PURPOSE: Characteristics of pulsatile flow in 3-dimensional arterial geometry and elastic vessel wall should be investigated in order to understand the physiological blood flow in human body. In this study, the modelling of the physiological blood flow in the elastic blood vessel is proposed. METHODS: The finite volume predictions are used to analyse the pulsatile flow characteristics in the elastic blood vessel. RESULTS AND CONCLUSION: Variations of the pressure and the velocity waveforms are obtained using the proposed modelling. The magnitudes of the pressure waveforms in the elastic blood vessel model are bigger than those of the rigid blood vessel model.
Blood Vessels* ; Human Body ; Pulsatile Flow*

PURPOSE: The objective of the present study is to investigate the steady and pulsatile flow phenomena of the blood substitute fluids in the circular and bifurcated vessels numerically and experimentally. METHODS: The particle image velocimetry (PIV) is adopted to visualize the flow fields in the circular and bifurcated vessels. In order to analyse the complex flow phenomena of the blood substitute fluids in the bifurcated vessel, the constitutive equations which are suitable to describe the rheological properties of the non-Newtonian fluids are determined and the steady and unsteady momentum equations are solved by the finite volume prediction. RESULTS AND CONCLUSION: Velocity vectors of the steady flow in the bifurcated tube obtained by the PIV system are in good agreement with those obtained by the numerical analysis. The experimental and numerical results show the recirculation zone in the outer wall distal to bifurcation.
Blood Substitutes* ; Pulsatile Flow* ; Rheology*

The objective of the present study is to obtain information on the hemodynamic characteristics in the anastomotic sites of femoral artery through the vascular implantation. Three dimensional steady and physiological blood flows in the femoral artery are simulated using the finite volume method. The geometrical shape of the anastomotic sites is made based on the vascular anatomy of a white rabbit. Wall shear stress distributions in the anastomotic sites for the physiological flow are compared with those for steady flow. Blood flow phenomena in the anastomotic sites of the femoral artery are discussed extensively.
Arteries ; Femoral Artery* ; Hemodynamics*

The hemodynamic characteristics of the cuff end-to-side anastomosis model are investigated using by the finite volume predictions. The flow rates and the impedance indices through of the cuff anastomosis model are compared with those of the anastomosis model without the cuff. Blood flow increased through the cuff anastomosis model than the standard anastomosis model. The impedance index decreased with the increase of flow rate. The impedance index at a given flow rate is reduced by the increase of anastomosis angle and further reduced by the addition of the cuff. The results suggest that the cuff anastomosis model should be applied for the low Reynolds number flow and/or the small artery anastomosis model.
Arteries ; Electric Impedance ; Hemodynamics*

An ex vivo assay determining the flavin-containing monooxygenase (FMO) activity in perfused rat liver has been developed by assessing the rate of thiobenzamide S-oxide (TBSO) formation from the infused thiobenzamide (TB). The hepatotoxicity by TB or TBSO was not a critical factor for maintaining the FMO activity for up to 50 min. The FMO activity expressed in nmoles TBSO produced/g liver/min was the same for the recycling and non-recycling perfusion. This implies that reduction of the oxidized TBSO back to the parent compound (TB) is negligible. Hydrolysis of the collected perfusates with either beta-glucuronidase or arylsulfatase did not increase the TBSO level and thus, TBSO does not appear to undergo conjugation either to glucuronide or sulfate esters. Thus, measuring the rate of TB S-oxidation in the isolated perfused liver with 1 mM TB for 50 min provides a useful tool for evaluation of the hepatic FMO activity in the absence of hepatic necrosis and without the interferences caused by further conjugation or back reduction of the TBSO to the parent TB.
Animals ; Esters ; Glucuronidase ; Humans ; Hydrolysis ; Liver* ; Necrosis ; Parents ; Perfusion ; Rats* ; Recycling

