The influence of flow distribution strategy for the quantification of pressure- and wall shear stress-derived parameters in the coronary artery: A CTA-based computational fluid dynamics analysis.

For image-based computational fluid dynamics (CFD) analysis to characterize the local coronary hemodynamic environment, the accuracy depends on the flow rate which is in turn associated with outlet branches' morphology. A good flow distribution strategy is important to mitigate the effect when certain branches cannot be considered. In this study, stenotic coronary arteries from 13 patients were used to analyze the effect of missing branches and different flow distribution strategies. Pressure- and wall shear stress (WSS)-derived parameters around the stenotic region (ROI) were compared, including fractional flow reserve (CT-FFR), instantaneous wave-free ratio (CT-iFR), resting distal to aortic coronary pressure (CT-Pd/Pa), time-averaged WSS, oscillatory shear index (OSI) and relative residence time (RRT). Three flow distribution strategies were the Huo-Kassab model at distal outlets (Type I), flow distribution based on outlet resistances (Type II), and a developed algorithm distributing flow at each bifurcation until the final outlets (Type III). Results showed that Type III strategy for models with truncated branch(es) had a good agreement in both pressure- and WSS-related results (interquatile range less than 0.12% and 4.02%, respectively) with the baseline model around the ROI. The relative difference of pressure- and WSS-related results were correlated with the flow differences in the ROI to the baseline mode. Type III strategy had the best performance in maintaining the flow in intermediate branches. It is recommended for CFD analysis. Removal of branches distal to a stenosis can be undertaken with an improved performance and maintained accuracy, while those proximal to the ROI should be kept.

Experimental study of airway pressure release ventilation in the treatment of acute respiratory distress syndrome.

Airway pressure release ventilation (APRV) is a ventilator mode which has demonstrated potential benefits in acute respiratory distress syndrome (ARDS) patients. We therefore sought to compare relevant pulmonary data and safety outcomes of this mode to the conventional ventilation and sustained inflation. Canines admitted after intravenous injection of oleic acid requiring mechanical ventilation were randomly divided into 3 groups (n=6), namely conventional ventilation group, low tidal volume ventilation with recruitment group (LTV+SI) and APRV group. The changes of oxygenation, ventilation, airway pressure, inflammatory reaction and hemodynamics at the basic state were observed at 0, 1, 2 and 4 h during the experiment. The levels of PaO2/FiO2 in APRV group were higher than LTV+SI group at 2 and 4 h (P<0.05). In APRV group, the PCO2 levels at 1, 2 and 4 h is much lower than LTV+SI group (P<0.05). Outcome variables showed no differences between APRV, LVT+SI and conventional mechanical ventilation for plateau airway pressure (24±1 vs. 29±3 vs. 25±4), mean arterial pressure (92.9±16.5 vs. 85.8±21.4 vs. 88.7±24.4), cardiac index (4.3±1.7 vs. 3.5±1.9 vs. 3.4±2.1), ERO2 (13.4±10.3 vs. 16.1±6.8 vs. 17.6±9.1), lac (2.5±1.7 vs. 3.1±1.6 vs. 3.9±1.9), tumor necrosis factor (TNF)-α (132±11 vs. 140±6 vs. 195±13) and matrix metalloproteinase (MMP)-9. For canines sustaining acute respiratory distress syndrome requiring mechanical ventilation, APRV can significantly improve oxygenation and keep hemodynamic stability compared with LTV+SI. The results of TNF-α and MMP-9 suggest that APRV could be as protective for ARDS as LTV with recruitment group.

Clinical observation on the treatment of acute liver failure by combined non-biological artificial liver.

The clinical efficacy and safety of different combinations of non-bio artificial liver in the treatment of acute liver failure was examined. A total of 61 cases were selected under blood purification treatment from the patients with severe acute liver failure admitted to the severe disease department of the hospital from December, 2010 to December, 2015. Three types of artificial liver combinations were observed, i.e., plasma exchange plus hemoperfusion plus continuous venovenous hemodiafiltration (PE+HP+CVVHDF), PE+CVVHDF and HP+CVVHDF. The heart rate (HR), mean arterial pressure (MAP), respiratory index (PaO2/FiO2), liver and kidney function indicator, as well as platelet and coagulation function were compared. A comparison before and after the treatment using the three methods, showed improvement in the HRs, MAPs, PaO2/FiO2, total bilirubins (TBIL) and alanine aminotransferases (ALT) (P<0.05), of which TBIL and ALT were decreased more significantly (P<0.01) in the PE+CVVHDF and PE+HP+CVVHDF groups. Only changes in the PE+HP+CVVHDF and PE+CVVHDF groups were statistically significant after prothrombin time and albumin treatment (P<0.05). The difference between the decrease in TBIL in the PE+HP+CVVHDF group and that in the HP+CVVHDF group was statistically significant (P<0.05). Treatment of the 61 patients using the artificial liver support system yielded a survival rate of 62.3% (38/61), and a viral survival rate of 35.0% (7/20); with the non-viral survival rate being 75.6% (31/41). In conclusion, following the treatment of three types of artificial livers, the function was improved to varying degrees, with the PE+HP+CVVHDF and the PE+CVVHDF method being better. By contrast, after the treatment of non-viral liver failure, the survival rate was significantly higher than the patients with viral liver failure.