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Biomedical subjects

A D Fleming

Publications and source records attributed to A D Fleming.

At least 19 recordsLinked to original sources
PubMed1994

Assessment of colour Doppler tissue imaging using test-phantoms.

An investigation has been carried out on the velocity resolution, spatial resolution and accuracy of Doppler images as part of a study into the Doppler display of cardiac tissue motion. Test-phantoms were designed to perform this work and images were captured on a computer. The characteristics of the phantom images and of the image capture process were studied. The smallest spatial detail that was observed in the Doppler image was 3 mm by 3 mm. Doppler receive gain and Doppler ensemble size both affected velocity resolution. Different target materials gave different measures for velocity resolution. This could be related to the different back-scatter intensities of the materials.

Computer Simulation↗
PubMed1994

Myocardial velocity gradients detected by Doppler imaging.

Using a scanner whose colour Doppler mode has been adapted to display tissue motion (instead of blood flow), velocity gradients have been detected across the myocardium. A velocity gradient is a gradual spatial change in the value of velocity estimates. Velocity gradients have potential for assessing regional myocardial contractility. 28 M-mode scans were performed on nine normal volunteers at different locations in the left-ventricle posterior wall. In each case simultaneous Doppler M-mode and pulse-echo M-mode images were obtained. Doppler velocity gradient (DVG) was calculated from Doppler M-mode images and rate of change of wall thickness (RCWT) was calculated from pulse-echo M-mode images. In all Doppler M-mode images statistically significant velocity gradients were observed. In all but one scan, cyclically consistent peaks in DVG occur relative to the electrocardiogram waveform. 99% of systolic and 89% of early diastolic peaks in RCWT have a corresponding peak in DVG. Velocity gradients are consistent with wall thickness changes, suggesting that they have potential for assessment of myocardial contractility.

Adult↗
PubMed1991

Relationship between fetal biophysical activities and umbilical cord blood gas values.

In a prospective study of 62 patients undergoing cesarean section before the onset of labor a fetal biophysical profile assessment was performed within 3 hours before the cesarean section. The presence or absence of the individual fetal biophysical activities (fetal heart rate reactivity, fetal breathing movements, fetal body movements, and fetal tone) were correlated with umbilical cord blood gas and acid-base measurements (artery and vein). Fetuses with nonreactive nonstress test results or the absence of breathing had significantly lower cord artery pH, PO2 bicarbonate, and base excess measurements but not a significantly different PCO2 level as compared with fetuses that had these activities present. Fetuses with the absence of movements or tone had lower pH, PO2 bicarbonate, and base excess levels and higher PCO2 levels as compared with fetuses with the presence of movements or tone, respectively. These blood gas and acid-base differences were observed in both umbilical cord artery and vein. Subsequent analysis of the blood gas and acid-base measurements of the fetuses with compromised biophysical activities revealed that there are different levels of acidemia, hypoxemia, and hypercapnia at which the individual biophysical activities are compromised. These data suggest that the first manifestations of fetal hypoxemia and acidemia are nonreactive nonstress test results and loss of fetal breathing; in advanced acidemia, hypoxemia, and hypercapnia fetal movements and fetal tone are compromised.

Carbon Dioxide↗
PubMed1991

The relationship between umbilical artery Doppler velocimetry and fetal biometry.

The relationship between peak-systolic/end-diastolic ratio of the umbilical artery waveform and fetal biometry was studied in 127 uncomplicated pregnancies with established dates between 20 and 40 weeks' gestation. At each ultrasonographic examination fetal biometry included measurement of the biparietal diameter, head circumference, abdominal circumference, and femur length. The peak-systolic/end-diastolic ratio was measured by either a continuous or a pulsed-wave method. There were significant linear negative correlations between all the biometric parameters, as well as between the ultrasonographically estimated fetal weight and peak-systolic/end-diastolic ratio. Of the individual ultrasonographic parameters the femur length (for gestations less than 30 weeks) and the abdominal circumference (for gestations greater than or equal to 30 weeks) were found to be best correlated with the peak-systolic/end-diastolic ratio. Regression curves, including the 10th and the 90th percentile, were developed between each biometric parameter (biparietal diameter, head circumference, abdominal circumference, and femur length), as well as between estimated fetal weight and peak-systolic/end-diastolic ratio. The estimated fetal weight nomogram had the best sensitivity (48%) in predicting intrauterine growth retardation. These nomograms should prove most useful in assessing downstream placental vascular resistance in high-risk patients with unknown dates.

