Exploring the association of two oxygenators in parallel or in series during respiratory support using extracorporeal membrane oxygenation

Abstract

Objective To characterize the pressures, resistances, oxygenation, and decarboxylation efficacy of two oxygenators associated in series or in parallel during venous-venous extracorporeal membrane oxygenation support. Methods Using the results of a swine severe respiratory failure associated with multiple organ dysfunction venous-venous extracorporeal membrane oxygenation support model and mathematical modeling, we explored the effects on oxygenation, decarboxylation and circuit pressures of in-parallel and in-series associations of oxygenators. Results Five animals with a median weight of 80kg were tested. Both configurations increased the oxygen partial pressure after the oxygenators. The return cannula oxygen content was also slightly higher, but the impact on systemic oxygenation was minimal using oxygenators with a high rated flow (~ 7L/minute). Both configurations significantly reduced the systemic carbon dioxide partial pressure. As the extracorporeal membrane oxygenation blood flow increased, the oxygenator resistance decreased initially with a further increase with higher blood flows but with a small clinical impact. Conclusion Association of oxygenators in parallel or in series during venous-venous extracorporeal membrane oxygenation support provides a modest increase in carbon dioxide partial pressure removal with a slight improvement in oxygenation. The effect of oxygenator associations on extracorporeal circuit pressures is minimal.

Comparison of Serial and Parallel Connections of Membrane Lungs against Refractory Hypoxemia in a Mock Circuit

“…Despite these case reports, it remains unclear whether the parallel or serial connection is more effective in refractory hypoxic failure during VV-ECMO. Regarding this question, a research of the literature led to a previous study that compared parallel and serial connections of ECMO oxygenators in a porcine animal model [13]. In this study, Melro et al suggested only a minimal effect on oxygenation of either parallel or serial connection compared to a single ECMO oxygenator with the same blood flow.…”

“…Despite these case reports, it remains unclear whether the parallel or serial tion is more effective in refractory hypoxic failure during VV-ECMO. Regarding t tion, a research of the literature led to a previous study that compared parallel a connections of ECMO oxygenators in a porcine animal model [13]. In this study, al.…”

Hypoxemia during veno-venous extracorporeal membrane oxygenation. When two is not better than one

“…The study by Melro et al ( 6 ) has certain limitations, which have been duly acknowledged by the authors. Although their calculations are mathematically sound, they may not account for all the variables being considered, and importantly, only one type of oxygenator was used, followed by extrapolation to a two oxygenator model.…”

“…In these extreme situations, when a patient with no lung contribution and very high cardiac output has persistent severe hypoxemia or hypercarbia, adding a second oxygenator to the extracorporeal circuit, whether in parallel or in series, might be an intuitive option. In this issue of the Revista Brasileira de Terapia Intensiva , Melro et al., ( 6 ) using a porcine model, evaluated the impact on blood oxygenation of these two circuit configurations. Additionally, decarboxylation efficacy, as well as pressure and resistance changes to the circuit imposed by the “virtual” presence of a second oxygenator, were analyzed.…”

“…( 9 , 10 ) However, this was only achieved at the cost of unusually high ECMO flows (> 7L/min), mandating the placement of a second drainage cannula, with a consequent increase in both invasiveness and likelihood of access-related complications. However, and based on the results by Melro et al., ( 6 ) adding a second oxygenator should probably not be included in the possible strategies to improve oxygenation but instead might be used if adequate decarboxylation is not obtained with a high sweep gas flow and minimized CO 2 production. Hence, when faced with hypoxemia during VV-ECMO, intensivists should consider other options.…”