Pulmonary air 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 air embolism is a well-known complication of thoracic trauma, surgery, and a variety of diagnostic and therapeutic procedures. Small quantities of air has been reported in the central veins in up to 23% of patients during contrast material administration for CT scans 3.
Non iatrogenic causes
Non-iatrogenic air 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 oligemia, 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 air 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 air 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.
- 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 air 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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- 4. Han D, Lee KS, Franquet T et-al. Thrombotic and nonthrombotic pulmonary arterial embolism: spectrum of imaging findings. Radiographics. 2003;23 (6): 1521-39. Radiographics (full text) - doi:10.1148/rg.1103035043 - Pubmed citation