Blood Flow Velocity Waveforms Research Articles

An Embedded Device for Real-Time Noninvasive Intracranial Pressure Estimation.

The monitoring of intracranial pressure (ICP) is indicated for diagnosing and guiding therapy in many neurological conditions. Current monitoring methods, however, are highly invasive, limiting their use to the most critically ill patients only. Our goal is to develop and test an embedded device that performs all necessary mathematical operations in real-time for noninvasive ICP (nICP) estimation based on a previously developed model-based approach that uses cerebral blood flow velocity (CBFV) and arterial blood pressure (ABP) waveforms. The nICP estimation algorithm along with the required preprocessing steps were implemented on an NXP LPC4337 microcontroller unit (MCU). A prototype device using the MCU was also developed, complete with display, recording functionality, and peripheral interfaces for ABP and CBFV monitoring hardware. The device produces an estimate of mean ICP once per minute and performs the necessary computations in 410 ms, on average. Real-time nICP estimates differed from the original batch-mode MATLAB implementation of theestimation algorithm by 0.63 mmHg (root-mean-square error). We have demonstrated that real-time nICP estimation is possible on a microprocessor platform, which offers the advantages of low cost, small size, and product modularity over a general-purpose computer. These attributes take a step toward the goal of real-time nICP estimation at the patient's bedside in a variety of clinical settings.

ANTENATAL INVESTIGATION OF DUCTUS VENOSUS VELOCITY AS A METHOD OF DETECTING THE FETAL HEART FAILURE, CAUSED BY PARVOVIRUS B19 INFECTION

Background. The article describes the methods and results of investigation of blood flow velocity waveforms in fetal ductus venosus (DV). These studies are used to visualize the degree of fetal heart failure and determine its further clinical course.Objective. The study was aimed to predict the development of heart failure in the fetuses that were infected with parvovirus B19 infection during 11-14 gestation weeks by measuring the Doppler parameters of blood flow velocity in the DV.Methods. Our investigation involved 20 pregnant women aged from 18 to 30 years old who were infected with parvovirus B19 infection during the period from 11 to 14 weeks of gestation. The DV was determined by means of color Doppler. Fetal echocardiography (EchoCG) was performed by means of the ultrasound scanner Philips HD IIXE device (USA) using a transabdominal convex probe with the frequency of 3.5 MHz, operating in a CDC mode and the frequency filter at 100 Hz. The A-wave directivity evaluation in the DV was investigated according to the Guideline Principles of the Fetal Medicine Foundation (www.fetalmedicine.com). Statistical processing of data was carried out using the package of applied programs Microsoft Office Excel 2016 and Statistica 6, Stata 12.Results. In 16 of 20 (80%) fetuses we did not observe any absent or reversed A-wave flow in the DV during atrial contraction as well as any fetal echocardiographic pathological signs. In 2 (10%) cases a reversed A-wave flow in the DV in a combination with EchoCG-signs of overload of left side of heart, resulting in enlargement (dilatation) of left atrium and left ventricle were detected. In 2 (10%) cases the presence of a reversed A-wave flow in the DV and EchoCG-signs of fetal heart failure (reduction of cardiac output, significant dilatation of left ventricle) were evidenced.The results of the study confirm that with the expansion of fetal nuchal translucency thickness, the systolic blood flow velocity in the DV increases with the correlation coefficient r=0.594, which proves a linear dependence between these two ultrasonography parameters.Conclusions. The linear correlation between the presence of a reversed A-wave blood flow velocity in the DV and the overload of left side of fetal heart, development of heart failure (20% of the total number of examined women) were proved.

OP 34 Systolic notch in severe preeclampsie – A Doppler marker of maternal hemodynamic dysfunction?

