Ali Kashefi

Artificial lungs are commonly used in cardiopulmonary-bypass surgery (CPB), extracorporeal life support (ECLS), and extracorporeal carbon dioxide removal therapy (ECCO2R). In this study, a semi-empirical model for O₂ and CO₂ transfer in an oxygenator was formulated to evaluate the gas exchange performance at different blood/gas flow rates and various inlet conditions. The model uses experimentally obtained mass transfer coefficients together with blood-gas and acid-base inlet parameters to determine the corresponding outlet values by considering the mass transfer equations for both O₂ and CO₂. Increasing the blood flow rate (17L/min) decreases pO₂ at the outlet (from 376 to 120mmHg), but linearly increases the total oxygen transfer rate (OTR) from 76 to 450mL/min. CTR, the CO₂ transfer rate (64648mL/min), depends primarily on the ratio of gas to blood flow rate (1:15:1). In addition, venous concentrations of O₂CO₂ play a pivotal role in the overall gas exchange efficiency of the oxygenator. Conclusively, a good agreement (R²=0.99) could be observed between the experimental data and the models predictions for OTR and CTR alike at standard inlet conditions. The model's capabilities can be extended by modeling gas exchange during CPB, ECLS and ECCO2R therapies for different connection configurations.

Extracorporeal circulation (ECC) is frequently implemented in a vast array of modalities such as hemodialysis, cardiopulmonary bypass, extracorporeal membrane oxygenation (ECMO), and others. Patients receiving any such therapy are frequently encumbered with chronic inflammation, which is inherently accompanied by oxidative stress. However, ECC treatments themselves are also responsible for sustaining or promoting inflammation. On these grounds, an in vitro study was designed to investigate the therapeutic potential of molecular hydrogen (H₂) against pro-inflammatory agents in ECC settings. Five miniature ECMO circuits and a small vial (Control) were primed with heparinized blood from healthy adult donors (n = 7). Three of the ECMO systems were injected with lipopolysaccharide (LPS), out of which one was additionally treated with an H₂ gas mixture. After 6 h, samples were drawn for the assessment of specific biomarkers (MCP-1, MPO, MDA-a, TRX1, and IL-6). Preliminary results indicate a progressive oxidative and inflammatory response between the six systems. Circulation has triggered inflammation and blood trauma, but the staggering influence of LPS in this outcome is indisputable. Accordingly, hydrogen’s remedial potential becomes immediately apparent as biomarker concentrations tend to be lower in the H₂-handled circuit. Future research should have distinct objectives (e.g., dosage/duration/cycle of hydrogen administration) in order to ascertain the optimal protocol for patient treatment.

Extracorporeal gas exchange therapies evolved considerably within the first three–four decades of their appearance, and have since reached a mature stage, where minor alterations and discrete fine-tuning might offer some incremental improvement. A different approach is introduced here, making use of modern, purely diffusive membrane materials, and taking advantage of the elevated concentration gradient ensuing from gas pressure buildup in the gas chamber of the oxygenator. An assortment of silicone membrane gas exchangers were tested in vitro as per a modified protocol in pursuance of assessing their gas exchange efficiency under both regular and high-pressure aeration conditions. The findings point to a stark performance gain when pressurization of the gas compartment is involved; a 40% rise above atmospheric pressure elevates oxygen transfer rate (OTR) by nearly 30%. Carbon dioxide transfer rate (CTR) does not benefit as much from this principle, yet it retains a competitive edge when higher gas flow/blood flow ratios are employed. Moreover, implementation of purely diffusive membranes warrants a bubble-free circulation. Further optimization of the introduced method ought to pave the way for in vivo animal trials, which in turn may potentially unveil new realms of gas exchange performance for therapies associated with extracorporeal circulation.