Sensitivity of the Step Test to Detect Improvement in Dyspnea Following Bronchodilation in Patients With Chronic Obstructive Pulmonary Disease (CODEx)

• Symptom perception [ Time Frame: change from baseline in Borg Scale at 3 min of exercise ] [ Designated as safety issue: No ]
  Patients will be asked to score their dyspnea and leg discomfort perception using a 10-point Borg scale.
  
  

• Cardiac and ventilatory outcomes [ Time Frame: Change from baseline at 3 minutes of exercise ] [ Designated as safety issue: No ]
  Metabolic, cardiac and ventilatory parameters will be measured using a portable telemetric system. Principal outcomes will be oxygen uptake (VO2), carbon dioxide output (VCO2), ventilation (VE), breathing frequency (BF), tidal volume (Vt) and heart rate (HR).
  
  
• Inspiratory capacity [ Time Frame: Change from baseline at the end of the exercise. ] [ Designated as safety issue: No ]
  Inspiratory capacity will be measured at rest and at the end of the 3-min step test (immediately following the assessment of dyspnea at 3 minutes).
  
  
• Pleural pressure [ Time Frame: Change from baseline at 1, 2 and 3 minutes of exercise ] [ Designated as safety issue: No ]
  Tidal excursion in pleural pressure will be measured using an oesophageal balloon-catheter system that will be positioned using standardized technique10. Oesophageal pressure signal will be sampled at a rate of 100 Hz.
  
  
• Pulmonary function [ Time Frame: At baseline and 60-min after the nebulization of either placebo and bronchodilator ] [ Designated as safety issue: No ]
  Pulmonary function will be measured by spirometry and plethysmography in the initial visit. In the subsequent visits, pulmonary function will be evaluated by spirometry before and 60-min after the nebulization of either placebo or bronchodilator.
  
  
• Maximal oxygen consumption [ Time Frame: Change from baseline at 1, 2 and 3 minutes of exercise ] [ Designated as safety issue: No ]
  Exercise capacity will be directly assessed following an incremental cycle exercise test. The exercise capacity was defined as the maximal oxygen consumption (VO2 peak, ml/kg/min) by direct measurements of gas exchanges.
  
  
• Maximal inspiratory pressure (PImax) [ Time Frame: Change from baseline after 3 minutes of exercise ] [ Designated as safety issue: No ]
  The maximum inspiratory pressure (PImax) will be measured during a sniff manoeuvre. These measurements will allow to construct the ratio of respiratory effort (tidal Pes/PImax) to thoracic displacement (VT/predicted VC), an index of neuromechanical coupling
  
  

For this project, 40 patients with COPD will be recruited in 2 centres (in the Institute of Cardiology and Pneumology of Quebec and in the Chest Institute of Montreal). For each patient, three visits will be performed. During the first visit, baseline pulmonary function and maximal exercise capacity will be evaluated and the patients will be familiarized with step test proceedings. Between the different visits, a 3-7 days period will be respected. During the second and the third visits, 4 step tests will be performed at 4 different rates, following one of the two conditions (placebo or bronchodilatation). This project will propose two randomization levels. The first randomization will be relative to the choice of the condition used during the second visit (placebo ou bronchodilatation) and the second one for the rates order (14, 16, 20, 24 steps/min). During each performed exercise, cardiorespiratory and pulmonary parameters will be measured using a portable system.