Purpose: Acute organophosphate (OP) poisoning may be monitored by measuring the acetylcholinesterase (AChE). It is important to assess severity and establish prognostic tests in the early stage of OP poisoning. The aim of this study was to look at the relationship between various clinical aspects of the OP poisoning, prognostic indicators of OP poisoning including Simplified Acute Physiology Score (SAPS) 3, and the associated changes in AChE levels. Methods: Clinical data and initial AChE levels from thirty-seven patients with OP poisoning were prospectively reviewed from 12 teaching hospitals in South Korea from August 2005 to July 2006. Clinical manifestations at the time of arrival such as miosis, respiratory abnormality, salivation, urinary incontinence, GCS score, AVPU scale, need for intubation, and mechanical ventilation requirements were recorded. SAPS 3 was calculated using clinical data and laboratory results. Results: The median level of AChE was 9.8 (1.3-53.6) U/gHb. There was no significant difference in AChE levels between the groups with and without cholinergic symptoms. The median level of AChE of the patients who required intubation and those who did not were 3.5 U/gHb and it 19.7 U/gHb respectively (Mann-Whitney test; p<0.001). The AChE levels were also significantly different (p=0.007) in patients who needed mechanical ventilation compared to those who did not with AChE levels found to be 3.1 U/gHb and it was 14.8 U/gHb, respectively. Level of consciousness assessed using the AVPU scale was correlated with AChE levels (Kruskal-Wallis test; p=0.013). GCS score were correlated with AChE levels (p=0.007, Spearman's rho = 0.454). In addition, the lower the level of initial AChE, the longer the ICU stay (p=0.029, Spearman's rho=-0.380). SAPS 3 was inversely correlated with the initial AChE (p<0.001, Spearman's rho=-0.633). Conclusion: In the acute OP poisoning, low AChE levels appear to help indicate the severity of poisoning. The initial AChE level may be a useful prognostic parameter for acute OP poisoning.
Acetylcholinesterase ; Consciousness ; Hospitals, Teaching ; Humans ; Intubation ; Miosis ; Organophosphate Poisoning ; Prognosis ; Prospective Studies ; Republic of Korea ; Respiration, Artificial ; Salivation ; Urinary Incontinence

Purpose: Dichlorvos has been in widespread use as an organophosphate (OP) insecticide compound. The purpose of this study was to access the epidemiology and clinical features of dichlorvos in Korea. Methods: This was a 38 multi-center prospective study of dichlorvos poisoning using surveys, a structural reporting system and review of hospital records from August 2005 to July 2006. A total of 54 patients with acute dichlorvos poisoning on a national basis were enrolled. We analyzed the epidemiologic characteristics and clinical manifestations of dichlorvos poisoning. In addition, the clinical features of dichlorvos poisoning were compared with others OP compounds. Results: During the study period, compounds involving pure OP poisoning were dichlorvos (22.7%), methidathion (8.4%), and phosphamidon (6.7%). In acute dichlorvos poisoning, all ingestion routes were oral. Intentional poisoning involved 74.1% of cases. The common initial complaints involved gastrointestinal (64.8%), systemic (61.1%), central or peripheral nervous system (53.7%), and respiratory symptoms (50.0%). The median arrival time to hospital after dichlorvos poisoning was 2.6 hours and mean hospitalization duration was 7.1 days. 2-PAM was administered in 35 patients in mean doses of 6.3 g/day intravenously. Atropine was administered in 30 patients with a mean dose of 62.8 mg/day (maximal 240 mg/day). Overall mortality rate for dichlorvos poisonings were 14.8% (8/54). Immediate causes for death included sudden cardiac arrest or ventricular dysrhythmias (50%), multi-organ failure (25%), acute renal failure (12.5%), and unknown causes (12.5%). Conclusion: When compared to previous reports, dichlorvos poisoning displayed relatively moderate severity. The presence of a lower GCS score, altered mental status, serious dysrhythmias, systemic shock, acute renal failure, and respiratory complications upon presentation were associated with a more serious and fatal poisoning.
Acute Kidney Injury ; Atropine ; Death, Sudden, Cardiac ; Dichlorvos ; Eating ; Hospital Records ; Hospitalization ; Humans ; Korea ; Organothiophosphorus Compounds ; Peripheral Nervous System ; Phosphamidon ; Pralidoxime Compounds ; Prospective Studies ; Shock

The objectives of this investigation were to evaluate biomechanical factors in the atherosclerotic process using human in vivo hemodynamic parameters and computed numerical simulation qualitatively and quantitatively. The three-dimensional spatial patterns of steady and pulsatile flows in the left coronary artery were simulated, using a finite volume method. Coronary angiogram and Doppler ultrasound measurement of the proximal left coronary flow velocity were performed in humans. Inlet wave velocity distribution obtained from in vivo data of the intravascular Doppler study allowed for input of in vitro numerical simulation. Hemodynamic variables, such as flow velocity, pressure and shear stress of the left anterior descending coronary bifurcation site were calculated. We found that there were spatial fluctuation of flow-velocity and recirculation areas at the curved outer wall of the left anterior descending coronary artery, which were due to the differences of flow-velocity and shear stress, especially during the declaration phase of pulsatile flow. This study suggests that rheologic properties may be a part of the atherogenic process in the coronary bifurcated and curved areas.
Biomechanics ; Blood Flow Velocity/physiology ; Blood Pressure/physiology ; Coronary Arteriosclerosis/physiopathology* ; Coronary Arteriosclerosis/etiology* ; Coronary Vessels/physiopathology* ; Hemodynamics/physiology* ; Homeostasis/physiology ; Human ; Models, Cardiovascular* ; Pulsatile Flow ; Stress, Mechanical

