Lynch, James H. MD1; Deaton, Travis G. MD2
The human body is exposed constantly to subtle changes in pressure on a regular basis. These changes occur when riding in an elevator, during commercial air travel, or even walking into a climate-controlled building. Aside from occasionally feeling the minor pressure change in our middle ear, the body is well adapted to dealing with these small variations without injury. With recreational activities and sports at extreme altitudes or ocean depths, however, the change in surrounding pressure has the potential to cause significant morbidity. In this article, we will discuss the clinical manifestations and initial treatment of injuries resulting from barotrauma while participating in sports at the extremes of pressure.
Physics of Pressure
The effect of ambient pressure changes on gas-filled structures in the body is governed by a predictable mathematical relationship. Boyle’s law states “at a given temperature, the volume of gas is inversely proportional to the ambient pressure” and is expressed as P1V1 = P2V2 (21). The mean ambient atmospheric pressure at sea level is described as 1 atm of pressure. This same measurement can be expressed equivalently as 14.7 pounds per square inch−2, 29.92 inches of Hg, or 760 mm Hg (all equal 1 atm of pressure). As seen in Figure 1, ambient pressure decreases with a rise in altitude. A hike to Mount Kilimanjaro at an altitude above 19,000 ft will result in half the ambient pressure felt at sea level. Based on Boyle’s law, the decrease in the ambient pressure at altitude results in attempted expansion of a confined volume of gas. Conversely scuba divers who descend underwater to 33 ft will double the ambient pressure compared with sea level. This rapidly increasing ambient pressure during a dive will result in contraction of volume in confined gas spaces.
Injury patterns associated with barotrauma can be classified into two separate groups: those that occur with increasing pressure and those that occur with decreasing pressure. Scuba diving provides a good representation of how these pressure changes affect the human body.
Diving Injuries on Descent
As noted previously, significant changes in ambient pressure occur as a diver leaves the surface and begins a dive. When a diver reaches 33 ft of sea water, the pressure is doubled. For each additional 33 ft of descent, another 1 atm of pressure is added. This rapid change in pressure has effects on gas-filled spaces in and near the body, and a diver must actively respond to avoid injury and the resulting morbidity associated with barotrauma. Common injury patterns during descent are described hereafter.
Middle ear squeeze
The middle ear is a semienclosed structure with the Eustachian tube connecting the middle ear to the oropharynx (Fig. 2). Swallowing, yawning, and Valsalva maneuvers open the Eustachian tube and allow gas to flow into or out of the middle ear, keeping pressure on both sides of the semiflexible tympanic membrane equal. If the Eustachian tube is not patent due to an upper respiratory tract infection, allergies, or abnormal anatomy, for instance, additional gas is not able to enter the middle ear. Middle ear barotrauma (or “squeeze”) occurs when a pressure differential develops between the middle ear and the pressure outside of the tympanic membrane. Early symptoms include dizziness, sensation of fullness in the ear, muffled or decreased hearing, and ear pain. When extreme pressure gradients are not relieved, a middle ear effusion, hemotympanum (Fig. 3), or rupture of the tympanic membrane can occur. Mitigation strategies include proper ear equalization techniques, moderation of descent rate, and avoidance of diving while congested or ill. Divers are taught to stop their descent if they are unable to equalize middle ear pressures, although they may be able to restore Eustachian tube function by rising several feet in the water column and performing a Valsalva maneuver (11). When a middle ear squeeze is present in only one ear, alternobaric vertigo may develop, which is most pronounced in the vertical position and tends to worsen the greater the pressure differential between ears (5,19). Vertigo in the underwater environment can cause loss of situational awareness and buoyancy control, further worsening the diver’s condition.
The controversial use of topical and systemic decongestants has been recommended by some providers to decrease the incidence of middle ear and sinus barotraumas (24). Oral decongestants (pseudoephedrine and phenylephrine) and antihistamines (diphenhydramine, loratadine, and cetirizine) are widely used. Topical spray decongestants (oxymetazoline) and topical steroids (fluticasone) also have been recommended in addition to saline nasal spray. The strongest evidence (at least level 2a) supports the use of decongestants in the prevention of middle ear barotrauma with oral decongestants seeming to be more effective than topical (nasal) (1,3,12). Finally nonsteroidal anti-inflammatory medications as well as acetaminophen have been used to reduce the inflammation and edema of the mucous membranes (17). While medications are often prescribed to divers with congestion, providers must carefully consider potential drug interactions, adverse effect profiles, and therapeutic half-life in relation to planned diving activity.
