Low Blood Arterial Oxygenation During Venovenous Extracorporeal Membrane Oxygenation: Proposal for a Rational Algorithm-Based Management.

PURPOSE: Venovenous extracorporeal membrane oxygenation (VV-ECMO) is a therapeutic option in the management of the most severe forms of acute respiratory distress syndrome. Oxygenation during VV-ECMO depends on many parameters, and its management is complex. The management of ECMO is still not completely codified. The aim of this study was to rationalize the management of hypoxemia during VV-ECMO. METHODS: To build a comprehensive flow diagram for management of hypoxemia during VV-ECMO, we considered (1) relationship between O2 arterial saturation and its determinants; (2) analysis of physiopathology of oxygenation under VV-ECMO; and (3) main guidelines and recommendations recapitulated in troubleshooting charts. RESULTS: We propose a stepwise approach that could guide specific intervention to improve oxygenation during VV-ECMO. The first step is to obtain adequate pump flow, the main determinant of oxygenation, by eliminating a mechanical problem or inadequate venous drainage. Second, if hypoxemia persists, algorithm considers multiple reasons for inadequate oxygenation, namely: (1) excessive recirculation, (2) excessive cardiac output (decrease of ratio pump flow/cardiac output), (3) decrease in SvO2 (oxygen saturation in mixed venous blood), (4) malfunction of oxygenator, and (5) deterioration of residual lung function. Finally, for each modification of oxygenation parameters, specific measures are proposed to restore an adequate oxygenation by extracorporeal membrane oxygenation. CONCLUSION: If hypoxemia occurs during VV-ECMO, collecting oxygenation parameters and a clear step-by-step algorithm could guide specific intervention to improve oxygenation. This flow diagram is in accordance with current recommendations recapitulated in guidelines or troubleshooting chart but more accurate and complete. Although rational and appealing, it remains to be tested together with a number of still unsolved issues.

A numerical model of blood oxygenation during veno-venous ECMO: analysis of the interplay between blood oxygenation and its delivery parameters.

Veno-venous extracorporeal membrane oxygenation (VV-ECMO) is an important tool in the management of most severe forms of acute respiratory failure. The determinants and management of oxygen delivery in patients treated with VV-ECMO is a complex topic. The physiological principles of oxygenation on VV-ECMO are reviewed in many textbooks. However a numerical model is an additional instrument to be used in understanding and exploring this intricate subject matter. We present a numerical model of blood oxygenation during VV-ECMO. Using this model we examined the role and impact of each determinant on blood oxygenation. The numerical analysis of variation and interplay between each oxygenation determinants during VV-ECMO is presented in graphical form. These results corroborate all the findings of previous studies. The proposed numerical model facilitates understanding of oxygenation physiology during VV-ECMO; it can be used for a medical simulation system and for teaching the principles of oxygenation during VV-ECMO.

Giant magneto optical properties in the double perovskites Ba2B'RuO6(B' = Er, Tm).

This study aimed to investigate new double perovskite oxides in search of new promising functional material with properties of interest for high density storage applications. The crystal structure, magnetic, electronic and magneto-optical properties of the rare-earth-based double perovskites Ba2B'RuO6(B' = Er, Tm) were investigated through full-potential linearized augmented plane wave method within the context of density functional theory (DFT) in Wien2k code. We used generalized gradient approximation (GGA) and GGA + U approaches to calculate magneto-optical properties, including spin-orbit coupling due to 4f and 4d-electrons. The obtained DFT-optimized structures was cubic (space group: Fm = 3m), and the calculations (GGA + U) showed that the compounds Ba2ErRuO6is semiconductor and the Ba2TmRuO6is half-metal. The magneto-optical Kerr effect showed pronounced peaks at angles of 17.7∘and 5.6∘for an energy around 0.2 eV for both compounds, which could potentially have important applications in the infrared region or for blue and violet radiation.

A new formula for determining arterial oxygen saturation during venovenous extracorporeal oxygenation.

PURPOSE: Venovenous extracorporeal membrane oxygenation (VV-ECMO) is used to treat severe forms of acute respiratory distress syndrome (ARDS). VV-ECMO management may be confusing due to the lack of information about the interplay between the determinant parameters and their impact on oxygenation. We found a relationship between arterial oxygen saturation (SaO(2)) and its relevant parameters. The aim of this study was to assess the validity of this model. METHODS: We report our experience in 17 patients under VV-ECMO for severe ARDS. We compared, at two different levels of pump flow, SaO(2) and the oxygen saturation measured in the pulmonary artery (SpaO(2)) with the predicted saturation using the formula: SpaO(2) = (EF/CO)SmO(2) + (1 - EF/CO)SvO(2) + 10(-2)PmO(2), where PF is pump flow, R is recirculation, EF is effective flow [= (1 - R)PF], SmO(2) is saturation of the oxygenator outgoing blood, CO is cardiac output, SvO(2) is saturation of mixed venous blood, and PmO(2) is oxygen partial pressure of the oxygenator outgoing blood. RESULTS: There was no significant difference between predicted and measured SpaO(2): the mean predicted and measured SpaO(2) values were 90.7 ± 2.8 % and 90.4 ± 2.7 % , respectively (p = 0.696, r = 0.966). Bland-Altman analysis showed good agreement between predicted and measured SpaO(2). Predicted SpaO(2) and SaO(2) was well correlated (r = 0.80). CONCLUSIONS: We have presented an explicit relationship between SaO(2) and its direct determinants during VV-ECMO. Good agreement was found with the measured values of SaO(2), but the model remains to be fully validated before its use in clinical practice.