ABSTRACT
The implantation of biventricular assist device (BiVAD) is more challenging than that of left ventricular assist device for the interaction in the process of multiple input and output. Besides, ventricular assist device (VAD) often runs in constant speed (CS) mode in clinical use and thus BiVAD also faces the problems of low pulsation and imbalance of blood volume between systemic circulation and pulmonary circulation. In this paper, a delay assist mode for a VAD by shortening the support time of VAD was put forward. Then, the effect of the delay mode on cardiac output, pulsation and the function of the aortic valve was observed by numerical method and the rules of hemodynamics were revealed. The research showed that compared with VAD supported in CS mode, the VAD using delay mode in systolic and diastolic period proposed in this paper could meet the demand of cardiac output perfusion and restore the function of the arterial valves. The open ratio of aortic valve (AV) and pulmonary valve (PV) increased with the time set in delay mode, and the blood through the AV/PV helped to balance the left and the right cardiac volume. Besides, delay mode also improved the pulsation index of arterial blood flow, which is conducive to the recovery of the ventricular pulse function of patients.
Subject(s)
Humans , Cardiovascular System , Diastole , Heart Failure , Heart Rate , Heart-Assist Devices , Hemodynamics , Models, CardiovascularABSTRACT
Right ventricular (RV) failure has become a deadly complication of left ventricular assist device (LVAD) implantation, for which desynchrony in bi-ventricular pulse resulting from a LVAD is among the important factor. This paper investigated how different control modes affect the synchronization of pulse between LV (left ventricular) and RV by numerical method. The numerical results showed that the systolic duration between LV and RV did not significantly differ at baseline (LVAD off and cannula clamped) (48.52%
Subject(s)
Humans , Heart Failure/therapy , Heart-Assist Devices , Systole , Ventricular Dysfunction, Right , Ventricular Function, RightABSTRACT
Objective To investigate a self-designed catheter pump by using computational fluid dynamics (CFD) method, so as to predict its hydraulic performance and risk of thrombosis formation. Methods The thrombosis prediction models proposed by Grigioni and Danny Bluestein were used. The shear stress and exposure time during platelet motion were calculated by CFD method, and parameters of platelet activation state (PAS) were obtained for prediction of thrombogenic performance. Results At the flow rate of 4 L/min and rotating speed of 10 000 r/min, the differential pressure of the pump reached 14.763 kPa and the hydraulic performance was proved to fit the requirement of left ventricular assist device. The PAS values of Grigioni model and Danny Bluestein model were 6.35×10-6 and 7.68×10-4,respectively, both at a very low level, indicating a low possibility of thrombus formation. Conclusions This study investigated the feasibility of thrombosis prediction based on simulation method and the predicted hydraulic performance and thrombosis will provide references for further design optimization.
ABSTRACT
Objective To observe the psychological state of patients with ophthalmic surgery, and investigated the effect of nursing intervention on the psychological state of them. Methods 120 patients with ophthalmic surgery were selected randomly, including 40 youth, 40 middle-aged and 40 elderly, they were subsequently divided randomly into the control group and the nursing intervention group with 20 of youth, middle- aged and elderly separately. The control group received preoperative health education ae-cording to nursing process, the nursing intervention group was given nursing intervention based upon routine nursing. Anxiety standard score was evaluated by the self-rating anxiety scale (SAS) when upon admission,one day before surgery, and upon discharge. Results The anxiety standard score of the patients admitted into hospital was above the critical standard score (50), the anxiety standard score of patients when the day before surgery was significantly above that upon admission, but was less than the critical standard score when they left hospital, and it was significantly less than that upon admission. There was no statistical sig-nificance of anxiety standard score between the control group and the nursing intervention group when they were admitted into hospital, it was significantly less than that of the control group when the day before surgery and when they left hospital. The anxiety standard scores of the elderly and the middle- aged of the control group were more and significantly more than the youth's when the day before surgery separately, and both of theirs were more than the youth's when they left hospital. After nursing intervention, the anxiety standard score of the elderly and the middle- aged were significantly more and more than the youth when the day before surgery separately, and the elderly was more than the youth when they left hospital, there was no statistical significance between the youth and the middle- aged. The anxiety standard score of the youth and the middle- aged were significantly less than that of the control group separately when the day before surgery and when they left hospital, that elderly was less than that of the control group. Conclusions Anxiety existed in almost all patients with ophthalmic surgery, and it reached high degree the day before surgery. It appeared more in the middle-aged than among the youth and the elderly. Nursing intervention shows positive effect on the psychological state of patients with ophthalmic surgery, and it influences more on the youth and the middle-aged than on the elderly. Therefore, it is necessary to give different periopera-tire nursing intervention to the patients with ophthalmic surgery.
ABSTRACT
Objective To discuss the effect of health education in prevention of recurrence of glaucoma. Methods 62 cases of patients with glaucoma surgery were given the health education on disease knowledge, intraocular pressure monitoring, diet, living, sports, etc. The intraocular pressure and recurrence of glaucoma before and after health education were compared. Results 58 cases of patients with intraoeular pressure to achieve anticipated criteria, the average intraocular pressure was (17.9 ± 1.7)mm Hg (1 mm Hg=0.133 kPa), which was greatly alleviated compared with that before health education. 4 patients with recurrence, the recurrence rate was 6.45%, the average intraocular pressure was (27.9 ± 2.3) nun Hg. After health education, the excellent rate of patients' total score on the glaucoma- related knowledge ac -quired was 83.9%, which was higher than that pre-education level. After health education, patients' self-care capacity was markedly improved, compared with pre-education level. Conclusions It is effective to prevent the recurrence of glaucoma, improve the glaucoma- related knowledge and self- care level by strengthen health education for patients with glaucoma.
ABSTRACT
One of the internal reasons resulting in hemolysis and thrombi is the hemodynamics. Many studies show that irregular flow patterns and shear stress result in the damage of blood cells. With the rapid development of computer technology, simulation for such microdynamics becomes possible. Computational fluid dynamics was applied to predict the flow in the streamlined blood pump and a pump with straight vanes. After the analysis of flow patterns and the distribution of shear stress, it was concluded that in the same boundary conditions, the blood pump based on streamlined design had better hemodynamics than the pump with straight vanes and caused less