Adolescent↗
PubMed1991

Comparison of humerus length with femur length in fetuses with Down syndrome.

A recent report by FitzSimmons et al. demonstrated a greater frequency of upper- versus lower-extremity shortening in autopsies of second-trimester fetuses with trisomy 21. We undertook this study to determine whether this upper-limb shortening could be detected by prenatal ultrasonography in the second trimester and therefore identify fetuses at risk for trisomy 21. A retrospective review of all prenatal sonograms preceding genetic amniocentesis was conducted. Between 1987 and 1990 11 consecutive fetuses between 15 and 22 weeks' gestation with trisomy 21 were identified by genetic amniocentesis. Femur and humerus lengths were plotted on growth curves created from 1470 normal patients between 12 and 26 weeks. Gestational age was confirmed by last menstrual period and biparietal diameter. In fetuses with trisomy 21, seven of 11 humeri were less than 5th percentile, for a sensitivity of 64%, whereas only two of 11 femurs were less than 5th percentile, for a sensitivity of 18%. Biparietal diameter/femur length and biparietal diameter/humerus length ratios were also tested to predict Down syndrome. In only 2 of 11 cases was the biparietal diameter/femur length ratio greater than 95th percentile, whereas the biparietal diameter/humerus length ratio was greater than 95th percentile in 7 of 11. Since all seven were identified by shortened humerus alone, we conclude that humerus length versus gestational age is the simplest and most effective screen. The positive predictive value of an abnormally short humerus length in detecting Down syndrome was 6.8% in our population where the prevalence of Down syndrome was 1 of 173. The present study supports the observations of FitzSimmons et al. that shortened humerus length has a greater sensitivity than femur length in cases of trisomy 21. We conclude that in fetuses at risk for trisomy 21 humerus length should be determined, because it may, if shortened, aid in the prenatal diagnosis.

Anthropometry↗
PubMed1991

The relationships among umbilical artery velocimetry, fetal biophysical profile, and placental inflammation in preterm premature rupture of the membranes.

The relationships among umbilical artery velocimetry, fetal biophysical profile, and placental inflammation in 44 consecutive patients with preterm premature rupture of the membranes were determined. All patients were followed up with daily fetal biophysical profiles and systolic/diastolic ratios. After delivery, placental pathologic examination for histologic evidence of infection (umbilical vasculitis) was performed in all cases according to a standard protocol. The longitudinal trends of fetal biophysical profile scores and systolic/diastolic ratios were analyzed for patients with and without umbilical vasculitis. Analysis of the longitudinal trend during the period of 2 to 7 days before delivery showed that there were no differences of biophysical scores of systolic/diastolic ratios in either group. However, in the last examination, within 24 hours of delivery, patients with umbilical vasculitis had higher systolic/diastolic ratios and lower biophysical profile scores as compared with previous examinations. In addition, the biophysical profile score of the last examination 24 hours before delivery in patients with umbilical vasculitis was found to be significantly lower as compared with patients without umbilical vasculitis (mean +/- SD, 6.6 +/- 2.3 versus 8.2 +/- 2.4, respectively). These data suggest that subclinical stages of infection are associated with biophysical alterations of the fetoplacental unit (i.e., simultaneous decrease in fetal biophysical activities and increase in systolic/diastolic ratios). Daily umbilical artery systolic/diastolic ratios, in conjunction with biophysical profiles, may be useful to follow up patients with preterm premature rupture of the membranes.

Blood Flow Velocity↗
PubMed1991

Abruptio placentae.

