Chronic obstructive pulmonary disease, or COPD, is a progressively worsening disease that causes difficulty breathing. The disease includes chronic bronchitis, a chronic cough with mucus lasting at least three months, and emphysema, abnormal enlargement of the tiny air sacs inside the lungs resulting from destruction of the lining of the lungs. Chronic obstructive pulmonary disease develops slowly and may go untreated for years. Once symptoms appear, there is no known cure for the disease. Doctors classify progression of the disease into four different stages, based on the severity of the symptoms.
Stage 1 COPD is characterized by a mild form of the disease. People with Stage 1 COPD experience a slight reduction in air flow, approximately 80 percent of normal lung capacity, as measured by Pulmonary Function Tests, or PFTs. This limited air flow results in mild shortness of breath. Stage 1 may be accompanied by coughing and mucus expulsion. People with Stage 1 COPD may not realize that their lung function is impaired.
During the second stage of COPD, patients experience increasing lung airflow problems. As measured by a PFT, lung capacity decreases to 50 to 80 percent of normal, resulting in moderate to severe shortness of breath, especially during times of physical exertion. Patients may experience heavy coughing with mucus. During Stage 2 COPD, patients often seek medical treatment for the chronic respiratory symptoms, and this is usually the first stage that medication is prescribed.
Patients progressing to Stage 3 COPD see their lung capacity drop to 30 to 50 percent of normal, as measured by PFTs. Severe shortness of breath, known as dyspnea, begins to develop at this stage. Patients often suffer from severe periods of exacerbated dyspnea, with or without heavy coughing and mucus, which can lower quality of life. Patients also experience reduced exercise capacity and frequent fatigue.
Stage 4 COPD is characterized by severe problems in airflow. Lung capacity falls to less that 30 percent of normal, although patients may experience symptoms of Stage 4 COPD with a lung capacity that is greater than 30 percent. Patients experience severe shortness of breath, with periods of exacerbated symptoms that may become life-threatening. Quality of life is heavily impacted, and patients may become severely disabled.