Fig. 2

Metabolomics analysis of serum samples. A Typical ¹H nuclear magnetic resonance spectrum. 1. low-density lipoprotein/very-low-density lipoprotein; 2. leucine; 3. isoleucine; 4. valine; 5. 3-hydroxybutyric acid; 6. lactate; 7. alanine; 8. acetate; 9. lipid; 10. glutamine; 11. acetone; 12. acetoacetate; 13. pyruvate; 14. citrate; 15 Creatine. creatine; 16. choline; 17. glucose; 18. tyrosine; 19. phenylalanine; 20. methylhistidine. Score scatter plots of orthogonal partial least-squares discriminant analysis from serum samples and variable importance in projection shows the difference between B community-acquired pneumonia with and without acquired respiratory distress syndrome groups; and C before and after treatment in the community-acquired pneumonia with acquired respiratory distress syndrome group. Leu leucine, 3-HB 3-hydroxybutyrate, Lac lactate, Acn acetone, Cit citrate, Cho choline, Aca acetoacetate