Can a membrane oxygenator be a model for lung NO and CO transfer?

The research explores if a membrane oxygenator can function as a model for lung nitric oxide (NO) and carbon monoxide (CO) transfer. They found that despite structural differences, the oxygenator could serve as a functional model by keeping variables constant and allowing alternations in key areas.

Methodology

• The researchers used a membrane oxygenator circuit, filled with horse blood and flowing at a rate of 2.5 liters per minute, to create the model for testing lung NO and CO transfer.
• The gas channel of the circuit was ventilated with nitric oxide (NO), carbon monoxide (CO), and oxygen (O2) at specified concentrations and flow rates.
• They then calculated the NO and CO diffusing capacities (Dno and Dco) based on the inlet and outlet gas concentrations and the flow rates.

Findings

• Both Dno and Dco increased (P = 0.002) in accordance to the blood volume/surface area.
• They both also fell with increasing gas flow but increased with hemolysis (P = 0.001). However, only the increase in Dno indicated a dependence on red cell diffusive resistance.
• The change in Dno and Dco did not occur with changing rates of blood flow.
• While Dco increases (P = 0.009) with increasing Po2, it appears to be reaction limited along with being diffusion limited, unlike Dno which is only diffusion limited.

Conclusion

• The research concluded that despite the structural differences, a membrane oxygenator can serve as a functional model of lung NO and CO transfer.
• It allows for the alternation of various aspects like membrane area/blood volume, blood flow, gas flow, oxygen tension, and red cell integrity, while keeping other variables constant.
• They also indicated that in this apparatus, red cells and plasma provide a significant barrier to NO diffusion, but not for CO diffusion. Using this model reflects similar specific transfer conductance of blood per milliliter for both NO and CO, which is comparable to previous estimates.