Gas Transfer Performance of a Hollow Fiber Silicone Membrane Oxygenator: Ex Vivo Study

Based on the results of in vitro studies of many experimental models, a silicone hollow fiber membrane oxygenator for pediatric cardiopulmonary bypass (CPB) and extracorporeal membrane oxygenation (ECMO) was developed using an ultrathin silicone hollow fiber with a 300 microm outer diameter and a wall thickness of 50 microm. In this study, we evaluated the gas transfer performance of this oxygenator simulating pediatric CPB and ECMO conditions. Two ex vivo studies in a pediatric CPB condition for 6 h and 5 ex vivo studies in an ECMO condition for 1 week were performed with venoarterial bypass using healthy calves. At a blood flow rate of 2 L/min and V/Q = 4 (V = gas flow rate, Q = blood flow rate) (pediatric CPB condition), the O2 and CO2 gas transfer rates were maintained at 97.44 +/- 8.88 (mean +/- SD) and 43.59 +/- 15.75 ml/min/m2, respectively. At a blood flow rate of 1 L/min and V/Q = 4 (ECMO condition), the O2 and CO2 gas transfer rates were maintained at 56.15 +/- 8.49 and 42.47 +/- 9.22 ml/min/m2, respectively. These data suggest that this preclinical silicone membrane hollow fiber oxygenator may be acceptable for both pediatric CPB and long-term ECMO use.     

Development of silicone rubber hollow fiber membrane oxygenator for ECMO

Silicone rubber hollow fiber membrane produces an ideal gas exchange for long-term ECMO due to nonporous characteristics. The extracapillary type silicone rubber ECMO oxygenator having an ultrathin hollow fiber membrane was developed for pediatric application. The test modules were compared to conventional silicone coil-type ECMO modules. In vitro experiments demonstrated a higher O2 and CO2 transfer rate, lower blood flow resistance, and less hemolysis than the conventional silicone coil-type modules. This oxygenator was combined with the Gyro C1E3 centrifugal pump, and three ex vivo experiments were conducted to simulate pediatric V-A ECMO condition. Four day and 6 day experiments were conducted in cases 1 and 2, respectively. Case 3 was a long-term experiment up to 2 weeks. No plasma leakage and stable gas performances were achieved. The plasma free hemoglobin was maintained within a normal range. This compact pump-oxygenator system in conjunction with the Gyro C1E3 centrifugal pump has potential for a hybrid total ECMO system.     

Extracorporeal membrane oxygenator compatible with centrifugal blood pumps

Coil-type silicone membrane oxygenators can only be used with roller blood pumps due to the resistance from the high blood flow. Therefore, during extracorporeal membrane oxygenation (ECMO) treatment, the combination of a roller pump and an oxygenator with a high blood flow resistance will induce severe hemolysis, which is a serious problem. A silicone rubber, hollow fiber membrane oxygenator that has a low blood flow resistance was developed and evaluated with centrifugal pumps. During in vitro tests, sufficient gas transfer was demonstrated with a blood flow less than 3 L/min. Blood flow resistance was 18 mm Hg at 1 L/min blood flow. This oxygenator module was combined with the Gyro C1E3 (Kyocera, Japan), and veno-arterial ECMO was established on a Dexter strain calf. An ex vivo experiment was performed for 3 days with stable gas performance and low blood flow resistance. The combination of this oxygenator and centrifugal pump may be advantageous to enhance biocompatibility and have less blood trauma characteristics.     

