The results showed that patients had a previous home oxygen therapy (OR: 3.331; 95% CI: 1.422–7.806; P = 0.006), higher CAT score (OR: 1.122; 95% CI: 1.008–1.250; P = 0.036), and lower CD4+CD8+ T cells percentage (OR: 0.574; 95% CI: 0.332–0.992; P = 0.047) were associated with a higher risk of respiratory failure (Table 3, Fig. 2). This evidence concerns the gene CD8A and respiratory failure.