End-diastolic Flow Velocity Research Articles

Hemodynamic effects of high-frequency oscillating ventilation in preterm and term infants

To study the effects of high frequency oscillating ventilation (HFOV) on cerebral and abdominal circulation we measured blood flow velocities in three cerebral arteries and in the A. mesenterica superior by pulsed doppler ultrasound in 13 preterm (mean gestational age 28 weeks [25-31]) and 3 term infants during conventional ventilation (intermitted positive pressure ventilation, IPPV) and HFOV. In the preterm infants systolic blood flow velocities decreased under HFOV in all cerebral arteries. Statistically significant differences were found in the A. cerebri anterior (45.8 cm/s [sd +/- 20.6] versus 34.3 [sd +/- 10.8]; p < 0.02) and in the A. basilaris (52.8 cm/s [sd +/- 26.4] versus 44.1 [sd +/- 18.7]; p < 0.05). There was also a distinct decrease of systolic blood flow velocity in the A. mesenterica (111 cm/s [ +/- 31.3] versus 61.8 cm/s [sd +/- 18.6]; p < 0.002). The enddiastolic blood flow velocity and the Resistance Index of Pourcelot did not change significantly. The systemic blood pressure did not change during conventional ventilation or HFOV. Mean airway pressure and pCO2 were lower during HFOV, but there was not strong correlation with the reduction of flow velocities in the studied arteries (r = 0.48). In the three term infants presenting with a persistent pulmonary hypertension of the newborn, there was an increase in systolic and enddiastolic flow velocities in all studied arteries under HFOV.

Cerebral blood flow velocity in term newborns following intrapartum fetal asphyxia

Twenty-six term newborns with intrapartum fetal asphyxia, determined biochemically (umbilical artery base deficit > 12 mmol/l), were compared with 59 normal newborns to determine the effect of intrapartum fetal asphyxia on newborn blood pressure and cerebral blood flow velocity following delivery. Cerebral blood flow velocity observations with concurrent measures of blood pressure and heart rate were obtained during the 24 h after delivery and after 24 h. After delivery, diastolic blood pressure in the newborns of the asphyxia group was significantly greater than that of the newborns of the normal group and this difference persisted after 24 h. Cerebral blood flow velocity in the newborns of the asphyxia group was of the same order as that of the newborns of the normal group during the 24 h after delivery. However, there was a significant increase in both peak systolic and end-diastolic blood flow velocity after 24 h. The duration of metabolic acidosis may be a factor in the occurrence of this delayed cerebral blood flow velocity response. Observations of cerebral blood flow velocity should be continued for more than 24 h following delivery to determine the effect of intrapartum fetal asphyxia.

Fetal cerebral blood flow velocity during labor and the early neonatal period.

This study was performed to elucidate circulatory changes in the fetal cerebral circulation during uncomplicated labor and in early neonatal life. Eighteen healthy term singleton fetuses were followed longitudinally during labor. Using the transabdominal approach, and the color Doppler technique, the middle cerebral artery was identified and Doppler flow velocity waveforms recorded between and during uterine contractions. Neonatal recordings were made by insonating the middle cerebral artery from the temporal region before and immediately after the cutting of the umbilical cord, and at 1 hour and 1 day after birth. The recorded Doppler signals were evaluated for pulsatility index, heart rate, peak systolic flow velocity, end-diastolic flow velocity and time-averaged maximum velocity. There was no change in the pulsatility index between and during contractions (1.39 +/- 0.36 and 1.40 +/- 0.39, respectively, mean +/- SD). A significant decrease in the pulsatility index compared to fetal values was seen 4 min after birth (1.06 +/- 0.30, p < 0.01). One hour after birth, the pulsatility index values increased significantly (1.52 +/- 0.25, p < 0.001), to fall again between I hour and 1 day after birth (0.95 +/- 0.26, p < 0.001). Mechanical compression of the skull, blood gas changes and a decrease in ductal shunting may all have contributed to these changes. The present study has shown physiological neonatal circulatory adaptation and onset of breathing to cause manifest changes in cerebral blood flow velocity.

Quantitative flow measurements for classification of ovarian tumors by transvaginal color Doppler sonography in postmenopausal patients.

