RCPs play an important role in managing obstructive lung diseases through early recognition and intervention
Emphysema is a general term that refers to a chronic pulmonary disease characterized by shortness of breath, coughing, sputum production, airflow limitation, and impaired gas exchange. Emphysema along with chronic bronchitis are collectively referred to as chronic obstructive pulmonary disease (COPD).
COPD affects between 11 million and 30 million people in the United States,1-4 and represents the fifth leading cause of death.1,3-5 The death rate from COPD has increased by 22% in the past decade.1,5 The mortality rate 10 years after diagnosis is greater than 50%, and this percentage is on the rise.1,5 Cigarette smoking is an important etiologic factor. Prevalence, incidence, and mortality increase with age, and are higher in males than in females.2 Prevalence is especially rising in women, largely as a result of increased cigarette smoking by females.2
In chronic pulmonary disease, the predominant pathology in large airways is mucous gland hyperplasia. This results in the excess sputum production characteristic of chronic bronchitis.6 Variable degrees of smooth muscle hyperplasia may also be present. The small airways, however, are the main sites of airway obstruction in COPD. Small airways exhibit characteristic changes including inflammation, fibrosis, mucus production, and narrowing.
There are several important risk factors for emphysema:
- LifestyleCigarette smoking is by far the most important risk factor for emphysema (80% of all cases). Cigar and pipe smoking can also cause emphysema. Air pollution and industrial dusts and fumes are other important risk factors.
- AgeChronic bronchitis is more common in people over 40 years old; emphysema occurs more often in people 65 years of age and older.
- Socioeconomic ClassEmphysema-related deaths are about twice as high among unskilled and semiskilled laborers as among professionals.
- Family ClusteringIt is thought that heredity predisposes people in certain families to the development of emphysema when other causes, such as smoking and air pollution, are present.
- Lung InfectionsLung infections make all forms of emphysema worse.
In the general population, emphysema usually develops in older individuals with a long smoking history. However, there is also a form of emphysema that runs in families. People with this type of emphysema have a hereditary deficiency of a blood component, an enzyme inhibitor called alpha1-antitrypsin (AAT). This type of emphysema is sometimes called early-onset emphysema because it can appear when a person is as young as 30 or 40 years old. It is estimated that there are between 75,000 and 150,000 Americans who were born with AAT deficiency. Of this group, emphysema afflicts an estimated 20,000-40,000 people (1% to 3% of all cases of emphysema). The risk of developing emphysema for an AAT-deficient individual who also smokes is much greater than for others.
The first symptoms of chronic bronchitis are cough and mucus production. These symptoms resemble a chest cold that lingers on for weeks. Later, shortness of breath develops. Cough, sputum production, and shortness of breath may become worse if a person develops a lung infection. A person with chronic bronchitis may later develop emphysema as well. In emphysema, shortness of breath on exertion is the predominant early symptom. Coughing is usually minor and there is little sputum. As the disease progresses, the shortness of breath occurs with less exertion, and eventually may be present even when at rest. At this point, a sputum-
producing cough may also occur. Either chronic bronchitis or emphysema may lead to respiratory failurea condition in which there occurs a dangerously low level of oxygen or a serious excess of carbon dioxide in the blood.
Emphysema is a disease in which cigarette smoke causes overproduction of the enzyme elastase, one of the immune systems infection-fighting biochemicals. This results in irreversible destruction of a protein in the lung called elastin, which is important for maintaining the structure of the walls of the alveoli, the terminal small air sacs of the respiratory system. As the walls of the alveoli rupture, the number of alveoli is reduced and many of those remaining are enlarged, making the lungs of the patient with emphysema less elastic and overinflated. Due to the higher pressure inside the chest that must be developed to force air out of the less elastic lungs, the bronchioles, small air tubes of the respiratory system, tend to collapse during exhalation. Stale air gets trapped in the air sacs and fresh air cannot be brought in.
The preclinical course of patients with emphysema is highly variable. Patients with a history of lung disease early in life may exhibit reduced pulmonary function in adulthood. Smoking in patients with a history of childhood lung disease may lead to a progressive decline in lung function. Other patients who smoke probably begin adulthood with normal lung function. Forced expiratory volume in 1 second (FEV1) usually remains within normal limits until middle age, when a rapid decline in pulmonary function ensues. Generally, this decline stops in patients who quit smoking. The clinical symptoms of emphysema generally will appear in patients who continue to smoke.
