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Barotrauma is the direct result of a pressure difference between the body's air-filled cavities, which are subject to the effects of Boyle's law and the surrounding environment. While scuba diving, barotrauma can occur during ascent or descent, with most symptoms developing during a descent. On descent, a negative pressure develops within enclosed air spaces relative to the ambient surrounding pressure. If air is unable to enter these structures, equalization does not take place, and the air-filled cavities collapse. If the cavity is a rigid structure and unable to collapse, the negative pressure may result in fluid being displaced from the blood vessels of the surrounding mucosa into the intravascular space. The resulting injury pattern can include pain, hemorrhage, edema, vascular engorgement, and tissue damage.
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If air is unable to escape on ascent, an expansion of gas within enclosed air spaces causes a positive pressure to develop. This may result in the rupture of such spaces or the compression of adjacent structures. Many of the symptoms of barotrauma in the human body result in a “squeeze” phenomenon. These trapped gas disorders are differentiated by the gas-filled part of the body that is affected.
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Barometric pressure changes can result in disorders of the external, middle and inner ear. The tympanic membrane (TM) separates the middle ear from the outer ear. The eustachian tube functions as a valve allowing air pressure to equalize between the middle ear and ambient environment.
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Barotitis media is the most common diving-related barotrauma and involves the middle ear. It is commonly referred to as middle ear squeeze or ear block. Equalization via the eustachian tube will occur when there is a pressure differential of approximately 15 to 20 mm Hg. The diver becomes symptomatic if equalization is unsuccessful and the pressure differential reaches or approaches 100 mm Hg.
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Middle ear squeeze commonly develops on descent between 10 and 20 ft below the surface. The symptoms include a fullness in the ears, severe pain, tinnitus, vertigo, nausea, disorientation, and transient, conductive hearing loss. Up to 10% of divers may have no pain during descent but will become symptomatic after the dive. If the diver is unable to equalize the pressure and continues to descend, symptoms may be exacerbated and the TM may rupture and bleed. With perforation, the caloric stimulation of cold water entering the middle ear can cause vertigo, nausea, and disorientation. Physical examination may reveal erythema or retraction of the TM, blood behind the TM, a ruptured TM, or a bloody nasal discharge.
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Treatment for middle ear squeeze should be directed toward its prevention before pain develops. Scuba divers should attempt to clear their ears every 2 to 3 ft during descent. Under normal situations, pressure in the middle ear is equalized without incidence by actively opening the eustachian tube, which opens and exposes the middle ear to ambient pressures. Divers must learn to open the eustachian tube through various maneuvers such as blowing the nose against pinched nostrils or repositioning the jaw (false yawning), while keeping a regulator in their mouth. Another suggested treatment for barotitis is the Frenzel maneuver. This is performed by pinching the nose closed, placing the tongue on the roof of the mouth, then moving the tongue backward and upward as when starting to swallow. This is repeated as many times as necessary until equalization occurs.
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Equalization may be compromised if the eustachian tube is obstructed by swelling of the mucosa, the presence of polyps, previous trauma, allergies, upper respiratory infection, a sinus problem, or smoking. To decrease the incidence of ear discomfort and injury to the TM, a pre-dive treatment of a topical vasoconstrictor nasal spray (oxymetazoline hydrochloride, 0.05%) may be beneficial when used approximately 15 minutes before beginning a dive. The recommended pediatric dosage for ages ≥6 years is two to three sprays in each nostril. Oxymetazoline hydrochloride is not recommended for children younger than 6 years. Pseudoephedrine may also be considered as a pre-dive treatment. For ages 6 to 12, the recommended dose is 30 mg PO. For children older than 12 years, the adult dose of 60 mg PO may be used. If pain persists after the dive, analgesics may be used. If a pre-dive decongestant was not used, it may be considered at this time.
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Any patient with barotitis media is to be instructed to refrain from diving until all signs and symptoms have resolved. Erythema generally resolves within 1 to 3 days, whereas it will take 2 to 4 weeks when there is blood behind the TM. A perforated TM must heal before any further diving is attempted. A 10-day course of oral antibiotics and otic suspension is indicated if there is a perforation of the TM. ENT follow-up is given upon discharge from the emergency department.