Color Doppler and Duplex measurements were obtained in 83 (42 benign, 41 malignant) ovarian tumors in postmenopausal patients. An ATL UM9/HDI was used. The following flow criteria were analyzed: lowest resistance index (RI) and pulsatility index (PI), total number of arteries and number of central arteries and the maximum, mean and sum of systolic, end-diastolic and time-averaged maximum velocities of all intratumoral vessels. In 98% of malignant and in 85% of benign lesions, vessels were detected. All flow criteria showed highly significant differences between benign and malignant tumors (p < 0.0001). However, there was a considerable overlap between benign and malignant tumors (e.g. the median of the lowest RI was 0.62 (range 0.26-1.0) for benign and 0.40 (0.22-0.66) for malignant tumors; the median of the maximum systolic velocity was 17.5 cm/s (range 5.2-61.5 cm/s) for benign and 47.05 cm/s (14.6-105.0 cm/s) for malignant tumors). Differentiation of malignant tumors by the lowest RI and PI, number of arteries and maximum of systolic flow velocities gave a sensitivity of 77-85%, specificity of 77-83% and accuracy of 80-84%. Differentiation was superior by calculation of the maximum end-diastolic velocities and by the summation of the systolic, end-diastolic and time-averaged maximum flow velocities: sensitivity 90-9.5% specificity 83-86% and accuracy 87-91%. This study confirms that a single measurement is not sufficient for an accurate differentiation of ovarian lesions and, besides the measurement of minimum RI and PI, the measurements of flow velocities as Doppler criteria play an important role.

Doppler colour flow imaging of fetal intracerebral arteries and umbilical artery in the small for gestational age fetus.

To assess with Doppler colour flow imaging whether a brain-sparing effect is present in all cerebral arteries of the circle of Willis in the small for gestational age fetus, to determine which cerebral flow velocity parameter is most discriminating in this pathological condition, and to relate this parameter to the umbilical artery pulsatility index. Prospective, cross-sectional, matched case-control study. Academic department of obstetrics and gynaecology. Twenty-eight small for gestational age fetuses and 28 normal controls at 24 to 38 weeks of gestation. Blood flow velocity waveforms from the umbilical and fetal intracerebral arteries were studied with Doppler colour flow imaging for measurement of peak systolic, end-diastolic and time averaged velocities, and calculation of the pulsatility index. Comparison of intracerebral and umbilical artery waveform parameters between small for gestational age fetuses and controls. Acceptable flow velocity waveforms were obtained in the intracerebral circulation in more than 85%. In small for gestational age fetuses, all intracerebral arteries displayed reduced downstream impedance. The end-diastolic velocities of the middle and anterior cerebral artery are the most discriminative factors between small for gestational age fetuses and controls. The highest sensitivity was reached for the umbilical artery pulsatility index. Doppler colour flow imaging allows easy identification of fetal intracerebral arterial vasculature. Whereas for the intracranial vasculature, the end-diastolic blood flow velocities in the anterior and middle cerebral artery are the most sensitive parameters discriminating between small for gestational age and controls, umbilical artery pulsatility index remains the best indicator for the small for gestational age fetus.

Ultrasonographic evaluation of vertebral artery to detect vertebrobasilar axis occlusion.

