Pulmonary Gas Exchange Abnormalities in Patients With Mild COPD
Pulmonary Gas Exchange Abnormalities in Patients With Mild COPD
People with mild chronic obstructive pulmonary disease (COPD) can have significant
 physiological abnormalities and breathing inefficiency which become more pronounced during
 the stress of exercise, leading to intolerable breathing discomfort (dyspnea). To better
 understand the mechanisms of respiratory symptoms and exercise limitation in mild COPD, we
 will examine detailed lung function tests and other important measurements during rest and
 exercise in people with mild COPD compared with healthy non-smokers. This will be the first
 study to uncover the fundamental causes of breathing inefficiency and the related shortness
 of breath during physical exertion in patients with mild COPD. We hope to demonstrate that
 one simple measurement during exercise [the relation (ratio) between the total amount of air
 breathed (ventilation) and the amount of carbon dioxide breathed out] gives meaningful
 information about the extent of damage to the small airways and blood vessels in mild COPD
 and the overall gas exchanging function of the lungs, without the need for an arterial blood
 sample.

 This is a case-controlled observational study not involving an intervention. Participants
 will complete 2 visits approximately 1 week apart, each conducted at the same time of day.
 Visit 1 will consiste of screening for iligibility, symptom and activity assessments,
 pulmonary function tests and an incremental cycle cardiopulmonary exercise test (CPET) for
 familiarization purposes. Visit 2 will include spirometry followed by an incremental cycle
 CPET with detailed measures of ventilatory, gas exchange, sensory-perceptual and arterial
 blood gas responses.
Inclusion Criteria:

 -  Stable symptomatic patients with GOLD grade 1B mild COPD;

 -  at least 50 years of age;

 -  a cigarette smoking history ≥20 pack-years;

 -  a Baseline Dyspnea Index focal score ≤9;

 -  post-bronchodilator forced expiratory volume in 1 second (FEV1) ≥80 %predicted and an
 FEV1/forced vital capacity (FVC) ratio <0.7 and < lower limit of normal.

 Exclusion Criteria:

 -  clinically significant comorbidities;

 -  contraindications to exercise testing;

 -  history/clinical evidence of asthma;

 -  body mass index <18.5 or >30 kg/m2;

 -  use of supplemental oxygen.