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 Boyles Law chart. With a full lung breath-hold, overexpansion injuries can occur with rises of only 3 to 4 feet within the water column.
Boyles Law DEPTH PRESSURE SKIN DIVER SCUBA DIVER BREATH HOLD ASCENT DENSITY
5 L gas
5 L gas
5 L gas
5 L gas
5 L gas
10 L gas
15 L gas
20 L gas
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:
- Shortness of breath, accessory muscle use during inspiration
- Chest pain that increases with inspiration
- Shallow or guarded breathing
- Irregular pulse rate
- Bulging neck veins (JVD)
- Bluish tinge to skin caused by poor oxygenation, called Cyanosis
- Unequal chest rise (paradoxical breathing)
- Diminished lung sound to auscultation (utilizing a stethoscope)
Treatment for this injury pattern includes:
- Activation of the local 911 service ASAP (paramedic capability if available)
- Limit patient activity and exertion.
- Allow patient to maintain position of comfort to facilitate ease in breathing.
- Administer supplemental oxygen if trained and unit is available (15 litres per minute (lpm) via non-rebreather mask).
- Monitor patients respiratory and heart rates.
- If shock is present, keep patient warm and lay flat if possible.
- Perform a Field Neurological Evaluation to determine the potential for arterial gas embolism (AGE) or decompression sickness.
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 patients ability to breathe and decreases the return of blood to the heart. In turn, it limits the hearts 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:
- Extreme shortness of breath
- Absent breath sounds on the injured side
- Subcutaneous emphysema
- Tracheal deviation (this is a late sign and its absence should not guide treatment)
- Cardiac or respiratory arrest
Treatment for the diver with a tension pneumothorax includes all of the steps listed above and the following:
- Ensure that an advanced life support (ALS) paramedic ambulance is en route as soon as possible.
- Ensure the patient has a patent airway with adequate breathing.
- Administer supplemental oxygen if trained and unit is available.
- If the patient is not breathing, begin rescue breathing with supplemental oxygen via pocket mask or BVM (if trained, and equipment is available).
- Ensure adequate circulation; initiate CPR if indicated by absence of pulse.
- Paramedics in certain areas can alleviate this condition with the introduction of a needle into the space thereby releasing the pressure. This procedure is called needle chest decompression.
"The need for recognition and treatment in the presence of a tension pneumothorax is immediate!
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:
- Shortness of breath
- Chest pain or discomfort
- Rapid heart rate, called tachycardia
- Low blood pressure, called hypotension
- Swelling around neck
- Faint or muffled heart sounds on auscultation
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:
- Immediate activation of the 911 system, ALS ambulance response
- High-flow oxygen administration, 15 lpm via non-rebreather mask, if trained and unit is available
- BLS measures
- Treat for shock
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.Table of Contents
|For information on how you can help, or how RIPTIDE can help you, please contact us at:|
P.O. Box 593
Hurley, NY 12443
tel/fax: (845) 331-3383
|Created by Dolphin Diving - copyright 990901|