Development of a New Hollow Fiber Silicone Membrane Oxygenator: In Vitro Study

An experimental silicone hollow fiber membrane oxygenator for long-term extracorporeal membrane oxygenation (ECMO) was developed in our laboratory using an ultrathin silicone hollow fiber. However, the marginal gas transfer performances and a high-pressure drop in some cases were demonstrated in the initial models. In order to improve performance the following features were incorporated in the most recent oxygenator model: increasing the fiber length and total surface area, decreasing the packing density, and modifying the flow distributor. The aim of this study was to evaluate the gas transfer performances and biocompatibility of this newly improved model with in vitro experiments. According to the established method in our laboratory, in vitro studies were performed using fresh bovine blood. Gas transfer performance tests were performed at a blood flow rate of 0.5 to 6 L/min and a V/Q ratio (V = gas flow rate, Q = blood flow rate) of 2 and 3. Hemolysis tests were performed at a blood flow rate of 1 and 5 L/min. Blood pressure drop was also measured. At a blood flow rate of 1 L/min and V/Q = 3, the O2 and CO2 gas transfer rates were 72.45 +/- 1.24 and 39.87 +/- 2.92 ml/min, respectively. At a blood flow rate of 2 L/min and V/Q = 3, the O2 and CO2 gas transfer rates were 128.83 +/- 1.09 and 47.49 +/- 5.11 ml/min. Clearly, these data were superior to those obtained with previous models. As for the pressure drop and hemolytic performance, remarkable improvements were also demonstrated. These data indicate that this newly improved oxygenator is superior to the previous model and may be clinically acceptable for long-term ECMO application.     

Experimental study of pumpless ECMO during 24 hours using extracapillary blood flow type polypropylene membrane oxygenator

To remove carbon dioxide in acute respiratory failure, pumpless ECMO (extra-corporeal membrane oxygenation) experiment was carried out using extracapillary blood flow type membrane oxygenator, which was developed by our department and which has many advantages, compact, small priming volume and low pressure drop. The oxygenator is consisted with 17 cm in length, 200 microns in inner diameter, made of polypropylene with micropores. And it has 0.7 m2 of surface area and 60 ml of priming volume. In 14 canines, acute respiratory failure were made by hypoventilation (T.V. = 10 ml/kg, R.R. = 5 times/min). We compared with hypoventilation group (group 1, n = 5) and pumpless ECMO group (group 2, n = 9). Pumpless ECMO circuit is A-V bypass between femoral artery and femoral vein. The following results were obtained. 1. In group 1 severe hypoxia and hypercapnea were observed, and all 5 canines were dead within 4 hours. 2. In group 2 hypoxia and hypercapnea were improved by pumpless ECMO, and 4 in 9 lived for 24 hours. 3. Function in CO2 transfer with the P.H.O. is maintained in satisfactory condition for 24 hours. 4. The oxygenator seems to be available for long-term pumpless ECMO. 5. Degeneration of mitochondria in the acute respiratory failure was observed by electron microscopic examination. 6. Further examinations about the intracellular respiration and metabolism in pumpless ECMO should be needed.     

Development of a new hollow fiber silicone membrane oxygenator for ECMO: the recent progress.

Throughout the last 50 years, many improvements have been made for a more effective oxygenator. A large plate type membrane oxygenator, used by Clowes, and a coil type, used by Kolff, has evolved into the small hollow fiber oxygenator. The complex bubble oxygenator, or rotating disk oxygenator, has become a small disposable bubble oxygenator. The currently available oxygenators are extremely small, efficient, and can be used for extended periods of time. However, there are some problems with extracorporeal membrane oxygenation (ECMO). Currently in the United States, there are no clinically applicable hollow fiber ECMO oxygenators available, in spite of the extended ECMO application. Therefore, the development of a small, yet efficient, silicone hollow fiber membrane oxygenator for long-term ECMO usage was attempted. Based on the results of many experimental models, preclinical oxygenator models for long-term ECMO were developed in our laboratory using an ultra-thin silicone rubber hollow fiber membrane.     

New Generation Extracorporeal Membrane Oxygenation With MedTech Mag‐Lev,a Single‐Use,Magnetically Levitated,Centrifugal Blood Pump: Preclinical Evaluation in Calves

