Porth's Essentials of Pathophysiology, 4e

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Disorders of Ventilation and Gas Exchange

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into the airways. They include cystic fibrosis, in which airway obstruction is caused by impairment of normal mucociliary function; congenital and acquired immu- nodeficiency states, which predispose to respiratory tract infections; lung infection (e.g., tuberculosis, fungal infections, lung abscess); and exposure to toxic gases that cause airway obstruction. Manifestations Bronchiectasis is usually manifested by a chronic produc- tive cough, often with several hundred milliliters of foul- smelling, purulent sputuma day. 16 Hemoptysis is common. Dyspnea and wheezing occur in about 75% of patients. 6 Weight loss, anemia, and other systemic manifestations are common. 10 Clubbing of the fingers is infrequent in mild cases, but common in severe disease. Obstructive pulmonary dysfunction with hypoxemia is seen in moder- ate to severe cases. However, due to improved treatment with better antibiotics and physical therapy, outcome and life expectancy have improved considerably. Diagnosis andTreatment Diagnosis is based on history and imaging studies. The condition often is evident on chest radiographs. High- resolution CT scanning of the chest allows for definitive diagnosis. Accuracy of diagnosis is important because interventional bronchoscopy or surgery may be pallia- tive or curative in some types of obstructive disease. Treatment consists of early recognition and manage- ment of infections along with regular postural drainage and chest physical therapy. Persons with this disorder benefit from many of the rehabilitation and treatment measures used for chronic bronchitis and emphysema. Cystic Fibrosis Cystic fibrosis (CF), which is a major cause of severe chronic respiratory disease in children and young adults, is an inherited disorder involving fluid secre- tion by the exocrine glands in the epithelial lining of the respiratory, gastrointestinal, and reproductive tracts. 48–51 In addition to chronic respiratory disease, CF is mani- fested by pancreatic exocrine deficiency and elevation of sodium chloride in the sweat. Nasal polyps, sinus infec- tions, pancreatitis, and cholelithiasis also are common. Excessive loss of sodium in the sweat predisposes young children to salt depletion episodes. Most males with CF have congenital bilateral absence of the vas deferens with azoospermia. Cystic fibrosis is inherited as an autosomal recessive trait. Homozygotes have all or substantially all of the clinical symptoms of the disease, compared with het- erozygotes, who are carriers of the disease but have no recognizable symptoms. Cystic fibrosis occurs most fre- quently in white populations of northern Europe, North America, and Australia/New Zealand. 51 Although it occurs less frequently among African, Hispanic, Middle Eastern, South Asian, and Eastern Asian populations, it may occur in these populations as well.

fourth generation of bronchi (see Chapter 21, Fig. 21-4). These bronchi become severely dilated and end blindly in dilated sacs, with collapse and fibrosis of more distal lung tissue. Cylindrical bronchiectasis involves uniform and moderate dilation of the sixth to eighth genera- tions of airways. It is a milder form of disease than saccular bronchiectasis and leads to fewer symptoms. Varicose bronchiectasis involves the second through eighth branchings of bronchi and results in bronchi that resemble varicose veins. Bronchiolar obliteration is not as severe and symptoms are variable. Bronchiectasis can present in either of two forms: a local obstructive process involving a lobe or segment of a lung or a diffuse process involving much of both lungs. 16 Localized bronchiectasis is most commonly caused by conditions such as tumors, foreign bodies, and mucus plugs that produce atelectasis and infection due to obstructed drainage of bronchial secretions. It can affect any area of the lung, the area being deter- mined by the site of obstruction or infection. Generalized bronchiectasis usually is bilateral and most commonly affects the lower lobes. It is due largely to inherited impairments of host mechanisms or acquired disor- ders that permit introduction of infectious organisms FIGURE 23-11. Bronchiectasis.The resected upper lobe shows widely dilated bronchi, with thickening of the bronchial walls and collapse and fibrosis of the pulmonary parenchyma. (From Bearsley MB,TravisWD, Rubin E.The respiratory system. In: Rubin R, Strayer DS, eds. Rubin’s Pathology: Clinicopathologic Foundations of Medicine. 6th ed. Philadelphia, PA: Wolters Kluwer Health | Lippincott Williams &Wilkins; 2012:545.)