Barotrauma is physical tissue damage caused by a pressure difference between an unvented space inside the body and surrounding gas or fluid. The damage is due to shear or overstretching of tissues. As a gas-filled space expands or contracts, it can cause damage to the local tissue. Occasionally, tears in tissue can allow gas to enter the body through the initial trauma site. This causes potential blockage of circulation at distant sites or interferes with normal organ function. Barotrauma can cause sinus injury, ear injury, facial injury, tooth injury, gastrointestinal (GI) cramping, pneumothorax, pulmonary hemorrhage, and subcutaneous emphysema. Sometimes pulmonary barotrauma is a precursor to arterial gas embolism. The most commonly affected sites are the middle ear and sinuses.
Barotrauma occurs most commonly while scuba diving, but also may occur during flying, mountain climbing, or skiing. During scuba diving, barotrauma may be caused by ascending or descending too rapidly or by breath holding. The squeezes are caused by the inability to equalize pressure on the descent. Types are mask, sinus, and ear. Mask squeeze can cause skin ecchymosis in the mask pattern, conjunctival hemorrhage, and rarely, orbital hemorrhage. Ear squeeze can occur in the ear canal or middle ear. Risk factors for barotrauma include asthma, chronic obstructive pulmonary disease (COPD), seizures, sinus and ear problems, syncope, panic disorders, vertigo, poor training, inexperience, and Eustachian tube dysfunction.
Any patient receiving mechanical ventilation is at risk for barotrauma, but it is most commonly associated with acute respiratory distress syndrome (ARDS). Historically, this was the most common complication of mechanical ventilation, but modern strategies have mitigated the incidence of ventilator-associated ARDS by limiting tidal volume (6 to 8 mL/kg) and plateau pressure to less than 30 to 50 cm. As an indicator of transalveolar pressure, which predicts alveolar distention, plateau pressure is the best predictor of risk, but there is no accepted safe pressure at which there is no risk. Aspiration of stomach contents and pre-existing diseases such as pneumonia and chronic lung disease also increase risk.
About 500 to 1000 nonfatal dive injuries in the United States and Canada each year. Many of these are related to barotrauma.
Barotraumas of descent are caused by a lack free exchange of gas in a closed space in contact with the diver. The resulting pressure difference between the tissues and the gas space and the unbalanced force due to this pressure difference causes deformation of the tissues resulting in cell rupture.
Barotraumas of ascent are also caused by prevention of the free exchange of volume of the gas in a closed space. In this instance, pressure change causes a difference in tension of the adjacent tissues exceeding their tensile strength. Aside from rupture of tissues, the overpressure may cause gases to enter the tissues further down the circulatory system. This pulmonary barotrauma (PBt) of ascent is also known as a pulmonary over-inflation syndrome (POIS), lung over-pressure injury (LOP), and burst lung. Consequent injuries may include pneumothorax, mediastinal, interstitial, or subcutaneous emphysema, and possibly arterial gas embolism, not usually all at the same time.
Breathing gas at depth during SCUBA causes the in gas in the lungs to be at a higher pressure than the atmospheric pressure. While a free diver can dive to 33 feet or 10 meters and safely go up without exhaling because the gas in the lungs had been inhaled at atmospheric pressure, a diver who inhales compressed gas from scuba at 10 meters and ascends without exhaling will rupture his lungs and have extensive pulmonary barotrauma. The lungs in the second scenario would contain twice the amount of gas at atmospheric pressure and therefore need to expand to twice the normal volume upon surfacing.
Descending diving injuries include the squeezes, specifically, ear or sinus squeeze which can result in middle ear pain, sinus pain, vertigo, and/or tinnitus. With ear squeeze, pressure does not equalize in middle ear through the Eustachian tube. This is common when diving with an upper respiratory tract infection (URI) and may result in severe pain and eardrum rupture. Water can then enter the middle ear causing vertigo/incapacitation. If pressure does not equalize in frontal or maxillary sinus which is common when diving with URI, one may have severe pain.
Breath-holding causes lung trauma-pulmonary overpressure syndrome (POPS) during ascent. Compressed air in lungs expands, and lung tissue ruptures, resulting in pneumothorax, pneumomediastinum, subcutaneous emphysema, or pulmonary arterial gas embolism. This may occur with an ascent from shallow depths. Symptoms are usually present on surfacing or within 10 minutes.
Signs and symptoms include shortness of breath, crackles, crepitance, tachypnea, respiratory distress, substernal chest pain, and in the case of pneumothorax, diminished breath sounds.
Breath-holding can cause an arterial gas embolism during ascent leading to lung tissue tears, air entering pulmonary circulation, air entering the left heart, pumped to systemic circulation, and clogging of the cerebral circulation.
When taking the history of a diver, it is important to note the events preceding the dive, temperature, sea conditions, dive conditions, depth of dive, the onset of symptoms concerning the dive profile (on the descent, at the bottom, on ascent or after surfacing). Ask about chest pain, shortness of breath, hemoptysis, epistaxis, vertigo, nausea, vomiting or loss of consciousness. On physical exam check sinuses for anatomic obstructions or hemorrhage. Check tympanic membranes for fluid, hemorrhage or rupture.
A complete neurologic exam is indicated for anyone with pulmonary barotrauma to screen for signs of arterial gas embolism (AGE) which could include numbness, weakness, paralysis, visual deficits, ataxia, aphasia, sensory loss, nystagmus, and confusion.
History and physical is the most important key to making this diagnosis. Laboratory studies are not very useful. Arterial blood gas may be of value to look for a-a gradient in those suspected of having an air embolism. Rising creatine phosphokinase (CPK) levels may signal worsening tissue damage due to microemboli.
Perform radiographic studies as needed according to symptoms: chest x-ray, CT head. An echocardiogram may show gas bubbles in the heart in patients with AGE.
Treat supportively for mild injuries such as sinus squeeze, middle ear squeeze. Use NSAIDs, decongestants, or analgesics as needed. For tympanic membrane (TM) rupture, prescribe oral amoxicillin/clavulanate and fluoroquinolone ear drops. Otolaryngology referral is also warranted for TM ruptures.
Most pulmonary barotrauma can be treated conservatively with rest and oxygen as needed. The exception is pneumothorax with often requires decompression (needle, pigtail, or chest tube).
Differential diagnoses include acute coronary syndrome (ACS), substance abuse/intoxication, asthma exacerbation, myocardial infarction, stroke pulmonary embolism, head injury, hypothermia, shock, otitis media/externa, bacterial sinusitis, pneumothorax, pneumonia, dental caries, dental infection, arterial gas embolism, and decompression sickness (DCS).
The prognosis for barotrauma is good, most of these conditions are self-limiting.