Microporous Membrane Oxygenator Research Articles

Effect of Normobaric versus Hypobaric Oxygenation on Gaseous Microemboli Removal in a Diffusion Membrane Oxygenator: An In Vitro Comparison

Gaseous microemboli (GME) are an abnormal physiological occurrence during cardiopulmonary bypass and extracorporeal membrane oxygenation (ECMO). Several studies have correlated negative sequelae with exposure to increased amounts of GME. Hypobaric oxygenation is effective at eliminating GME in hollow-fiber microporous membrane oxygenators. However, hollow-fiber diffusion membrane oxygenators, which are commonly used for ECMO, have yet to be validated. The purpose of this study was to determine if hypobaric oxygenation, compared against normobaric oxygenation, can reduce introduced GME when used on diffusion membrane oxygenators. Comparison of a sealed Quadrox-iD with hypobaric sweep gas (.67 atm) vs. an unmodified Quadrox-iD with normal atmospheric sweep gas (1 atm) in terms of GME transmission during continuous air introduction (50 mL/min) in a recirculating in vitro circuit, over a range of flow rates (3.5, 5 L/min) and crystalloid prime temperatures (37°C, 28°C, and 18°C). GME were measured using three EDAC Doppler probes positioned pre-oxygenator, post-oxygenator, and at the arterial cannula. Hypobaric oxygenation vs. normobaric oxygenation significantly reduced hollow-fiber diffusion membrane oxygenator GME transmission at all combination of pump flows and temperatures. There was further significant reduction in GME count between the oxygenator outlet and at the arterial cannula. Hypobaric oxygenation used on hollow-fiber diffusion membrane oxygenators can further reduce GME compared to normobaric oxygenation. This technique may be a safe approach to eliminate GME during ECMO.

In vitro elimination of gaseous microemboli utilizing hypobaric oxygenation in the Terumo® FX15 oxygenator.

This study examines the efficacy of hypobaric oxygenation as it relates to the elimination of gaseous microemboli (GME) at designated flow, pressure and temperature combinations. Hypobaric oxygenation was employed for experimental trials (n=60), but not for control trials (n=60), while circuit design, data measurements and testing conditions were maintained for both settings. Hypobaric oxygenation conditions were created by applying 100% oxygen at sub-atmospheric sweep gas pressures of 0.67 atmospheres to the gas phase of an integrated hollow-fiber microporous membrane oxygenator. GME were quantified using an Emboli Detection and Classification system (EDAC), while a continuous air infusion, at a rate of 100 ml/min, was applied to the circuit. Trials were conducted at 37°C, 28°C, and 18°C and at two flow and line pressure combinations of: 3.5 L/min & 150 mmHg and 5 L/min & 200 mmHg. Sub-atmospheric sweep gas pressures allowed adequate oxygenation independent of carbon dioxide removal while significantly reducing the potential entrance of nitrogen into the blood. GME was reduced significantly across all temperatures and flows when compared to control trials; GME counts were reduced by 99.7% post-oxygenator and 99.99% at the arterial cannula. Correlation between the use of hypobaric oxygenation and GME counts suggests hypobaric oxygenation could play a significant role in the reduction of GME.

Elimination of Gaseous Microemboli From Cardiopulmonary Bypass Using Hypobaric Oxygenation

