Pulmonary gas emboli are a specific type of pulmonary emboli.
Presentation can vary dependant on the degree of air emboli where patients with small amount of air can be asymptomatic. Commonly reported clinical manifestations include sudden dyspnoea, chest pain, hypotension and/or convulsions 4.
They can arise from both iatrogenic and non-iatrogenic causes.
Venous gas embolism is a well-known complication of thoracic trauma, surgery, and a variety of diagnostic and therapeutic procedures. Small quantities of air have been reported in the central veins in up to 23% of patients during contrast material administration for CT scans 3.
Non-iatrogenic gas embolism can sometimes occurs in SCUBA divers as a result of gas bubble formation in the blood, which occurs due to rapid reduction in the ambient pressure during a diver's ascent.
Chest radiographs are usually normal unless there is a massive load of emboli. In the event of a large volume of air emboli, there may be areas of hyperlucency overlying the heart shadow, main pulmonary artery, or hepatic veins. Features of focal pulmonary oligaemia, pulmonary oedema, or enlargement of the central pulmonary arteries or superior vena cava may be seen.
May show some of the above plain film features in detail as well as allow direct visualisation of gas in the systemic veins, right sided cardiac chambers or main pulmonary arteries.
Treatment and prognosis
The risk of death is affected by both the amount of gas and the speed of introduction; the minimum lethal volume and injection rate in humans are thought to be around 300-500 mL and 100 mL/sec, respectively 4. Treatment is to position the patient in a left lateral decubitus or Trelendenburg position, with the aim to prevent the air from leaving the right heart into the pulmonary arteries. 100% supplemental oxygen can also be used to decrease the size of the bubble by reducing its nitrogen content.
- pulmonary oedema due to air embolism
- cardiovascular dysfunction and failure: can occur from obstruction of the right ventricular pulmonary outflow tract or obstruction of the pulmonary arterioles by a mixture of gas bubbles and fibrin clots formed in the heart 3
- cerebral air embolism: which in turn may result in cerebral oedema or ischaemic stroke
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