Abstract 271: Continuous Amplitude Spectral Area May Reflect Adequacy of Myocardial Perfusion Before Attempting Defibrillation

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Raúl J Gazmuri ◽  
Christopher L Kaufman ◽  
Herbert K Whitehouse ◽  
Alvin Baetiong ◽  
Jeejabai Radhakrishnan
Keyword(s):  
Blood Flow ◽  
Myocardial Perfusion ◽  
High Flow ◽  
Low Flow ◽  
Swine Model ◽  
Coronary Perfusion ◽  
Electrical Shock ◽  
Spectral Area ◽  
Electrical Shocks ◽  
Initial Shock

Background: Previous studies have shown that analysis of the VF amplitude-spectral area (AMSA) contains information predictive of electrical shock success. However, the underlying factors that determine AMSA remain elusive. We developed an open-chest swine model of VF in which we modeled “average CPR” followed by “highly effective CPR” using extracorporeal circulation (ECC) and assessed AMSA in relation to adequacy of coronary perfusion. Methods: VF was electrically induced and left untreated for 8 min in 8 pigs after which ECC was started and maintained for 10 min adjusting the flow to generate a coronary perfusion pressure (CPP) of 10 mmHg (low-flow ECC). After delivery of an initial shock, the ECC flow was increased and titrated to secure a mean aortic pressure of 40 mmHg (high-flow ECC) delivering additional electrical shocks at 60 s intervals. Blood flow through the left anterior descending (LAD) artery was reported relative to baseline (LAD rel). AMSA was measured continuously with a 2.1 s timeframe and a Tukey window that moved ahead every 0.5 s, and was averaged every min for this report (Figure). Results: AMSA increased during the initial 5 min of low-flow ECC, but subsequently decreased (Figure). The initial shock uniformly failed to terminate VF prompting increases in ECC to high-flow, which then resulted in the return of spontaneous circulation in each instance after 3 to 5 shocks. During the high-flow ECC, AMSA initially increased but then gradually decreased for reasons that are not clear. Before attempting defibrillation, AMSA was positively correlated with LAD rel (r=0.73, p=0.04). Conclusion: The study provides intriguing data showing changes in AMSA that are time dependent and likely influenced by myocardial perfusion and the effects of electrical shocks on the myocardium. The present study also suggests that the level of AMSA prior to attempting defibrillation may be influenced by the efficacy with which the CPR intervention generates coronary blood flow.

Abstract 10911: Amplitude Spectral Area to Guide Shock and Epinephrine Delivery in a Swine Model of Ventricular Fibrillation and Closed-Chest Resuscitation

Circulation ◽  
2021 ◽  
Vol 144 (Suppl_2) ◽  
Author(s):  
Salvatore Aiello ◽  
Jenna Mendelson ◽  
Alvin Baetiong ◽  
Jeejabai Radhakrishnan ◽  
Raul J Gazmuri
Keyword(s):  
Statistical Significance ◽  
Sudden Cardiac Arrest ◽  
Coronary Perfusion Pressure ◽  
Spontaneous Circulation ◽  
Swine Model ◽  
Coronary Perfusion ◽  
Shock Delivery ◽  
Electrical Shock ◽  
Spectral Area ◽  
Tailored Approach

Introduction: VF accounts for ~30% of all sudden cardiac arrest episodes. VF signal analysis in the frequency domain - calculating the amplitude spectral area (AMSA) - can inform on the probability that an electrical shock could terminate VF followed by return of spontaneous circulation (ROSC). BLS guidelines require delivery of shocks every 2 min and epinephrine every 4 min. Yet, shocks often do not terminate VF and may injure the myocardium. We have previously reported that guiding the timing of shock delivery based on AMSA reduces myocardial injury and improves outcome. Epinephrine is given to increase the coronary perfusion pressure (CPP) and therefore myocardial blood flow but has detrimental effects on post-resuscitation myocardial function and possibly on neurological outcome. Hypothesis: Monitoring AMSA during CPR could be used not only to guide shock delivery but also to avoid administering epinephrine when AMSA predicts a high probability of shock success, reserving epinephrine when AMSA predicts a low probability of shock success and additional CPP increase might be helpful. Methods: In a swine model of electrically induced VF and mechanical chest compressions, two resuscitation protocols were compared in 8 pigs each: (1) A guidelines-driven (GD), delivering shocks and epinephrine guided by the current BLS protocol and (2) An AMSA-driven, delivering shocks and epinephrine guided by AMSA (ADSE). VF was untreated for 10 min and pigs that achieved ROSC were monitored for 240 min. Results: Compared to GD, ADSE was associated with a shorter time to ROSC (400±80 vs 569±16 sec, p=0.034) and higher survival rate at 240 minutes with borderline statistical significance (7/8 vs 3/8, p=0.059). ADSE required fewer shocks (3±2 vs 5±2, p=0.026) and received fewer doses of epinephrine (median [interquartile range], 1[1-1] vs 2[1.3-3], p=0.038). Conclusions: Resuscitation with the ADSE protocol was superior to the GD protocol resulting in a shorter time to ROSC with improved survival requiring fewer shocks and fewer epinephrine doses. The ADSE protocol represents a more tailored approach to resuscitation enabling delivery of resuscitation interventions with higher precision and consequently minimizing their associated adverse effects.