Numerous gaseous microemboli (GME) are delivered into the arterial circulation during cardiopulmonary bypass (CPB). These emboli damage end organs through multiple mechanisms that are thought to contribute to neurocognitive deficits after cardiac surgery. Here, we use hypobaric oxygenation to reduce dissolved gases in blood and greatly reduce GME delivery during CPB. Variable subatmospheric pressures were applied to 100% oxygen sweep gas in standard hollow fiber microporous membrane oxygenators to oxygenate and denitrogenate blood. GME were quantified using ultrasound while air embolism from the surgical field was simulated experimentally. We assessed end-organ tissues in swine postoperatively using light microscopy. Variable sweep gas pressures allowed reliable oxygenation independent of carbon dioxide removal while denitrogenating arterial blood. Hypobaric oxygenation produced dose-dependent reductions of Doppler signals produced by bolus and continuous GME loads in vitro. Swine were maintained using hypobaric oxygenation for 4 hours on CPB with no apparent adverse events. Compared with current practice standards of oxygen/air sweep gas, hypobaric oxygenation reduced GME volumes exiting the oxygenator (by 80%), exiting the arterial filter (95%), and arriving at the aortic cannula (∼100%), indicating progressive reabsorption of emboli throughout the CPB circuit in vivo. Analysis of brain tissue suggested decreased microvascular injury under hypobaric conditions. Hypobaric oxygenation is an effective, low-cost, common sense approach that capitalizes on the simple physical makeup of GME to achieve their near-total elimination during CPB. This technique holds great potential for limiting end-organ damage and improving outcomes in a variety of patients undergoing extracorporeal circulation.

Evaluation of Quadrox-i® Adult Hollow Fiber Oxygenator with Integrated Arterial Filter

Gaseous microemboli (GME) remain a challenge for cardiopulmonary bypass procedures in adult as well as pediatric cardiac surgery patients. The present study tested the effectiveness of a new adult membrane oxygenator in models both with and without an integrated arterial filter to evaluate GME trapping capability and determine membrane pressure drops at various flow rates and temperatures. The experimental circuit included a RotaFlow centrifugal blood pump, Quadrox-i® (n= 8) or Quadrox® (n= 8) adult microporous membrane oxygenator, and Sorin adult tubing package. A Sorin Cardiovascular® VVR® 4000i venous reservoir served as pseudo-patient. The circuit was primed with 900 mL heparinized human red blood cells and 300 mL Lactated Ringer’s solution. The final hematocrit was 36%. Tests were performed at different flow rates (4 L/min, 5 L/min, and 6 L/min) and temperatures (35° and 30°). Five mL of bolus air was injected into the venous line over 15 seconds using a syringe connected to a 3/8 × 1/2 luer connector. The Quadrox-i® adult microporous membrane oxygenator with integrated arterial filter had a similar pressure drop at 4 L/min and 35°C compared with Quadrox® membrane oxygenator whereas it had higher pressure drops at 5 L/min and 6 L/min (p<.001). Quadrox-i® adult microporous membrane oxygenator reduced the total emboli count and total emboli volume delivered to the pseudo-patient at all flow rates (p<.001). The emboli handling of Quadrox-i® adult microporous membrane oxygenator was not affected by flow rate and temperature. Compared with the traditional Quadrox® oxygenator, Quadrox-i® adult microporous membrane oxygenator with integrated arterial filter and Softline coating has improved GME handling capacity.

Comparison of Two Different Minimized Extracorporeal Circulation Systems: Hematological Effects after Coronary Surgery

Cardiopulmonary bypass induces hemolysis and activation of inflammatory and coagulation systems as a result of a combination of mechanical trauma and biological mechanisms. The aim of our study was to evaluate the performance of two different minimized extracorporeal circulation (ECC) systems and to compare their influence on blood components. From January 2003 to December 2008, 1,218 patients underwent coronary artery bypass grafting with minimized ECC. The PRECiSe system (41%) consists of a microporous capillary membrane oxygenator (MO) and a diagonal pump (DeltaStream DP2). The MECC system (59%) is composed of a polymethylpentene MO with a plasma-tight diffusion membrane and a centrifugal pump (RotaFlow). Serial blood samples were taken preoperatively (T0), on arrival to intensive care unit (T1), 6 hours postoperatively (T2), and at discharge (T3). Demographic data, intraoperative, and technical parameters were similar in both groups. At T1 and T2, the platelet count in the PRECiSe group was significantly lower than that in the MECC group (p < 0.01). Furthermore, at T1, levels of lactate dehydrogenase were significantly higher in the PRECiSe group (p < 0.05). In addition, postoperative blood loss was significantly higher using the PRECiSe system (p < 0.05). In conclusion, cardiac surgery with the MECC system is associated with less postoperative bleeding and improved blood cell preservation.