Despite our heightened awareness of placental abruption, this condition remains largely unpreventable. The incidence of placental abruption may actually be on the rise due to increasing use of cocaine and "crack" and a greater contribution from abdominal trauma. Whether recurrence of abruption associated with hypertension can be prevented with low-dose aspirin is yet to be determined. Unfortunately, although our recognition of this condition may have improved, placental abruption remains a high cause of perinatal morbidity and mortality.

Abdominal Pain↗
PubMed1991

The relationship between fetal biophysical assessment, umbilical artery velocimetry, and fetal acidosis.

In a prospective study of 62 patients undergoing cesarean delivery before the onset of labor, fetal biophysical assessment and umbilical artery systolic-diastolic ratios (S/Ds) were performed within 3 hours of delivery. There was a significant relationship between the fetal biophysical profile score and cord arterial as well as cord venous pH. However, there was no identifiable relationship between S/D and cord arterial or venous pH. The efficacies of the biophysical components alone (nonstress test [NST] and fetal biophysical profile) and in combination with S/D to predict fetal acidosis were determined. The NST had the best sensitivity (100%) and negative predictive value (100%). The fetal biophysical profile had the best specificity (91%), positive predictive value (62%), and overall efficiency (90%). The S/D had the lowest sensitivity (66%), specificity (42%), positive predictive value (16%), negative predictive value (88%), and overall efficiency (45%). The addition of S/D to the NST or fetal biophysical profile did not improve diagnostic accuracy. These data suggest that the NST should be used as a primary test for the antepartum detection of fetal acidosis, whereas the fetal biophysical profile is a reasonable adjunct test. The umbilical artery S/D, as determined by continuous-wave Doppler velocimetry, has no value as a primary method or an adjunct in the antepartum detection of fetal acidosis.

Acidosis↗
PubMed1990

Uterine activity compared with symptomatology in the detection of preterm labor.

The relative contribution of uterine activity obtained by home monitoring with a guard ring tocodynamometer compared with seven specific signs and symptoms reported during patient/nurse contact as an aid in detecting preterm labor has not been studied. In this prospective, multicenter study, patients at risk for developing early labor who were randomized to receive home uterine activity monitoring and perinatal nursing support were assessed. The initiator of provider contact (uterine activity detected on routine transmission, patient-perceived signs and symptoms of preterm labor during perinatal nurse contact, or both) resulting in a diagnosis of preterm labor was recorded. Contraction data were then analyzed for an association with preterm labor. There was a strong association of increased uterine activity (four or more contractions per hour) on a repeat monitoring strip with preterm labor (P less than .001). Among patients diagnosed with preterm labor, 31% had increased uterine activity detected on a routine transmission without patient-reported signs and symptoms, compared with 24% who were diagnosed as the result of patient-reported symptoms without increased uterine activity. Daily objective uterine activity data alone have greater incremental value over and above other signs and symptoms as an aid to the physician in diagnosing preterm labor.

Female↗
PubMed1990

The contribution of symptomatology and/or uterine activity to the incidence of unscheduled visits.

Home uterine activity monitoring and perinatal nursing support have been shown to be associated with a decrease in preterm births with no increase in the number of unscheduled patient visits. This prospective, randomized multicenter study compared the frequency of unscheduled visits in patients receiving home uterine activity monitoring and perinatal nursing support with that of patients receiving education regarding the detection and reporting of preterm labor symptomatology. The contribution of patient-reported signs and symptoms versus objective uterine activity data to unscheduled visits is assessed. The overall frequency of unscheduled visits was similar in both groups. In the home uterine activity monitoring and perinatal nursing support group, the contributions of uterine activity versus signs and symptoms to the diagnosis of preterm labor were equal, with 36% of patients diagnosed with preterm labor sent to the physician for increased uterine activity and 36% for signs and symptoms. The sensitivity for the group receiving monitoring and nursing support in detecting preterm labor was 93%. The majority of false-positive visits were associated with patient symptoms. These data show that this combination service does not lead to a clinically significant increase in unscheduled visits. Further, the visits resulting from the combination service provide a sensitive predictive method to aid physicians in detecting early labor.

Clinical Trials as Topic↗
PubMed1990

Relationship of uterine contractility to preterm labor.