scholarly journals Increased plasma angiotensin II in postural tachycardia syndrome (POTS) is related to reduced blood flow and blood volume

2006 ◽  
Vol 110 (2) ◽  
pp. 255-263 ◽  
Author(s):  
Julian M. Stewart ◽  
June L. Glover ◽  
Marvin S. Medow
Keyword(s):  
Blood Flow ◽  
Angiotensin Ii ◽  
Blood Volume ◽  
High Flow ◽  
The Other ◽  
Low Flow ◽  
Postural Tachycardia Syndrome ◽  
Peripheral Blood Flow ◽  
Ang Ii ◽  
Postural Tachycardia

POTS (postural tachycardia syndrome) is associated with low blood volume and reduced renin and aldosterone; however, the role of Ang (angiotensin) II has not been investigated. Previous studies have suggested that a subset of POTS patients with increased vasoconstriction related to decreased bioavailable NO (nitric oxide) have decreased blood volume. Ang II reduces bioavailable NO and is integral to the renin–Ang system. Thus, in the present study, we investigated the relationship between blood volume, Ang II, renin, aldosterone and peripheral blood flow in POTS patients. POTS was diagnosed by 70° upright tilt, and supine calf blood flow, measured by venous occlusion plethysmography, was used to subgroup POTS patients. A total of 23 POTS patients were partitioned; ten with low blood flow, eight with normal flow and five with high flow. There were ten healthy volunteers. Blood volume was measured by dye dilution. All biochemical measurements were performed whilst supine. Blood volume was decreased in low-flow POTS (2.14±0.12 litres/m2) compared with controls (2.76±0.20 litres/m2), but not in the other subgroups. PRA (plasma renin activity) was decreased in low-flow POTS compared with controls (0.49±0.12 compared with 0.90±0.18 ng of Ang I·ml−1·h−1 respectively), whereas plasma Ang II was increased (89±20 compared with 32±4 ng/l), but not in the other subgroups. PRA correlated with aldosterone (r=+0.71) in all subjects. PRA correlated negatively with blood volume (r=−0.72) in normal- and high-flow POTS, but positively (r=+0.65) in low-flow POTS. PRA correlated positively with Ang II (r=+0.76) in normal- and high-flow POTS, but negatively (r=−0.83) in low-flow POTS. Blood volume was negatively correlated with Ang II (r=−0.66) in normal- and high-flow POTS and in five low-flow POTS patients. The remaining five low-flow POTS patients had reduced blood volume and increased Ang II which was not correlated with blood volume. The data suggest that plasma Ang II is increased in low-flow POTS patients with hypovolaemia, which may contribute to local blood flow dysregulation and reduced NO bioavailability.

The Effect of Altered Cerebral Blood Flow on the Cerebral Kinetics of Thiopental and Propofol in Sheep

2000 ◽  
Vol 93 (4) ◽  
pp. 1085-1094 ◽  
Author(s):  
Richard N. Upton ◽  
Guy L. Ludbrook ◽  
Cliff Grant ◽  
David J. Doolette
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Random Order ◽  
High Flow ◽  
Low Flow ◽  
Flow State ◽  
Concentration Difference ◽  
Blood Flows ◽  
Kinetics Of ◽  
The Brain

