ObjectiveTandem mass spectrometry is used to observe the changes in amino acids level in peripheral blood of patients with chronic obstructive pulmonary disease (COPD) of different severity, and explore the related factors that affect the level of amino acids in COPD patients.MethodsA collection of 99 COPD patients from the First Affiliated Hospital of Jinzhou Medical University between May 2020 and August 2020 were divided into GOLD Ⅰ/Ⅱ group, GOLD Ⅲ group and GOLD Ⅳ group according to the results of their lung function. Thirty healthy physical examination subjects during the same period were enrolled as a healthy control group. Peripheral amino acids were detected by liquid chromatography-tandem mass spectrometry (LC-MS).ResultsThe metabolism of 11 amino acids was correlated with the onset of COPD and the disorder of amino acid metabolism became more significant with the aggravation of the disease, and branched-chain amino acids (leucine, valine) had statistically significant differences in the COPD patients with different GOLD grades (P<0.05 and VIP>1). The difference between glutamate and glutamine was statistically significant only in GOLD Ⅳ stage (P<0.05 and VIP>1). The content of tyrosine and phenylalanine gradually increased with the increase of disease severity, and had significant difference in GOLD stage Ⅳ (P<0.05).ConclusionsCOPD patients with different GOLD grades have obvious amino acid metabolism disorders, including insufficient intake of essential amino acids and increased amino acids related to muscle protein catabolism. Understanding the mechanism between amino acid metabolism and COPD may provide a new direction for the diagnosis and treatment of the disease.