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Barotrauma can occur during either descent or ascent. If air is unable to escape the middle ear through the eustachian tube during ascent, a diver may develop symptoms of reverse ear squeeze.
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Alternobaric vertigo may develop during descent, but it is more common during ascent. A sudden change in middle ear pressure or asymmetrical middle ear pressure may result in decreased perfusion, affecting vestibular function. Symptoms include transient vertigo, tinnitus, nausea, vomiting, and fullness in the affected ear. Symptoms may last minutes to several hours after the completion of a dive. Decongestants, antiemetics, and medication for vertigo are recommended.
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Barotitis externa occurs when the external auditory canal, which is normally a patent air-filled cavity that communicates with the surrounding environment, is occluded during descent. At the initiation of descent, the air would normally be replaced by water. If the external canal is obstructed, the enclosed air space will be subject to the increased ambient pressure, resulting in an external ear squeeze or barotitis externa. Obstruction can be caused by cerumen, ear plugs, or other foreign bodies. A diver may experience pain with or without bloody otorrhea.
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Barotitis interna or inner ear squeeze is uncommon but may result in permanent injury to the structures of the inner ear. It often follows a vigorous Valsalva maneuver. In addition to sudden sensorineural hearing loss, symptoms include severe pain or pressure, vertigo, tinnitus, ataxia, nausea, vomiting, diaphoresis, and nystagmus. These patients must be seen emergently. The potential for recovery within a few months is very good in most patients treated conservatively. Others, however, may require surgical intervention.
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Altitude-Related Barotitis
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Barotitis media is the most common barotrauma of air travel. During ascent to altitude, gas will normally escape through the eustachian tube every 500 to 1000 ft to equalize pressures. As altitude decreases, the gas within the middle ear will contract. As with diving, equalization may be accomplished by yawning, swallowing, or performing the Valsalva maneuver. Children who are asleep should be awakened 5 minutes before descent and instructed to swallow more frequently. For infants, a bottle should be given during takeoff and landing. Although this may reduce the likelihood of barotitis media, it may increase the incidence of gastrointestinal distress after takeoff from swallowed air.
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Normally, air can pass in and out of the sinus cavities without difficulty. However, if a person has a cold or sinus infection, air may be trapped and will be subject to the barometric pressure changes. Barosinusitis is the second most common ailment among scuba divers. Failure of the air-filled frontal or maxillary sinuses to equilibrate results in headache, epistaxis and pain or pressure above, behind, or below the eyes, which is commonly referred to as sinus squeeze. Pain may persist for hours and may be accompanied by a bloody nasal discharge. The ethmoid and sphenoid sinuses rarely contribute to this type of barotrauma.
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The treatment for barosinusitis is similar to the treatment of barotitis media. The most effective treatment involves the use of a vasoconstrictor nasal spray before initiating a dive or before starting a descent from altitude in an airplane. Antibiotics should be started and continued for 14 to 21 days.
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Reverse sinus squeeze is felt during a diving ascent when an obstruction of the sinuses results in excessive pressure. A sharp pain will be felt in the affected sinus. Numbness may be felt along the infraorbital nerve if the maxillary sinus is affected. The diver should descend to a greater depth, relieving some of the discomfort, and then ascend at a slower rate.
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Barodentalgia or tooth squeeze results from trapped air and is often associated with recent dental extraction, dental fillings, periodontal infection, periodontal abscess, or tooth decay. Although this is a rare problem, individuals with pre-existing dental or periodontal disease are more susceptible to this barotrauma. Treatment is directed toward preventative dental care and pain control. Following dental procedures, a minimum of 24 hours is advised before initiating a scuba dive.
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During descent, the increased ambient pressure will tend to exert increasing pressure against the air-filled face mask of a scuba diver. The diver may develop facial or eye pain, subconjunctival hemorrhages, subconjunctival edema, epistaxis, and periorbital edema. Face mask squeeze is commonly prevented by using a low-volume face mask that minimizes the amount of air and allows for additional small amounts of air to be blown into the mask from the nose.
