Statistical analysis
Statistical analyses were performed using IBM SPSS Statistics for
Windows version 22.0 (IBM Corp., Armonk, NY). Between-group comparisons
were performed using Pearson’s chi-square test for parametric data and
Mann–Whitney U test for non-normally distributed numerical data. The
groups’ demographic data and laboratory parameters were compared using
independent-samples t test. Wilcoxon analysis was performed to compare
repeated measures for laboratory parameters within groups. Pearson
correlation analysis was used to evaluate correlation between COHb and
CRP, ferritin, D-dimer level, lymphocyte count, and the ratio of
arterial oxygen partial pressure to fractional inspired oxygen
(PaO2/FiO2). A p-value < 0.05
was considered statistically significant.