Effect of non-invasive ventilation during exercise on dynamic hyperinflation in chronic obstructive pulmonary disease

The trial will consist of three constant work rate Cardio Pulmonary Exercise Tests with and without Noninvasive Ventilation (BiLevel Positive Airway Pressure). The noninvasive ventilation will be administered once with a standard therapy and once with individually titrated expiratory pressure. The expiratory pressure will be determined by asking the patient to sit and receive different levels of pressure and perform an inspiratory capacity maneuver at each pressure. The pressure which provides the biggest inspiratory capacity will be the titrated expiratory pressure. This will be administered using a commercially available ventilator, the ResMed Stellar 150. The ventilator will be connected to the patient via a standard tube to a mask and a vent. The ventilator provides constant flow and a positive pressure to the mask. Both NIV arms will use the device in BiLevel pressure support mode. This mode has a square waveform with a high pressure during inspiration and a lower pressure during expiration. For both NIV arms, an inspiratory pressure of 15cmH2O will be used. The standard settings arm will use an expiratory pressure of 6cmH2O. The individual pressures will range from 2 - 10 cmH2O. The constant work rate exercise protocol will be done on a cycle ergometer. The work rate will be set after one minute of unloaded pedaling and the patient will be asked to pedal to exhaustion. The patients are expected to exercise from 4 - 20 minutes. The work rate will be chosen at 75% of the peak work rate found in an incremental maximal work rate test. The incremental test will be performed on the first day and the constant work rate tests will be in the subsequent days. The 3 constant work rate exercise tests will be separated by at least 1 hour but must be completed within 7 days of beginning to prevent bias due to change in baseline health.