Chronic obstructive pulmonary disease (COPD) is an umbrella term for a group of respiratory tract diseases that are characterised by airflow obstruction or limitation. It is usually caused by smoking.
Conditions included in this umbrella term are:
Other names
COPD is also known as CORD, COAD, COLD which respectively stand for chronic obstructive respiratory, airways, or lung disease. COPD has been referred to as CAL which stands for chronic airway limitation.
Working definition
COPD is a chronic, progressive disorder related to tobacco abuse and characterized by airways obstruction (FEV1 <80% predicted and FEV1 / VC ratio <70%).
Causes
The main risk factor in the development of COPD is smoking. Approximately 15% of all chronic smokers will develop the disease. In supseptible people, this causes chronic inflammation of the bronchi and eventual airway obstruction. Other etiologies include alpha 1-antitrypsin deficiency, byssinosis, and idiopathic disease.
Progression
COPD has 3 phases--mild, moderate and severe. The mild phase has few signs or symptoms, although there may be occasional shortness of breath on exertion, recurrent respiratory infections and/or a morning cough. As a patient progresses into the moderate phase, the symptoms are seen with increased frequency and severity. In the severe form, the patient often experiences severe cough, constant wheezing, and shortness of breath with minimal exertion or rest. At the severe stage, progression to respiratory failure and death is common. Progression is typically caused by the patient's continued exposure to tobacco smoke. Although medications often decrease symptoms, it is not believed that they prevent the progression if the patient continues to smoke.
Acute Exacerbations
COPD is also characterized by exacerbations which typically present with a rapid progression of the chronic symptoms. Classically, an exacerbation is notable by increased shortness of breath, wheezing, and sputum production. Hypoxia is common as well. Exacerbations are likely brought on by infectious agents. Bronchodilators, antibotics, and oral or intravenous steroids are used to treat these episodes. Exacerbations can lead to respiratory failure; if this occurs, a patient is treated with noninvasive positive pressure ventilation or standard mechanical ventilation until the lung function improves.
Diagnosis
The diagnosis of COPD is usually suggested by symptoms; it is a clinical diagnosis and no one test is definitive. A comprehensive history from the patient, physical examination, and confirmation of airflow obstruction using spirometry are all vital in establishing the diagnosis.
The FEV1/FVC ratio is decreased with COPD, meaning a person can't force out as much air as predicted from their lungs in one second. (Normally someone can expire about 80% of their vital capacity in one second; however, this is typically reduced in COPD). With this condition there may be air-trapping as documented by an increased residual volume (the amount of air left in the lungs after a full breath out), or hyperinflation as documented by an an increased total lung capacity (the amount of air in the lungs after a full inhalation).
Management
COPD is not curable. Medicines are often used to control symptoms or to reverse acute exacerbations. COPD in all forms typically progresses if the patient continues to smoke. Therefore, smoking cessation is one of the most important factors in slowing down the progression of COPD.
The use of bronchodilators, nebulisers and corticosteroids has been shown to be effective. Patients with chronic disease and significant lung function impairment (FEV1 < 50%) may also benefit from the regular use of inhaled steroids. Oxygen therapy is the only current medical intervention that is proven to prolong the lives of patients with this disease process. Oxygen is only indicated in patients with severe hypoxia documented by a physician.
Surgical management includes single or double lung transplant, and lung volume reduction surgery (LVRS), which is currently being evaluated in a large, national trial in the UK.
Many patients with COPD should be considered for pulmonary rehabiliation. The American Thoracic Society Consensus is an excellent reference.
