CHAPTER 11. PULMONARY DISEASE
Kim K. Kuebler and Rhalene Gabuat Patajo
The increased prevalence of nonmalignant pulmonary disease is often underestimated because chronic obstructive pulmonary disease (COPD) is often underdiagnosed and poorly defined (Global Initiative for Chronic Obstructive Lung Disease [GOLD], 2005; Voelkel & Agusti, 2004). COPD is a major cause of morbidity and mortality throughout the world and is the fourth leading cause of death in the United States. In 2000, COPD was listed as the underlying cause of death for almost 119,000 American adults, which is a 67% increase compared with 52,000 deaths in 1980 (Centers for Disease Control and Prevention [CDC], 2002). By 2020, COPD is predicted to become the third leading cause of death in the United States and worldwide (GOLD, 2005; National Heart, Lung, and Blood Institute [NHLBI], 2001).
The increase in age-adjusted mortality rates for COPD between 1965 and 1998 distinguishes it from other diseases such as coronary heart disease or stroke, which have demonstrated a decrease in mortality rates over the same period of time (Anderson, 2002; Minino, Arias, Kochanek et al., 2002). COPD is the only leading cause of death in the United States for which the death rate is increasing (Doherty, 2005). The World Health Organization (WHO) estimates that 2.5 million deaths worldwide were the result of COPD in 2001 (WHO, 2003). In 2002 in the United States, the annual direct costs for COPD were more than $32 billion (Hilleman, Dewan, Malesker et al., 2000; NHLBI, 2002). Because of the morbidity and mortality associated with COPD, the economic implications of COPD in the United States are significant.
Of the estimated 24 million cases in the United States, less than 50% of these patients are given an accurate diagnosis of COPD (Mannino, Homa, Akinbami et al., 2002). The lack of proper diagnosis is fueled in part by clinical misconceptions of the demographics of this disease (Dransfield & Bailey, 2005). For the first time in history, the number of deaths in the United States from COPD was higher among women than among men in 2000, and the COPD death rate for women tripled from between 1980 and 2000 (CDC, 2002). In addition, the majority of COPD cases occur in patients younger than 65 years; in 2000, only 30% of reported cases occurred in older age groups. This evidence challenges the traditional assumption that COPD is a disease of the elderly male patient (CDC, 2003).
Pulmonary function and exercise abilities differ between geriatric and younger populations (Chan & Welsh, 1998). The elderly are susceptible to an increased risk of pulmonary disease over time, and the presentation of these diseases will differ in the middle-aged adult and the elderly (Chan & Welsh, 1998). The elderly patient will have less respiratory reserve to blunt a hypoxic or hypercarbic drive or to perceive the experience of dyspnea (Chan & Welsh, 1998). The burden of COPD in an increasingly aging society is likely only to increase, and so the importance of integrating palliative management for the myriad accompanying symptoms is critical.
DEFINITION
The current and widely accepted definition of COPD was proposed by WHO and NHLBI through an initiative identified as GOLD (2005). This collaborative project identified new guidelines for the diagnosis and treatment of COPD (Bramen & Peters, 2005). Prior to the GOLD guidelines, COPD was defined as a disease process caused by chronic bronchitis and emphysema. This definition has been replaced by new information suggesting that COPD is a result of airflow limitation—a reaction to the abnormal inflammatory response in the lungs from prolonged exposure to noxious gases. The American Thoracic Society (ATS) and the European Respiratory Society (ERS) offer a joint definition of COPD identical to the GOLD guidelines, describing COPD as “a preventable and treatable disease state characterized by airflow limitation that is not fully reversible” (ATS, 2004). “Airflow limitation is usually progressive and is associated with an abnormal inflammatory response of the lungs to noxious particles of gases primarily caused by cigarette smoking” (ATS, 2004). Although the new GOLD definition for COPD no longer identifies this disease as an irreversible process, both guidelines recommend the use of staging criteria to prognosticate COPD, ranging from “at risk” to “very severe” disease (ATS, 2004; GOLD, 2005). However, COPD is considered a progressive disease, and the goal of care is often to reduce the progression of disability and symptoms.
