Objective To establish a personalized Stanford type B aortic dissection numerical simulation model, and using computational fluid dynamics (CFD) numerical simulation to obtain the hemodynamic behavior and law of the type B aortic dissection at different stages of development. Methods Based on the theory of three-dimensional model reconstruction, we used CT images of a patient with type B aortic dissection in the Xiamen Cardiovascular Hospital of Xiamen University, relevant medical image processing software to reconstruct a personalized aortic three-dimensional model, and CFD to reconstruct the model which was simulated in fluid mechanics. Results The three-dimensional reconstruction model could intuitively observe the changing trend of the false cavity at different stages of the dissection development. Through fluid mechanics simulation, the blood flow rate, pressure, wall shear stress, vascular wall Von Mises stress and other parameters at different stages of the dissection development were obtained. Conclusion The hemodynamic behavior and law of relevant parameters in the development stage of aortic dissection are analyzed. The combination of the values of relevant parameters and clinical medical detection and diagnosis can well predict the development of the disease, and finally provide more theories and methods for the scientific diagnosis of aortic dissection.
Objective To analyze the risk factors for ventilator-associated pneumonia( VAP) in adult patients undergoing cardiac surgery with cardiopulmonary bypass ( CPB) . Methods A total of 127 consecutive adult patients who received postoperative ventilation for more than 48 hours between January 2002 and June 2008 in the cardiac surgical intensive care unit( CSICU) were included in this study. The patients were assigned into a VAPgroup( n =64) and a control group( n = 63) . Pre-, intra-, and postoperative factors were collected and analyzed between two groups, and the multivariate analysis( logistic regression)were used to identify the risk factors of VAP. Results The overall incidence of VAP was 5.1%. The mortality of VAP was 28. 1% . Compared to the control group, the patients in the VAP group had longer duration of cardiopulmonary bypass time, ventilation time, more blood products usage and the duration of stay in CSICU( P lt; 0. 001) , higher morbidity of low cardiac output syndrome and tracheotomy( P lt; 0. 01) and higher rate of aortic surgery and mortality( P lt; 0. 05) . The preoperative left ventricular ejection fraction ( LVEF) and postoperative oxygenation index( PaO2 /FiO2 ) were lower in the VAP group than those of the control group( P lt; 0. 001) . Five variables were found to be significantly related to the development of VAP by multivariate analysis: CPB time gt; 120 min( OR = 6. 352, P = 0. 000) ; PaO2 /FiO2 lt; 300 mm Hg( OR =3. 642, P = 0. 017) , transfusion of blood products ≥1500 mL( OR = 5. 083, P = 0. 039) , ventilation time≥5 days( OR = 9. 074, P = 0. 047) and tracheotomy( OR = 19. 899, P = 0. 021) . A total of 102 pathogens were obtained by sputum culture in 64 VAP patients. There were 62( 60. 8% ) cases of gram negative bacilli, 19 cases( 18. 6% ) of gram positive cocci and 21( 20. 6% ) cases of eumycetes. Conclusion This study shows that the cardiopulmonary bypass time, ventilation time, hypoxemia, blood products transfusion and tracheotomy are risk factors most likely associated with VAP development.
