Chronic obstructive pulmonary disease is a disease characterized by small airways inflammation and obstruction. The small airways disease produces hyperinflation (air trapping), which increases with exercise. Continuous positive airways pressure may reduce small airways obstruction and therefore air trapping. Pulmonary function tests including lung volumes at rest and and after exercise will be measured. In addition, exercise endurance time before treatment and after treatment will be measured.

Continuous positive airways pressure which prevent small air ways collapse and may also clear secretions. At first stage the optimal pressure for reducing air trapping will be determined. In addition, all patients will undergo a maximal exercise test. A baseline complete pulmonary function test is performed followed by continuous positive air way pressure at the pre-determined pressure. This will be followed by exercise at 60% of maximal obtained previously.

Inclusion Criteria:

• chronic obstructive lung disease stage 2-3 GOLD
• FRC > 120%

Exclusion Criteria:

• active ischemic heart disease
• heart failure
• peripheral vascular disease