Injections and Surgical Procedures:
A syringe or IV can accidentally inject air into your system. In fact, air embolism is pretty common during brain surgery and almost 80% of such surgery have air embolism. However, doctors are trained to detect them in advance and take preventive and curative measures for the same.
Any injury to the lungs can cause air bubbles to enter your bloodstream. This can also happen when a person is on the ventilator and has damaged arteries or veins.