Hyperkapnie

Hyperkapnie, or hypercapnia, is a medical condition defined by an abnormally elevated arterial partial pressure of carbon dioxide (PaCO2). In adults, PaCO2 above 45 mmHg is typically considered hypercapnia. It can occur acutely or chronically and is often associated with respiratory acidosis, though metabolic compensation may modify the pH in chronic cases.

Causes of hypercapnia include impaired ventilation due to lung diseases such as chronic obstructive pulmonary disease (COPD) and obesity hypoventilation syndrome, neuromuscular disorders that weaken breathing, central nervous system depression from medications or injury, chest wall abnormalities, and conditions with increased CO2 production or reduced CO2 elimination. It commonly results from hypoventilation, ventilation–perfusion mismatch, or both.

Clinical features vary with duration. Acute hypercapnia may present with headache, confusion, dizziness, dyspnea, tachycardia, flushed skin, and, in severe cases, altered level of consciousness or coma. Chronic hypercapnia may be less symptomatic but can cause sleepiness, cognitive impairment, and signs of the underlying disease; it is often accompanied by metabolic compensation with elevated bicarbonate on blood tests.

Diagnosis rests on arterial blood gas analysis showing elevated PaCO2, with evaluation of acid-base status (pH and bicarbonate). Oxygenation (PaO2) and the overall clinical context guide management. Imaging and additional tests help identify underlying causes.

Management focuses on treating the cause and supporting ventilation. In many cases, supplemental oxygen is used to maintain adequate oxygenation, but in susceptible patients (notably some COPD cases) oxygen must be carefully titrated to avoid worsening hypercapnia. Respiratory support, including noninvasive or invasive ventilation, is employed for respiratory failure. Treatment may also include bronchodilators, antibiotics for infection, and measures addressing the underlying condition.

Prognosis depends on the cause and duration; acute, reversible hypercapnia can improve with appropriate therapy, while chronic hypercapnia reflects ongoing respiratory disease and carries greater long-term risks.