We performed the present study to determine whether the site of occlusion in the vertebrobasilar circulation could be identified by the measurement of blood flow velocity in the bilateral vertebral arteries. Using color-coded duplex carotid ultrasonography, we measured the time-averaged mean and end-diastolic flow velocities with incident angle correction in 130 bilateral vertebral arteries between the C3 and C6 segments of the spine in 65 stroke patients with or without occlusive diseases in the vertebrobasilar circulation. The site of occlusion was confirmed by cerebral angiography. The subjects included 12 patients with unilateral subclavian artery occlusion (SA group), 11 patients with unilateral occlusion at the origin of the vertebral artery (V1 group), 6 patients with unilateral vertebral artery occlusion before the branching of the posterior inferior cerebellar artery (V2 group), 14 patients with unilateral vertebral artery occlusion after the branching of the posterior inferior cerebellar artery (V3 group), 5 patients with basilar artery occlusion (BA group), 5 patients with unilateral posterior cerebral artery occlusion (PCA group), and 12 patients without any occlusive lesions in the vertebrobasilar circulation (control group). In the control group the mean and end-diastolic blood flow velocities were 25.5 +/- 6.9 cm/s and 16.2 +/- 4.3 cm/s, respectively, and the side-to-side differences of these velocities were 4.8 +/- 5.2 cm/s and 4.7 +/- 4.1 cm/s, respectively. All patients in the SA group demonstrated retrograde flow on the affected side. In the V1 group no flow signals were detected on the occluded side. In the V2 group the mean velocity (7.2 +/- 3.1 cm/s) was lower than in the control group, and the end-diastolic velocity was zero on the affected side. In the V3 group the mean and end-diastolic velocities (11.5 +/- 3.1 cm/s and 5.9 +/- 2.8 cm/s, respectively) on the occluded side were lower than in the control group. Flow velocities on the unaffected side were higher than those on the affected side in the SA, V1, V2, and V3 groups. However, there were no differences in flow velocity between the control, BA, and PCA groups. Measurement of vertebral artery blood flow velocity may help in localizing the site of occlusion in the subclavian and vertebral arteries.

Early postnatal cerebral doppler changes in relation to birth weight

Serial Doppler studies of the anterior cerebral artery were performed on 50 healthy term infants in the first 5 days of life. This study aims to establish a normative database for cerebral Doppler measurements in infants born appropriate for gestational age (AGA) and to compare them with those born small for gestational age (SGA). The difference between SGA and AGA infants was documented. In AGA infants, the Pourcelot's resistance index (PI) decreased over the first 5 days, while both the peak systolic flow velocity and end diastolic flow velocity increased. In SGA infants, the PI was significantly lower in the first 24 h of life. This was accounted for by an increase in the end diastolic flow velocity which may be a continuation of the intrauterine situation. The significance of the difference is discussed.

Transcranial Doppler Ultrasonography With Induction of Anesthesia for Neurosurgery

Intracranial hypertension can occur with induction of anesthesia; however, the clinical significance of this is unclear. We used transcranial Doppler (TCD) ultrasonography in neurosurgical patients during induction of anesthesia and endotracheal intubation to assess the incidence of high intracranial pressure (ICP) waveforms and to correlate TCD observations with specific anesthetics and anesthetic regimens. The middle cerebral artery was monitored by TCD during induction of anesthesia and endotracheal intubation in 196 patients undergoing elective neurosurgery. Middle cerebral artery blood flow velocity (MCABFV) and physiologic data were observed continuously and recorded at the following times: preinduction, induction, intubation, and postintubation. Induction with thiopental or etomidate decreased MCABFV, intubation increased MCABFV, and postintubation ventilation decreased MCABFV. MCABFV was higher throughout the induction sequence in the 92 patients with tumors. Although there were numerous individual exceptions, changes in mean arterial pressure correlated statistically with changes in MCABFV. No patient had an end-diastolic flow velocity of 0. We reached the following conclusions: (a) TCD is a straightforward modality that can be used to monitor dynamic cerebrovascular events during induction of anesthesia; (b) MCABFV is increased with brain tumors; (c) thiopental and etomidate rapidly decrease and intubation rapidly increases MCABFV; and (d) routine TCD monitoring for high ICP waveforms during anesthetic induction for routine elective neurosurgery appears to be unwarranted.

Role of Doppler sonography in fetal/maternal medicine

Doppler velocimetry of umbilical, fetal, and uteroplacental vessels provides important information on fetal and uterine hemodynamics and has therefore become one of the most dynamic areas of perinatal research. Examinations of umbilical artery velocity waveforms have gained recognition as a valuable clinical method of fetal surveillance in risk pregnancies. Pathological Doppler findings, especially the finding of absent or reverse end-diastolic (ARED) flow velocity, are associated with fetal hypoxia and adverse outcome of pregnancy. The first follow-up studies indicate that abnormal Doppler findings are associated with impaired postnatal neurological development. Velocimetry of the fetal middle cerebral artery provides important information on redistribution of fetal blood flow in hypoxia; its place in clinics remains to be established. Similarly, more studies are needed to evaluate the use of Doppler velocimetry in labor. Possibly, the Doppler method may facilitate the interpretation of equivocal cardiotocography (CTG) tracings. New evidence has been collected on the correlation between hemodynamic findings and the morphology of the placenta and the placental bed. One of the very important applications of Doppler velocimetry is the evaluation of pharmacological effects on fetal circulation of drugs used for treatment in pregnancy and labor.