Background Thiopental and propofol are highly lipid-soluble, and their entry into the brain often is assumed to be limited by cerebral blood flow rather than by a diffusion barrier. However, there is little direct experimental evidence for this assumption. Methods The cerebral kinetics of thiopental and propofol were examined over a range of cerebral blood flows using five and six chronically instrumented sheep, respectively. Using anesthesia (2.0% halothane), three steady state levels of cerebral blood flow (low, medium, and high) were achieved in random order by altering arterial carbon dioxide tension. For each flow state, 250 mg thiopental or 100 mg propofol was infused intravenously over 2 min. To quantify cerebral kinetics, arterial and sagittal sinus blood was sampled rapidly for 20 min from the start of the infusion, and 1.5 h was allowed between consecutive infusions. Various models of cerebral kinetics were examined for their ability to account for the data. Results The mean baseline cerebral blood flows for the "high" flow state were over threefold greater than those for the low. For the high-flow state the normalized arteriovenous concentration difference across the brain was smaller than for the low-flow state, for both drugs. The data were better described by a model with partial membrane limitation than those with only flow limitation or dispersion. Conclusions The cerebral kinetics of thiopental and propofol after bolus injection were dependent on cerebral blood flow, despite partial diffusion limitation. Higher flows produce higher peak cerebral concentrations.

scholarly journals Remodeling of Resistance Arteries in Renal Failure: Effect of Endothelin Receptor Blockade

2001 ◽  
Vol 12 (10) ◽  
pp. 2040-2050 ◽  
Author(s):  
KERSTIN AMANN ◽  
GABRIEL MIL TENBERGER-MIL TENYI ◽  
AURELIA SIMONOVICIENE ◽  
ANDREAS KOCH ◽  
STEPHAN ORTH ◽  
...  
Keyword(s):  
Renal Failure ◽  
Blood Flow ◽  
High Flow ◽  
Mesenteric Arteries ◽  
Low Flow ◽  
Normal Flow ◽  
Flow Conditions ◽  
First Order ◽  
The Media ◽  
Intimal Thickness

Abstract. Remodeling of vessels is a known feature of renal failure, but it is unclear whether this represents an appropriate or inappropriate response to the known changes in blood flow, shear stress, and wall tension. To investigate remodeling in response to variations in blood flow, first-order mesenteric arteries were exposed to high- and low-flow conditions via the ligation of second-order branches, according to the technique described by Pour-ageaud and De Mey. The resulting changes in vessel geometric features, relative proportions of intima and media, submicroscopic structure, and immunostaining for proliferating cell nuclear antigen (PCNA), endothelin-1 (ET-1), and ETAreceptors were assessed in first-order mesenteric arteries under low-flow and high-flow conditions. Subtotally nephrectomized (SNX) animals were compared with sham-operated rats. Animals either were left untreated or were treated with the ETAreceptor antagonist (ET-RA) LU-135252, because of suggestions in the literature that ET is involved in vascular remodeling in uremia. A highly significant increase in intimal thickness was noted in low-flow arteries (4.21 ± 1.39 μm) of SNX animals, compared with normal-flow arteries (2.06 ± 0.61 μm), but this increase was not observed in sham-operated rats (1.38 ± 0.77 in low-flow arteriesversus2.40 ± 0.35 μm in normal-flow arteries). The increase in intimal thickness in low-flow arteries was abrogated by ET-RA. The medial thickness was increased in untreated SNX animals (19.5 ± 3.61 μm), compared with sham-operated rats, and this increase was also prevented by ET-RA. The medial thickness was not affected by low flow in either sham-operated or SNX animals. In parallel, the number of PCNA-positive intimal cells was higher in low-flow, but not high-flow, arteries of SNX rats, compared with sham-operated rats. No significant change was observed in sham-operated animals. In the media, the number of PCNA-positive cells was higher in untreated SNX animals than in sham-operated rats. The number was even more markedly increased in high-flow, but not low-flow, vessels. This increase was abrogated by ET-RA. It is concluded that, in uremic animals, the response of the intima to low flow and the response of the media to high flow are exaggerated. Both responses are apparently mediated by ET.

scholarly journals Targeted Delivery of Electrical Shocks and Epinephrine, Guided by Ventricular Fibrillation Amplitude Spectral Area, Reduces Electrical and Adrenergic Myocardial Burden, Improving Survival in Swine

2021 ◽  
Author(s):  
Salvatore R. Aiello ◽  
Jenna B. Mendelson ◽  
Alvin Baetiong ◽  
Jeejabai Radhakrishnan ◽  
Raúl J. Gazmuri
Keyword(s):  
Ventricular Fibrillation ◽  
Targeted Delivery ◽  
Myocardial Dysfunction ◽  
Spontaneous Circulation ◽  
Left Ventricular ◽  
Rank Test ◽  
Swine Model ◽  
Spectral Area ◽  
Electrical Shocks ◽  
Outcome Improvement