We have evaluated the feasibility of a newly developed single‐use, magnetically levitated centrifugal blood pump, MedTech Mag‐Lev, in a 3‐week extracorporeal membrane oxygenation (ECMO) study in calves against a Medtronic Bio‐Pump BPX‐80. A heparin‐ and silicone‐coated polypropylene membrane oxygenator MERA NHP Excelung NSH‐R was employed as an oxygenator. Six healthy male Holstein calves with body weights of about 100 kg were divided into two groups, four in the MedTech group and two in the Bio‐Pump group. Under general anesthesia, the blood pump and oxygenator were inserted extracorporeally between the main pulmonary artery and the descending aorta via a fifth left thoracotomy. Postoperatively, both the pump and oxygen flow rates were controlled at 3 L/min. Heparin was continuously infused to maintain the activated clotting time at 200–240 s. All the MedTech ECMO calves completed the study duration. However, the Bio‐Pump ECMO calves were terminated on postoperative days 7 and 10 because of severe hemolysis and thrombus formation. At the start of the MedTech ECMO, the pressure drop across the oxygenator was about 25 mm Hg with the pump operated at 2800 rpm and delivering 3 L/min flow. The PO₂ of the oxygenator outlet was higher than 400 mm Hg with the PCO₂ below 45 mm Hg. Hemolysis and thrombus were not seen in the MedTech ECMO circuits (plasma‐free hemoglobin [PFH] < 5 mg/dL), while severe hemolysis (PFH > 20 mg/dL) and large thrombus were observed in the Bio‐Pump ECMO circuits. Plasma leakage from the oxygenator did not occur in any ECMO circuits. Three‐week cardiopulmonary support was performed successfully with the MedTech ECMO without circuit exchanges. The MedTech Mag‐Lev could help extend the durability of ECMO circuits by the improved biocompatible performances.     

Description of a flow optimized oxygenator with integrated pulsatile pump

Extracorporeal membrane oxygenation (ECMO) is a well-established therapy for several lung and heart diseases in the field of neonatal and pediatric medicine (e.g., acute respiratory distress syndrome, congenital heart failure, cardiomyopathy). Current ECMO systems are typically composed of an oxygenator and a separate nonpulsatile blood pump. An oxygenator with an integrated pulsatile blood pump for small infant ECMO was developed, and this novel concept was tested regarding functionality and gas exchange rate. Pulsating silicone tubes (STs) were driven by air pressure and placed inside the cylindrical fiber bundle of an oxygenator to be used as a pump module. The findings of this study confirm that pumping blood with STs is a viable option for the future. The maximum gas exchange rate for oxygen is 48mL/min/L(blood) at a medium blood flow rate of about 300mL/min. Future design steps were identified to optimize the flow field through the fiber bundle to achieve a higher gas exchange rate. First, the packing density of the hollow-fiber bundle was lower than commercial oxygenators due to the manual manufacturing. By increasing this packing density, the gas exchange rate would increase accordingly. Second, distribution plates for a more uniform blood flow can be placed at the inlet and outlet of the oxygenator. Third, the hollow-fiber membranes can be individually placed to ensure equal distances between the surrounding hollow fibers.     

A description of a prototype miniature extracorporeal membrane oxygenation circuit using current technologies in a sheep model

In the United States, standardization of neonatal extracorporeal membrane oxygenation (ECMO) circuit was achieved during the 1980s. Since that time, the consoles and components of the ECMO circuit have remained fundamentally unchanged (bladder, rollerpump, silicone membrane oxygenator). Extracorporeal technology, however, has witnessed many significant advancements in components during the past two decades. These new technologies have characteristics that may improve outcomes when applied in the ECMO arena. Understanding how these technologies perform in long-term applications is necessary. Therefore, the purpose of this project is to evaluate the performance of a miniature ECMO circuit consisting of current generation technologies in an animal model. An ECMO circuit (prime volume 145 mL) was designed that included a hollow fiber oxygenator and a remote mounted centrifugal pump. All circuit tubing and components were surface coated. Three sheep (approx 13 kg) were placed on ECMO using standard neck cannulation techniques and maintained according to clinical protocols. Technical implementation, oxygenator function, and hematological parameters were accessed. Duration of ECMO was 20, 48, and 58 hours. There was no evidence of oxygenator failure, as measured by pressure drop and oxygen transfer, in any of the procedures. No plasma leak was observed in any oxygenators. Platelet count trended downward after 24 hours. Visual inspection after ECMO showed very little evidence of gross thrombosis. This ECMO circuit design departs dramatically from the typical North American systems. The use of this console and components facilitated a 70% reduction in priming volume over a traditional ECMO circuit. Further investigations should be conducted to determine if circuit miniaturization can reduce the morbidity associated with blood product consumption and the bloods contact with the artificial surfaces of the ECMO circuitry.     

