An air pocket is a pocket of air or gas somewhere in the body where it does not belong. There are some areas in which such pockets may be normal; the stomach, for example, often has some air in it, which people bring up when they belch, and gas and air can also be present in the intestines, in which case they are expressed from the body by other means. Some of this is the result of swallowed air, and some of it is created by microorganisms in the gut that generate gases as they digest food. When air is somewhere where it shouldn't be, however, it can become a problem.
There are a number of ways in which an air pocket can form. Trauma is a common cause, with a membrane being breached and allowing air into a location which it does not normally appear. Pockets and bubbles can also be caused by air in a needle or intravenous tube, by air in a feeding tube, and so forth.
One type can form between the layers of the pleura that surround the lungs, causing a condition called pneumothorax or collapsed lung. The air creates pressure, which forces a lung to collapse, causing difficulty breathing. This commonly occurs as a result of trauma, although spontaneous pneumothorax can occur in some patients.
Air pockets can also form on the brain. This is usually caused by trauma, which breaches the layers of bone and tissue which protect the brain, and it can force out the cerebrospinal fluid that protects the brain, endangering the patient. Air can also be present in the fluid that surrounds the spine.
In the blood, air pockets can cause a condition called pulmonary embolism, in which the air blocks a blood vessel. This condition can be fatal if it happens in the wrong place, and it can certainly impair circulation and put someone at risk of tissue death. Pulmonary embolisms can happen as a result of medical mistakes, and as a result of moving from an area of low pressure to an area of high pressure quickly, so that dissolved gases in the blood form bubbles before they can be expressed.
Air pockets can be diagnosed with medical imaging studies, in which the air will show up in the area being studied. Ultrasounds, MRIs, and a variety of other techniques can be used to find them. These deposits of air generally need to be addressed quickly to prevent complications.