COPD encompasses both chronic bronchitis and emphysema. Chronic bronchitis occurs in most patients with COPD in the earlier phases of the disease, whereas emphysema is less common and often presents much later in the course of disease, accompanied by significant symptom burden (cachexia, dyspnea, fatigue, etc.). Chronic bronchitis is defined by the ATS/ERS guidelines as “chronic productive cough, lasting for three months over two successive years in a patient in whom other causes of productive cough have been excluded” (ATS, 2004). Emphysema is further defined as “permanent enlargement of the airspaces distal to the terminal bronchioles, accompanied by destruction of the walls of the alveoli without obvious fibrosis” (ATS, 2004).
THE COPD PATIENT
Many clinicians hold stereotypical views on the “typical” COPD patient as being elderly and male. The validity of this traditional approach to COPD was analyzed through a retrospective study of more than 2100 COPD patients managed by the National Jewish Medical and Research Center (Tinkelman & Corsello, 2003). This study was designed to evaluate the socioeconomic, demographic, and resource utilization of current COPD patients. The investigators concluded that COPD patients are younger than previously identified and are typically described by the following characteristics:
▪ Continues to smoke cigarettes despite having moderate to severe disease
▪ Just as likely to be female (52.7%) as male (47.3%)
▪ Older than 40 years
▪ Just as likely to be employed as unemployed
▪ Is not diagnosed in the early stages of disease
▪ Has increased use of health care services compared to same-age individuals in the general population (Doherty, 2005; Tinkelman & Corsello, 2003)
The diagnosis of COPD has been historically assigned to patients who have emphysema, chronic bronchitis, or a mixture of the two. Many patients will complain of having increased dyspnea over several years and are positive for chronic cough, poor exercise tolerance, and evidence of airway obstruction such as overinflated lungs and poor gas exchange (West, 2003). Appropriate diagnosis, therefore, is absolutely essential when effectively managing a specific pulmonary disease.
ETIOLOGY AND PATHOPHYSIOLOGY
The classic epidemiologic studies of Fletcher and Peto (1977) revealed that death and disability from COPD were related to an accelerated decline in lung function over time, with a loss of more than 50 mL per year in the forced expiratory volume over 1 second (FEV 1) compared with a normal loss of approximately 20 mL per year. A reduction in FEV 1 in the face of progressive disease over time contributes to increased dyspnea on exertion and slowly advances to respiratory failure (Barnes, 2004).
There is considerable debate regarding the reasons for the accelerated loss of FEV 1 and its relation to the pathogenesis of COPD. However, there are four major mechanisms that have been implicated (Barnes, 2004):
1. Loss of elasticity and the destruction of the alveolar attachments of airways during expiration
2. Increased cholinergic bronchomotor tone in the airways via release of acetylcholine by way of the parasympathetic nervous system
3. Narrowing of small airways as a result of inflammation and scarring
4. Mucus blocking of small airways
All four of these mechanisms can interact with one another and are often induced from cigarette smoking and the inhalation of noxious particles. Narrowing of the small airways results in hyperinflation of the lungs and air trapping contributing to dyspnea and cough (Barnes, 2004). The structural changes that occur in the aging lung and chest wall produce predictable alterations in pulmonary function tests. The elderly patient will tend to have a decrease in his or her vital capacity, which is a direct result of the following (Chan & Welsh, 1998):
▪ Increased chest wall stiffness (muscle atrophy, weakness, arthritis, etc.)
▪ Loss of elastic recoil of the lung and supportive connective tissue
▪ Decreased respiratory force generated by respiratory muscles
Obstructive and Restrictive Airway Disease
The differentiations in obstructive and restrictive airway diseases are often blurred and may give rise to the difficulties in definition, diagnosis, and management of specific diseases (i.e., asthma, COPD, bronchitis, emphysema, and malignancies). Obstructive airway disease is an increased resistance to airflow and can be caused by conditions that occur inside the pulmonary lumen, within the wall of the airway, and/or in the peribronchial region (West, 2003). Airway lumen, for example, may be blocked by excessive secretions often found in patients with chronic bronchitis. Other examples of airway lumen blockage include a partially occluded lumen from pulmonary edema, aspiration of a foreign object, or any substance that creates a partial or complete blockage within the airway lumen (West, 2003).
Disease that affects the internal wall of the airway includes the contraction of the bronchial smooth muscle that occurs in asthma as a result of the inflammatory process of the airway epithelium. Hypertrophy of the mucus glands that accompanies chronic bronchitis can also interfere with airway obstruction within the lumen (West, 2003). Prolonged exposure to noxious gas contributes to the destruction of the lung parenchyma, which causes a loss of the radial traction of the connective tissues within the lung and consequent airway narrowing (West, 2003).