Introduction A systolic notch in the uterine artery (UtA) is an ominous sign in severe preeclampsia (PE) and is scarcely referenced in the literature (Thaler, 1992; Polat, 2015). Timing and hemodynamic conditions for its appearance remain unclear. Objectives As PW velocity (PWV) is times faster than blood flow velocity, signs of PW reflection should be present in the blood flow velocity waveform (FVW), but is not easily visible. In PE maternal condition is impaired by cardiac dysfunction (Melchiorre, 2011) and arterial PW reflection is increased (Khalil, 2014). We speculate that a systolic notch coincides with the earlier arrival of a stronger reflected PW. Patients and methods The entire transit time of an outgoing and reflected PW is given by the time to inflection, T-infl, in the pressure waveform (Phan 2016). Half of this time corresponds to the 1-way travel time T from the aortic valve to the prodominant sites of reflection (Curtis 2007) and approximately to the UtA: T = (T-infl)/2 = t(AoV-UtA). UtA Doppler was performed in patients with PE. When a systolic notch was present, the time to inflection was assessed. A rough estimate of PWV was calculated dividing the 1-way travel distance D by the 1-way travel time T: PWV = D/T. The 1-way travel distance D = d(AoV-UtA), corresponds approximately to the sum of the lengths of aorta, common and internal iliac artery. Vessel lengths were taken from the literature and yield D = 56 cm (Matthys, 2007, Sherwin, 2003). Results In 6 singleton pregnancies with severe PE we found a systolic notch. Mean gestational age at the time of Doppler sampling was 29 ± 3wks and delivery by cesarean section was indicated within 1 week in all patients. Mean time to inflection, T-infl (±SD) was 123 ± 9 ms. Thus mean 1-way travel time T is 61 ms and mean maternal PWV = D/T = 560 mm/61 ms = 9.16 m/s. Conclusion The observed timing of the systolic notch in severe PE is considerably shorter than PW travel time in normal pregancy (Macedo 2008) and inicates the arrival of the reflected PW at the site of Doppler sampling. In addition, PWV was found to be abnormally increased, in accordance with reported PWV in PE (Khalil 2014, Katsipi 2014). Thus a systolic notch may be explained by increased PW reflection and may indicate maternal hemodynamic dysfunction.

The effect of maternal hyperoxygenation on fetal circulatory system in normal growth and IUGR fetuses. What we can learn from this impact

Purpose: The objectives of study were to assess and compare the effects of maternal hyperoxygenation on fetal circulation, in fetuses with intrauterine growth retardation and normal fetal growth.Methods: Twelve singleton pregnant women with normal fetal growth and 12 singleton pregnant women with intrauterine growth restriction were recruited. Mean gestational age of 35.2 ± 3.5 and 34.7 ± 3.9 weeks, respectively. Doppler blood flow velocity waveforms were obtained from the middle cerebral artery, umbilical, main and proximal right pulmonary arteries. Pulsatility indices were calculated for all the vessels. Peak systolic velocity was determined for the middle cerebral artery. Following baseline measurements; each woman received 70% humidified oxygen for 10 min. Doppler measurements were then repeated.Results: The pulsatility index in the middle cerebral artery increased significantly from 1.5 ± 0.27 to 1.88 ± 0.48, respectively (p = .006) in the high-risk group. However, it did not change significantly in the low-risk group. Hyperoxygenation caused a significant decrease in pulsatility indices in the pulmonary arteries for both groups.Conclusions: Hyperoxygenation interrupts the relative brain-sparing effect in the intrauterine growth retardation group, but it did not significantly change the pulsatility index of the middle cerebral artery in fetuses with adequate weight. The pulsatility index in the pulmonary arteries decreased significantly following hyperoxygenation.

Doppler Ultrasonography of the Central Retinal Vessels in Children With Brain Death.