Technical Indicators to Evaluate the Degree of Large Clot Formation Inside the Membrane Fiber Bundle of an Oxygenator in an In Vitro Setup

The most common technical complication during ECMO is clot formation. A large clot inside a membrane oxygenator reduces effective membrane surface area and therefore gas transfer capabilities, and restricts blood flow through the device, resulting in an increased membrane oxygenator pressure drop (dpMO). The reasons for thrombotic events are manifold and highly patient specific. Thrombus formation inside the oxygenator during ECMO is usually unpredictable and remains an unsolved problem. Clot sizes and positions are well documented in literature for the Maquet Quadrox‐i Adult oxygenator based on CT data extracted from devices after patient treatment. Based on this data, the present study was designed to investigate the effects of large clots on purely technical parameters, for example, dpMO and gas transfer. Therefore, medical grade silicone was injected into the fiber bundle of the devices to replicate large clot positions and sizes. A total of six devices were tested in vitro with silicone clot volumes of 0, 30, 40, 50, 65, and 85 mL in accordance with ISO 7199. Gas transfer was measured by sampling blood pre and post device, as well as by sampling the exhaust gas at the devices’ outlet at blood flow rates of 0.5, 2.5, and 5.0 L/min. Pre and post device pressure was monitored to calculate the dpMO at the different blood flow rates. The dpMO was found to be a reliable parameter to indicate a large clot only in already advanced “clotting stages.” The CO₂ concentration in the exhaust gas, however, was found to be sensitive to even small clot sizes and at low blood flows. Exhaust gas CO₂ concentration can be monitored continuously and without any risks for the patient during ECMO therapy to provide additional information on the endurance of the oxygenator. This may help detect a clot formation and growth inside a membrane oxygenator during ECMO even if the increase in dpMO remains moderate.     

The Influence of a Heparin-Coated Oxygenator During Cardiopulmonary Bypass on Postoperative Lung Oxygenation Capacity in Pediatric Patients with Congenital Heart Anomalies

A bstract Background : Cardiopulmonary bypass (CPB) causes an inflammatory response and remarkably depresses the oxygenation capacity of the lung in pediatric patients with pulmonary hypertension. Although a heparin-coated circuit is more biocompatible than an uncoated circuit, the beneficial effect of a heparin-coated circuit on the postoperative lung function in the pediatric patients remains unknown. Methods : Sixty patients younger than 3-years-old undergoing heart operations for ventricular septal defect were divided into three groups: group I = children (n = 11) without pulmonary hypertension who underwent CPB with an uncoated oxygenator; group II = children (n = 32) with pulmonary hypertension who underwent CPB with an uncoated oxygenator; and group III = children (n = 17) with pulmonary hypertension who underwent CPB with a heparin-coated oxygenator. A respiratory index (RI) was used to assess the oxygenation capacity of the lung. Results : RI in group II was significantly higher than in group I and intubation time in group II was significantly longer than in group I. There was a positive correlation between preoperative pulmonary-systemic blood pressure ratio and RI at 3 hours post-CPB. Three and six hours post-CPB, RI in group III was significantly lower than in group II, but there was no significant difference in RI between both groups at 12 hours post-CPB. Conclusions : Pulmonary hypertensive pediatric patients were vulnerable to postperfusion lung injury. Beneficial effects of a heparin-coated oxygenator in a CPB circuit was limited to the early hours post-CPB and the postoperative clinical course was not modified by the heparin-coating of a membrane oxygenator.     

静脉-动脉体外膜肺氧合过程发生氧合器假性氧合不良的识别与处理

目的总结主动脉夹层患者在接受体外膜氧合(ECMO)支持过程中发生氧合器假性氧合不良的处理。方法1例患者清醒、自主呼吸、因心衰以“心肌炎”于外院行静脉-动脉(V-A)ECMO治疗60 h后完善彩超等检查,怀疑“马凡综合征”转入我科,ECMO辅助至第70 h患者自述呼吸困难,痰多,经皮血氧饱和度(SpO2)进行性下降至89%,调节ECMO氧浓度至100%后监测氧合器后动脉血气氧分压(PaO2)为92 mmHg,怀疑氧合器“假性氧合不良”,于氧合器动、静脉段先后使用分流量为0.7 L/min和1.4 L/min的旁路处理,并适当安抚患者,辅助至第94 h确诊主动脉夹层后,于急诊下行Bentall+二尖瓣成形+冠状动脉旁路移植术。结果ECMO总辅助时间94 h,其中院外60 h,院内34 h,平均血流量为3.5 L/min,平均氧浓度为60%,辅助至第70 h出现假性氧合不良,经处理后患者SpO2上升至100%,患者诉症状减轻,外科手术顺利,术毕顺利脱离心肺转流,经评估无需继续ECMO辅助,术后28 h苏醒,50 h脱离呼吸机,10 d后康复出院。结论熟悉插管、氧合器等参数有助于鉴别ECMO辅助过程的“假性氧合不良”现象,避免更换氧合器,节约医疗成本的同时保障了患者安全。     

