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Pulmonary Barotrauma
What you need to know!

William and Diane Mulhall

In order to treat and ultimately help divers with pulmonary barotrauma, we must first understand what barotrauma is, and the mechanisms and factors that create the ideal situations that bring on these injuries.

Barotrauma refers to the physical damage (trauma) to any part of the body as a result of unequal air pressure (baro), either from the compression or expansion of the involved body part or organ. Based on this interpretation, pulmonary barotrauma relates to physical damage to the lungs or pulmonary system as a direct result of unequal air pressures. The injuries that we will focus upon include pneumothorax, tension pneumothorax, and pneumomediastinum.

What is the mechanism that causes pulmonary barotrauma? These injury patterns are caused by an increase in pressure within the lungs, and an overexpansion (stretching) of the lung tissue. Most commonly, these injuries can be attributed to breath-hold ascents, by which a diver inadvertently holds his or her breath during a controlled or uncontrolled ascent to the surface or in the water column. By doing so, the volume of air held within the lungs expands as the ambient air pressure around the diver decreases. This expansion causes a dramatic increase in pressure within the lungs along with overexpansion of the lung tissue. In turn, the alveoli (air sacs) tear or rupture, allowing air to leak out into the spaces around and between the lungs, and potentially into the pulmonary circulation. Although breath-hold ascents are the most common cause of pulmonary barotrauma, abnormally weak air pockets within the lungs, known as blebs or bullae, can also be linked to these injuries even in the absence of breath holding.

When discussing lung overexpansion injuries, it is important to understand that the greatest percentage of gas expansion takes place between 2 atmospheres absolute (ATA), or 33 feet of seawater, and 1 ATA, or 0 feet. This is illustrated in the Boyle’s Law chart. With a full lung breath-hold, overexpansion injuries can occur with rises of only 3 to 4 feet within the water column.

Boyle’s Law

0 ft

33 ft

66 ft

99 ft
wpe3.jpg (2824 bytes)

14.6 psi

29.4 psi

44.1 psi

58.8 psi

5 L gas
in 1V

5 L gas
in 1/2V

5 L gas
in 1/3V

5 L gas
in 1/4V
wpe5.jpg (6124 bytes)

5 L gas
in 1V

10 L gas
in 1V

15 L gas
in 1V

20 L gas
in 1V
wpeF.jpg (5703 bytes) wpeE.jpg (7236 bytes)




P = pressure V = volume L = litre
ATA = atmosphere absolute (Bar) psi = pounds per square inch D = density

When injury to the alveoli occurs, the escaping air can travel and become trapped in certain areas within the body. This air trapping is what then creates the injury called pneumothorax.


Pneumo (air) and thorax (thoracic or chest cavity) together refer to the abnormal collection of air within the pleural space. This space is in fact a potential space between the inner lining of the thoracic cavity (parietal pleura) and the outer lining of the lung (visceral pleura). As you now know, increases in lung pressure coupled with lung tissue overexpansion cause alveoli to tear or rupture allowing air to escape from the lungs, and into this potential space between these two layers. The expansion of this space then leads to a reduction in effective lung expansion, therefore compromising respiration. The progression of this injury is directly proportionate to the size or extent of the injury site. The larger the tear or rupture, the faster the progression.

Once on the surface, many pulmonary barotrauma injuries become obvious almost immediately. Yet in certain circumstances, the subtlety of signs and symptoms can be easily overlooked or ignored. It is important to keep in mind that divers with barotrauma injury are also highly suspect for Arterial Gas Embolism and Decompression Sickness.

The diver with a simple pneumothorax may present with any of the following signs and symptoms:

Treatment for this injury pattern includes:

If this condition is not recognized, or is left untreated for any period of time, it can progress into a life-threatening condition called Tension Pneumothorax. This condition presents itself when the air becoming trapped within the pleural space begins to build pressure, and pushes the damaged lung to the opposite or uninjured side. A tension pneumothorax requires immediate treatment due to the infringement upon the circulatory system and the uninjured lung. This severely hampers the patient’s ability to breathe and decreases the return of blood to the heart. In turn, it limits the heart’s ability to fill, causing hypotension, shock and sometimes death. It is important to remember that, based on the mechanisms described above, a pneumothorax that occurs at depth has great potential to develop into a tension pneumothorax due to the expansion of the trapped air within the pleural space.

The diver with a tension pneumothorax may present with any and all of the symptoms of a pneumothorax and additionally may show:

Treatment for the diver with a tension pneumothorax includes all of the steps listed above and the following:

"The need for recognition and treatment in the presence of a tension pneumothorax is immediate!

Mediastinal Emphysema

Media- (middle) -stinal (sternum) emphysema (trapped air) is an injury caused by pulmonary overexpansion. Air escapes from the alveoli through a rupture or a tear and travels through the interstitial tissue into the area known as the mediastinum. This area is directly around the heart and major airways. Once in the mediastinal region, this air can either collect or continue to travel to other areas including the neck, chest, and abdomen.

The signs and symptoms associated with mediastinal emphysema include the following:

Although mediastinal emphysema does not normally present with the same urgency as tension pneumothorax, these patients need field neurological evaluation to monitor for signs of AGE.

Additional treatment includes:

Subcutaneous Emphysema

Sub- (under/beneath) -cutaneous (pertaining to the skin) emphysema (trapped air) is a clinical presentation associated with a number of conditions. In the context that we are dealing with, it is an associated sign of all of the injury patterns that we have discussed.

In and of itself, no treatment is required for subcutaneous emphysema. It is extremely important that this is recognized as a presentation for more clinically significant injuries. Any diver presenting with subcutaneous emphysema must be evaluated at a medical facility immediately. Activation of emergency medical services with supportive treatment initiated until definitive treatment can be obtained.

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