The two major causes of air embolism are iatrogenic and environmental. Iatrogenic complications are those that occur as a result of a diagnostic or therapeutic procedure. Situations in which iatrogenic injury is a possibility include insertion, maintenance, or removal of the central line. The risk is highest during catheter insertion because the large-bore needle, which is in the vein, is at the hub while the catheter is threaded into the vein. Air can be pulled into the circulation whenever the catheter is disconnected for a tubing change or the catheter-tubing system is accidentally disconnected or broken. When the catheter is removed, air can also enter the fibrin tract that was caused by the catheter during the brief period between removal and sealing of the tract. Other procedures that can lead to air embolism are cardiac catheterization, coronary arteriography, transcutaneous angioplasty, embolectomy, and hemodialysis. Some surgical procedures also place the patient at particular risk, including orthopedic, urologic, gynecologic, open heart, and brain surgery, particularly when the procedure is performed with the patient in an upright position. Conditions such as multiple trauma, placenta previa, and pneumoperitoneum have also been associated with air embolism.

Environmental causes occur when a person is exposed to atmospheric pressures that are markedly different from atmospheric pressure at sea level. Two such examples are deep-sea diving (scuba diving) and high-altitude flying. Excessive pressures force nitrogen, which is not absorbable, into body tissues and the circulation. Nitrogen accumulates in the extracellular spaces, forms bubbles, and enters into the bloodstream as emboli.

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