What imaging modalities are used to diagnose air embolism (pulmonary embolism)?

From the Guidelines

Computed tomography (CT) is the preferred imaging modality for diagnosing air embolism, particularly CT without contrast, which can detect as little as 0.5 mL of air in the cerebral circulation. When air embolism is suspected, a non-contrast CT scan of the affected area (brain, chest, or abdomen) should be performed immediately, as air is rapidly absorbed and may not be visible on delayed imaging 1. Air appears as low-density (dark) areas within blood vessels or cardiac chambers.

Key Considerations

• Chest X-rays can detect large air emboli in the right ventricle or pulmonary arteries but lack sensitivity for smaller emboli.
• Transthoracic or transesophageal echocardiography is valuable for real-time detection of intracardiac air and can help assess hemodynamic consequences.
• MRI is generally not recommended due to longer acquisition times and lower sensitivity for air detection.
• Prompt imaging is crucial as air can be absorbed within 48 hours, potentially leading to false negatives with delayed imaging.
• The diagnosis of air embolism often relies on clinical suspicion in the appropriate context, such as during central line placement, neurosurgical procedures, or barotrauma, even when imaging findings are subtle or absent 1.

Imaging Modalities

• CT pulmonary angiography is the major diagnostic modality currently used for suspected pulmonary embolism 1.
• Ventilation and perfusion scans remain largely accurate and useful in certain settings.
• Lower-extremity ultrasound can substitute by demonstrating deep vein thrombosis; however, if negative, further studies to exclude PE are indicated.

From the Research

Imaging Modalities for Air Embolism

• Transesophageal echocardiography (TEE) is a useful imaging modality for detecting air embolism, as seen in studies 2, 3, 4, 5
• TEE can provide direct visualization of air embolism in the heart chambers and pulmonary artery 2, 4
• Spiral CT (sCT) is also a valuable imaging modality for diagnosing pulmonary embolism, with high sensitivity and specificity 6

Detection of Air Embolism

• TEE can detect air embolism with high sensitivity, especially when used in conjunction with other diagnostic tools such as ETCO2 2
• Automatic detection of venous air embolism using TEE is feasible and may provide significant support to anaesthesiologists in clinical practice 5
• The use of intraoperative TEE to diagnose acute pulmonary embolism via direct visualization is limited, but indirect TEE evidence of pulmonary artery obstruction may be helpful in supporting a diagnosis of pulmonary embolism 3

Clinical Applications

• TEE-guided aspiration of venous air embolism can be an effective treatment for air embolism during surgical procedures 4
• Early recognition of severe air embolism and prompt hyperbaric oxygen therapy are essential to avoid serious complications 2
• Continuous monitoring with TEE is crucial for detecting air embolism, especially during neurological surgery in the semi-sitting position 5