Extracorporeal membrane oxygenation circuitry

The extracorporeal membrane oxygenation circuit is made of a number of components that have been customized to provide adequate tissue oxygen delivery in patients with severe cardiac and/or respiratory failure for a prolonged period of time (days to weeks). A standard extracorporeal membrane oxygenation circuit consists of a mechanical blood pump, gas-exchange device, and a heat exchanger all connected together with circuit tubing. Extracorporeal membrane oxygenation circuits can vary from simple to complex and may include a variety of blood flow and pressure monitors, continuous oxyhemoglobin saturation monitors, circuit access sites, and a bridge connecting the venous access and arterial infusion limbs of the circuit. Significant technical advancements have been made in the equipment available for short- and long-term extracorporeal membrane oxygenation applications. Contemporary extracorporeal membrane oxygenation circuits have greater biocompatibility and allow for more prolonged cardiopulmonary support time while minimizing the procedure-related complications of bleeding, thrombosis, and other physiologic derangements, which were so common with the early application of extracorporeal membrane oxygenation. Modern era extracorporeal membrane oxygenation circuitry and components are simpler, safer, more compact, and can be used across a wide variety of patient sizes from neonates to adults.

Micro-scale Modeling of Flow and Oxygen Transfer in Hollow Fiber Membrane Bundle

The aim of this work was to develop a modeling approach to solve the flow and oxygen transfer when the blood passes through the hollow-fiber membrane bundle. For this purpose, a "two-region" modeling approach was developed regarding the hollow fiber and blood regions. The oxygen transfer in these regions was defined with separate diffusion processes. Two dimensional single and multi-fiber geometries were created and flow solutions were obtained for a non-Newtonian fluid. The convection-diffusion-reaction equation was solved to produce the oxygen partial pressure distributions. As a benefit of coupling the interstitial flow field into the oxygen transfer through the hollow-fiber membrane bundle, the membrane resistance was taken into consideration. Thus, varying oxygen partial pressures were observed on the outer fiber surface, which is contrary to the common simplifying assumptions of negligible membrane resistance and uniform oxygen content on the fiber surface (Traditional approach). It was illustrated that, the current approach can be utilized to predict the mass transfer efficiencies without overestimating as compared to the predictions obtained with the traditional approach. Utilization of the current approach was found to be beneficial for the geometries with lower packing density which allows significant P(O2) variations on the fiber surfaces. For the geometries with dense packings, the above simplifying assumptions could be applicable. The model predictions were validated with the experimental measurements taken from a benchmark device.

Is the air handling capability of the quadrox D pump dependent within an ECMO circuit? An in vitro study

The occurrence of gaseous microemboli (GME) within the extracorporeal membrane oxygenation circuit is largely overlooked, as are methods to ameliorate this occurrence. We aimed to determine if the air handling capability of the Quadrox D oxygenator was dependent upon whether it was used in conjunction with a centrifugal or roller pump; and if application of a Pall air eliminating filter (AEF) would prevent circuit air introduction from intravenous infusions. Using a blood primed circuit 1 mL of air was infused pre pump. GME were quantified post pump and post oxygenator using the EDAC Quantifier. Trials were conducted at 1 and 2 L/min flow. To prevent GME recirculation a Capiox SX18 was used in circuit with negative pressure applied to its oxygenator; an EDAC cuvette distal to this device quantified GME recirculation. Following air infusion, 3-5 minute data recordings were carried out for each trial. Separate trials were carried out for centrifugal and roller pumps, and for each flow rate. The process was then repeated following the application of the AEF to the air infusion line. More GME were detected post Quadrox D when the centrifugal pump was used in comparison to the roller pump at 1 L/min (p < .05), and 2 L/min (p = .05). A greater volume of air was detected post Quadrox D when used in conjunction with the centrifugal device at 1 L/min (p < or = .05), and 2 L/min (p < or = .05). Application of the AEF resulted in zero GME detected at any circuit location. The results of this study confirm that a greater total count and volume of GME are detected distal to the Quadrox D when used in conjunction with a Rotaflow centrifugal pump. Application of a Pall AEF to infusion and drug lines can prevent air introduction from this source.

Clinical evaluation of the Terumo Capiox FX05 hollow fiber oxygenator with integrated arterial line filter

Perfusion techniques and equipment in pediatric open heart surgery have continued to focus on decreasing prime volumes and lowering surface areas of the cardiopulmonary bypass circuit. While this has improved drastically over the last 20 years, greater demand is being placed on the perfusionist to reduce the deleterious effects of bypass without compromising safety or efficiency. Specifically, manufacturers of disposable perfusion equipment have focused on providing pediatric perfusionists with oxygenators that provide the smallest prime and surface area possible while attempting to maximize performance. Recently,Terumo Cardiovascular has introduced the Capiox FX05, a neonatal hollow fiber oxygenator that includes an integrated arterial line filter. The FX05 provides a blood flow range of 0.1-1.5 L/min and a low priming volume of 43 mL. Additionally, it is coated with X Coating, a biocompatible, hydrophilic polymer surface coating that reduces platelet adhesion and protein denaturation. The purpose of this study was to test the FX05 for gas transfer, blood path resistance, and blood handling characteristics in a standardized clinical setting. Heat exchange coefficients were also calculated during the cooling and warming period. Other data analyzed includes bypass circuit prime volumes and initial patient hematocrit along with the total operative homologous blood donor exposures. In summary, the FX05 offers good gas exchange capabilities and a low pressure drop during normal cardiopulmonary bypass parameters along with the safety of an integrated arterial line filter. Furthermore, the FX05 with integrated filter allows a reduction in overall bypass prime volume and surface area while promoting the reduction of homologous blood transfusions, optimizing hemostasis.

