COPD’s pathology includes loss of tissue elasticity, emphysematous bullae, small airway obstruction, and destruction of lung parenchyma. Persons with COPD are typically separated into one of two catagories: “pink puffers” (normal PaCO2, PaO2 > 60 mmHg) or “blue bloaters” (PaCO2 > 45 mmHg, PaO2 < 60 mmHg). Pink puffers have severe emphysema, and characteristically are thin and free of signs of right heart failure. Blue bloaters, on the other hand, have frequent episodes of right heart failure, and produce copious sputum resulting in coughing and respiratory infections. Blue bloaters presents more of a chronic bronchitis picture although they too may exhibit emphysematous changes.
Pink puffers (normal PaCO2, PaO2 > 60 mmHg) have emphysematous lung tissue destruction. Diffusing capacity is decreased by destroyed pulmonary capillaries. ABG’s are near normal due to compensatory hyperventilation. The only subtle changes typically are a PaO2 slightly depressed (often in the mid 70’s, resulting in mild pulmonary vasoconstriction), and a low-normal PaCO2.
Blue bloaters (PaCO2 > 45 mmHg, PaO2 < 60 mmHg) suffer from pulmonary hypoxic vasoconstriction from the marked hypoxia and respiratory acidosis. This in turn leads to right ventricular hypertrophy and cor pulmonale. The right heart failure then leads to systemic venous congestion, peripheral edema, hepatic congestion, and ascites. Secondary erythrocytosis may occur, spurred by the hypoxia. Changes on ABG’s are much more pronounced.