnancies with strictly defined suspected intrauterine growth restriction and/or hypertensive disease of pregnancy ('well-defined studies;); the rest included a great variety of high-risk pregnancies (general risk studies'). The studies were analyzed with particular regard 50 the heterogeneity and to outcome. Audits of the perinatal deaths reported in the randomized controlled trials were performed by a panel of 32 international experts. Results The 'well-defined studies ' had a more uniform study design as compared to the 'general risk studies' and they showed a significant reduction in antenatal admissions (odds ratio, 0.56; 95% confidence interval, 0.43 - 0. 72), inductions of labor (0. 78; 0.63 -0. 96), elective deliveries (inductions of labor and elective Cesarean sections) (0. 73; 0.61-0.88) and Cesarean sections (0. 78; 0, 65 - 0. 94). By perinatal audit it was found that more perinatal deaths in the 'well-defined studies' were potentially avoidable by use of Doppler Velocimetry (P < 0.0005) and the rate of avoidable perinatal deaths was higher among controls (50%) than cases (20%) in this group. Conclusion The randomized controlled trials on umbilical artery Doppler Velocimetry show major differences regarding study design and technical and clinical issues and, therefore, they should not be pooled in a simple meta-analysis. By stratification it was found that only in pregnancies with suspected intrauterine growth restriction and/or hypertensive disease of pregnancy will the use of umbilical artery Doppler Velocimetry reduce the number of perinatal deaths and unnecessary obstetric interventions. (Less)

Thomas J. Beutner - One of the best experts on this subject based on the ideXlab platform.

  • Molecular filter based planar Doppler Velocimetry
    Progress in Aerospace Sciences, 1999
    Co-Authors: Gregory S. Elliott, Thomas J. Beutner
    Abstract:

    Abstract Molecular filter based diagnostics are continuing to gain popularity as a research tool for investigations in areas of aerodynamics, fluid mechanics, and combustion. This class of diagnostics has gone by many terms including Filtered Rayleigh Scattering, Doppler Global Velocimetry, and Planar Doppler Velocimetry. The majority of this article reviews recent advances in Planar Doppler Velocimetry in measuring up to three velocity components over a planar region in a flowfield. The history of the development of these techniques is given with a description of typical systems, components, and levels of uncertainty in the measurement. Current trends indicate that uncertainties on the order of 1 m/s are possible with these techniques. A comprehensive review is also given on the application of Planar Doppler Velocimetry to laboratory flows, supersonic flows, and large scale subsonic wind tunnels. The article concludes with a description of future trends, which may simplify the technique, followed by a description of techniques which allow multi-property measurements (i.e. velocity, density, temperature, and pressure) simultaneously.

David S Nobes - One of the best experts on this subject based on the ideXlab platform.