Background: Evaluation of donor lung function relies on the arterial oxygen partial pressure to inspired oxygen fraction ratio (PaO2 /FiO2 ) measurement. Hemodynamic, metabolic derangements, and therapeutic intervention occurring during brain dead observation may influence the evaluation of gas exchange.
Methods: We performed a mathematical analysis to explore the influence of the extrapulmonary determinants on the interpretation of PaO2 /FiO2 in the brain-dead donor and during Ex-Vivo Lung Perfusion (EVLP).
Results: High FiO2 and increased mixed venous oxygen saturation, caused by increased delivery and reduced consumption of oxygen, raise the PaO2 /FiO2 despite substantial intrapulmonary shunt. Anemia does not modify the PaO2 /FiO2 -intrapulmonary shunt relationship. During EVLP, the reduced artero-venous difference in oxygen content increases the PaO2 /FiO2 without this corresponding to an optimal graft function, while the reduced perfusate oxygen-carrying capacity linearizes the PaO2 /FiO2 -intrapulmonary shunt relationship.
Conclusions: Adopting PaO2 /FiO2 to evaluate graft suitability for transplantation should account for extrapulmonary factors affecting its interpretation.
Keywords: ex vivo lung perfusion; intrapulmonary shunt; lung transplantation; mixed venous oxygen saturation; multiorgan donor.
© 2022 The Authors. Artificial Organs published by International Center for Artificial Organ and Transplantation (ICAOT) and Wiley Periodicals LLC.