Sinus cavities in the facial region present another gas-filled space with potential for trapped gases to cause injury if pressure equalization does not occur. Etiology of sinus barotrauma includes sinus or upper respiratory infections, allergies, nasal polyps, and enlarged turbinates. Patients typically describe facial pain, headache, dental pain, and occasional epistaxis. The majority of sinus barotrauma occurs in the frontal sinus, likely due to the long and delicate nasofrontal duct connecting the frontal recess with the frontal sinuses. Involvement of the maxillary, ethmoid, and sphenoid sinuses occurs less frequently and results from blockage of the ostia by inflammation or polyps. Recurrent sinus barotrauma may benefit from functional endoscopic sinus surgery to reestablish drainage and ventilation of the affected sinuses (14).
Although not a true anatomic space, the face mask worn by divers creates a potential closed gas-filled space between the mask and periorbital soft tissues. As a diver descends, the volume of gas inside the mask contracts. The pressure differential can be equalized by blowing small amounts of air from the nose into the mask, but if this does not occur, the low pressure in the mask can result in petechial and subconjunctival hemorrhage. While not life threatening, case reports suggest orbital subperiosteal hematoma can occur with potentially vision-threatening ocular complications. If any concerns exist, emergent referral to an ophthalmologist should be considered (2). Cosmetic results cause significant concern for patients, and they should be educated that petechial and subconjunctival hemorrhage can last several weeks before resolution (Fig. 4).
Diving Injuries on Ascent
When a diver prepares to return to the surface at a conclusion of a dive, the gas-filled spaces in the body have equilibrated to the increased pressure at depth. Upon rising in the water column, the ambient pressure decreases and a new set of potential concerns develop.
If a diver is completing a dive at 99 ft of sea water, the surrounding ambient pressure is 4 atm. During the ascent to the surface at 1 atm of pressure, the volume of any retained gas in the gastrointestinal tract will expand to four times the initial volume. Expanding gas volume can result in significant cramping, pain, distention, and bloating if not appropriately vented. Consideration should be made to carefully choose predive food and beverages for those with known sensitivities.
A reverse squeeze of the middle ear or sinus cavity can occur when a diver ascends and the trapped gases attempt to expand inside a fixed volume. In the case of a middle ear reverse squeeze, increasing pressure and pain are normally due to congestion, but also are attributable to abnormalities adjacent to the Eustachian tube such as polyps, septal deviation, or previous scarring. Often yawning or swallowing will open the Eustachian tube and allow trapped gases to vent. If time and dive profile allows, then a brief descent to assist with venting middle ear gases may be helpful. If this does not occur, the diver must ascend to the surface despite the increasing pain, and tympanic membrane or round window rupture can occur. Symptoms such as hearing loss, tinnitus, vertigo, or nausea and vomiting suggest possible rupture of the round window, and a prompt referral to an otolaryngologist for surgical evaluation is necessary to address potential formation of a perilymphatic fistula.
While pulmonary barotrauma occurs much less frequently than middle ear or sinus symptoms, the resulting injury is considerably more severe and potentially life threatening. The lungs and tracheobronchial tree become a closed space when the breath is held. Using the previous example, a scuba diver ascending in the water column from a depth of 99 ft to the surface will result in gas expansion in the lungs to four times the initial volume. If this ascent is performed with the breath held against a closed glottis, the gas will rupture alveoli in an effort to decrease the pressure gradient between the lungs and the ambient pressure. Thus the axiom taught to all student scuba divers is never hold your breath during a dive.
The group of disorders that make up the pulmonary over inflation syndrome (POIS) include arterial gas embolism, pneumothorax, mediastinal emphysema, and subcutaneous emphysema (20). The clinical manifestations of POIS depend on where the free gas collects following alveolar rupture. An arterial gas embolism occurs when air enters the pulmonary capillary beds, wherein it is transported to the left side of the heart and pumped to the peripheral arteries. If this gas forms a bubble that is too large to pass through distal arteries, the distal tissue is deprived of oxygen with resulting ischemia. When a diver develops loss of consciousness or focal neurologic symptoms consistent with a stroke after returning to the surface, it is assumed an air gas embolism has occurred in the central nervous system vasculature. Case reports involving student divers in a shallow pool suggest death can occur during ascent from depths of only a few feet while holding breath against a closed glottis (23). Unless the victim is recompressed promptly to reduce the bubble size and permit blood to flow again, death or permanent disability may result. Supplemental oxygen and monitoring should be performed as available, and emergent transportation to the nearest recompression facility should be arranged.