The Effect of High Pressure on Microporous Membrane Oxygenator Failure

A retrospective study to determine the relationship between early microporous membrane oxygenator (MMO) failure and blood pressure at the MMO outlet (Pmo) was conducted using data collected with 19 dogs (22 +/- 1 kg, mean +/- SEM) undergoing routine normothermic cardiopulmonary bypass. Because gas flow was maintained at a high level, it could not be used to control CO2 exchange. Instead, blood PCO2 was controlled by adding CO2 to the sweep gas. Blood PO2 was controlled as suggested by the manufacturer, by adjusting the %O2 in the gas phase (g). Blood flow was 2575 +/- 54 ml/min; Pmo ranged from 173 to 790 mm Hg; and hematocrit was 33 +/- 1%. O2 exchange was calculated from blood gas parameters. Changes in the diffusion potential of O2 (delta PO2) and CO2 (delta PCO2) and MMO performance (P, taken as oxygen exchange normalized to a diffusion potential of 100 mm Hg) indicated MMO failure. Initial values, taken within 60 min of bypass initiation, were compared to final values taken at 226 +/- 9 min of bypass. Despite higher final delta PO2 (411 +/- 9 vs. 538 +/- 19 mm Hg, p less than 0.0001 paired t-test) and delta PCO2 (18.6 +/- 2.4 vs. 30.5 +/- 4.7 mm Hg, p less than 0.0017), arterial blood PO2 decreased (159 +/- 15 to 89 +/- 6 mm Hg, p less than 0.0005) and PCO2 increased (36.4 +/- 1.5 to 46.1 +/- 3.0 mm Hg, p less than 0.0039), and the performance decreased [24.5 +/- 1.1 to 20.1 +/- 0.7 (ml/min)/(100 mm Hg), p less than 0.0001].(ABSTRACT TRUNCATED AT 250 WORDS)

Initial clinical experience with the admiral oxygenator combined with separated suction

The Admiral, a new microporous membrane oxygenator with a low surface area, decreased priming volume and two separate reservoirs, was tested in 30 adult patients. This study was undertaken to evaluate blood path resistance, gas exchange capabilities and blood trauma in clinical use, with and without shed blood separation. Patients were divided into 3 groups. Group 1 had valve surgery without separation of suction, Group 2 had coronary artery bypass grafting (CABG) with direct blood aspiration and Group 3 had coronary artery bypass grafting with shed blood separation. The suctioned, separated, cardiotomy blood in Group 3 was treated with an autotransfusion device at the end of bypass before being returned to the patient. Theoretical blood flow could be achieved in all cases without problem. The pressure drop through the oxygenator averaged 88 +/- 13 mmHg at 4 l/min and 109 +/- 12 mmHg at 5 l/min. O(2) transfer was 163 +/- 27 ml/min. Free plasma haemoglobin rose in all groups, but significantly less in group 3. Lactate dehydrogenase (LDH) rose significantly in Groups 1 and 2. Platelets decreased in all groups without significant differences. Clinical experience with this new oxygenator was safe, the reduced membrane surface did not impair gas exchange and blood trauma could be minimized easily by separating shed blood, using the second cardiotomy reservoir.