Background We previously reported that resuscitation delivering electrical shocks guided by real‐time ventricular fibrillation amplitude spectral area (AMSA) enabled return of spontaneous circulation (ROSC) with fewer shocks, resulting in less myocardial dysfunction. We now hypothesized that AMSA could also guide delivery of epinephrine, expecting further outcome improvement consequent to less electrical and adrenergic burdens. Methods and Results A swine model of ventricular fibrillation was used to compare after 10 minutes of untreated ventricular fibrillation a guidelines‐driven (n=8) resuscitation protocol, delivering shocks every 2 minutes and epinephrine every 4 minutes, with an AMSA‐driven shocks (n=8) protocol, delivering epinephrine every 4 minutes, and with an AMSA‐driven shocks and epinephrine (ADSE; n=8) protocol. For guidelines‐driven, AMSA‐driven shocks, and ADSE protocols, the time to ROSC (mean±SD) was 569±164, 410±111, and 400±80 seconds ( P =0.045); the number of shocks (mean±SD) was 5±2, 3±1, and 3±2 ( P =0.024) with ADSE fewer than guidelines‐driven ( P =0.03); and the doses of epinephrine (median [interquartile range]) were 2.0 (1.3–3.0), 1.0 (1.0–2.8), and 1.0 (0.3–3.0) ( P =0.419). The ROSC rate was similar, yet survival after ROSC favored AMSA‐driven protocols (guidelines‐driven, 3/6; AMSA‐driven shocks, 6/6; and ADSE, 7/7; P =0.019 by log‐rank test). Left ventricular function and survival after ROSC correlated inversely with electrical burden (ie, cumulative unsuccessful shocks, J/kg; P =0.020 and P =0.046) and adrenergic burden (ie, total epinephrine doses, mg/kg; P =0.042 and P =0.002). Conclusions Despite similar ROSC rates achieved with all 3 protocols, AMSA‐driven shocks and ADSE resulted in less postresuscitation myocardial dysfunction and better survival, attributed to attaining ROSC with less electrical and adrenergic myocardial burdens.

scholarly journals Care of Maintenance Hemodialysis Patients through Intelligent Algorithm-Based Low-Dose Digital Subtraction Angiography

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Jianhua Hong
Keyword(s):  
Heart Failure ◽  
Blood Flow ◽  
Digital Subtraction Angiography ◽  
Low Dose ◽  
High Flow ◽  
Conventional Group ◽  
Low Flow ◽  
Maintenance Hemodialysis ◽  
Cardiac Complications ◽  
Digital Subtraction

Objective. The study aimed to explore the application value of artificial intelligence (AI)-based low-dose digital subtraction angiography (DSA) in the care of maintenance hemodialysis (MHD) patients. Methods. The characteristics of DSA imaging were analyzed, and the refinement efficiency of the AI algorithm was discussed, expected to assist clinicians in the care and treatment of patients. 100 MHD patients who were in the hospital were selected as the research subjects. They were randomly divided into the conventional DSA group (conventional group) and the AI algorithm-based DSA group (AI-based DSA group). The conventional group used conventional DSA images to guide the care of HM patients, and the AI-based DSA group used the AI algorithm to optimize DSA images. Results. It was found that the AI-based DSA group was better than the conventional DSA group in terms of image sharpness and shaded areas, and the image mean square error (MSE) loss value was smaller ( P < 0.05 ). The patients were followed up for 3 months. In the AI-based DAS group, the blood flow of the drainage vein (DV), the blood flow of the proximal vein (PA), and the blood flow of the brachial artery (BA) were greater than those of the conventional group ( P < 0.05 ). During the 3-month follow-up period, in the conventional group, thrombosis occurred in 4 patients, low-flow AVF occurred in 5 patients, high-flow AVF occurred in 3 patients, and heart failure occurred in 5 patients. In the AI-based DSA group, thrombosis occurred in 2 patients, low-flow AVF occurred in 2 cases, high-flow AVF occurred in 1 case, and heart failure occurred in 3 cases. There were no other cardiac complications in both groups. Conclusion. DSA images optimized by the AI algorithm are suitable for clinical diagnosis and have practical application value.