The purpose of this observational study is to explore if bedside Doppler ultrasonography of the central retinal vessels has the potential to become an ancillary study to support the timely diagnosis of brain death in children. Seventeen-month prospective observational cohort. Forty-four bed pediatric medical and surgical ICU in an academic teaching hospital. All children 0-18 years old who were clinically evaluated for brain death at Children's National Health Systems were enrolled and followed until discharge or death. None. All patients had at least one ophthalmic ultrasound within 30 minutes of each brain death examination. The central retinal artery peak systolic blood flow velocity, resistive index, pulsatility index, and Doppler waveforms were evaluated in each patient. Thirty-five ophthalmic ultrasounds were obtained on 13 patients, 3 months to 15 years old, who each had two clinical examinations consistent with brain death. The average systolic blood pressure during the ultrasound examinations was 102 mm Hg (± 28), diastolic blood pressure 65 mm Hg (± 24), mean arterial pressure 79 mm Hg (± 23), heart rate 133 beats/min (± 27), temperature 36°C (± 0.96), arterial CO2 35 mm Hg (± 9), and end-tidal CO2 23 mm Hg (± 6). For all examinations, the average peak systolic velocity of the central retinal artery was significantly decreased at 4.66 cm/s (± 3.2). Twelve of 13 patients had both resistive indexes greater than or equal to 1, average pulsatility indexes of 3.6 (± 3.5) with transcranial Doppler waveforms consistent with brain death. Waveform analysis of the 35 ultrasound examinations revealed 11% with tall systolic peaks without diastolic flow, 17% with oscillatory flow, 29% showed short systolic spikes, and 23% had no Doppler movement detected. A rippling "tardus-parvus" waveform was present in 20% of examinations. This study supports that the combination of qualitative waveform analysis and quantitative blood flow variables of the central retinal vessels may have the potential to be developed as an ancillary study for supporting the diagnosis of brain death in children.

P18.03: Human uterine artery blood flow velocity waveforms following maternal glucose loading related to fetal size: a cross‐sectional observational study

P18.03: Human uterine artery blood flow velocity waveforms following maternal glucose loading related to fetal size: a cross‐sectional observational study

Noninvasive simultaneous measurement of blood pressure and blood flow velocity for hemodynamic analysis.

We describe a noninvasive and simultaneous measurement method of beat-by-beat blood pressure and blood flow velocity waveforms in the radial artery using tonometry and Doppler flowmetry. We conducted a subjective experiment in which hold-down pressure of tonometry was controlled for determining optimal hold-down pressure and the measurement accuracy under the optimal hold-down pressure was evaluated. As a result, blood pressure and blood flow velocity could be measured simultaneously without the influence of the hold-down pressure on the blood flow velocity. It was possible to analyze hemodynamic indicators, such as wave intensity and vascular impedance, with blood pressure and blood flow using the system. The proposed system for detecting unexpected fluctuations in blood pressure and the involved mechanisms may contribute to the treatment of cardiovascular diseases.

Placental structural abnormalities have detrimental hemodynamic consequences in a rat model of maternal hyperglycemia

IntroductionHuman type 1 diabetic pregnancy is associated with placental structural and hemodynamic abnormalities. We hypothesized that in rat fetuses of hyperglycemic dams, placental and fetal blood flow velocity waveforms demonstrate compromised hemodynamics when compared to control fetuses, and these hemodynamic parameters correlate with placental structural abnormalities at near term gestation. MethodsStreptozotocin-induced maternal hyperglycemia group comprised 10 dams with 107 fetuses and the control group 20 dams with 219 fetuses. Doppler-ultrasonographic examinations were performed at gestational days 13–14, 16–17, and 19–21. After the last examination, placentas were collected for morphologic, gene expression, and cytokine analysis. ResultsUmbilical artery (UA), descending aorta (DAO), and ductus venosus (DV) pulsatility indices (PI) were significantly higher at each study point in maternal hyperglycemia compared to controls. Placental size, glycogen storages, venous thrombosis formation, and fluid accumulation were increased in maternal hyperglycemia. Epidermal growth factor receptor (Edgfrb), platelet derived growth factor receptor beta polypeptide (Pdgfrb), and tumor necrosis factor receptor superfamily, member 12α (Tnfrsf12α) expressions were decreased. Interleukin (IL) −2 and −4 concentrations were decreased, and IL-1beta levels were increased in maternal hyperglycemia. UA PIs correlated positively with DV PIV, DAO PI, fluid accumulation, and glycogen storages. UA PIs correlated negatively with IL-4, Edgfrb, and Pdgfrb. DiscussionIn maternal hyperglycemia, placental and fetal hemodynamics were compromised during the last trimester of pregnancy compared to normoglycemic pregnancies. Placental structural, metabolic, and growth related gene expression, and inflammatory marker abnormalities were associated with hemodynamic compromise.

Human umbilical and fetal cerebral blood flow velocity waveforms following maternal glucose loading: a cross-sectional observational study.

