The leading and almost only cause of COPD in France is smoking. One of the first symptoms of COPD is breathlessness.
The disease gradually causes narrowing, which obstructs the bronchi. Respiratory capacity reduces over time. Declining process of COPD has then started, and the smoker will never recover his/her full respiratory capacity. Undiagnosed, and without stopping smoking, the disease progresses inexorably to respiratory failure. Ultimately, the only option is oxygen therapy.