ヘパリン起因性血小板減少症を合併した症例に対する体外循環について

Microemboli may impair cognitive function in patients undergoing heart surgery. Prebypass filtration has been shown to reduce particle load in the cardiopulmonary bypass (CPB) priming fluid. This study was performed to detect the embolic load of CPB priming fluid, to determine the efficacy of a 0.2 microm prebypass filter (PBF) in reducing emboli in the range of 0.1-5 microm and to provide guidelines for the handling of the device. A total of 12 CPB circuits were tested in two groups, using a laser light scattering particle counter, sensitive to microemboli in the range of 0.1-5 microm. In control group A, priming fluid before administration to the CPB circuit was analyzed. Group B circuits contained microporous membrane oxygenators (N = 5); group C consisted of CPB circuits with excluded membrane oxygenators (N = 7). When group A was compared to groups B and C, significantly more microemboli were found in the categories 0.2 microm, 0.5 microm, 0.8 microm for both groups B and C (p < .05). Group C circuits had higher microemboli counts in the categories 1.5 microm and 3 microm (p < .05) when compared to group B. Microemboli bigger than 0.2 microm could be eliminated after 2 min of prebypass filtration with a CPB flow of 5 L/min. The number of microemboli smaller than 0.2 microm was reduced substantially. Small microemboli with a size of 0.1 microm originate mainly from the priming solution. Microemboli in the range of 0.2 microm, 0.5 microm, and 0.8 microm originate mainly from the CBP circuit. In circuits with bypassed membrane oxygenators, a higher microemboli count in the range of 1.5 microm and 3 microm may be explained by a possible filtering capacity of membrane oxygenators. The 0.2 microm PBF is an effective tool to reduce the particle load in the CPB priming fluid.

Introduction of a New Oxygenator Including a Tight Fiber for Long-term ECMO in Infants

Plasma leakage is a known complication in the use of a microporous membrane oxygenator in extracorporeal membrane oxygenation cases. An oxygenator with a tight fiber offers an alternative whereby plasma leakage can be prevented. We report the use of such an oxygenator in 13 extracorporeal membrane oxygenation cases in which no problems were encountered regarding blood trauma and plasma leakage.

Prolonged Extracorporeal Membrane Oxygenation Support for Acute Respiratory Distress Syndrome

When all conventional treatments for respiratory failure in patients with acute respiratory distress syndrome (ARDS) have failed, extracorporeal membrane oxygenation (ECMO) can provide a chance of survival in these desperately ill patients. A 49-year-old male patient developed septic shock and progressive ARDS after liver abscess drainage. Venovenous ECMO was given due to refractory respiratory failure on postoperative day 6. Initially, two heparin-binding hollow-fiber microporous membrane oxygenators in parallel were used in the ECMO circuit. Twenty-two oxygenators were changed in the first 22 days of ECMO support because of plasma leak in the oxygenators. Each oxygenator had an average life of 48 hours. Thereafter, a single silicone membrane oxygenator was used in the ECMO circuit, which did not require change during the remaining 596 hours of ECMO. The patient's tidal volume was only 90 mL in the nadir and less than 300 mL for 26 days during the ECMO course. The patient required ECMO support for 48 days and survived despite complications, including septic shock, ARDS, acute renal failure, drug-induced leukopenia, and multiple internal bleeding. This patient received an unusually long duration of ECMO support. However, he survived, recovered well, and was in New York Heart Association functional class I-II, with a forced expiratory volume in 1 second of 81% of the predicted level 18 months later. In conclusion, ECMO can provide a chance of survival for patients with refractory ARDS. The reversibility of lung function is possible in ARDS patients regardless of the severity of lung dysfunction at the time of treatment.

Gaseous Microemboli and the Influence of Microporous Membrane Oxygenators

Gaseous microemboli (GME) are still an unsolved problem of extracorporeal circuits. They are associated with organ injury during cardiopulmonary bypass. Microbubbles of different sizes and number are generated in the blood as the result of different components of the extracorporeal circuit as well as surgical maneuvers. The aim of our study was to observe the behavior of microporous membrane oxygenators to GME in the daily use and in an in vitro model. For the detection of microbubbles, we used a two-channel ultrasonic bubble counter based on 2-MHz Doppler-System with special ultrasound probes. The amount and size of GME were monitored before and after membrane. In 28 scheduled cases with 3 different oxygenators and variability of surgical procedures, we observed the bubble activity in the extracorporeal circuit. In addition, we used an in-vitro model to study the ability of six different oxygenators by removing air in various tests. The oxygenators tested were manufactured with different membrane technologies. The results of our investigations showed varying membrane design lead to a partial removal of GME as well as a change in size and numbers of microbubbles.

