lhypercapnie

Hypercapnia, also called hypercarbia, is an elevation of carbon dioxide (CO2) in the blood, typically defined by a PaCO2 above 45 mmHg on arterial blood gas. It results from an imbalance between CO2 production and its elimination by the lungs, most often due to inadequate ventilation.

Common causes include chronic hypoventilation from diseases such as chronic obstructive pulmonary disease (COPD) and obesity hypoventilation syndrome; acute respiratory failure from severe infections or airway obstruction; central nervous system depression from drugs or brain injury; neuromuscular disorders that weaken respiratory muscles; and chest wall or thoracic conditions that limit ventilation. Increased CO2 production from fever or sepsis can contribute, particularly in vulnerable patients.

Clinical presentation varies with severity and the rapidity of onset. Acute hypercapnia may cause headache, dizziness, confusion, and flushing; severe cases can lead to somnolence, depressed level of consciousness, seizures, or coma. Hypoxemia may accompany hypercapnia, though oxygen levels can be normal in some presentations.

Diagnosis relies on arterial blood gas measurement showing elevated PaCO2 and respiratory acidosis, sometimes with concurrent hypoxemia. Capnography may be used in ventilated patients to monitor CO2 levels. Chest imaging and tests for underlying causes are often performed.

Management focuses on treating the underlying cause and supporting ventilation. Options range from noninvasive ventilation (nIV) to invasive mechanical ventilation for patients with respiratory failure. Oxygen therapy should be titrated carefully to avoid worsening hypercapnia in susceptible patients. In COPD, avoiding excessive suppression of respiratory drive is important. Prognosis depends on the cause and the rapidity of intervention.