Patients with emphysema usually present with shortness of breath, cough, and/or wheezing. Coughing usually indicates excess mucus production. The shortness of breath is a result of increased work of breathing through obstructed airways, and is usually initially associated with increasing levels of exertion. Over time, the dyspnea worsens to the point of occurring at rest. Wheezing occurs as a result of airway narrowing, mucosal edema, and retained secretions. Typically, patients with chronic pulmonary disease have been described as either blue bloaters or pink puffers. Blue bloaters have central cyanosis with secondary polycythemia and edema. Arterial blood gas (ABG) evaluation usually reveals evidence of hypoxemia (Po2, 45-55 mm Hg), carbon dioxide retention (Pco2, 50-60 mm Hg), and compensated respiratory acidosis (pH, 7.38-7.42).4 Pink puffers do not have secondary polycythemia, and edema is not present. They have less hypoxemia (Po2, 60-80 mm Hg) and no carbon dioxide retention (Pco2, 30-40 mm Hg).4 Many patients have features of both conditions.
Diagnosis of Emphysema
The first step in diagnosing emphysema is a good medical evaluation, including a medical history and a physical examination of the chest. In addition, the physician may request one or more of the following tests.
Pulmonary Function Tests
Using a spirometer, an instrument that measures the air taken into and exhaled from the lungs, the physician can determine two important values: vital capacity (VC), the largest amount of air expelled after the deepest inhalation; and (FEV1), the maximum amount of air expired in one second. Pulmonary function tests can be performed in the physicians office.
Chest radiographs can detect only about half of the cases of emphysema. They are rarely useful for diagnosing chronic bronchitis.
Blood may be drawn from an artery to determine the amount of oxygen and carbon dioxide present. Low oxygen and high carbon dioxide levels are often indicative of chronic bronchitis, but not always of emphysema.
Many patients with lung disease also develop heart problems. The ECG identifies signs of heart disease.
Principles of Management
The general principles of management of emphysema are slowing disease progression, preventing infection, treating reversible symptoms, and educating patients. The RCP is intimately involved in all four cornerstones of care.
Slow Disease Progression
If the extent of disease is not completely irreversible (end-stage), progression of disease can be slowed by smoking cessation, reduction of exposure to environmental or occupational irritants, and therapy with supplemental oxygen.
Patients with emphysema should be encouraged to have annual influenza vaccinations. Some authorities also recommend vaccination against pneumococcal disease. Many bacterial and other organisms have been found in the sputum of patients with chronic pulmonary disease. These include: Haemophilus influenzae, Streptococcus pneumoniae, Streptococcus viridans, Klebsiella species, Moraxella (formerly called Branhamella) catarrhalis, Staphylococcus aureus, Staphylococcus epidermidis, and Candida albicans (a fungus). Broad-spectrum antibiotic prophylaxis has not been shown to decrease the frequency of infections, but may decrease the severity and duration of symptoms.
Treat Reversible Symptoms
Pharmacotherapy with b-agonists and long-acting theophylline preparations may reverse the symptoms of airway obstruction. Additional medications are reviewed below.
Education should be an integral part of chronic pulmonary disease management. Patients and their families should be given basic facts about the disease process and offered a list of resources in the event they desire additional information. Medication issues should be addressed. If appropriate, the subject of intubation and resuscitative intervention should be reviewed and the patients desires should be delineated.
Pharmacologic Agents for Reversible Bronchospasm
Pharmacologic agents for managing reversible bronchospasm associated with COPD include theophylline, b-agonists, corticosteroids, anticholinergic agents, mucolytic agents, and, if appropriate, alpha1-antitrypsin.
Although theophylline has limited bronchodilator effects, it may cause improved peripheral ventilation, resulting in a fall in trapped gas volume and an increase in exercise tolerance. It can improve mucociliary clearance and the overall work of breathing. Theophylline augments central respiratory drive and may also improve diaphragm muscle activity and decrease vascular and pulmonary bronchiolar resistance. There is some evidence that theophylline may provide protection against episodic bronchospasm. Animal studies suggest a possible anti-inflammatory effect.3,7 Long-acting preparations taken in the early evening have the added advantages of controlling nocturnal symptoms and increasing compliance.8
Selective b2-agonists cause vasodilation of peripheral and pulmonary vessels. Cardiovascular effects include reflex tachycardia and reduction of biventricular afterload in patients with severe COPD. A major problem with potent b2-agonists is their action on muscle receptors to accelerate the relaxation phase of slow-contracting fibers, thus producing tremor. b-agonists may improve mucociliary clearance. Tolerance may be a problem. The most common difficulty limiting the efficacy of b-agonists is inadequate dosage resulting from inefficient use. The use of inhaled b-agonists may reduce the systemic effects such as the tremor.3,7
For patients with emphysema, inhaled b2-agonist bronchodilators are used either as PRN medications for relief of acute respiratory distress or for long-term maintenance treatment. Agents with a rapid onset of action (albuterol) are used for PRN relief, and those with a long duration of action (salmeterol) are used for maintenance therapy. No single b2-agonist available in the United States to date has been effective for both purposes.