Reduction of Microemboli Count in the Priming Fluid of Cardiopulmonary Bypass Circuits

Microemboli may impair cognitive function in patients undergoing heart surgery. Prebypass filtration has been shown to reduce particle load in the cardiopulmonary bypass (CPB) priming fluid. This study was performed to detect the embolic load of CPB priming fluid, to determine the efficacy of a 0.2 μm prebypass filter (PBF) in reducing emboli in the range of 0.1–5 μm and to provide guidelines for the handling of the device. A total of 12 CPB circuits were tested in two groups, using a laser light scattering particle counter, sensitive to microemboli in the range of 0.1–5 μm. In control group A, priming fluid before administration to the CPB circuit was analyzed. Group B circuits contained microporous membrane oxygenators (N = 5); group C consisted of CPB circuits with excluded membrane oxygenators (N = 7). When group A was compared to groups B and C, significantly more microemboli were found in the categories 0.2 μm, 0.5 mμ, 0.8 μm for both groups B and C (p &lt; .05). Group C circuits had higher microemboli counts in the categories 1.5 μm and 3 μm (p &lt; .05) when compared to group B. Microemboli bigger than 0.2 μm could be eliminated after 2 min of prebypass filtration with a CPB flow of 5 L/min. The number of microemboli smaller than 0.2 μm was reduced substantially. Small microemboli with a size of 0.1 μm originate mainly from the priming solution. Microemboli in the range of 0.2 μm, 0.5 μm, and 0.8 μm originate mainly from the CBP circuit. In circuits with bypassed membrane oxygenators, a higher microemboli count in the range of 1.5 μm and 3 μm may be explained by a possible filtering capacity of membrane oxygenators. The 0.2 μm PBF is an effective tool to reduce the particle load in the CPB priming fluid.

The transition from the bubble oxygenator to the microporous membrane oxygenator.

The transition from bubble oxygenators to microporous membrane oxygenators is a good example of how industry working with customers and material suppliers can help improve a surgical technique, such as cardiopulmonary bypass. The development is characterized by many individuals who, through their inventiveness and determination, made the transition possible. While the medical personnel involved in the transition may be well known to professionals in the medical field by their other endeavors, many of the key engineers and industry entrepreneurs are mainly unknown. The purpose of this paper is to outline key elements of engineering and material science in the history of the transition, and also to identify some of the key individuals as well (Figure 1).

Spontaneous gas bubbling in microporous oxygenators.

During operation of the microporous membrane oxygenators at some conditions, gas microbubbles penetrate into the blood. This effect, so-called spontaneous bubbling, takes place even when the blood pressure is higher than the gas pressure. This phenomenon was confirmed experimentally both in a model cell with hydrophobic microporous hollow fibers being used in the oxygenators and in in vitro tests on the actual microporous hollow fiber oxygenator. We proposed a mechanism of spontaneous gas bubbling into liquid that contains dissolved gases. Because of a partial pressure gradient, the dissolved gases and water vapors are transported from blood into the gas pore. This causes Stefans gas flow directed from the liquid-gas interface. Because of the high hydraulic resistance of the micropores, gas pressure at the meniscus increases up to gas bubbling. A mishandled priming of the oxygenator as well as the blood pressure pulsation caused by the roller pump operation contribute to spontaneous gas bubbling in the microporous oxygenators. The flow and pressure in the hydrophobic pores were calculated for various gases.

Biocompatibility of a silicone-coated polypropylene hollow fiber oxygenator in an in vitro model

Background. A silicone-coated microporous hollow-fiber membrane oxygenator has been developed to prevent plasma leakage during long-term use. The objective of this study was to evaluate the biocompatibility of the oxygenator. Methods. A silicone-coated oxygenator was compared with an uncoated oxygenator in an in vitro model of cardiopulmonary bypass. Simulated circulation was maintained for 6 h at 37°C. Results. Platelet counts decreased significantly ( p < 0.05) and leukocyte counts tended to decline; however, the differences between groups were not significant. Concentrations of C3a increased significantly in both groups ( p < 0.05), but levels were significantly less in the silicone-coated oxygenator ( p = 0.008). In contrast, concentrations of C4a, β-thromboglobulin, and granulocyte elastase increased significantly ( p < 0.05), but the differences between groups were not significant. Conclusions. Silicone coating over a microporous hollow-fiber membrane may improve biocompatibility by reducing C3a activation.