2380Mechanisms of myocardial ischemia during exercise in microvascular angina

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
H Rahman ◽  
M Ryan ◽  
M Lumley ◽  
H McConkey ◽  
F Khan ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Nitric Oxide Synthase ◽  
Myocardial Perfusion ◽  
Coronary Blood Flow ◽  
Coronary Perfusion ◽  
Fractional Flow ◽  
Microvascular Angina ◽  
Flow Reserve ◽  
Oxide Synthase

Abstract Background Coronary microvascular dysfunction (MVD) is defined by impaired flow augmentation in response to a vasodilator, the pathophysiological basis of which is unclear. This study sought to address two major gaps in our understanding of MVD: firstly, whether diminished flow reserve is due to structural changes within the microvasculature or potentially reversible dysfunction and secondly to unravel the mechanism of exercise-induced ischemia in the absence of obstructive disease. Methods Simultaneous intracoronary pressure and flow velocity recordings were made in the left anterior descending artery of patients with angina and no obstructive epicardial disease (Fractional Flow Reserve >0.80). Measurements were made at rest, during adenosine-mediated hyperaemia and supine bicycle exercise. Wave intensity analysis was used to quantify waves that accelerate and decelerate coronary blood flow, coronary perfusion efficiency being defined as the proportion of total wave energy that accelerates blood flow. Patients were prospectively classified into MVD (coronary flow reserve <2.5) and controls with researchers blinded to the classification throughout the protocol. Myocardial perfusion and vascular function were assessed by 3T cardiac MRI and venous occlusion plethysmography with forearm blood flow (FBF) assessment during serial infusions of acetylcholine, adenosine and the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (L-NMMA). Results 78 patients were enrolled (42 patients had MVD and 36 were controls), with no differences in cardiovascular risk factors between groups. The MVD group had elevated coronary blood flow (21.3±6.4 vs. 15.1±4.5cm s–1; p<0.001) and global myocardial perfusion (1.36±0.37 vs. 1.13±0.22ml/min/g; p=0.01) at rest. Maximum coronary and myocardial blood flow during hyperaemia was similar in both groups. During exercise, MVD patients achieved similar peak flow (30.5±10.0 vs. 26.3±7.7cm s–1; p=0.07) despite a higher rate-pressure product (20777±5205 vs. 17450±4710bpm.mmHg; p=0.01). Coronary perfusion efficiency, decreased with exercise in the MVD group (61±11% vs. 44±10% p<0.001) but was unchanged in controls. On MRI, MVD had lower hyperaemic endo-epicardial perfusion ratio than controls (0.94±0.08 vs. 1.04±0.13; p=0.001). Augmentation of FBF with acetylcholine was attenuated in MVD patients compared to controls (p=0.02) but the response to adenosine was similar (p=0.13). Infusion of L-NMMA caused a significantly greater reduction in FBF in MVD patients compared to controls (p<0.001). Exercise Physiology in MVD Conclusion Impaired flow reserve in MVD represents a dysfunctional state, characterised by inappropriately elevated resting flow due to increased nitric-oxide synthase mediated vasodilatation. There is abnormal flow distribution in the myocardium predisposing to subendocardial ischaemia, associated with and exacerbated by impaired cardiac-coronary coupling during exercise. These novel findings may represent distinct therapeutic targets. Acknowledgement/Funding British Heart Foundation

A delivery-independent blood flow effect on skeletal muscle fatigue

1986 ◽  
Vol 61 (3) ◽  
pp. 1084-1090 ◽  
Author(s):  
J. K. Barclay
Keyword(s):  
Blood Flow ◽  
Muscle Fatigue ◽  
Control Period ◽  
State Level ◽  
Experimental Period ◽  
High Flow ◽  
Low Flow ◽  
Constant Flow ◽  
High O2 ◽  
O2 Delivery

