The present invention relates to the treatment of pulmonary diseases. More specifically, the invention relates to new methods of detecting and treating chronic obstructive pulmonary disease (COPD). In particular, the invention relates to a method of measuring one or more lipid metabolites in human body fluids as an indicator/biomarker of the progress of chronic obstructive pulmonary disease. The present invention also relates to a method of detecting and/or monitoring chronic obstructive pulmonary disease in a subject, the method comprising measuring the level of at least one lipid metabolite in a sample from the subject, wherein said level is indicative of COPD. The present invention also relates to a method of assessing the efficacy of a COPD treatment in a subject, the method comprising a step of measuring the level of at least one lipid metabolite in a sample from the subject, wherein said level is indicative of COPD severity or status.