Flow Estimation Method of Centrifugal Left Ventricular Assist Device Based on Motor Parameters / 医用生物力学

Objective To study CH-VAD blood pump developed by CH Biomedical Inc., a method for estimating the real-time flow of blood pump was established by using the voltage, current, speed, duty cycle, and fluid viscosity as the input data. Methods The blood pump system was disassembled into two modules, the motor and the centrifugal pump. Firstly, the output torque of the motor was calculated according to the voltage, current, speed and duty cycle of the motor, then the relationship between flow and torque at different speeds and viscosities was tested through experiments, and a fitting model was established based on the experimental data. Results The fit goodness of Pump 1 and Pump 2 reached 0.982 6 and 0.982 9,respectively. The fitting parameters were used for verification. When the viscosity changed, the root mean square error for the estimated flow of Pump 1 and Pump 2 was 0.260 and 0.274 L/min, respectively. The fitting parameters and estimated results of the two blood pumps were in good agreement. The flow estimation method could follow the actual flow waveform in real time, and the accuracy of the estimated average flow was not affected by the pulsation. Conclusions The flow estimation method proposed in this paper is suitable for CH-VAD blood pumps. It can accurately estimate the flow of blood pumps in the range of speed 1 600-3 600 r/min, flow 0.4-8 L/min, viscosity 1.2-5 mPa·s, and can follow the flow waveform well under pulsating conditions.

Emergency treatment of centrifugal pump dysfunction in extracorporeal membrane oxygenation / 中华危重病急救医学

Objective:To summarize the treatment process of rapid decrease in blood flow due to centrifugal pump dysfunction during extracorporeal membrane oxygenation (ECMO) and its related thinking.Methods:On September 25, 2021, the ECMO treatment of a 14-year-old boy with severe mycoplasma pneumonia, severe viral pneumonia and acute respiratory distress syndrome (ARDS) admitted to the department of critical care medicine of the First Affiliated Hospital of Wannan Medical College was analyzed.Results:Oxygenation of the child was difficult to maintain under invasive mechanical ventilation, and lung consolidation progressed seriously. After evaluation, venous-venous ECMO (VV-ECMO) was implemented, then oxygenation was improved. In the 120th hour after VV-ECMO establishment, the blood flow sudden decreased, the speed was 3 822 r/min, while the flow was only 0.2 L/min, more over there was no change in the flow when the speed was increased. Before that, the ECMO speed was 3 530 r/min, and the flow was up to 3.4 L/min and stable. After rapid screening, it was determined that the centrifugal pump was dysfunction. ECMO was successfully replaced and the flow was satisfactory.Conclusions:At present, most ECMO centers do not routinely monitor the pressure before and after the pump. There is a lack of visual and quantitative techniques or indicators to judge the pump's function, and there is also a lack of corresponding clinical experience in treatment. This paper summarizes the investigation and treatment process of ECMO pump dysfunction of this case to provide reference.

Life Support Systems in Terms of Energy

BACKGROUND: The pro's and con's of pulsatile versus nonpulsatile perfusion during acute and chronic mechanical circulatory support is a longstanding controversial issue, some investigators have suggested that the simplest explanation for this controversy is a failure to quantitate adequately the pulsatile components of flow in studies. The aim of this study was to examine the pulsatility generated by centrifugal pump (CP) and a pulsatile extracorporeal life support (twin pulse life support, T-PLS) in terms of energy equivalent pressure (EEP) and surplus hemodynamic energy (SHE). METHODS: In each of the 5 cardiac arrested pigs, the outflow cannula of the CP or T-PLS was inserted into the ascending aorta, and the inflow cannula of the CP or T-PLS was placed in the right atrium. Extracorporeal circulation was maintained for 30 minutes using a pump flow of 75 ml/kg/min by CP or T-PLS, respectively. Pressure and flow were measured in the right internal carotid artery. RESULTS: No statistical difference was observed between CP and T-PLS in terms of mean carotid artery pressure. However, pulse pressure, the percent change from mean arterial pressure to EEP, and SHE in T-PLS were higher than CP (pulse pressure: 36.1 +/- 3.6 mmHg vs 9.1 +/- 1.3 mmHg, P < 0.05, the percent change from mean arterial pressure to EEP: 19.8 +/- 6.2% vs 0.2 +/- 0.3%, P < 0.05). CONCLUSIONS: In a cardiac arrested animal model, CP revealed nonpulsatility and pulsatility generated by T-PLS was effective in terms of EEP and SHE.

Hematological Differences between Roller Pump and Centrifugal Pump in Cardiopulmonary Bypass / 대한마취과학회지

BACKGROUND: Prolonged extracorporeal circulation entails tremendous threats of red cell lysis, severe bleeding problems due to platelet injury and activation, and endothelial damages by sequestered leukocytes. In consideration of these problems, a new centrifugal pump was developed and tested clinically to evaluate its effectiveness. METHODS: We compared the effects of a centrifugal pump with those of a roller pump on hematological responses during cardiopulmonary bypass (CPB) in 20 coronary artery bypass surgery patients. The patients were divided into two groups of 10 each. The studied parameters included WBC counts, platelet counts, plasma Hb and D-dimer. Blood samples were taken after sternotomy, at 60 min, 120 min and 180 min after CPB start, and at 2 hr after CPB stop. RESULTS: No differences between the groups were found in bypass time, aortic cross clamp time, extracorporeal circulation flow and hematocrit. The centrifugal pump group demonstrated less platelet depletion (p<0.05), hemolysis (plasma Hb, p<0.05) and fibrinolysis (D-dimer, p<0.05). These differences were CPB time dependent and became statistically significant after 120 min bypass. CONCLUSION: We conclude that roller pump still can be safely used for standard cardiac procedures with bypass time less than 120 minutes and the centrifugal pump has significant potential to be safely applied to CPB for long ypass time in order to avoid postperfusion syndrome.

Orthotopic Liver Transplantation in Dogs by Veno - venous bypass using Centrifugal Pump / 대한마취과학회지

The Orthotopic liver transplantation for the terminal liver diseases has been performed frequently since the introduction of new immuno-suppressive agent (cyclosporin A), technical advances in surgical skill, uae of biopump during anhephatic stage, rapid infusion system for transfusion and thromboelastography for coagulopathies were used. In Korea, only one case of orthotopic liver transplantation succeeded in 1988, but the animal experiments have been going on for many years in many institutes. Orthotopic liver transplantation in dogs using centrifugal pump (Bio-pump) were experienced and the results were analysed; 1) There were no differences in hemodynamic parameters during anhepatic stage with assistance of Biopump compared with preanhephatic stage. 2) The mean flow rate of Biopump during anhepatic stage was 0.75+/-0.09L/min, and maximun and minimum flow rate were 1.5L/min. and 0.4L/min, respectively. 3) Mean artery pressure, cardiac output and systemic vascular resistance after reperfusion of transplanted liver were significantly reduced compared with the values of before reperfusion; meanwhile, mean pulmonary artery pressure, pulmonary capillary wedge pressure and pulmonary vascular resistance were not significantly different. 4) After reperfusion of transplanted liver serum potassium level was significantly increased to 6. 07+/-1.8 mEq/L and the amount of base was significantly decrease to-12.9+/-5.9 mEq/L. By using Bio-pump the degree of hemodynamic changes could be reduced during the clamping of inferior vena cava and hepatic vein.