However, one inhaled b2-agonistformoterolis a highly selective bronchodilator that has the unique combination of a rapid onset of bronchodilation (within 1 to 3 minutes; comparable to albuterol) and a long duration of action (>12 hours; comparable to salmeterol). Clinical experience with formoterol in asthma is extensive. Approval by the Food and Drug Administration for marketing formoterol for use in the treatment of emphysema is expected in the near future.
Use of inhaled corticosteroids has increased despite controversy about efficacy in chronic pulmonary disease. Corticosteroids penetrate the cytoplasm of cells, bind to steroid receptors, and influence RNA sequences, thereby modulating protein synthesis. In addition, they directly influence the release of other mediators, such as leukotrienes, and thus inhibit the inflammatory process. They also interfere with neutrophil activity and block portions of the complement system.3
While the presence of inflammatory changes in the airways of patients with COPD provides a rationale for the use of cortico-steroids,2,3 the association between these changes, lung function, and the therapeutic response to corticosteroids has not yet been established clearly. Whether a response to 30 mg of prednisolone over 2 weeks predicts an ongoing improvement with inhaled cortico-steroid treatment is debatable and results are awaited from ongoing studies.
Anticholinergic agents are potent bronchodilators. Atropine inhibits vagal bronchospasm. Many side effects preclude routine use. Ipratropium is three to five times more potent than atropine as a bronchodilator and is poorly absorbed through the gastrointestinal tract, which minimizes systemic toxicity.3 However, onset of action is slow, and it must be used regularly, mitigating use for episodic bronchospasm.3
These agents have variable effectiveness in patients with chronic pulmonary disease. They work by liquefying mucus through hydration or by changing its chemical structure, leading to improved transport and clearance of secretions by the ciliary network in the bronchial tree. Unfortunately, agents such as ammonium chloride and guaifenesin require extraordinarily large doses for any objective effect, and acetylcysteine irritates the airways of many patients.3
Replacement therapy with biosynthetic alpha1-antitrypsin is the primary therapy for alpha1-antitrypsindeficient individuals.
Surgical procedures for emphysema are very rare. They are expensive and often not covered by insurance. The great majority of patients cannot be helped by surgery, and no single procedure is ideal for those who can be helped. In January 1996, the government temporarily suspended Medicare payments for lung reduction surgery.
- Lung Transplantation. Lung transplantation has been successfully employed in some patients with end-stage emphysema. In the hands of an experienced team, the 1-year survival rate is more than 70%.
- Lung Volume Reduction. These procedures remove 20% to 30% of severely diseased lung tissue; the remaining parts of the lung are joined together. Mortality rates can be as high as 15% and complication rates are even higher. When the operation is successful, patients report significant improvement in symptoms.
Smoking cessation is perhaps the single most important nonpharmacologic therapy. Usually, long-term cessation will allow for reversal of the reversible portion of obstructive disease. Supplemental oxygen may sustain arterial Po2 in late-stage or end-stage patients. Oxygen therapy may also prolong survival.9 Rehabilitation to learn how to live with chronic pulmonary disease may help prolong quality of life. Education is important and may increase compliance. Surgical interventions such as those mentioned above are not routinely performed.
A structured, outpatient pulmonary rehabilitation program improves functional capacity in certain patients with emphysema. Services may include general exercise training, administration of oxygen and nutritional supplements, intermittent mechanical ventilatory support, continuous positive airway pressure (CPAP), relaxation techniques, breathing exercises and techniques (such as pursed lip breathing), and methods for mobilizing and removing secretions.
Emphysema is a disease that can be treated and controlled, but not cured. Survival of patients with emphysema is clearly related to the degree of their lung function when they are diagnosed and the rate at which they lose this function. Overall, the median survival is about 10 years for patients with emphysema who have lost approximately two thirds of their lung function at diagnosis.
Opportunities for Intervention
The RCP has an important role in the management of obstructive lung diseases. Recognition is the first step toward avoidance. By educating the patient about possible triggers associated with his or her occupation and/or environment, the respiratory care practitioner provides a greater opportunity for trigger identification.
Surveillance programs are a keystone for prevention. They may identify individuals who are at an increased risk for developing asthma or emphysema in the workplace, and detect disease at an early stage when intervention options are likely to be successful. The most sensitive health surveillance programs currently available include preemployment and periodic examinations, immunologic monitoring, and periodic spirometric surveys.
Cigarette smoking provides, for the smoker, the most intense exposure to pollution of any kind, and it can contribute significantly to the exposure of other people indoors. Measures to encourage smokers to quit, and young people not to start smoking in the first place, offer perhaps the greatest opportunity for reducing the prevalence of chronic lung disease.
Finally, particular care is required to avoid the exposure of young children to high levels of pollution, whether of outdoor or indoor origin. Not only are there links between such exposures and the occurrence of respiratory illnesses, but these early experiences also may contribute to the development of emphysema later in life.
John D. Zoidis, MD, is a contributing writer for RT Magazine.
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