Pulsatile blood flow plays an important role in maintaining normal vascular endothelial function. Quantitative measurement of pulsatility of artery blood pressure and blood flow in dogs and effects of enhanced external counterpulsation (EECP) on the pulsatility were taken in this study. Common carotid artery blood pressure and blood flow were measured in 6 beagle dogs that had suffered from an acute myocardial infarction 6 weeks before. A 6F tip transducer catheter was inserted into the right common carotid artery to measure blood pressure, and blood flow was measured in the left common carotid artery by an electromagnetic blood flow probe under anesthesia before and during EECP. Blood pulse pressure, pulsatility index (ratio of peak pressure to end diastolic pressure) and standard deviation of blood pressure were calculated to evaluate the pulsatility of arterial blood pressure. Blood pulse flow, pulsatility index (ratio of peak flow to trough flow) and standard deviation of blood flow were calculated to evaluate the pulsatility of blood flow. Mean vascular resistance (MVR) was calculated as MVR = mean blood pressure/mean blood flow. Blood pulse pressure, pulsatility index and standard deviation of blood pressure were elevated from 30 +/- 9 mmHg, 1.26 +/- 0.05 and 8.7 +/- 2.5 mmHg to 43 +/- 8 mmHg (P < 0.05), 1.54 +/- 0.13 and 12.4 +/- 2.0 mmHg (P < 0.05) before and during EECP, respectively. Blood pulse flow, pulsatility index and standard deviation of blood flow were elevated from 317 +/- 48 ml/min, 2.85 +/- 0.21 and 96 +/- 21 ml/min to 447 +/- 88 ml/min, 4.56 +/- 0.90 and 131 +/- 39 ml/min before and during EECP (P < 0.05). MVR was decreased from 578 +/- 72 before EECP to 476 +/- 85 Wood units during EECP(P < 0.05). These data demonstrate that EECP gives an elevation of pulsatility to blood pressure and blood flow, thus it may lead to the decrease of vascular resistance.
Animals ; Blood Pressure ; Carotid Arteries ; physiology ; Counterpulsation ; Dogs ; Hemodynamics ; Pulsatile Flow ; Regional Blood Flow ; Vascular Resistance

To understand the local hemodynamics of modified TF-AHCB carotid bifurcation model, using particle image velocimetry technique to measure the instantaneous velocity distribution of the model attatched to a circuit. The velocity was controlled by regulating the height of the reservoir. The working fluid consists of glycerine and water mixture with viscosity of 3.75 mPa.s similar to human blood. Instantaneous velocity fields were obtained by PIV and the shear stresses were calculated according to the velocity. The results showed that inside the model, there were a large flow separation and an anticlockwise rotating vortex on the lateral wall of ICA, The location and distance of the vortex changed with the flow velocity. The higher the flow velocity, the smaller the vortex distance, and the farther the location. The shear stresses on the lateral wall were significantly lower in all work condition. And there a low shear stress kernel when the velocity was lower than 0.839 m/s. The location of the low shear stress was just the position of atherosclerosis. The flow pattern inside the model consists of large flow separation and vortex zones. And there are low shear stress zones at the lateral wall of ICA, Where are thought to be associated with the genesis of atherosclerosis.
Blood Flow Velocity ; Carotid Arteries ; physiology ; Models, Cardiovascular ; Pulsatile Flow ; Regional Blood Flow ; physiology ; Rheology ; methods ; Stress, Mechanical

The parameters which can influence heat transfer of tongue were analyzed in order to reveal the reason why the tongue temperature fields of people with different diseases are distinct. Firstly, the research parameters were determined by experiment results, including the reference humidity of tongue surface, metabolic heat of tongue tissue, the entrance position of root vessel, the diameter of root vessel, the blood flow rate, and the bifurcation exponent of vascular tree. Then the effect of each parameter on the value and the distributing rule of tongue temperature field was analyzed by using a mathematic model of lingual temperature field. Results show that all these parameters have effects on the temperature value of tongue. The reference humidity of tongue surface, the metabolic heat of tongue tissue and the entrance position of root vessel are distinct influences on the distributing rule of tongue temperature.
Body Temperature ; physiology ; Humans ; Humidity ; Models, Theoretical ; Regional Blood Flow ; Thermal Conductivity ; Tongue ; blood supply ; physiology

Utilizing the third-order polynomial curve fitted to the experimental data, which represents the relationship between cerebral blood flow (CBF) and mean artery blood pressure (MABP), we constructed a lumped-parameter dynamic model with 5 elements. In this model; the resistance is not constants it is determined by the fitted curve. We simulated the process of CBF autoregulation numerically by solving the govern equation of this model and got quite accurate results. Furthermore, we studied the influence of hemodynamic parameters on the CBF autoregulation by this model and proved that the characteristic resistance is the most important factor.
Blood Flow Velocity ; Blood Pressure ; physiology ; Cerebrovascular Circulation ; physiology ; Homeostasis ; Humans ; Hypotension ; physiopathology ; Models, Biological ; Oxygen ; metabolism ; Regional Blood Flow

To explore the changes of wall shear stress(WSS) effect on arterial endothelial cell(EC) apoptosis after reducing arterial blood flow. The reducing flow model was established in 60 rabbits. Endothelial stretched preparations were made at 8 different time intervals from 0 to 30 days. The apoptosis rate of arterial endothelial cells (AEC) was measured with TdT-mediated dUTP-biotin nick end labeling(TUNEL) method. The results showed that the apoptosis rate of AEC was significantly higher from 1 day to 7 days after decreasing WSS than that of control, which peaked on day 3. While with progressively increasing in WSS, the apoptosis rate restored to the level of control from 14 days to 30 days. These suggest that the apoptosis state of AEC might be markedly influenced by the changes of WSS. The persist decreasing of WSS may be the important factor which induces the cell apoptosis.
Animals ; Apoptosis ; Arteries ; cytology ; physiology ; Endothelium, Vascular ; cytology ; physiology ; Male ; Rabbits ; Regional Blood Flow ; Shear Strength