Transient adhesion of platelets in pump-oxygenator systems: influence of SMA and nitric oxide treatments

We employed gamma scintigraphy to quantify the transient accumulations of platelets in pump-oxygenator systems employed in cardiopulmonary bypass (CPB). A flat sheet microporous polypropylene membrane oxygenator (Cobe Duo) was employed, with and without siloxane/caprolactone oligomer coating (SMA) (n = 8 each). The effect of nitric oxide gas infusion on platelet deposition was also evaluated for the uncoated Cobe Duo system (n = 10 each). Scintigraphic images of radiolabelled cells were obtained and converted to numbers of all platelets, labeled and unlabeled, adhering to the pump and oxygenator surfaces. These numbers were compared, by study group, for a 90-min period of normothermic CPB in the adult pig, employing standard prime and anticoagulation regimens. Platelets adhered in large numbers to control oxygenators, reaching maxima (> 20% of the circulating platelet mass) 30 min following institution of CPB, and decreasing for the duration of CPB. SMA treatment significantly decreased platelet adhesion following a 5-10-min transient accumulation period. Nitric oxide infusion significantly reduced platelet adhesion throughout the CPB period. Platelet accumulations on the high fluid shear centrifugal pump surfaces increased monotonically to maxima at about the same time as for the oxygenators, but did not decrease thereafter. Higher platelet surface densities were observed on the centrifugal pump surfaces than on the oxygenator surfaces. CPB with the untreated circuit tended to reduce circulating platelet counts vs theoretical values based on hemodilution alone. In contrast, SMA significantly increased the circulating platelet count versus the untreated control group. These results indicate that platelet adherence to the foreign surfaces of CPB equipment are influenced in characteristic ways by time and fluid shear. SMA treatment and nitric oxide infusion both reduce platelet adhesion to oxygenator surfaces. SMA treatment spares these cells for the circulation.

The effects of gaseous nitric oxide on platelets and leukocytes in membrane oxygenators

Nitric oxide (NO), known as a potent endogenous platelet anti-adhesive, anti-aggregating, and disaggregating radical, was shown to reduce platelet trapping in microporous membrane oxygenators [1]. In an additional study we investigated the effects of gaseous NO on platelet and leukocyte activation markers during extracorporeal circulation. Two parallel separated extracorporeal circuits (n = 6) were filled with heparinized (1 IE/ml) fresh drawn blood from one healthy volunteer. The gas inlets of both oxygenators (M8 Jostra/Germany) received dry gas (21% oxygen, 5% carbon dioxide, 84% nitrogen); gaseous NO (20 ppm) was added to the gas inlet of one of the oxygenators, whereas the other one was used for control. Blood samples obtained from a venous reservoir and from the blood donor were investigated by flow cytometry for the following markers: leukocytes-CD11a, CD11b, HLA-DR, CD62L (L-selectin), and CD14. Platelets-P-selectin (CD62P), CD42b (GPlb), CD41a (GPIIbIIIa), and activated conformationally changed GP-IIbIIIa. Additional, platelets were stimulated with ADP (10 µM), epinephrine (10 µM), or both (each 5 µM) to investigate platelet reactivity. Further analysis included: coagulation parameters (fibrinogen, ATIII, heparin-time, prothrombin-time, fibrin monomers); platelet counts (in quadruplet); blood gas analysis; and leukocyte differential count. The main results are: (i) NO significantly attenuated platelet trapping within the membrane oxygenator (Fig ​(Fig1);1); (ii) In both oxygenators only small amounts (1-2%) of circulating activated (P-selectin or activated GPIIbIIIa) platelets were detectable over time; (iii) platelet reactivity to stimulating agents decreased during circulation, indicating platelet damage; (iv) NO seemed to preserve platelet reactivity to some degree which was pronounced with duration of circulation (Fig ​(Fig2);2); (v) there was no significant difference in loss of leukocytes, ie trapping of PMN and monocytes (lymphocytes remained stable) between the two oxygenators; (vi) leukocyte adhesion molecule expression was significantly altered during circulation, however, no differences were found between NO and control: HLA-DR and CD14 increased on monocytes, CDlla increased on lymphocytes, CDllb increased on monocytes and PMN, and L-selectin was reduced on monocytes and PMN, whereas L-selectin expression on lymphocytes increased over time; (vii) no significant differences were found lor coagulation parameters or blood gas analysis. Figure 1 Platelet (squares) and hemoglobin (circles) values in percent from baseline (start). *P < 0.05, **P < 0.01, paired t-test. Figure 2 Activated GPIIb-IIIa on platelets stimulated with 10 µM ADP (A), 10 µM epinephrine (EPI) (B), or 5 µM ADP + 5 µM EPI (C) at different timepoints. Note the time-dependent loss of reactivity to stimulating agents in both ...