At least thirty-four days of animal continuous perfusion by a newly developed extracorporeal membrane oxygenation system without systemic anticoagulants

We developed an extracorporeal membrane oxygenation (ECMO) system with high antithrombogenicity and durability characteristics for prolonged continuous cardiopulmonary support. The oxygenator consists of a special hollow-fiber-type polyolefin gas-exchange membrane, which has an ultrathin dense layer in contact with the blood, in order to prevent plasma leakage during protracted use (Platinum Cube NCVC). The centrifugal pump (RotaFlow) is free of seals. The entire blood-contacting surface of the system is coated with a newly developed heparin material (Toyobo-NCVC coating). We performed a venoarterial bypass in a goat, and the ECMO system was driven for 34 days without systemic anticoagulants. Plasma leakage from the oxygenator did not occur, and sufficient gas exchange performance was maintained. Thrombus formation was hardly observed in the ECMO system except in the casing margins of the oxygenator. This ECMO system showed potential for long-term cardiopulmonary support with minimal or no use of systemic anticoagulants.     

Extracorporeal life support during and after bilateral sequential lung transplantation in patients with pulmonary artery hypertension

The use of extracorporeal membrane oxygenator instead of standard cardiopulmonary bypass during lung transplantation is debatable. Moreover, recently, the concept of prolonged postoperative extracorporeal membrane oxygenator (ECMO) support has been introduced in many transplant centers to prevent primary graft dysfunction (PGD) and improve early and long-term results. The objective of this study was to review the results of our extracorporeal life support strategy during and after bilateral sequential lung transplantation (BSLT) for pulmonary artery hypertension. We review retrospectively our experience in BSLT for pulmonary artery hypertension between January 2010 and August 2018. A total of 38 patients were identified. Nine patients were transplanted using cardiopulmonary bypass (CPB), in eight cases CPB was followed by a prolonged ECMO (pECMO) support, 14 patients were transplanted on central ECMO support, and seven patients were transplanted with central ECMO support followed by a pECMO assistance. The effects of different support strategies were evaluated, in particular in-hospital morbidity, mortality, incidence of PGD, and long-term follow-up. The use of CPB was associated with poor postoperative results and worse long-term survival compared with ECMO-supported patients. Predictive preoperative factors for the need of intraoperative CPB instead of ECMO were identified. The pECMO strategy had a favorable effect to mitigate postoperative morbidity and mortality, not only in intraoperative ECMO-supported patients, but even in CPB-supported cases. In our experience, ECMO may be considered as the first choice circulatory support for lung transplantation. Sometimes, in very complex cases, CBP is still necessary. The pECMO strategy is very effective to reduce incidence of PGD even in CPB-supported patients.     

Establishment of a novel miniature veno‐venous extracorporeal membrane oxygenation model in the rat

