Circulatory abnormalities are common in respiratory failure. Other findings may include hypertension and warm skin with bounding pulses or hypotension. These are dependent both on the direct effects of hypoxia and acidosis and on the reflex responses to them, including release of catecholamines. Polycythemia or an increased red blood cell mass is a complication of longstanding hypoxemia due to increased levels of erythropoietin. Polycythemia often is not evident in patients with chronic hypoxemia due to lung disease.
Pulmonary hypertension is regularly present in respiratory failure.
Alveolar hypoxia, potentiated by hypercapnia, causes pulmonary arteriolar constriction. If chronic, this is accompanied by hypertrophy and hyperplasia of the affected smooth muscles and anatomical narrowing of the pulmonary arterial bed. The increased pulmonary vascular resistance increases the afterload on the right ventricle. This may induce right ventricular failure, that is, an increase in right ventricular diastolic pressure and systematic venous pressure. This in turn causes enlargement of the liver and peripheral edema, the entire sequence being termed cor-pulmonale .