Our aim was to study umbilical and fetal cerebral arterial blood flow velocity waveforms related to fetal biometric measures and maternal body mass index, glucose levels and parity following maternal oral glucose loading. The study had an experimental design in a cross-sectional observational study including 105 low-risk pregnancies (30-32weeks of gestation). Ultrasound Doppler measurements of umbilical and middle cerebral arterial (UA and MCA) velocity waveforms were performed before and at 2h after completed 75-g oral glucose tolerance tests (OGTT). We assessed changes in UA and MCA pulsatility indices (PI). MCA PI was significantly reduced following OGTT (p<0.001); these changes were not related to changes in fetal heart rate (r=-0.11, p=0.278). UA PI was also significantly reduced following OGTT (p=0.033); these changes were related to fetal heart rate (r=-0.47, p<0.001). This reduction was not significant (p=0.230) when the PI values were adjusted for fetal heart rate. The ratio MCA PI to UA PI was reduced (p=0.001). The effect of OGTT on MCA PI was not related to fetal abdominal circumference whereas the effect on the adjusted UA PI values was correlated to abdominal circumference (r=-0.20, p=0.045) but not to abdominal circumference Z-score (r=-0.16, p=0.115). The influence of OGTT on the Doppler parameters as well as heart rates was not related to prepregnant body mass index, glucose levels before or after OGTT, parity, fetal sex or gestational age. Maternal glucose loading seems to decrease fetal cerebral blood flow impedance independent of fetal size.

A study of role of Doppler ultrasound in Pregnancy induced hypertension (PIH) and perinatal outcome

Background: The main purpose of providing antenatal care is to identify women at risk of complications as a result of impaired uteroplacental circulation such as Pregnancy induced hypertension (PIH) and Preclampsia. Aim: To describe practical application of doppler ultrasound in obstetrics with analysis of blood flow velocity waveform in PIH and to examine perinatal outcome in pregnancies with altered Doppler indices. Material and Method: This is a prospective study of 41 pregnant women with pregnancy induced hypertension (PIH) evaluated sonographically with colour Doppler and to be followed subsequently for any adverse perinatal outcome. Result: Out of 41 cases 73.1% of cases were found in 20-29 yrs age group. 26 cases had abnormal uterine artery Doppler indices accounting for 63.46%, while 15 cases had a normal Doppler indices accounting for 36.53%. Out of 41 cases, 25 cases had abnormal Middle cerebral artery. In our study 14 cases had abnormal umbilical artery Doppler indices accounting for 34.2%, while 27 cases had a normal Doppler indices accounting for 65.8%., out of 41 cases in our study 6 cases had Reversal of a wave in Ductus Venosus waveform that is in 14.6%. In this study total 5 cases (35.7%) of perinatal mortality were seen. Conclusion: The knowledge of uterine and umbilical artery waveform may help to improve pregnancy management and any permit identification and assessment of pregnancy induced hypertension at earliest gestation age as compared to other antepartum test modalities.

Ductus venosus blood flow velocity waveforms during the early second trimester of pregnancy in a Thai population.

To establish reference ranges for ductus venosus (DV) blood flow velocities and indices during the early second trimester. A cross-sectional DV Doppler study of fetuses at 15-22 weeks of gestation was conducted at Songklanagarind Hospital, Songkhla, Thailand, during 2013-2014. The peak forward velocities were recorded and the DV indices were calculated. Predicted reference ranges based on the 5th and 95th percentiles according to the week of gestation were constructed. Among 371 fetuses, measurement of DV Doppler waveforms in the sagittal plane was achieved in 97.5% of cases. With advancing pregnancy (weeks 15 to 22), the DV velocities during ventricular systole, early diastole, and atrial contraction increased from 47.48 cm/s to 68.22 cm/s, 42.23 cm/s to 60.52 cm/s, and 15.94 cm/s to 34.84 cm/s, respectively. The time-averaged maximum value increased from 37.61 cm/s to 55.42 cm/s. The DV indices-pulsatility index for the vein, peak velocity index for the vein, preload index, and systolic/a-wave ratio-decreased from 0.79 to 0.59, 0.71 to 0.53, 0.63 to 0.47, and 2.72 to 1.90, respectively. The systolic/diastolic ratio remained relatively constant at 1.12. Normal reference ranges for DV flow velocities and indices during the early second trimester were established.