To examine individual variation in drug metabolism catalyzed by flavin-containing monooxygenase (FMO), 179 Korean volunteers' urinary molar concentration ratio of theobromine (TB) and caffeine (CA) was determined. Their urine was collected for 1 hr (between 4 and 5 hrs) after they drank a cup of coffee containing 115 mg CA and analyzed by an HPLC system. The lowest TB/CA ratio obtained was 0.40, the highest ratio was 15.17 (38-fold difference), and the median ratio for all subjects was 1.87. The mean was 2.66 with 2.36 S.D.. In 134 nonsmokers, the mean ratio was 2.35 +/- 1.93, that of 51 males was 2.30 +/- 2.26 and 83 females was 2.37 +/- 1.85, respectively. There was no significant gender difference in the obtained TB/CA ratio (Mann-Whitney test; p=0.518). There were no smokers among the 83 female volunteers. In the remaining 96 male subjects, the ratio obtained in 51 nonsmokers was 2.30 +/- 2.06 and that of 45 smokers was 3.62 +/- 3.19. This indicated that the TB/CA ratio was increased significantly in smokers (p=0.007). However, when the TB/CA ratios (FMO activity) obtained in all 179 Korean volunteers are compared with the urinary concentration ratios of paraxanthine (PX) plus 1,7-dimethylurate (17U) to CA (CYP1A2 activity), there was a weak but significant correlation (Pearson's correlation coefficient test; r2=0.28, p<0.0001). This indicates that, although the urinary TB/CA ratio mostly represents FMO activity, minor contribution by CYP1A2 activity cannot be ignored. In conclusion, the FMO activity measured by taking the urinary TB/CA ratio from normal healthy Korean volunteers shows marked individual variations without significant gender differences and the increased TB/CA ratio observed in cigarette smokers may have been caused by the increased CYP1A2 activity.
Caffeine* ; Chromatography, High Pressure Liquid ; Coffee* ; Cytochrome P-450 CYP1A2 ; Drinking* ; Ethanol ; Female ; Humans ; Male ; Metabolism ; Molar ; Theobromine* ; Tobacco Products ; Volunteers

The present study in angulated coronary stenosis used human in vivo hemodynamic parameters and computed simulation, both qualitatively and qualitatively, to evaluate the influence of flow velocity and wall shear stress (WSS) on coronary atherosclerosis, the changes of hemodynamic indices following coronary stenting, and their effect on evolving in-stent restenosis. Initial and follow-up coronary angiographies in patients with angulated coronary stenosis were performed (n=60). The optimal degree of coronary stenting for angulated coronary stenosis had two models, the less than 50% angle changed group (model 1, n=33) and the more than 50% angle changed group (model 2, n=27). This angle change was based on the percentage change of vascular angle between pre- and post-intracoronary stenting. The flow-velocity wave obtained from in vivo intracoronary Doppler study data was used for in vitro numerical simulation. Spatial and temporal patterns of the flow-velocity vector and recirculation area were drawn throughout the selected segment of coronary models. WSS of pre- and post-intracoronary stenting was calculated from three-dimensional computer simulation. As results, follow-up coronary angiogram demonstrated significant difference in the percentage of diameter stenosis between the two groups (group 1: 40.3 +/- 30.2 vs. group 2: 25.5 +/- 22.5%, p < 0.05). Negative shear area on 3D simulation, which is consistent with the re-circulation area of flow vector, was noted on the inner wall of the post-stenotic area before stenting. The negative WSS disappeared after stenting. High spatial and temporal WSS before stenting fell within the range of physiologic WSS after stenting. This finding was more prominent in model 2 (p < 0.01). The present study suggests that hemodynamic forces exerted by pulsatile coronary circulation, termed WSS, might affect the evolution of atherosclerosis within the angulated vascular curvature. Moreover, geometric characteristics, such as the angular difference between pre- and post- intracoronary stenting might define optimal rheologic properties for vascular repair after stenting.
Adult ; Aged ; Biomechanics ; *Coronary Circulation ; Coronary Stenosis/*physiopathology/therapy ; Female ; *Hemodynamics ; Human ; Male ; Middle Age ; *Stents ; Stress, Mechanical