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Under normal circumstances, the stomach and intestines contain approximately 1 quart of gas. Ingesting carbonated beverage, chewing gum (and swallowing air), eating large meals, and pre-existing gastrointestinal problems increase the amount of gas in the intestines. Gas expansion will cause discomfort, abdominal pain, belching, flatulence, nausea, vomiting, shortness of breath, or hyperventilation. Although aerogastralgia is rarely a serious problem, significant distention of the abdominal contents may result in venous pooling and syncope. In addition, tachycardia, hypotension, and syncope may result from a vasovagal response to severe pain. Gastric rupture has also been reported.
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Symptoms are prevented or relieved by belching or passing flatus. Wearing clothes that are loose and nonrestrictive is also of benefit.
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The second most common cause of death among scuba divers is pulmonary barotrauma. Air in the lungs can compress during descent. If the lung volume were to decrease below residual volume, hemoptysis, hemorrhage, and pulmonary edema could occur. However, breathing from a compressed air source, this loss of volume will be prevented. Pulmonary overpressurization syndrome (POPS) is an example of the positive-pressure barotrauma that can be seen during ascent. The alveoli become overinflated and can rupture, causing a pneumothorax in an estimated 10% of the pulmonary barotrauma victims. Ruptured pulmonary veins allow air emboli to enter the systemic circulation. These can occur if the scuba diver fails to exhale adequately on ascent or in the presence of predisposing lung disease. To reduce the risk of pulmonary barotrauma, divers are trained to not hold their breath. This is important not only during ascent, but also in the event a diver is not aware of an unintended decrease of depth. This holds true for novice divers who may not yet be skilled at managing depth regulation using a buoyancy device, or for children who may have smaller lungs and body mass making it more difficult to maintain a constant depth. Also at risk for pulmonary barotrauma are divers with obstructive airway diseases, including asthma and chronic obstructive pulmonary disease.
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While it is rare to develop a pneumothorax during a dive, it represents a significant problem when it does. On ascent, air trapped in the pleural space will expand and a simple pneumothorax may progress to a tension pneumothorax, shock, and loss of consciousness. These complications may also occur during air transport in an unpressurized aircraft. At increased risk for a pneumothorax are patients with a past history of spontaneous pneumothorax, pulmonary bullae, or cystic lung disease.
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Treatment of a scuba diving pneumothorax is no different than the treatment of other traumatic or nontraumatic pneumothoraxes. Hyperbaric (recompression) treatment is avoided since it can convert a simple pneumothorax to a tension pneumothorax. If hyperbaric treatment will be necessary, chest tubes must be placed before initiating recompression.
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Pulmonary barotrauma can result in an air embolism, which is the most serious dysbaric injury. Specific signs and symptoms will be determined by the final destination of air emboli. Because of the buoyancy of air and the fact that scuba divers are usually upright during ascent, the brain is most commonly affected. The onset of symptoms can be immediately on ascent, or within 10 to 20 minutes of surfacing. Neurologic symptoms that develop later than this are more likely caused by decompression sickness. A rapid onset and severe symptoms are suggestive of a poorer prognosis with both air embolism and decompression sickness. These patients require aggressive care, which includes 100% oxygen, intravenous fluids, and hyperbaric treatment. They are placed in the Trendelenburg or left lateral decubitus position (Durant's maneuver) to minimize the passage of air emboli to the brain. Air emboli affect the heart if they embolize to the coronary circulation, causing coronary artery occlusion, dysrhythmias, shock, and cardiac arrest. Although these complications are rare compared with other dysbaric injuries, they represent a significant risk to the victim.
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Cerebral arterial gas embolism (CAGE) is air in the arterial system of the brain and is more common than air embolization to the heart or spinal cord. Neurologic symptoms are similar to those of a stroke and include numbness, dizziness, headaches, weakness, visual field deficits, confusion, behavioral changes, amnesia, paralysis, vertigo, blindness, aphasia, deafness, sensory deficit, seizures, focal deficits, and loss of consciousness. It should be noted that CAGE is not restricted to open water scuba diving. There have also been documented pediatric cases of CAGE in swimming pools,4,5 in water as shallow as 2 ft.