Reproduction of ICP Waveform Changes in a Mathematical Model of the Cerebrospinal Circulatory System.

This study describes the establishment of a model of cerebral blood flow dynamics using cerebral blood flow velocity and intracranial pressure waveforms.

Blood flow velocity waveforms in the middle cerebral artery during cycle exercise and recovery

The blood flow velocity waveforms in the middle cerebral artery (MCA) were measured under incremental cycle exercises and following recovery using the transcranial Doppler ultrasound velocimeter. At rest, the flow waveform in the MCA is characterized by a high forward flow at end-diastole, which is as much as half peak-systolic velocity. The peak-systolic velocity Vs was found to markedly rise in proportion with exercise intensity under mild and moderate intensities (up to 110 W) of exercise, while it tended to keep constant values under higher exercise intensities (above 110 W). The end-diastolic velocities Vd showed no significant change under mild exercise intensity and gradually increased under moderate exercise intensities. It was also found that the Vd values decreased more rapidly than Vs in the recovery phase. Such nonlinear changes in Vs and Vd indicate that the influence of exercise on cerebral blood flow is more complicated than previously thought.

Doppler Audio Signal Analysis as an Additional Tool in Evaluation of Umbilical Artery Circulation

Purpose To investigate the predictive capacity of a new method for sound spectrum analysis of Doppler signals recorded from the umbilical artery in high-risk pregnancies. Material and Methods The retrospective study comprised 127 pregnant women with various pregnancy complications between 23 and 39 gestational weeks. Umbilical artery blood flow velocity waveforms were recorded with Doppler ultrasound and characterized by pulsatility index (PI) and blood flow class (BFC). Doppler audio signals were stored on a digital video recorder and the sound frequency at the energy level 15 dB below its peak (MAXpeak-15 dB) was estimated off-line. The prediction of probability for composite adverse pregnancy outcome (operative delivery for fetal distress, admission to neonatal intensive care unit, perinatal death) was evaluated using the area under the curve (AUC) of the receiver operating characteristics (ROC) curve. Results With increasing umbilical artery BFC, the MAXpeak-15 dB frequencies decreased (p < 0.0001) and the PI increased (p < 0.0001). The ROC AUCs for adverse outcome for MAXpeak-15 dB and for PI were 0.842 and 0.836 (p = 0.88), respectively. For the combination of MAXpeak-15 dB and PI, the corresponding AUC was 0.894, significantly higher than that of PI (p < 0.03) and of MAXpeak-15 dB (p < 0.05). Conclusion Umbilical artery Doppler sound spectrum analysis might be a useful supplement to PI in the clinical evaluation of fetoplacental circulation.

OP20.07: Human umbilical and fetal cerebral blood flow velocity waveforms following maternal glucose loading: a cross‐sectional observational study

OP20.07: Human umbilical and fetal cerebral blood flow velocity waveforms following maternal glucose loading: a cross‐sectional observational study

Wavelet Analysis of Doppler Flow Velocity Waveforms from the Ocular Circulation Detects Abnormalities in Micro-vascular Function in Heart Failure

Aims: Many pathological processes may result in Heart Failure (HF), however, the final clinical phenotype appears to be common to all aetiologies. Microvascular abnormalities in HF have been demonstrated in a variety of vascular beds however the effect of HF on the retrobulbar circulation is not known. We employed a novel method of analysing blood flow velocity waveforms in order to quantify changes in the Doppler signal obtained from the retrobulbar arteries between HF patients and controls. FMD was also assessed. Methods and Results: 32 patients with systolic HF on maximal medical therapy and 10 age and sex-matched controls were studied. Doppler waveforms were obtained from the ophthalmic, central retinal and brachial artery in all subjects. Waveforms were analysed using a wavelet technique which expressed each waveform in constituent frequency bands, allowing direct comparisons to be made. Significant differences were found in ophthalmic and central retinal waveforms but not brachial waveforms between patients and controls. Flow mediated dilatation was also found to be abnormal in patients. Conclusion: This study suggests that abnormalities in microvascular function in the retrobulbar circulation are present in HF and that these changes can be detected by a novel wavelet analysis technique.