Recently, veno‐venous extracorporeal membrane oxygenation (V‐V ECMO) has been commonly used in the world to support patients with severe respiratory failure. However, V‐V ECMO is a new technology compared to veno‐arterial extracorporeal membrane oxygenation and cardiopulmonary bypass, and there are few reports of basic research. Although continuing research is desired, clinical research that standardizes conditions such as patients’ background characteristics is difficult. The purpose of this study was to establish a simple and stably maintainable miniature V‐V ECMO model to study the mechanisms of the biological reactions in circulation during V‐V ECMO. The V‐V ECMO system consisted of an original miniature membrane oxygenator, polyvinyl chloride tubing line, and roller pump. The priming volume of this system was only 8 mL. Polyethylene tubing was used to cannulate the right femoral vein as the venous return cannula for the V‐V ECMO system. A 16‐G cannula was passed through the right internal jugular vein and advanced into the right atrium as the conduit for venous uptake. The animals were divided into 2 groups: SHAM group and V‐V ECMO group. V‐V ECMO was initiated and maintained at 50‐60 mL/kg/min, and oxygen was added into the oxygenator during V‐V ECMO at a concentration of 100% (pump flow:oxygen = 1:10). Blood pressure was measured continuously, and blood cells were measured by blood collection. During V‐V ECMO, the blood pressure and hemodilution rate were maintained around 80 mm Hg and 20%, respectively. Hb was kept at >10 g/dL, and V‐V ECMO could be maintained without blood transfusion. It was possible to confirm oxygenation of and carbon dioxide removal from the blood. Likewise, the pH was adequately maintained. There were no problems with this miniature V‐V ECMO system, and extracorporeal circulation progressed safely. In this study, a novel miniature V‐V ECMO model was established in the rat. A miniature V‐V ECMO model appears to be very useful for studying the mechanisms of the biological reactions during V‐V ECMO and to perform basic studies of circulation assist devices.     

Impact of high mechanical shear stress and oxygenator membrane surface on blood damage relevant to thrombosis and bleeding in a pediatric ECMO circuit

The roles of the large membrane surface of the oxygenator and the high mechanical shear stress (HMSS) of the pump in the extracorporeal membrane oxygenation (ECMO) circuit were examined under a pediatric support setting. A clinical centrifugal pump and a pediatric oxygenator were used to construct the ECMO circuit. An identical circuit without the oxygenator was constructed for comparison. Fresh human blood was circulated in the two circuits for 4 hours under the identical pump speed and flow. Blood samples were collected hourly for blood damage assessment, including platelet activation, generation of platelet-derived microparticles (PDMP), losses of key platelet hemostasis receptors (glycoprotein (GP) Ibα (GPIbα) and GPVI), and high molecular weight multimers (HMWM) of von Willebrand factor (VWF) and plasma free hemoglobin (PFH). Platelet adhesion on fibrinogen, VWF, and collagen was further examined. The levels of platelet activation and generation of PDMP and PFH exhibited an increasing trend with circulation time while the expression levels of GPIbα and GPVI receptors on the platelet surface decreased. Correspondingly, the platelets in the blood samples exhibited increased adhesion capacity to fibrinogen and decreased adhesion capacities on VWF and collagen with circulation time. Loss of HMWM of VWF occurred in both circuits. No statistically significant differences were found in all the measured parameters for blood damage and platelet adhesion function between the two circuits. The results indicate that HMSS from the pump played a dominant role in blood damage associated with ECMO and the impact of the large surface of the oxygenator on blood damage was insignificant.     

Use of the CDI blood parameter monitoring system 500 for continuous blood gas measurement during extracorporeal membrane oxygenation simulation

The Oximetrix III Opticath (Abbott Critical Care Systems) is used for continuous measurement of venous saturation in a variety of applications, including extracorporeal membrane oxygenation (ECMO), despite clinical reports that have presented data showing poor accuracy of these devices. The CDI Blood Parameter Monitoring System 500 (Terumo) is an inline blood gas monitoring tool commonly used during cardiopulmonary bypass procedures to continuously assess oxygen saturation, blood gases, potassium, and bicarbonate. The purpose of this experiment was to compare the Opticath and the CDI 500 in trending venous blood saturation during a simulation of ECMO. An ECMO simulation circuit consisting of a silicone rubber membrane oxygenator and a stainless steel heat exchanger was constructed, and a standard venous reservoir bag was used to represent the patient. The CDI and the Opticath were incorporated side by side into a shunt that originated just before the oxygenator and returned flow to the venous line. The circuit was primed with fresh porcine blood and conditioned with the addition of CO2 to simulate typical venous blood under ECMO conditions. After an initial calibration procedure, samples were drawn and analyzed by an AVL Opti CCA (Roche/Osmetech) every 4-8 hours for a period of 7 days, with calibration of each device at sample intervals. The data were plotted, and a least squares regression line was calculated. The average error for venous saturation of the CDI and Opticath after 72 hours was 3.86 and 9.51 respectively. At 168 hours, error for the CDI was 8.37, and the Opticath had an error of 14.78. A correlation analysis of the CDI and AVL CCA analyzer yielded a correlation coefficient of r = .88 at 72 hours and r = .84 at 168 hours. Correlation between the Opticath and the AVL CCA yielded a correlation coefficient of r = .77 at 72 hours and r = .55 at 168 hours. Based on these findings, the CDI 500 is an effective tool for monitoring venous blood saturation under simulated conditions of ECMO. Keywords: CDI 500, Opticath, extracorporeal membrane oxygenation, venous saturation.     