An increased uterine contraction rate is associated with preterm labor. The contraction rate in individual patients, however, has not been evaluated critically as to its predictive value in forecasting early labor. In this randomized multicenter study, 105 patients at high risk for preterm delivery monitored their contraction rate at home on a daily basis. An analysis was conducted to determine the association of at least four contractions per hour on a routine strip followed by at least four contractions per hour on a repeat tracing with subsequent preterm labor. Using this threshold, 70% of the patients were correctly classified. This contraction rate resulted in a sensitivity of 57%, a specificity of 80%, a positive predictive value of 72%, and a negative predictive value of 68%. A threshold rate of at least four contractions per hour on a remonitor strip identifies a patient at increased risk for preterm labor (P = .003).

Cardiotocography↗
PubMed1990

Perinatal outcomes of twin pregnancies at term.

A review of a two-year experience in our community disclosed that 57% of twin pregnancies (118/207) deliver at term. Little attention has been focused on perinatal outcomes of twin pregnancies remaining undelivered after 36 completed weeks. Therefore, we reviewed our experience to determine whether our practice should change to maximize perinatal care. Nearly all the study pregnancies (115/117, or 97.5%) delivered by the estimated date of confinement. Fetal malpresentation, failure to progress and the patient's lack of desire for a vaginal birth after cesarean delivery were common reasons for the high cesarean rate (62/117, or 52%). The neonatal outcomes were favorable regardless of the route or interval between deliveries. Discordant fetal growth was found in only eight cases (6.8%). No perinatal deaths occurred, and five-minute Apgar scores less than 7 (2/234, or 0.9%) and rates of anomalies (5/234, or 2.1%) were not different from those in singleton pregnancies delivering during the same period. Using the principles of obstetric practice used in our community, we would expect the perinatal outcomes in term twin gestations to be favorable.

Cesarean Section↗
PubMed1990

Home uterine activity monitoring is associated with a reduction in preterm birth.

The value of home uterine activity monitoring plus perinatal nursing support in the prevention of preterm birth among high-risk patients has been demonstrated by several studies. Other reports with less stringent guidelines and less intensive nursing contact have questioned the contribution of home uterine activity monitoring and perinatal nursing support to a preterm birth prevention program. In this large, prospective, randomized multicenter study, patients were assigned to receive either daily monitoring and nursing contact or a preterm birth prevention program including intensive education and more frequent prenatal visits. Among the monitored patients, there was a significant increase in early detection of preterm labor (2 cm or less), successful tocolysis, and prolongation of pregnancy to term. Thirty-one percent of these diagnoses of preterm labor resulted from evaluation of increased uterine activity without associated patient-perceived symptoms. We conclude that a program of daily uterine activity monitoring and perinatal nursing support results in earlier diagnosis of preterm labor and subsequently more effective tocolysis.

Cardiotocography↗
PubMed1990

Preventing preterm birth in twin gestation: home uterine activity monitoring and perinatal nursing support.

In this investigation, 45 women with twin gestations in four centers were randomly assigned to either daily home uterine activity monitoring and perinatal nursing support (19) or an education group (26). Patients in the home uterine activity monitoring and perinatal nursing support group monitored uterine activity twice daily, transmitted the data each day, and had 24 hour-a-day access to nursing support. Education patients were counseled regarding the common signs and symptoms of preterm labor. Both groups had scheduled prenatal visits at least every 2 weeks. Sixteen (62%) of the education group and 14 (74%) of the home uterine activity monitoring and perinatal nursing support group developed preterm labor, values that were not significantly different. Of the monitored group who experienced preterm labor, all 14 were dilated 3 cm or less at diagnosis of the first preterm labor, compared with ten of 16 in the education group (P = .01; one-tailed Fisher test). The mean cervical dilatation at the first preterm labor episode in the group receiving daily monitoring and contact (1.6 cm) was significantly less (P = .01) than that in the education group (2.9 cm). Thus, fewer preterm births were recorded in the home uterine activity monitoring and perinatal nursing support group and significantly fewer patients delivered because of failed tocolysis (P = .03).

Adult↗