Blood flow velocity in the uterine and external iliac arteries before and after termination of pregnancy

In normal pregnancy, there is a marked increase in the uteroplacental blood flow, which is accomplished by a decrease in the peripheral resistance. The purpose of the present study was to investigate whether changes occur in the uterine and external iliac arteries during early pregnancy and after termination of pregnancy. Twenty pregnant women between the 7th and the 23rd weeks of pregnancy were investigated. They were examined before termination of pregnancy and followed up after the termination. The examinations were done using a pulsed duplex scanner (Acuson model 128XP/10 computed sonography system). In the right and left uterine arteries, there is a close correlation between both the peak flow velocity ( r = 0.84; P < 0.01) and the end diastolic flow velocity ( r = 0.71; P < 0.01) and the duration of pregnancy. The V max and V min in the external iliac arteries did not significantly change. The peak flow velocity ( V max) in the right uterine artery was gradually reduced after termination of pregnancy. It was 0.81 (0.22) m/s before termination of pregnancy, reduced to 0.72 (0.22) m/s in the 1st post-operative day, and to 0.68 (0.21) m/s in the 2nd post-operative day. There was also a significant decrease of the end-diastolic flow velocity ( V min), from 0.24 (0.10) m/s before termination of pregnancy to 0.15 (0.08) m/s in the 1st post-operative day. The left uterine artery showed similar changes. There is a strong correlation between V max and V min in both uterine arteries (in the right r = 0.71; in the left r = 0.57) indicating an influence on resistance indices. Compliance and resistance of the uterine arterial vascular bed is reflected by the end-diastolic flow velocity. They start to change at a very early gestation. The resistance indices gave poor information concerning these changes since both V max and V min increase simultaneously.

Possible Correlations of Ocular Blood Flow Parameters with Intraocular Pressure and Visual-Field Alterations in Glaucoma: A Study by Means of Color Doppler Imaging

The authors evaluated, by means of color Doppler imaging, the blood flow of the ophthalmic artery, ciliary arteries and central retinal artery in normal and glaucomatous subjects. In normals they found that flow velocities of all considered vessels progressively decline while resistivity indices increase with advancing age. In glaucomatous subjects there was a statistically significant reduction of the mean systolic peak flow velocity of the ophthalmic artery in comparison with normals. Glaucomatous eyes with uncontrolled IOP and with visual-field worsening showed a statistically significant decrease in the end-diastolic flow velocities and an increase in the resistivity index values in ciliary arteries.

CK-BB as indicator of prenatal brain-cell injury in fetuses with absent or reverse end-diastolic flow velocities of the umbilical arteries

The purpose of this study is to determine the levels of brain type isoenzyme of creatine kinase (CK-BB) as a possible indicator of a pre-existing intrauterine brain-cell damage in cord blood sera of fetuses with preceding absent or reverse end-diastolic flow velocities of the umbilical arteries (AREDFV). CK-BB isoenzyme activities were determined in umbilical cord sera of 13 newborn infants with preceding AREDFV and in 14 fetuses with low end-diastolic flow velocities (LEDFV) of the umbilical arteries. 50 newborn infants with elective cesarean section and normal umbilical artery blood flow velocity waveforms were used as controls. Two-tailed Student's t-test and Fischer's exact test were used for statistical evaluation of the results. CK-BB isoenzyme activity did not depend on gestational age. Fetuses with AREDFV showed a significant increase in CK-BB values, whereas fetuses with LEDFV had CK-BB activities within the normal range of the controls. The elevated CK-BB values of the AREDFV group were not correlated with fetal acidosis at birth. Brain-cell injury with leakage of CK-BB isoenzyme might be present in fetuses with AREDFV even before (preterm) delivery.

