Fig. 3.

Several blood oxygenation parameters were altered in patients with lower PaO₂. Oxygen saturation (SaO₂) (A), haemoglobin (Hb) (B), pH (C), PaCO₂ (D) and 2,3-BPG (E) levels in the two patient subgroups, accordingly to the PaO₂ median value. The oxygen saturation was obtained with the oxymeter and the PaCO₂ and pH by emo-gas analysis. 2,3-BPG levels were assessed by specific immunoenzymatic assays in RBCs of COVID-19 patients and reported here expressed as nmol/mL. Data are reported as mean ± SD. Differences between groups were evaluated by a non-parametric test (Mann-Withney test) and parametric test (Unpaired-t-test): ∗ p < 0.05 vs. PaO₂ ≥ 67. GraphPad Prism 8 was used to create the figure.