Which ABG values indicate acute respiratory failure?

Which ABG values indicate acute respiratory failure?

• A. Low PaO2 and high PaCO2
• B. High PaO2 and low PaCO2
• C. Normal ABG values
• D. Low PaO2 and low PaCO2

Answer: (A)

Acute respiratory failure happens when gas exchange is not meeting the body's needs, so oxygenation drops and ventilation may be impaired. On ABG, hypoxemia is shown by a low PaO2, and ventilatory failure is shown by a high PaCO2. When both are present—low PaO2 and high PaCO2—that pattern most clearly indicates acute respiratory failure, because the lungs are failing to both oxygenate blood and remove CO2. If PaO2 is low but PaCO2 is normal or low, that can occur with rapid breathing and isn’t the classic picture of respiratory failure. High PaO2 with low PaCO2 shows adequate oxygenation with hyperventilation, not failure. Normal ABG values obviously don’t indicate failure.

Acute respiratory failure happens when gas exchange is not meeting the body's needs, so oxygenation drops and ventilation may be impaired. On ABG, hypoxemia is shown by a low PaO2, and ventilatory failure is shown by a high PaCO2. When both are present—low PaO2 and high PaCO2—that pattern most clearly indicates acute respiratory failure, because the lungs are failing to both oxygenate blood and remove CO2.

If PaO2 is low but PaCO2 is normal or low, that can occur with rapid breathing and isn’t the classic picture of respiratory failure. High PaO2 with low PaCO2 shows adequate oxygenation with hyperventilation, not failure. Normal ABG values obviously don’t indicate failure.