Cigarette smoke accounts for more than 90% of cases of COPD in developed countries; however, COPD occurs in only a minority of smokers (10% to 20%), indicating individual variations in susceptibility to this disease (Barnes, 2004). Research in this area is ongoing and includes evaluation of patient-specific phenotype, pathologic mediators of disease, involved cellular mechanisms, and newly identified environmental factors.
Emphysema
Emphysema is characterized by an enlargement of the air spaces (alveoli) distal to the terminal bronchiole with associated airway lumen destruction (West, 2003). The associated loss of elasticity and the destruction of the alveolar attachments in the lung promote narrow airways and air trapping (hyperinflation) (Barnes, 2004). Cigarette smoke may stimulate the neutrophil to release excessive amounts of the enzyme lysosomal elastase. This results in the destruction of elastin, an important structural protein in the lung (West, 2003). Neutrophil elastase also binds to type IV collagen, an important molecule that influences the strength of the pulmonary capillary and the integrity of the alveolar wall (West, 2003).
Chronic Bronchitis
This disease is associated with an excessive production of mucus secretions within the bronchial tree. Hypertrophy of the mucus glands in the large airway and chronic inflammation of the airway contribute to airway narrowing—a result of lumen thickening, inflammation, and scarring in the small airways (West, 2003). In chronic bronchitis, excessive amounts of mucus are found in the airways, and thickened mucus may occlude some small bronchi (West, 2003). Small airways are narrowed and show inflammatory changes that include cellular infiltration and airway edema. Granulation tissue and peribronchial fibrosis occur over time (West, 2003).
Asthma
Asthma is an inflammatory response of the airways to various stimuli (antigens) that potentiate airway narrowing. The airways of an asthmatic patient respond to stimuli by hypertrophied smooth muscle that contracts and produces bronchoconstriction. The bronchial airway contains hypertrophy of the mucus glands and edema of the bronchial wall with an increased integration of eosinophils and lymphocytes (West, 2003).
Restrictive Disease
Restrictive diseases are those in which the expansion of the lung is restricted because of alterations in the lung parenchyma or because of disease of the pleura, chest wall, or neuromuscular apparatus. They are characterized by a reduced vital capacity and a small resting lung volume, but the airway resistance is not increased. It is important to note that restrictive and obstructive conditions can be present concurrently.
▪ Diffuse interstitial pulmonary fibrosis Thickening of the interstitium of the alveolar wall may be caused by an immunologic reaction. The patient presents with dyspnea, rapid and shallow breathing, and an irritating, unproductive cough.
▪ Sarcoidosis Granulomatous tissue is present in several organs (lymph nodes, lungs, skin, eyes, liver, spleen, etc.). Fibrotic changes in the alveolar walls are seen, and pulmonary fibrosis and cor pulmonale may develop.
▪ Hypersensitivity pneumonitis This occurs with exposure to inhaled organic dusts. Fibrotic changes occur in advanced cases, and the patient is frequently dyspneic.
▪ Interstitial disease caused by drugs, poisons, radiation Busulfan, nitrofurantoin, amiodarone, bleomycin, antineoplastic drugs, and oxygen may cause an acute pulmonary reaction, which can proceed to interstitial fibrosis. Therapeutic radiation causes acute pneumonitis followed by fibrosis.
▪ Collagen disease Interstitial fibrosis may be found in patients with generalized scleroderma, systemic lupus erythematosus, or rheumatoid arthritis.
▪ Lymphangitis carcinomatosa Spread of carcinoma tissue through pulmonary lymphatics leads to prominent dyspnea.
▪ Pneumothorax This occurs in a variety of conditions, including rupture of a bulla in COPD, rupture of a cyst in advanced fibrotic disease, or during mechanical ventilation with high airway pressures, and often precipitates breathlessness/dyspnea.
▪ Pleural effusion Fluid in the pleural space frequently accompanies serious disease, and the patient often reports dyspnea if the effusion is large.
▪ Scoliosis Bone deformities can cause an increased work of breathing.
▪ Ankylosing spondylitis Gradual immobility of the vertebral joints and fixation of the ribs result in reduced movement of the chest wall.
▪ Neuromuscular disorders Poliomyelitis, Guillain-Barré syndrome, amyotrophic lateral sclerosis, myasthenia gravis, and muscular dystrophies affect the muscles or nerves of respiration (West, 2003
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