The effect of maternal betamethasone administration on Doppler flow velocity parameters of the fetal branch pulmonary artery

To investigate the effects of antenatal betamethasone on fetal pulmonary blood flow velocity waveforms. The study comprised 28 women with singleton pregnancies at high risk for preterm delivery. They were treated with two doses of 12 mg betamethasone intramuscularly 24 h apart to enhance lung maturity. Flow velocity waveforms were recorded with Doppler ultrasound from the middle segment of pulmonary artery (PA). Compared with the pretreatment mean value, a significant decrease in the pulmonary artery pulsatility (PI) and the resistance indexes (RI) was noted at 24 h and 48 h after the administration of first dose of betamethasone (p = 0.022 and p = 0.018 for PI and p = 0.001 and p = 0.004 for RI, respectively). After 7 days, the pulmonary artery velocity waveforms returned to the types of waveform observed before treatment (p = 0.216 for PI and p = 0.249 for RI). Maternal antenatal betamethasone resulted in a significant transient decrease in the pulsatility and the resistance indexes in the pulmonary artery. These findings indicate a direct effect of betamethasone on fetal pulmonary circulation.

Advanced dynamic Doppler flow of the pulmonary artery in a normal population: reference values from 18 to 41 weeks of gestation calculated by automatic Doppler waveform analysis

The aim of the present cross-sectional prospective study was to establish Doppler reference ranges for blood flow velocity waveforms (V max, V mean and V min) and resistance indices (PI, RI) of the fetal pulmonary arteries using the new pulsed-wave color advanced dynamic flow (ADF) Doppler technique. Data were collected in 206 low-risk pregnancies at 18-41 weeks of gestation. The measurements were obtained in the proximal pulmonary artery near the first bifurcation in the absence of fetal body or breathing movements. The pulsatility index (PI) in the pulmonary artery showed mean increases of 2.43-3.59 between gestational weeks 18 and 42. A similar pattern was observed for the resistance index (RI) with increases of 0.79-0.90. Increases in systolic (V max), mean (V mean) and end diastolic (V min) blood flow velocities of 36.0-63.3, 10.8-19.9 and 5.71-7.53 cm/s, respectively, were noted during the observation interval. The ranges for blood flow velocities and impedance indices in the fetal pulmonary artery calculated by the authors may serve as reference values to help distinguish a normal patient population from patients carrying fetuses at high risk for neonatal lung disease in antenatal examinations.

Pregnancy in homozygous familial hypercholesterolemia – a successful case

Pregnancy in homozygous familial hypercholesterolemia – a successful case

Abnormal ductus venosus pulsatility index in the absence of concurrent umbilical vein pulsations does not indicate worsening fetal condition

Recordings of blood flow velocity waveforms in the ductus venosus (DV) and umbilical vein (UV) are routinely used in order to predict fetal condition in high-risk pregnancies. The aim of this study was to investigate the relationship between pathological blood flow in the two vessels and perinatal outcome. High-risk pregnancies (n = 11 863) admitted from 1993 to 2011 for blood-flow examination, including recordings of DV pulsatility index for veins (DV-PIV) and UV pulsations, were included. The results were related to perinatal outcome, using the last Doppler examination prior to delivery in the analysis. Abnormal DV-PIV was observed in 3.9% of cases, intra-abdominal UV pulsations in 1.3% and pulsations in the cord in 0.7%. As expected, the rate of UV pulsations increased with increasing DV-PIV Z-score. Fetuses with a pathological DV-PIV, but without UV pulsations, showed fewer signs of compromise. This was also true for cases with a DV-PIV ≥ 4 SDs above the mean (53.7% had steady flow in the UV). In contrast, the occurrence of UV pulsations seemed to be an indicator of fetal compromise, regardless of level of DV-PIV. Abnormal fetal venous blood velocity is related to adverse outcome in high-risk pregnancies. However, abnormal DV-PIV is not a reliable indicator of fetal compromise unless UV pulsations are concurrently present, and should not be regarded an indication for emergency delivery.