The student will be able to define restrictive lung diseases and differentiate their various forms including etiology, pathogenesis if known, and clinical presentation.
The student will be able to describe and recognize gross and microscopic features of acute and chronic restrictive lung diseases.
Restrictive lung diseases are characterized by reduced lung compliance that requires greater pressure to inflate the lungs and, clinically, typically are manifest as dyspnea. Restrictive lung disease can result from external compression of the lung parenchyma; examples include severe scoliosis, chest wall tumors, and expansion of the pleural space by fluid or air (Chaps. 26 and 29). This chapter will focus on restrictive lung diseases in which the restriction is intrinsic to the lung rather than due to external compression. Although many different restrictive lung diseases will be discussed, there are some common themes to restrictive lung disease. Many such diseases show thickening of alveolar septa and alveolar epithelial and endothelial injury that lead to V̇A/Q̇ mismatch. With progression of many such diseases, patients develop severe hypoxemia and respiratory failure. These are often complicated with pulmonary hypertension and cor pulmonale (right ventricular dilatation due to lung disease).
ACUTE RESTRICTIVE LUNG DISEASES
The acute respiratory distress syndrome (ARDS) is a clinical syndrome characterized by the acute onset of respiratory distress with hypoxemia, reduced lung compliance, and diffuse pulmonary infiltrates in the absence of primary left heart failure; a less severe form of the syndrome is acute lung injury (ALI) (Chap. 28). Diffuse alveolar damage (DAD) is the morphologic counterpart of ALI/ARDS. Though DAD can complicate many conditions (Table 23.1), more than one-half of cases occur in the settings of sepsis, diffuse pulmonary infections, gastric aspiration, and trauma.
Table 23.1Conditions associated with development of ALI and ARDS ||Download (.pdf) Table 23.1 Conditions associated with development of ALI and ARDS
|Infection ||Inhaled Irritants ||Physical Injury |
|Sepsis ||Oxygen toxicity ||Mechanical trauma, head injury |
Diffuse pulmonary infections
Fractures with fat embolism
|Gastric aspiration || || |
|Chemical Injury ||Hematologic Conditions ||Hypersensitivity Reactions |
|Heroin or methadone overdose ||Multiple transfusions ||Organic solvents |
|Acetylsalicylic acid ||Disseminated intravascular coagulation ||Misc. drugs |
|Barbiturate overdose || || |
|Paraquat poisoning || || |
|Pancreatitis ||Uremia ||Cardiopulmonary Bypass |
The pathogenesis of DAD begins with endothelial damage or, less frequently, epithelial damage. Within 30 minutes, macrophages secrete canonical proinflammatory cytokines including TNF-α, IL-1, and IL-8, leading to neutrophil chemotaxis and activation (Chap. 10). Activated neutrophils secrete oxidants, proteases, platelet activating factor (PAF), and leukotrienes, the results of which are tissue damage, edema, ...