This results in an injury referred to as a Pulmonary Barotrauma . The injury can range from mild, to a complete collapse of the lung. For this reason, it is very important to never hold one's breath on ascent. The air that escapes can move into a few different areas and cause different problems depending on the site. Sometimes the air can escape into the pulmonary venous system where it will move through the heart and into the arteries.
Arteries are the vessels that carry blood away from the heart to the different tissues of the body.
When this occurs, bubbles form in the blood, causing Arterial Gas Embolism . These bubbles continue to expand with decreasing pressure upon ascent which can cause problems if they reach a vessel that is too small for them to move through. When this occurs, the bubbles become stuck and blood is unable to move through the vessel. If this occurs in areas that supply major organs such as the heart or brain, serious damage can occur. Unfortunately, there is no way to predict where the bubbles will end up.