Gut chemical clues: could digestion differences explain COPD?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion criteria COPD subjects: * Ability to walk, sit down and stand up independently * Age 45 years - 100 years * Ability to lie in supine or elevated position for 1.5 hours * Diagnosis of moderate to very severe chronic airflow limitation and compliant to the following criteria: FEV1 \< 70% of reference FEV1 * Clinically stable condition and not suffering from a respiratory tract infection or exacerbation of their disease (defined as a combination of increased cough, sputum purulence, shortness of breath, systemic symptoms such as fever, and a decrease in FEV1 \> 10% compared with values when clinically stable in the preceding year) at least 4 weeks prior to the first test day * Shortness of breath on exertion * Willingness and ability to comply with the protocol Inclusion criteria control subjects: * Healthy male or female according to the investigator's or appointed staff's judgment * Ability to walk, sit down and stand up independently * Age 45 years - 100 years * Ability to lay in supine or elevated position for 1.5 hours * No diagnosis of COPD * Willingness and ability to comply with the protocol Exclusion Criteria all subjects: * Any condition that may interfere with the definition 'healthy subject' according to the investigator's judgment (healthy subjects only) * Subjects 86 years and older that fail to get physician eligibility confirmation * Insulin dependent diabetes mellitus * Established diagnosis of malignancy * History of untreated metabolic diseases including hepatic or renal disorder * Presence of acute illness or metabolically unstable chronic illness * Presence of fever within the last 3 days * Any other condition according to the PI or nurse that was found during the screening visit, that would interfere with the study or safety of the patient * Use of protein or amino acid containing nutritional supplements within 5 days of first study day * Use of short course of oral corticosteroids within 4 weeks preceding first study day * Failure to give informed consent or Investigator's uncertainty about the willingness or ability of the subject to comply with the protocol requirements * (Possible) pregnancy * Already enrolled in another clinical trial and that clinical trial interferes with participating in this study When during the period from enrollment to the test day any condition causing the subject to not meet inclusion criteria or to meet exclusion criteria, the subject will be excluded from the study.