Post-arterial filter gaseous microemboli activity of five integral cardiotomy reservoirs during venting: an in vitro study

During a previously published study on gaseous microemboli (GMEs) and perfusionist interventions, it was noted that emboli could be detected after the arterial filter when blood/air challenges entered the membrane oxygenator's integral cardiotomy. The findings indicated that further study into the oxygenator's integral cardiotomy reservoir was warranted. This is the first know published report that connects the vent return to GME activity after the arterial filter. To study the air handling ability of the membranes integral cardiotomy, an in vitro study was conducted on five hard shell coated membrane oxygenators (Terumo Capiox SX25, X coated; Sorin Synthesis, phosphorylcholine coated; Gish Vision, GBS coated; Medtronic Affinity NT, trillium coated; Maquet Quadrox, bioline coated). The oxygenators were matched with their own manufacturer's coated arterial filters (Medtronic 351T Arterial Filter, Sorin Synthesis Integrated Arterial Filter, Terumo CXAF200X Arterial Filter, Gish GAF40GBS-2 Arterial Filter, and Maquet Quart HBF140 Arterial Filter). There were three arms to the study, and three separate oxygenator/filter combinations were used in each arm. The first arm consisted of a pump flow of 4.0 L/min with only the filter purge blood entering the integral cardiotomy. In the second arm, 500 mL/min of simulated vent blood was added to the filter purge blood entering the integral cardiotomy. During the final arm, 200 mL/min of air was added to the vent blood as it entered the integral cardiotomy, to more closely simulate vent return during cardiopulmonary bypass. All GME activity in the oxygenator/filter combinations was examined using the Hatteland CMD20 Microemboli Counter. Placement of the Hatteland probes was 4 in after the hard shell reservoir outlet (PRO) and 12 in after the arterial filter (PAF). When vent blood flow was turned on, there was a significant increase in the PRO microemboli activity detected in all reservoirs. In the PAF position, three of the oxygenator/filter combinations were able to remove 98-99% of the GME, one removed 84.3%, and another removed only 55.5% of the GMEs coming out of the oxygenator's reservoir. All oxygenators were found to have a dramatic increase in reservoir GME activity when the vent was turned on. Depending on the oxygenator/filter combination, vent return into the oxygenator's integral cardiotomy resulted in the presence of significant amounts of GMEs after the arterial filter.

Preventing gaseous microemboli during blood sampling and drug administration: an in vitro investigation

The detection and prevention of gaseous microemboli (GMEs) during cardiopulmonary bypass has generated considerable interest within the cardiac surgical community. There have been several landmark papers that have used transcranial Doppler devices during cardiopulmonary bypass to detect gaseous microemboli activity in the patients' middle cerebral artery during perfusionist interventions. To determine if this source of emboli could be prevented, a shunt was developed between the oxygenator's sampling manifold and the oxygenator's venous line. This shunt bypassed the venous line and emptied into the oxygenator's integral cardiotomy. An in vitro experiment was performed using three open system oxygenators (Sorin Synthesis, Sorin PrimeOx2, and Terumo Capiox SX25) to compare post-arterial filter emboli detection using the Hatteland CMD20 Microbubble Detector under tightly controlled conditions. After injection of air through the sampling manifold, the PrimeOx2 and the Synthesis oxygenators had statistically significant fewer GMEs with the shunt used than when the shunt was not used. Using a shunt in the sampling manifold during perfusionist interventions will dramatically reduce or eliminate gaseous microemboli transmission to the patient during bypass with both the PrimeOx2 and Synthesis oxygenators. However, results indicate that further study of GME handling with all oxygenator's integral cardiotomies is warranted.

Retrospective analysis comparing hollow fiber and silicone membrane oxygenators for neonates on ECMO

There is little information showing the use of microporous polypropylene hollow fiber oxygenators during extra-corporeal life support (ECLS). Recent surveys have shown increasing use of these hollow fibers amongst ECLS centers in the United States. We performed a retrospective analysis comparing the Terumo BabyRx hollow fiber oxygenator to the Medtronic 800 silicone membrane oxygenator on 14 neonatal patients on extracorporeal membrane oxygenation (ECMO). The aim of this study was to investigate the similarities and differences when comparing pressure drops, prime volumes, oxygenator endurance, and gas transfer capabilities between the two groups.