Respiratory Acidosis

A primary increase in arterial carbon dioxide partial pressure; pH is decreased and total carbon dioxide content is increased if renal function is intact.

Respiratory acidosis is caused by carbon dioxide retention from alveolar hypoventilation, which may result from disorders that depress the central respiratory center, restrict chest wall mobility, reduce pulmonary alveolar surface area, or narrow the upper airway. The elderly are at risk because of their reduced vital capacity and ventilatory responses to hypoxia and hypercapnia. Common causes are drugs that can produce respiratory depression, neuromuscular disorders, and pulmonary disorders. Respiratory acidosis is often accompanied by hypoxia. Progressive respiratory failure often results in a metabolic encephalopathy with headache, drowsiness, and ultimately stupor and coma. Asterixis and myoclonus may develop.

Treatment aims to improve the underlying pulmonary disorder and may include intubation and assisted mechanical ventilation. Hypoxia must be corrected with the lowest possible oxygen concentration to avoid further depression of respiratory drive. Many patients also have concomitant metabolic alkalosis.