chronic obstructive pulmonary disease
ABBR: COPD
Any of a group of debilitating, progressive, and potentially fatal lung diseases that have in common increased resistance to air movement, prolongation of the expiratory phase of respiration, and loss of the normal elasticity of the lung. The chronic obstructive lung diseases include emphysema, chronic obstructive bronchitis, chronic bronchitis, and asthmatic bronchitis. Taken together, they make up the fourth most common cause of death in the U.S. The incidence of death from COPD is rising whereas the death rate from heart disease, cancer, and stroke (the three illnesses that currently cause more death in the U.S. than COPD) is falling. SYN: chronic airflow obstruction; chronic obstructive lung disease.
Etiology: Most patients with chronic airflow limitations are or were smokers, and their lung disease is a direct consequence of the toxic effects of tobacco smoke on the lung. A smaller number have been exposed to environmental tobacco smoke (second-hand smoke) or to dusts, chemicals, or smoke at work, or to environmental pollution. People who genetically lack the enzyme α-1 antitrypsin also develop COPD, typically at an earlier age than smokers (in their 40s instead of their 50s or 60s).
In the U.S. millions of people have COPD. About a half million Americans are admitted to hospitals each year with exacerbations of the disease.
Case Finding: All patients diagnosed with COPD should be screened once in their lives for alpha-1-antitrypsin deficiency.
Symptoms: Diseases in this group are typically marked by difficulty breathing during exertion, as well as chronic cough and sputum.
Diagnosis: When COPD is suspected, patients should undergo spirometry testing, with an evaluation of their lung volumes before and after treatment with bronchodilators. An FEV1/FVC ratio of less than 0.7 that does not improve with inhaled bronchodilation confirms the diagnosis.
Treatment: Acute exacerbations of COPD should be managed with inhaled bronchodilators, e.g., albuterol and ipratroprium, low flow oxygen (to raise the oxygen saturation to about 90%), antibiotics (if patients have more productive mucus than normal), and corticosteroids. For most patients who smoke, exacerbations occur several times a year. Patients with frequent exacerbations improve when treated with prophylactics such as azithromycin. Between exacerbations, disease management relies on smoking cessation and regular exercise (pulmonary rehabilitation), as well as supplemental oxygen, when it is needed. Additional preventive therapies include annual influenza vaccinations, and pneumococcal vaccination. Chronic management of COPD includes the use of anticholinergic agents, such as tiotropium, with long-acting beta agonists, like formoterol, and short-acting drugs, like albuterol. Corticosteroids have less benefit in chronic management (than in asthma) and can occasionally cause significant side effects. Aminophylline, a drug used extensively in the past for COPD, is now rarely used because of its interaction with other drugs and potential toxicity.
Patient Care: The respiratory therapist teaches breathing and coughing exercises and postural drainage to strengthen respiratory muscles and to mobilize secretions. Breathing retraining, e.g., pursed lip breathing, slows the respiratory rate, decreases airway resistance, and decreases dyspnea. Prolonging expiration to two or three times the length of inspiration reduces air-trapping and improves ventilation. The patient is encouraged to participate in a pulmonary rehabilitation program, as well as to stop smoking and avoid other respiratory irritants. Patients are instructed to avoid contact with other people with respiratory infections and taught the use of prescribed prophylactic antibiotics and bronchodilator therapy. Good oral and hand hygiene helps prevent infections. Frequent small meals of easily digested foods and adequate fluid intake are encouraged and are taken with oxygen by nasal cannula because eating may tire the patient. The patient's schedule alternates periods of activity with rest. The patient and family are assisted with disease-related lifestyle changes and are encouraged to express their feelings and concerns about the illness and its treatment. When exacerbations occur and symptoms and signs of bacterial infection are present, a five-day course of empirical antibiotic therapy should be given to the patient. Inhaled or oral steroids may alleviate airway inflammation. If these outpatient interventions are ineffective and the patient is deteriorating, the patient should seek help at local emergency departments or hospitals where care may include professional respiratory therapy.
The respiratory therapist monitors arterial blood gases and pulmonary function studies to determine the extent of the disease and proper treatment in consultation with the attending physician. Acute exacerbation occurs when the patient acquires a respiratory infection or other complication that must be recognized and treated promptly. Aerosol and humidity therapy is useful to thin and mobilize thick sputum and promote bronchial hygiene. Low-concentration oxygen therapy (usually no more than 2 to 3L/m) is applied as needed to keep the PAO2 between 60 and 80 mm Hg. Because COPD patients gradually develop high PaCO2 levels, the chemoreceptors in their brains become less sensitive to carbon dioxide as a trigger for ventilation and more dependent on hypoxemia as their ventilatory driver. Excessive oxygen may eliminate that hypoxic drive, resulting in decreased ventilatory rate and effort, confusion, drowsiness, and other signs of carbon dioxide narcosis, leading to death. Aerosolized bronchodilators are used to reduce dyspnea and promote improved cough. Mechanical ventilation is reserved for the patient in acute respiratory failure due to a superimposed condition that is reversible and not responding to initial therapy.
1. In hypoxic patients, oxygen therapy must be adjusted carefully to optimize arterial oxygen saturation.
2. Before traveling on airplanes, patients with COPD should consult their health care providers about special oxygen needs.
Some COPD patients (mainly emphysema patients) benefit from lung volume reduction surgery. Removal of diseased tissue, which provides little ventilation, allows the more functional tissue to expand and become useful in gas exchange. Lung transplantation is an option for selected patients with severe disease.
Exacerbation: Sudden worsening of COPD is manifested by a worsening of chronic shortness of breath and cough, often accompanied by an increase in respiratory rate and work of breathing. Exacerbations can be caused by environmental allergies (e.g., to pollen), by exposure to fire and smoke or other airway irritants, and by viral or bacterial infections. Bacterial infections should be suspected when the sputum produced by the patient increases in volume or changes to a more purulent appearance (e.g., when mucus changes from clear to creamy). Enhanced air filtration systems in the home or the workplace may protect patients with COPD from some exacerbations.