边缘性供心移植术中采用体外膜肺氧合技术四例

目的 研究体外膜肺氧合(ECMO)技术用于边缘性供心移植的临床效果.方法 4例患者心脏移植时采用ECMO技术,其供心的冷缺血时间长达4.8～8.0 h.术中采用ECMO技术代替体外循环,全流量控制在4.5～5.0 L/min,术后流量降到1/2左右时,改为经典的ECMO心脏辅助管路的连接方式,带ECMO辅助回到重症监护室,随后在合适的时机撤除ECMO的辅助.结果 4例手术均顺利完成,主动脉开放后心脏自动复跳.术中阻断时间为(90±3)min,转机(136±14)min,转流时的主动脉流量为50～70 ml·kg-1·min-1,氧流量为2～4 L/min.4例患者均于术后第2天撤除ECMO,术后ECMO辅助时间为(16±4)h.2例术后出现出血,1例右下肢出现淋巴漏和神经过敏,经过积极治疗后好转,无右心衰竭和三尖瓣明显返流现象.4例患者恢复顺利,出院时左心室舒张末径为37～43 mm,左心室射血分数为56 %～64 %,三尖瓣无返流或仅有轻度返流,心功能均为Ⅱ级.结论 以ECMO代替体外循环技术可以有效地保护供心,有利于经历长时间缺血的供心恢复功能.     

A Newly Developed Silicone-Coated Membrane Oxygenator for Long-Term Cardiopulmonary Bypass and Cardiac Support

Abstract: The surface of polypropylene hollow fiber was successfully coated with a very thin (0.2 μm) silicone layer. Experimental studies were performed in long-term (6 h) normothermic cardiopulmonary bypass (CPB) using 10 goats. A conventional membrane oxygenator (Mera Exce-lung HPO-lSH, MERA, Tokyo, Japan) was used for 5 goats as a control (Group C) and a new silicone-coated membrane oxygenator, which is of the same construction as that of the one used for Group C, for 5 (Group S). The O₂transfer and CO₂removal functions showed the same ranges. In the other parameters, there were no differences between the 2 groups. As for hemolysis, however, the plasma free hemoglobin of Group S was lower than that of Group C. Currently, 3 chronic percutaneous cardiopulmonary support (PCPS) experimental models have been conducted, and there has been no evidence of thromboembo-lism or deterioration of the oxygenator. In conclusion, this new oxygenator is suitable not only for CPB, but also for long-term cardiac support.     

Development of a new silicone membrane oxygenator for ECMO.

Two types small and efficient ECMO oxygenators were developed utilizing the most up to date hollow fiber technology. Newly silicone hollow fibers possess sufficient mechanical strength while maintaining ultra thin walls of 50 micro meter. Two types of oxygenators were made with this fiber. The fiber length for the type 1 module is 150mm with a priming volume 194 cc (surface area 1.3 m(2)) and type 2 has a fiber length of 100 mm with a 144 cc priming volume (the surface area 0.8 m(2)). The studies were performed at 0.5, 1.0 and 2.0 L/min of blood flow and these oxygenators demonstrated. O(2) gas transfer rate of 69+/-4 ml/min/L for type 1 and 68+/-6 ml/min/L for type 2. The CO(2) gas transfer rate was 25+/-2 ml/min/L for type 1 and 32+/-2 ml/min/L for type 2. These results demonstrate type 2 oxygenator has similar gas exchange capabilities to those of Kolobows' oxygenator which has about 2.0 times larger surface area. Additionally, comparative hemolysis tests were preformed with this new oxygenator and the Kolbow. The NIH value was 0.006 (g/100 L) for the type 1 oxygenator and 0.01 (g/100 L) for the Kolbow oxygenator. These results suggested that this ECMO oxygenator had sufficient gas exchange performance in spite of being smaller and induced minimal blood damage.