Difference in the Metabolic Characteristics of COPD Patients and Healthy Adults

Inclusion Criteria: Inclusion criteria for COPD 1. Patients should meet the above diagnostic criteria, and the severity of COPD is in the stage of GOLD 2 or 3 based on pulmonary function testing; 2. COPD patients in the stable phase, who present with mild symptoms of cough, expectoration and short breath; 3. 35 ≤ age ≤75 years, male or female; 4. Patients have clear consciousness and could communicate with others normally; 5. Patients could understand the full study protocol and written informed consent is signed by themselves or their lineal kin. Inclusion criteria for health volunteers 1. Healthy volunteers who could provide a recent medical examination report to confirm they have not any cardiovascular, respiratory, digestive, urinary, hematological, endocrine and neurological disease; 2. Age≥20 years, male or female; 3. Participants have clear consciousness and could communicate with others normally; 4. Participants could understand the full study protocol and have high adherence .Written informed consent is signed by themselves or their lineal kin. Exclusion Criteria: Exclusion criteria for COPD 1. Patients who fail to meet the diagnostic criteria for COPD, or COPD patients in the phase of acute exacerbation; 2. Patients have the following complications, which includes pneumonia, bronchial asthma, bronchiectasis, active tuberculosis, pneumothorax, chest trauma, tumors of the lung or thorax, and other confirmed respiratory diseases; 3. Patients have concomitant conditions of heart diseases, such as chronic stable angina pectoris; 4. Patients have serious concomitant conditions and fail to treat them effectively, such as diseases of the digestive, urinary, respiratory, hematological, and nervous system; 5. Patients have mental illness, severe depression, alcohol dependence or history of drug abuse; 6. Pregnant or lactating patients; 7. Patients are participating in other trials. Exclusion criteria of health volunteers 1. Participants have sudden severe diseases during the trial, such as cardiovascular diseases, liver diseases, kidney diseases, urinary diseases and hematological diseases. 2. Participants have mental illness, severe depression, alcohol dependence or history of drug abuse; 3. Pregnant or lactating participants ; 4. Participants are participating in other trials.