The hypothesis that hyperperfusion decreases muscle fatigue by increasing O2 and substrate delivery to the muscle was tested. Canine gastrocnemius-plantaris in situ preparations were stimulated at 5 Hz for 4 min during a free-flow control period and for 20 min during a pump-perfused experimental period. O2 delivery during these two periods was matched either by decreasing blood flow in animals breathing 100% O2 (high O2/low flow) [experimental-to-control ratio (E/C) = 0.97 + 0.02] or by increasing the blood flow in animals breathing 14% O2 (low O2/high flow) (E/C = 1.01 + 0.01). Plasma flow estimated from hematocrit to approximate substrate delivery was matched in the two contraction periods either by maintaining blood flow at the steady-state level (constant flow) (E/C = 0.98 + 0.10) or by increasing flow in animals with a dextran for 6% of blood volume exchange (dilute/high flow) (E/C = 1.02 + 0.02). E/C for initial developed tension was 1.00 + 0.02. Over 20 min, developed tension decreased 15.0 + 1.1% with low O2/high flow and 16.0 + 1.8% with dilute/high flow. Tension decreased by 28.0 + 3.0 and 27.8 + 1.5% with high O2/low flow and constant flow, respectively. Thus hyperperfusion decreased fatigue by a mechanism independent of increased O2 and substrate delivery.

scholarly journals Hemolysis at low blood flow rates: in-vitro and in-silico evaluation of a centrifugal blood pump

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Malte Schöps ◽  
Sascha H. Groß-Hardt ◽  
Thomas Schmitz-Rode ◽  
Ulrich Steinseifer ◽  
Daniel Brodie ◽  
...  
Keyword(s):  
Blood Flow ◽  
In Silico ◽  
Fluid Dynamic ◽  
High Flow ◽  
Low Flow ◽  
Bleeding Complications ◽  
Centrifugal Pumps ◽  
Operating Characteristics ◽  
Centrifugal Blood Pump

Abstract Background Treating severe forms of the acute respiratory distress syndrome and cardiac failure, extracorporeal membrane oxygenation (ECMO) has become an established therapeutic option. Neonatal or pediatric patients receiving ECMO, and patients undergoing extracorporeal CO2 removal (ECCO2R) represent low-flow applications of the technology, requiring lower blood flow than conventional ECMO. Centrifugal blood pumps as a core element of modern ECMO therapy present favorable operating characteristics in the high blood flow range (4 L/min–8 L/min). However, during low-flow applications in the range of 0.5 L/min–2 L/min, adverse events such as increased hemolysis, platelet activation and bleeding complications are reported frequently. Methods In this study, the hemolysis of the centrifugal pump DP3 is evaluated both in vitro and in silico, comparing the low-flow operation at 1 L/min to the high-flow operation at 4 L/min. Results Increased hemolysis occurs at low-flow, both in vitro and in silico. The in-vitro experiments present a sixfold higher relative increased hemolysis at low-flow. Compared to high-flow operation, a more than 3.5-fold increase in blood recirculation within the pump head can be observed in the low-flow range in silico. Conclusions This study highlights the underappreciated hemolysis in centrifugal pumps within the low-flow range, i.e. during pediatric ECMO or ECCO2R treatment. The in-vitro results of hemolysis and the in-silico computational fluid dynamic simulations of flow paths within the pumps raise awareness about blood damage that occurs when using centrifugal pumps at low-flow operating points. These findings underline the urgent need for a specific pump optimized for low-flow treatment. Due to the inherent problems of available centrifugal pumps in the low-flow range, clinicians should use the current centrifugal pumps with caution, alternatively other pumping principles such as positive displacement pumps may be discussed in the future.

scholarly journals Spheres in the vicinity of a bifurcation: elucidating the Zweifach–Fung effect

2011 ◽  
Vol 674 ◽  
pp. 359-388 ◽  
Author(s):  
V. DOYEUX ◽  
T. PODGORSKI ◽  
S. PEPONAS ◽  
M. ISMAIL ◽  
G. COUPIER
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Volume Fraction ◽  
Initial Distribution ◽  
High Flow ◽  
High Flow Rate ◽  
Low Flow ◽  
Two Dimensional ◽  
Flow Rates ◽  
Low Flow Rate

The problem of the splitting of a suspension in bifurcating channels divided into two branches of non-equal flow rates is addressed. As has long been observed, in particular in blood flow studies, the volume fraction of particles generally increases in the high-flow-rate branch and decreases in the low-flow-rate branch. In the literature, this phenomenon is sometimes interpreted as the result of some attraction of the particles towards this high-flow-rate branch. In this paper, we focus on the existence of such an attraction through microfluidic experiments and two-dimensional simulations and show clearly that such an attraction does not occur but is, on the contrary, directed towards the low-flow-rate branch. Arguments for this attraction are given and a discussion on the sometimes misleading arguments found in the literature is given. Finally, the enrichment of particles in the high-flow-rate branch is shown to be mainly a consequence of the initial distribution in the inlet branch, which shows necessarily some depletion near the walls.

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