Hypercapnia

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Background

  • PaCO2 >45
  • Exclusively caused by alveolar hypoventilation
    • Results from decrease in respiratory rate, tidal volume, or increase in dead space

Diagnosis

  • HA, confusion, lethargy, sz, coma
  • Extreme hypercapnia (acute elevation >100) can result in CV collapse

Work-Up

  • ABG
    • HCO3 increases 1 mEq/L for each 10mmHg increase in PaCO2 (acute)
    • HCO3 increasess 3.5 mEq/L for each 10mmHg increase in PaCO2 (chronic)

DDx

  1. Depressed central respiratory drive
    1. Structural CNS disease: brainstem lesions
    2. Drug depression of respiratory center: opioids, sedatives, anesthetics
    3. Endogenous toxins: tetanus
  2. Thoracic cage disorders
    1. Kyphoscoliosis
    2. Morbid obesity
  3. Neuromuscular impairment
    1. Neuromuscular disease: myasthenia gravis, Guillain-Barré
    2. Neuromuscular toxin: organophosphate poisoning, botulism
  4. Intrinsic lung disease associated with increased dead space
    1. COPD
  5. Upper airway obstruction

Treatment

  • Increase minute ventilation (rate and/or tidal volume)

See Also

Hypoxemia

Source

Tintinalli

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