Flow velocity in carotid artery in humans during immersions and underwater swimming

Heart rate and flow velocity in the common carotid artery were examined on eight subjects in various underwater conditions. The heart rate decreased more markedly during whole-body immersion than during head-out immersion. The end-diastolic flow velocity and the flow-velocity integral in a cardiac cycle during whole-body immersion increased more markedly than during head-out immersion. Differences in heart rate and flow velocity were not detected between sitting and prone positions in whole-body immersion. Heart rate increased at the beginning and after underwater swimming. The peak systolic flow velocity increased significantly after the end of underwater swimming. The flow-velocity integral in a cardiac cycle decreased during underwater swimming, but in a minute did not change significantly. These results suggest that facial immersion is important in eliciting pronounced carotid artery flow-velocity response in addition to the heart-rate response and that underwater exercise influences these responses. However, underwater posture apparently does not influence them.

Reverse End Diastolic Flow Velocity: Reassuring Biophysical Profile and Acute Fetal Demise

Reverse end diastolic velocity represents the most extreme alteration of the umbilical artery waveform. It has been associated with a high incidence of catastrophic pregnancy outcomes with a stillbirth rate of 33%. We report a case of sudden fetal death within 48 h of a reassuring biophysical profile in a triplet gestation at 31 weeks in which reverse end diastolic velocity was noted in the fetus which died. The postmortem finding of in utero congestive heart failure in this case supports the hypothesis that the alarming rate of stillbirths found in fetuses with absent reverse end diastolic velocity are not necessarily due to asphyxia. This experience illustrates a potential problem with following the fetus who exhibits reverse diastolic flow by traditional markers of fetal well-being such as the biophysical profile.

Flow velocity and pressure measurements in spinal dural arteriovenous fistulas

During ten operations for spinal dural arterio-venous fistulas (AVF), intraoperative measurement of flow velocity and intravascular pressure was performed. Flow velocities were recorded using a miniaturized Doppler probe. Intravascular pressure changes in the draining veins before and after AVF removal was measured with small needles. Varying the pCO2 between 20 mm Hg and 60 mm Hg, the flow velocities in arteries supplying the spinal cord were investigated so that the vasomotoric reactivity of the peripheral vessel wall in cord tissue was investigated before and after AVF occlusion. The flow velocities in dural AVF feeders were not as high as those known from cerebral angioma feeders. In addition, they often showed lowered end-diastolic flow velocity as a sign of increased vascular resistance, thus proving impaired venous outflow from the spinal canal. After excision of the local fistula, the vessels supplying and draining the spinal cord showed improved circulation. In the former recipient veins, no further flow could be recorded. The venous pressure in dural AVF was about 70% of the systemic arterial pressure. Fistulas presenting a high shunt volume on angiography showed only moderately increased venous pressure and a more pronounced pressure drop after fistula occlusion as compared with low-volume fistulas. The CO2 reactivity of vessels supplying the spinal cord was normal before and after AFV removal.

Reverse end-diastolic umbilical artery velocity in a case of intrauterine fetal death at 14 weeks' gestation

A case of intrauterine fetal death at 14 week's gestation in a mother with systemic lupus erythematosus is described. Doppler ultrasonography performed within 24 hours before fetal death showed reverse end-diastolic flow velocities on umbilical artery velocity waveforms. The placental alteration causing this early gestation is discussed.

Fetal echogenic gut: a marker of intrauterine gut ischaemia?

The pathophysiological significance of fetal echogenic gut (FEG) is unknown. Our aim was prospectively to evaluate FEG in infants with intrauterine growth retardation (IUGR) and absent umbilical artery end diastolic flow velocities. Over a 15 month period, nine infants with FEG met these criteria. Nine infants who, on antenatal assessment, had demonstrated IURG and absent umbilical artery end diastolic flow velocities, but no evidence of FEG, were selected as case-controls. Gastrointestinal function was then prospectively evaluated in both groups after delivery. All liveborn infants received nasogastric feeds of breast milk by 8 days of age. All in the FEG group developed marked abdominal distension, large, bile stained, nasogastric aspirates, and constipation requiring rectal washouts. This led to a discontinuation of enteral feeds on one or more occasions. Two patients in the FEG group required water soluble contrast enemas in order to relieve intestinal obstruction. In the control group, 3/9 patients had abdominal distension, but no rectal washouts were given and enteral feeds were not interrupted. The median (range) time to tolerate full enteral feeds was 15 (7-32) days in the FEG group, compared with 4 (1-8) days in the control group. In the FEG group 5/6 patients required parenteral nutrition for 5-27 days. In the control group one patient required parenteral nutrition over a period of four days only. No child had necrotising enterocolitis or cystic fibrosis. When FEG is observed in the fetus with IUGR, problems with enteral feeding should be anticipated.