Development of a membrane oxygenator for ECMO using a novel fine silicone hollow fiber.

One of the limitations of conventional silicone hollow fiber oxygenators compared with microporous membrane oxygenators is poor gas permeability. However, the silicone hollow fiber is free from plasma leakage, which is the major life limiting factor of the microporous membrane oxygenator. It has been difficult to fabricate a fine, thin hollow fiber for reduction of resistance to gas permeability because of the poor mechanical strength of conventional silicone materials. The authors developed a novel silicone material with sufficient mechanical strength, and a fine silicone hollow fiber with a diameter of 30 microns and wall thickness of 50 microns, which is approximately half that of a conventional silicone hollow fiber. Using this newly developed silicone hollow fiber, the authors developed a compact extracapillary flow membrane oxygenator. The oxygenator consists of fine silicone hollow fibers inserted in a housing made of polycarbonate. The housing is a cylindrical case, 20 cm long and 55 mm in inside diameter. The hollow fibers are cross-wound. The surface area of the membrane is 2.0 m2, and priming volume is 230 ml. Gas transfer performance of the newly developed oxygenator was evaluated by in vitro experiments. Oxygen and carbon dioxide transfer rates were 195 ml/min and 165 ml/min, at a blood flow rate 3 L/min. The novel silicone membrane oxygenator developed in this study can be used for extended duration in such applications as extracorporeal membrane oxygenation.

Leakage across hollow-fibre membranes in oxygenators: a pilot study.

The purpose of this study was to create an in vitro system to quantify the fluid loss over two different types of hollow-fibre membrane oxygenators. In the first stage of the study, the circuit was primed with 0.9% NaCl and the line pressure was 200 mmHg; in the second stage, the line pressure was 400 mmHg. The experiment was repeated using bovine blood. A clear difference (p < 0.005) was found in the first stage, accumulating to 47.46 ml (SD 0.41) in the Capiox-SX group and 72.33 ml (SD 3.77) in the Univox group after 4 h. This difference persisted when using bovine blood. Surprisingly, no differences in volume loss occurred when the line pressure was increased to 400 mmHg. In conclusion, leakage in hollow-fibre microporous polypropylene membrane oxygenators can be quantified and the amount of leakage appears to be dependent on the type of membrane and the manufacturing process.

Small Pore Size Microporous Membrane Oxygenator Reduces Plasma Leakage during Prolonged Extracorporeal Circulation: A Case Report

Plasma leakage has been regarded as the main technical problem during prolonged extracorporeal circulation (ECC) with microporous membrane oxygenators (MMOs). We report the case of a 15 year old male who underwent long term ECC for ARDS and in whom, by using new MMOs with reduced pore size, we were able to achieve prolonged artificial gas exchange efficiency with minimal plasma leakage. We conclude that reduced pore size MMOs might represent a valuable technical advance in extracorporeal oxygenation therapy.