Mediastinal and subcutaneous emphysema occur when ruptured alveoli allow gas to dissect through the interstitial space to the mediastinum and ultimately the subcutaneous soft tissues of the neck. Patients may describe burning or pain in the chest, neck pain or swelling, difficulty swallowing, and shortness of breath. Physical examination may reveal voice changes, Hamman’s sign, and a bull neck appearance, and the skin around the neck and upper chest may feel like tissue paper or puffed rice cereal from palpable air pockets. While these findings concern both patient and provider, these are rarely life threatening and should be treated symptomatically. Supplemental oxygen can be provided, and transportation to the nearest treatment facility should be arranged to rule out other more serious complications that can be associated with these findings.
Pneumothorax can occur when ruptured alveoli allow gas to collect in the pleural space with resulting partial or full collapse of the lung. Patients may complain of chest or back pain, shortness of breath, or anxiety. On physical examination, findings may include tachycardia, tachypnea, hypotension, hypoxia, or unilateral decreased breath sounds. If the injury occurs at depth and a diver ascends to the surface, a simple pneumothorax may expand with the decreasing ambient pressure and convert to a tension pneumothorax. Physical signs such as tracheal deviation and elevated jugular venous distension classically taught as demonstrating tension physiology have been shown to be unreliable markers of underlying tension pneumothorax (15). Emergent treatment for tension physiology should instead focus on evidence of respiratory distress, hypoxia, hypotension, and mental status changes. Unlike other diving-related emergencies that require urgent treatment with a recompression chamber, a pneumothorax requires standard medical treatment similar to non-diving-related patients. Supplemental oxygen should be provided for any concerns of hypoxia or low oxygen saturation. For patients with tension physiology, emergent needle or chest tube thoracostomy should be performed. If a simple pneumothorax is suspected without tension physiology, transportation to a treating facility can be arranged with close observation for changes in clinical status. During evacuation, keep in mind that increases in elevation will lower the ambient pressure causing the trapped gas to further expand. This could convert potentially a simple pneumothorax into a tension pneumothorax. All efforts should be made to keep air evacuation below 1,000 ft of altitude when possible.
Hiking, Mountaineering, Alpine Skiing, Heliskiing, and Heliboarding
With regard to traditional alpine sports and hiking at altitude, changes in ambient pressure are typically gradual during ascent and descent. Given the small rate of change, the body tends to equilibrate pressures without difficulties. In the sports of heliskiing and heliboarding, however, there can be significant altitude gains where a helicopter can reach elevations not practical with a ski lift. With each ride to the top of the slopes via helicopter and subsequent ski or snowboard runs, the athlete is exposed to large swings in atmospheric pressure over the course of a day. Despite this, the relative rates of change are not significant enough to make barotrauma a common issue encountered in these sports except for the following, albeit rare, exceptions.
Barodontalgia occurs when increases in pressure cause small pockets of gas in fillings, caps, crowns, root canals, or inflamed pulp to expand (6). Typically experienced with gains in altitude, early symptoms include teeth sensitivity while flying, driving, or hiking at elevation. If pressure changes continue, this may damage the dental work or even rupture the alveolar mucosa. The incidence of dental pain caused by pressure changes to high atmosphere is relatively low. In a German military study, only 30 out of 11,617 trainees (0.26%) participating in simulated high-altitude flights in a hypobaric chamber developed barodontalgia. The underlying cause in most of these cases was chronic pulpitis (13). Severe barodontalgia is rare but debilitating and may become a safety issue for extreme sports that require critical thinking skills or actions. The Federation of International Dentists recommends annual examinations for divers, submariners, pilots, and those who are exposed to regular changes in atmospheric pressure (18). In addition, recommendations are made to avoid changes in altitude for 24 h following dental treatment requiring anesthetic or 7 d following a surgical treatment.
Ski sickness is a poorly understood syndrome related to motion sickness that involves vertigo, headaches, nausea, and vomiting, often resulting from skiing in poor visibility. The initial case series published in the literature included 11 persons experiencing ski sickness, and a multifactorial etiology was proposed including changes in middle ear pressure during lift ascents and skiing descents, vestibular overstimulation, and psychological factors. Dr. Hausler, who initially described this clinical entity, estimates this could affect up to 10% of skiers. He also describes a high degree of success treating symptoms with vestibular suppressants (e.g., meclizine) (9).