To understand the local fluid dynamics for different designs of Fontan operation, five models were made of Pyrex glass to facilitate in vitro study. Models I, II and III had the same position as the center of the anastomosis of the IVC (inferior vena cava) with that of the SVC (superior vena cava), but Models IV and V had 10 mm offset between them. As well, the anastomotic junction angles were different (Models I and IV: 90 degrees, Models II and V: 70 degrees, Model III: 45 degrees). These models were then connected to a flow loop for flow visualization study. In Model I, no dominant vortex was seen in the central region of the junction, but a large unstable vortex was created in Models II and III. In Models IV and V, a significant stagnation region was created in the middle of the offset region. It also showed that the flow distribution from the IVC and SVC to the LPA (left pulmonary artery) and RPA (right pulmonary artery) depends more on the offset of the junction than on the anastomotic junction angle. Generally, as the total flow rates increased, the pressures in the models increased.
Blood Pressure ; Hemodynamics ; Human ; Models, Cardiovascular* ; Regional Blood Flow ; Gov't Venae Cavae/physiology*

A hemodynamic model of capillary and tissue, in which tissue pressure changed with swing manipulation of Traditional Chinese Medical Massage (TCMM), is presented in this paper to explain the hemodynamic mechanism of swing manipulation. Blood flowed in capillary with low Reynolds number. Plasma exuded through capillary according to the Starling's Law. Tissue pressure changed linearly with the massage force measured. Blood apparent viscosity, plasma protein concentration and red cell's hematocrit were taken into account. Capillary flow rate, blood apparent viscosity, filtration rate and filtration fraction with dynamical change of tissue pressure were calculated numerically, and were compared with those in static tissue pressure condition. Results showed that, dynamical change of tissue pressure led to the increase of capillary flow rate and the decrease of blood apparent viscosity, which qualitatively explained the hemodynamic mechanism of "promoting blood circulation and removing blood stasis" in swing manipulation of TCMM.
Biomechanical Phenomena ; Blood Flow Velocity ; Blood Viscosity ; Capillaries ; physiology ; Hematocrit ; Hemodynamics ; Humans ; Massage ; Models, Cardiovascular ; Pressure ; Regional Blood Flow

The reliability and reliable indexes of quantitative assessment of coronary flow reserve (CFR) by using time-intensity curve (TIC) via myocardial contrast echocardiography were investigated. The TIC variables were obtained by employing acoustic densitometry (AD) technique before and after acetylcholine (Ach) injection in 12 dogs. Meanwhile, the correlation between these variables and CFR was analyzed. Among the variables derived from TIC, peak intensity (PI), area under the curve (AUC) and descending slope (DS) were increased significantly (P < 0.05) with the increase of coronary blood flow after Ach injection. Conversely, time-to-peak (TP), half-time of descent (HT), and mean-transit-time (MTT) were decreased remarkably (P < 0.0001). The PI and AUC ratios from post- to pre-Ach injection were strongly associated with CFR with the correlation coefficient (r) being 0.8366 and 0.8824, respectively. It is reliable by using the variables derived from TIC with myocardial contrast echocardiography to quantitatively evaluate regional myocardial CFR. The PI and AUC ratios from post- to pre-Ach injection are the reliable indexes for quantitative assessment of CFR.
Blood Flow Velocity/physiology ; Contrast Media ; Coronary Circulation/*physiology ; Coronary Vessels/physiology ; Coronary Vessels/ultrasonography ; *Echocardiography/methods ; *Image Processing, Computer-Assisted ; Observer Variation ; Regional Blood Flow/drug effects ; Regional Blood Flow/physiology ; Reproducibility of Results ; Ultrasonography, Interventional

The maximum frequency waveforms of Doppler ultrasound blood flow signals were analyzed using a multi-scale wavelet transform. The variation of maxima of wavelet transform modulus under various scales was extracted from the time-scale representation. This novel approach was applied to the analysis of Doppler signals from carotid blood flow. It was found that the shape of this variation from cases with normal cerebral vessels differed from those associated with abnormal cases. The curve was fitted by a polynomial, and its coefficients were put into a back-propagation (BP) neural network to make a classification. The clinical experiments showed that this approach got good performance and could be a new means in the clinical diagnosis of cerebral vascular disease.
Algorithms ; Angiography ; Carotid Arteries ; physiology ; Echocardiography, Doppler ; Humans ; Neural Networks (Computer) ; Regional Blood Flow ; Wavelet Analysis

A theoretical model was developed to simulate the coupling between the adhered leukocyte and blood flow. Methods of computational fluid dynamics (CFD) were introduced to analyze the distributions of the shear stress and the pressure on the cell surface. Meanwhile, the hemodynamical parameters were measured with laser Doppler velocimetry. The results showed that the deformation index of the leukocyte was increased with initial contact angle and Reynolds number. The blood flow induced the redistributions of the shear stress and pressure on the surface of the cell, but the maximum shear stress was on the top point of the cell. It suggests that the non-uniform distribution of shear stress on the cell surface may play a particular role in the change of cell shape and functions.
Blood Circulation ; physiology ; Cell Adhesion ; Hemodynamics ; Humans ; Leukocytes ; cytology ; physiology ; Models, Biological ; Regional Blood Flow ; Shear Strength