- Air Emboli are a subtype of emboli composed of gaseous bubbles which deposit in vasculature and disrupt proper circulation.
- Most cases of air embolism are traumatic or iatrogenic and occur following surgical procedures, placement of intravenous catheters, or as a result of positive pressure mechanical ventilation. A very special etiology is "Decompression Sickness" which occurs in deep-sea divers who ascend to sea level too rapidly. At high pressures found in the deep sea, large amounts of gas, especially nitrogen, become dissolved within the blood; however, as the diver ascends these dissolved gases begin to re-form outright gas bubbles which deposit throughout the body, especially in skeletal muscle.
- When air emboli occur due to traumatic or iatrogenic injury, air is introduced into the low-pressure venous circulation and rarely into the high-pressure systemic circulation. Unless massive, most venously introduced air bubbles pass through the right heart and enter the fine pulmonary circulation where they deposit. Consequently, in most cases the primary manifestations of traumatic and iatrogenic air emboli are respiratory in nature. In the special case of Decompression Sickness, re-gassified bubbles develop throughout the pulmonary and systemic circulation, thus causing a broader set of clinical consequences.
- Traumatic or Iatrogenic Air Emboli
- In addition to simply occluding pulmonary vessels, air bubbles can denature plasma proteins at their surface which is thought to lead to inflammation within the lung. Together these processes result in ARDS.
- Decompression Sickness
- The Bends: Deposition of bubbles in skeletal muscles and joints causes arthralgia and myalgia
- The Chokes: Massive expansion of gas within the lung as well as deposition of bubbles within the pulmonary circulation can lead to emphysema, focal atelectasis, and ultimately lead to ARDS