Respiratory failure is a condition in which the respiratory system cannot maintain adequate oxygen levels, cannot adequately remove carbon dioxide, or both. Type 1 (hypoxaemic) respiratory failure involves low blood oxygen with a normal or low carbon dioxide level; it occurs when the lungs’ ability to transfer oxygen is impaired, as in pneumonia, pulmonary embolism, or acute respiratory distress syndrome. Type 2 (hypercapnic) respiratory failure involves a high carbon dioxide level in the blood; it occurs when the breathing drive or muscle power is insufficient to ventilate the lungs adequately, as in COPD, respiratory muscle weakness, or drug overdose.
Respiratory failure can cause increasing breathlessness, confusion, bluish discolouration of the lips and fingertips (cyanosis), and in severe cases, loss of consciousness. If untreated, it can cause cardiac arrest as the heart is progressively starved of oxygen. Respiratory failure is itself a recognised cause of cardiac arrest, particularly in severe asthma, airway obstruction, or massive pulmonary embolism.
Severe heart failure is an important cardiac cause of respiratory failure. When the left ventricle cannot pump effectively, pressure rises in the pulmonary veins, causing fluid to leak into the lungs (pulmonary oedema). This impairs gas exchange and produces acute breathlessness, particularly on lying flat. Treatment involves diuretics, oxygen, and addressing the underlying cardiac cause.
After cardiac arrest, management in the intensive care unit always involves respiratory support, typically mechanical ventilation through an endotracheal tube. The ventilator maintains gas exchange while the patient cannot breathe independently, and settings are carefully adjusted to maintain target oxygen and carbon dioxide levels as part of post-cardiac arrest care.
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