Parasports: Parachuting, Skydiving, Hang Gliding, and Wingsuiting
The term “parasports” refers to parachute-based sports including parachuting, skydiving, paragliding, parasailing, hang gliding, and wingsuiting (or wingsuit flying). While there are many variations of parasports that involve athletes falling rapidly to the earth from extreme altitudes with resulting pressure changes, the rate of barotrauma in these sports is significantly less than more serious traumatic injuries, such as fractures (4,25). Static line parachuting, hang gliding, and wingsuiting are typically performed at lower altitudes or off “bases”; therefore the concomitant risk of barotrauma in these sports is considerably less than with the extreme rapid altitude changes that exist in freefall skydiving.
Skydiving is a high-speed aerial sport involving flights in nonpressurized aircraft and rapid changes in altitude while jumping. During freefall, a skydiver can descend 1,000 ft of altitude in approximately 6 seconds and reach speeds greater than 120 miles·h−1. In contrast to mountaineering, in skydiving, the brief exposure to altitude and the rapid changes in gas volume and pressure are real physiologic challenges (10). The United States Parachute Association (USPA) reported 3 injuries per 10,000 skydives in 2012 and found most skydiving accidents result from poor judgment and human error (22). While ascending to altitude before a jump, reverse squeezes can occur in the middle ear and sinus cavities as the ambient pressure decreases and the gas in these potential spaces attempts to expand. The rapid change in altitude during freefall can result in middle ear squeeze and sinus squeeze. Any of these conditions can cause pain, vertigo, headache, and nausea and have the potential to affect the judgment and decision making capabilities of jumpers. Pain and disequilibrium associated with middle ear or sinus barotrauma at altitude can cause significant disorientation and disability in the plane, during freefall, or under canopy. Some athletes may be predisposed to barotrauma injuries. Certainly acute upper respiratory symptoms or rhinosinusitis may predispose a skydiver to middle ear or sinus barotrauma, but also a history of chronic ear, nose, and throat diseases has been reported in the literature to place a jumper at higher risk of ear pain associated with barotrauma (16).
While middle ear and sinus complications are well known among seasoned skydivers, the medical literature has little information regarding the incidence of barotrauma or any potential association with skydiving-related accidents. A small prospective observational cohort of civilian skydivers showed significant middle ear pressure changes during skydives, but no statistical significance in middle ear symptoms (8). Glorioso et al. (7) examined this same issue in a retrospective study of military free fall or high altitude–low opening (HALO) parachutists. In their study, the health care providers’ experiences in the HALO military clinic frequently encountered “ear blocks, tympanic membrane perforations, sinus blocks, and barodontalgia.” In this elite military population, these injuries often go unreported for fear of the HALO parachutists-in-training being medically disqualified from the course. In our personal experience, both authors of this manuscript have treated this same pattern of injuries, as we have each cared for multiple HALO jumpers with histories of sinus and middle ear barotrauma sustained during military freefall operations. We suspect, therefore, that this injury pattern is underreported. Given the lack of current evidence, future evaluation of the USPA skydiving injury and accident database may reveal further association between barotrauma and other injuries while jumping.
With regard to prevention and treatment, if a jumper is experiencing significant ear or sinus pain in the aircraft, the jump should be aborted, and the aircraft should make a slow, controlled descent and landing as soon as possible. Following this, jumpers should not return to altitude until symptoms are improved and they can clear their ears successfully at both ground level and altitude. Prevention and treatment in the case of barotrauma and skydiving is similar to scuba diving as described previously. A trial of decongestants may be warranted for those with a prior history of ear or sinus squeeze with skydiving (17).
As modern athletes pursue extreme sports and recreation at altitude or ocean depths, the changes in pressure they are exposed to may create injury patterns not traditionally seen on other playing fields. Sports with extreme changes in atmospheric pressure such as skydiving and scuba diving commonly place the athlete at risk for barotrauma injuries, especially in the middle ear and sinuses. With the proper training, equipment, and prevention strategies, athletes in these sports can protect themselves from most barotrauma injuries. Yet, when injuries occur and treatment is necessary, the modern sports medicine provider must be adept at recognizing these injury patterns and prescribing appropriate therapies.
We would like to thank Peter Cole, MD, and Guyon Hill, MD, for their critical review of this manuscript.
The views expressed in this manuscript are those of the authors and do not reflect the official policy or position of the Department of the Army, Department of the Navy, Department of Defense, or the U.S. Government.
There are no funding and conflict of interest declared for this study.
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