Respiratory acidosis, or primary hypercapnia, occurs when carbon dioxide production exceeds elimination via the lung and is mainly owing to alveolar hypoventilation. Concurrent increases in Paco2, decreases in pH and compensatory increases in blood HCO3- concentration are associated with respiratory acidosis. Respiratory acidosis can be acute or chronic, with initial metabolic compensation to increase HCO3- concentrations by intracellular buffering. Chronic respiratory acidosis results in longer lasting increases in renal reabsorption of HCO3-. Alveolar hypoventilation and resulting respiratory acidosis may also be associated with hypoxemia, especially evident when patients are inspiring room air (20.9% O2).
Keywords: Alveolar hypoventilation; Arterial blood gas; Hypercapnia; Metabolic compensation; Respiratory acidosis.
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