Chronic obstructive pulmonary disease (COPD) is a condition where the airflow in and out of the lungs is obstructed. A number of chronic lung conditions are bundled together as a common diagnosis of COPD. Emphysema, chronic bronchitis and chronic asthmatic bronchitis are all associated with blockage of the outflow of air through the bronchioles. Patients who are diagnosed with these diseases have similar symptoms and many overlapping characteristics. The diseases usually begin as emphysema or chronic bronchitis with separate causes and pathophysiology, however, it is observed that by the time patients seek treatment, the two diseases overlap and are thus simply defined as COPD.
Emphysema occurs due to damage to the walls of alveoli, which merge to form huge air sacs. A decrease in the surface area of pulmonary surface and its diffusion capacity. In many cases emphysema is asymptomatic, where autopsy demonstrates the presence of disease. The main factor responsible for causing emphysema is cigarette smoke. It has been established that 90% of emphysema cases are observed in smokers, however, 10% of all smokers develop emphysema. According to national health survey questionnaire approximately 4.7 million people are diagnosed with emphysema. Chronic bronchitis, is a clinical diagnosis for a person who presents coughing for three month uninterruptedly, over a period of two years. Smoking is the number one cause of chronic bronchitis, however, air pollution can also cause chronic inflammation in the bronchi, resulting in enhanced mucus production. According to American lung association data more than 10 million people were diagnosed with chronic bronchitis in 2011. In chronic bronchitis, the initial injury is observed on the bronchi. In emphysema the initial lesion occurs in alveoli, in chronic bronchitis it occurs on bronchi.
The mechanism behind development of emphysema has been associated with smoking related inflammation. The inflammation in lung tissue leads to secretion of digestive enzymes. Under normal circumstances, the activity of digestive enzymes is inhibited by Alpha-1 antitrypsin, which prevents tissue damage that can be triggered by overactive digestive enzymes. (McConnell, 2007). It has been demonstrated that cigarette smoke inhibits the activity of this protein, causing lung tissue degeneration. Mucus overproduction (metaplasia) is observed as a response to inflammatory signals which is the primary pathological basis in chronic bronchitis. Metaplasia is associated with enhanced production (oxidative stress, activation of mucin gene transcription, inflammation of bronchioles) and reduced elimination of mucus (reduced ciliary function, occlusion of airways and muscle weakness). (Kim & Criner, 2013)
The representative feature of emphysema is large air cavities or spaces throughout the lungs. These cavities are visible to the naked eye and are also known as blebs. The first distinguishable symptom of emphysema is difficulty in breathing and shortness of breath (dyspnea). Patients with emphysema also experience weight loss. A stereotype for an emphysema patient is a thin person who smokes and has chronic dyspnea. The patient’s chest appears barrel shaped. A characteristic feature of advanced stage emphysema is enlarged heart. The emphysema patients lose the elasticity of their lung tissue, which means that can breathe in, but do not have capacity to breathe out completely and their lungs are chronically inflated. However, emphysema patients are mostly well oxygenated and pink. They are sometimes described as pink puffer. The chronic bronchitis patients because of impediment to air flow and airtrapping experience wheezing, coughing and produce copious amount of mucus/sputum. They are unable to oxygenate properly and are hypoxic, however, their lungs are not inflated. They do not end up losing weight as they do not lose pulmonary membrane and are often referred to as blue/cyanotic bloaters. Chronic bronchitis patients cough with sputum and experience loud breathing/wheezing, which is not observed in emphysema. (Chang, Daly, & Elliott, 2006).
Emphysema and chronic bronchitis are both detected by evaluating patient history, spirometry, lung function test, X rays and CT scans. Emphysema is not a curable disease, once lung damage has occurred; it cannot be reversed. However, smoking cessation and some medications can improve the symptoms and stop further lung damage in both emphysema and chronic bronchitis patients. Bronchodilators ( adrenergic receptor agonists) such as albuterol, formoterol, salmeterol are usually given in combination with corticosteroids (to lower the inflammation). (Spina, Page, Metzger, & O’Connor, 2003). A more advances COPD diagnosis might also need oxygen replacement therapy or surgery. Patients with CB, can also get relief from OTC cough suppressants. The prognosis of chronic bronchitis is generally better than emphysema if smoking is stopped early in the disease development stage. The prognosis of emphysema is based on staging described by pulmonary function testing result.
References
Chang, E., Daly, J., & Elliott, D (2006). Pathophysiology applied to nursing practice. Elsevier, Australia.
Kim, V., Criner, G.J. (2013). Chronic Bronchitis and chronic obstructive pulmonary disease. Am. J. Respir. Crit. Care. Med. 187, 3; 228-237
McConnell, T.H. (2007). The Nature for disease, pathology for health professionals. Lippincott, Williams & Wilkins. Philadelphia, PA.
Spina, D, Page, C.P., Metzger, W.J., & O’Connor, B.J. (2003). Drugs for the treatment of respiratory diseases. Cambridge university press, Cambridge, UK.
