Figure 2 Comparison of mean carboxyhemoglobin (HbCO) levels in all patients before (black bar) and after (white bar) liver transplantation, which were significantly higher prior to transplant. HbCO levels before liver transplantation are also compared separately in those with (solid blue bar) and without (light blue bar) hepatopulmonary syndrome (HPS). The same comparison is likewise shown after transplantation (solid and light geen bars). Differences in the latter 2 comparisons did not reach statistical significance.