Evaluation of the oxygenation ratio as long-term prognostic marker after lung transplantation

We hypothesized that the arterial blood gas oxygen tension/fraction of inspired oxygen ratio (PaO2/FiO2) would prove to be useful as a mortality marker after lung transplantation (LT). The aims of this study were to define the prevalence of various ranges of PaO2/FiO2 during the first 24 hours after LT and to evaluate which measurement using the PaO2/FiO2 best correlates with mortality.

A retrospective study was performed that included all patients who underwent LT from 1997 to 2005. We collected PaO2/FiO2 ratios at 0, 12, and 24 hours after admission to the intensive care unit (ICU). We classified the 132 patients in 5 groups, based on PaO2/FiO2 (Group 1, PaO2/FiO2 <100; Group 2, PaO2/FiO2 100-199; Group 3, PaO2/FiO2 200-299; Group 4, PaO2/FiO2 300-399; Group 5, PaO2/FiO2 >or=400). The correlation between PaO2/FiO2 and mortality was studied using Cox regression.

Cox regression analysis showed that PaO2/FiO2 at 0 and 12 hours after admission to the ICU were not useful mortality markers. However, the PaO2/FiO2 at 24 hours after admission to the ICU was a useful long-term prognostic marker. PaO2/FiO2 >100 (groups 2, 3, 4, and 5) at 24 hours was significantly associated with less mortality when a lower PaO2/FiO2 was the reference (hazard Ratio: 0.08, 0.02, 0.05, and 0.02, respectively). On multivariate analysis PaO2/FiO2 >or=100 (groups 2, 3, 4, and 5) at 24 hours was significantly associated with less mortality when a lower PaO2/FiO2 was the reference (hazard ratio: 0.07, 0.003, 0.01, and 0.005, respectively).

A value of PaO2/FiO2 >100 mm Hg 24 hours after admission to the ICU is associated with a lower mortality.