Respiratory failure occurs when the respiratory system cannot maintain normal levels of oxygen, carbon dioxide, or both in arterial blood. Recognizing the pattern of gas-exchange failure helps explain its causes and guides treatment.
Respiratory failure is inadequate gas exchange by the respiratory system, so arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A typical reference value is an arterial oxygen partial pressure, PaO₂, above 80 mmHg (about 11 kPa), and an arterial carbon dioxide partial pressure, PaCO₂, below 45 mmHg (about 6.0 kPa).
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What is respiratory failure?
Inadequate gas exchange that prevents the respiratory system from keeping arterial oxygen, carbon dioxide, or both within normal levels.
How do hypoxemia and hypercapnia differ?
Hypoxemia is reduced oxygen in arterial blood; hypercapnia is elevated carbon dioxide in arterial blood.
What distinguishes Type 1 from Type 2 respiratory failure?
Type 1 is primarily a failure of oxygenation, with low PaO₂ and normal or low PaCO₂. Type 2 is inadequate alveolar ventilation with carbon dioxide retention and elevated PaCO₂.
What is atelectasis, and why is it relevant to Type 3?
Atelectasis is the collapse of functional lung units involved in gas exchange. It commonly occurs around surgery, including after anesthesia, and is a frequent mechanism of perioperative Type 3 respiratory failure.
What causes Type 4 respiratory failure?
It occurs when metabolic oxygen demands exceed what the cardiopulmonary system can provide, often because shock impairs perfusion of respiratory muscles.
Quiz questions
Which test is the gold standard for establishing respiratory failure?Answer: Arterial blood gas assessment
What does pulse oximetry estimate?Answer: The fraction of hemoglobin saturated with oxygen
What does capnometry measure?Answer: Carbon dioxide in exhaled air
For acute hypoxic respiratory failure when intubation is not indicated, which support may be used as first-line treatment?Answer: High-flow nasal oxygen
Which medication is used to treat respiratory failure caused by opioid overdose?Answer: Naloxone