Contractile responses of the human umbilical artery from pregnancies complicated by intrauterine growth retardation

The contractile properties of the umbilical artery to oxygen, U46619 (a stable thromboxane A2 mimetic) and 5-hydroxytryptamine (5-HT) were studied in normal term (> or = 37 weeks) and preterm (< 34 weeks) pregnancies, and in a group of pregnancies complicated by intrauterine growth retardation (IUGR). Isometric contractile responses in the preterm group to oxygen were reduced when compared with the term group, though no differences were found between these groups in the responses to either U46619 or 5-HT. In the IUGR group the responses to oxygen did not differ from gestationally matched normal pregnancies, though among those cases delivered preterm, the finding of absent end-diastolic flow velocity in the umbilical artery prior to delivery was associated with markedly diminished responses to oxygen. These data indicate the development of oxygen-induced contractions in the umbilical artery as pregnancy advances, which may fail to function in the severely growth-retarded fetus.

Low target birth weight or growth retardation? Umbilical Doppler flow velocity waveforms and histometric analysis of fetoplacental vascular tree

The placental vascular architecture of small-for-gestational-age fetuses seems to have an impact on the flow patterns in the umbilical arteries. Blood flow velocity waveforms of the umbilical arteries were measured by Doppler ultrasonography in nine small-for-gestational-age fetuses with elevated systolic/diastolic ratios of the umbilical arteries, seven small-for-gestational-age fetuses with normal flow patterns, and 14 appropriate-for-gestational-age fetuses with normal flow patterns. After delivery histomorphometric placental investigations were performed. Reduced end-diastolic flow velocities were significantly associated with both a reduction of vascularization within the terminal villi and adverse diffusion conditions, indicating insufficient functional maturity. The perfusion and diffusion capacity of small-for-gestational-age placentas with normal umbilical artery flow velocity waveforms was similar or even slightly better compared with the appropriate-for-gestational-age control values. These data suggest that Doppler flow velocimetry in the umbilical arteries is predictive of a vascular lesion within the placentas of small-for-gestational-age fetuses.

Velocity of Ophthalmic Arterial Flow Recorded by Doppler Ultrasound in Normal Subjects

Transcranial Doppler ultrasound (2 MHz) was used to measure ophthalmic arterial blood flow velocity in 60 normal subjects whose mean age (+/- standard deviation) was 54.9 +/- 17.3 years (30 women, mean age, 56.3 +/- 17.5 years and 30 men, mean age, 53.5 +/- 17.3 years). Three or more measurements were recorded from each eye at reference depths of 40 to 45 mm. The peak systolic flow velocity was 45.1 +/- 7.8 cm/sec, mean-enveloped flow velocity was 22.6 +/- 5.1 cm/sec, end diastolic flow velocity was 12.0 +/- 3.4 cm/sec, pulsatility index was 1.5 +/- 0.4, and resistivity index was 0.7 +/- 0.1. No significant differences of flow variables were found between genders. Statistically significant age-related losses of mean-enveloped flow velocity and end diastolic flow velocity were shown (P = .003 and .038). There were no significant differences of flow velocities between right and left eyes when comparing means. Differences greater than 20% between eyes were found in ten subjects (16.7%) for peak systolic flow velocity, in 18 subjects (30.4%) for mean-enveloped flow velocity, and in 21 subjects (34.8%) for end diastolic flow velocity, but resistivity indexes were comparable in all cases. Ten subjects had flow velocities measured at two different depths separated by 10 mm (40 to 45 mm vs 50 to 55 mm) in the same orbit and showed that peak systolic flow velocity and mean-enveloped flow velocity were significantly higher (P = .006 and .021) at the greater depth. Recognizable differences in shape of the spectrograms obtained from the younger subjects (< or = 30 years) and the older subjects (> or = 70 years) were found.