Barotrauma is tissue injury caused by a change in pressure, which compresses or expands gas contained in various body structures.
Increased pressure outside the body is transmitted equally throughout the blood and body tissues, which do not compress because they are composed mainly of liquid. Thus, the leg, for example, does not feel squeezed as water pressure increases. However, gases (such as the air inside the lungs, sinuses, or middle ear or inside a face mask or goggles) compress or expand as outside pressure increases or decreases. This compression and expansion can cause pain and damage to tissue. Barotrauma most often affects the ears. However, barotrauma affecting the lungs (pulmonary barotrauma) is the most serious.
Pulmonary (Lung) Barotrauma:
Because air under high pressure is compressed, each breath taken at depth contains many more molecules than a breath taken at the surface. At 33 feet (2 atmospheres absolute), for example, each breath contains twice as many molecules as a breath taken at the surface (and therefore depletes an air tank twice as rapidly). As pressure decreases, air expands—its volume increases. So, when divers fill their lungs with compressed air at 33 feet and ascend without freely exhaling, the volume of air doubles, causing the lungs to overinflate. Overinflation of the lungs can rupture small air sacs, allowing air to leak out. Air that leaks out of the lungs can be trapped in the space between the lungs and the chest wall and expand, causing the lungs to collapse (pneumothorax—see Pleural and Mediastinal Disorders: Pneumothorax). Alternatively, air may be forced out of the lungs into the tissues surrounding the heart (pneumomediastinum), under the skin of the neck and upper chest (subcutaneous emphysema), or into the blood vessels. Air in the blood vessels typically travels to other parts of the body (air embolism—see Diving and Compressed Air Injuries: Air Embolism), where it may block blood flow.
The most common cause of pulmonary barotrauma is breath-holding during an ascent from a scuba dive, typically resulting from running out of air at depth. In panic, divers may forget to exhale freely as air in the lungs expands during the ascent. Air embolism can occur in as little as 4 feet (about 1 meter) of water when people breathing pressurized air hold their breath while ascending rapidly. Pulmonary barotrauma can even happen in a pool when air is breathed in at the bottom of the pool (such as from an inverted bucket) and not exhaled during ascent.
Symptoms of barotrauma usually begin before or within minutes after divers reach the surface. Symptoms depend on which organ is affected. Divers often use the term “squeeze” for injuries other than those to the lungs caused by differences in pressure.
Pneumothorax and pneumomediastinum cause chest pain and shortness of breath. Some people cough up blood or develop bloody froth at the mouth when lung tissue is injured. Air in the tissues of the neck can impair the vocal cords, causing the voice to sound different or hoarse. Subcutaneous emphysema causes crackling when the affected area of skin is touched.
Mask Barotrauma (Mask Squeeze):
When divers do not properly equalize pressure in the face mask with the water pressure, the relatively lower pressure inside the mask causes it to act like a suction cup applied to the eyes and face. The difference in pressure inside and outside the mask causes blood vessels near the surface of the eyes (or on the face) to dilate, leak fluid, and finally burst and bleed. Although the eyes appear red and bloodshot, vision is not affected. Rarely, bleeding behind the eyes can occur, causing loss of vision. Bleeding of blood vessels in the face causes usually a bruised appearance.
Ear Barotrauma (Ear Squeeze):
If pressure in the middle ear becomes lower than the water pressure, the resulting stress causes a painful inward bulge of the eardrum (see Middle Ear Disorders: The Eustachian Tube: Keeping Air Pressure Equal). When the pressure difference becomes high enough, the eardrum ruptures, resulting in a rush of cold water into the middle ear, causing vertigo (severe dizziness with a spinning sensation), disorientation, nausea, and sometimes vomiting. These symptoms may place divers at risk of drowning. The vertigo diminishes as the water in the ear reaches body temperature. A ruptured eardrum impairs hearing and may lead to a middle ear infection hours or days later, causing pain and producing discharge from the ear. The inner ear can be injured as well, causing a sudden loss of hearing, buzzing in the ear (tinnitus), and vertigo.
Sinus Barotrauma (Sinus Squeeze):
Pressure differences have effects on the sinuses (air-filled pockets in the bones around the nose) that are similar to the effects of ear barotrauma. They cause facial pain, headaches, a feeling of congestion in the face or nose, or a bloody nose.
Dental Barotrauma (Tooth Squeeze):
Pressure in the air spaces at the roots of teeth or next to fillings can cause toothache or damage teeth.
Eye Barotrauma (Eye Squeeze):
Small air bubbles can form and become trapped behind hard contact lenses. The bubbles can damage the eyes and cause soreness, loss of vision, and the appearance of halos around lights.
Gastrointestinal Tract Barotrauma (Gut Squeeze):
Breathing improperly from a regulator or using ear and sinus pressure-equalization techniques may cause divers to swallow small amounts of air during a dive. This air expands during ascent, causing abdominal fullness, cramps, pain, belching, and flatulence. These symptoms usually resolve on their own. Rarely, the stomach or intestine bursts, causing severe abdominal pain and severe illness.
Doctors recognize barotrauma mainly by the nature of the symptoms and their onset in relation to diving. Depending on the symptoms, imaging tests may be done. For example, people with pulmonary barotrauma usually require chest x-rays.
Pressure in the lungs and airways is automatically equalized with outside pressure when a supply of pressurized air is available at depth, as from a diving helmet or air tank. This pressurized air also equalizes pressure in the sinuses, as long as the openings to the sinuses are not narrowed, for example, by inflammation due to allergies or an upper respiratory tract infection.
Pressure in a face mask is equalized by blowing out air from the nose into the mask. Divers equalize pressure differences in the middle ear by yawning or swallowing with the nostrils pinched, which opens the tube connecting the middle ear and the back of the throat (eustachian tube).
Wearing earplugs or a tight-fitting wet suit hood creates a closed space between the earplug and the eardrum in which pressure cannot be equalized. The pressure inside goggles cannot be equalized either. Therefore, neither earplugs nor goggles should be worn during diving. Tight-fitting wet suit hoods should be properly vented so that they do not block the external ear.
A decongestant (such as pseudoephedrine taken by mouth) is taken before diving by people with nasal congestion that could block nasal passages. Relief of congestion can facilitate equalization of pressures between the ears and sinuses, helping prevent sinus and ear barotrauma.
To prevent pulmonary barotrauma, people must freely exhale any air inhaled at depth—even the depth of a swimming pool—during ascent.
Some people with pneumothorax require treatments such as inserting a plastic tube into the chest cavity to allow air to drain and the lung to re-expand. Treatment of pneumomediastinum and subcutaneous emphysema usually is bed rest and supplemental oxygen.
Ear and sinus barotrauma are treated with nasal decongestants (such as oxymetazoline nasal spray) or oral decongestants. Occasionally, when recovery is slow, corticosteroids may be given as a nasal spray or pills. A ruptured eardrum usually heals by itself, although a middle ear infection requires antibiotics given by mouth or as eardrops. A rupture between the middle and inner ear may require prompt surgical repair to prevent permanent damage. A rupture of the stomach or intestines requires surgical repair.
Last full review/revision February 2009 by Alfred A. Bove, MD, PhD