Chapter 57. Diving Medicine

Constantly increasing in number, the recreational and commercial diving community frequently presents with problems poorly understood by the average physician and otolaryngologist unless they have had some training in diving medicine. The consequences of breathing compressed gas mixtures under increasing barometric pressure and subsequent decreasing barometric pressure are confusing unless one understands the physics and physiology of the pressure environment. A well-trained otolaryngologist can be better prepared to treat the conditions that divers encounter by understanding the cause of these conditions.

Living at the sea level, our bodies are surrounded by one atmosphere of pressure (eg, 14.7 psi, 760 mm Hg, and 1 bar). The entire earth's atmosphere exerts this pressure, and it is exerted uniformly against our bodies. Pascal's principle states that any change in pressure in an enclosed fluid is transmitted equally throughout that fluid. The human body, being to a large extent fluid, pushes out against the ambient pressure with the same force as the surrounding media. For this reason, divers can descend in the water to extreme depths with ease. It is only the air-filled spaces in our bodies that are affected by the changes in pressure. For each 33 ft of seawater (ie, 34 ft of fresh water, or 10 m) through which we descend, we add an additional atmosphere of pressure. The pressure is doubled going from sea level to 33 ft of seawater, but is not doubled again until 99 ft of seawater is reached (Figure 57–1).

Conversely, as one ascends from depth, the pressure is decreased at the same rate. Boyle's law states that if the absolute temperature remains constant, the volume of a gas varies inversely as the absolute pressure. Because water temperature remains within a small absolute range, as a diver descends in the water, the air-filled spaces decrease in volume proportionately. As the diver ascends, the air-filled spaces increase in volume proportionately. Since we double the pressure from the surface to 33 ft of seawater and not again until 99 ft of seawater, the greatest pressure and volume changes occur closest to the surface. With the exception of decompression sickness, most divers' problems occur in the shallow depths, even as shallow as 4 ft of seawater.

Dalton's law of partial pressure states that in a mixture of gases (eg, air), the total pressure exerted by that mixture is equal to the sum of the partial pressures of each gas in the mixture. Both nitrogen and oxygen, composing most of the air we breathe, increase in partial pressure as the ambient pressure increases. Henry's law of solubility of gases states that as the partial pressure of a gas increases, more of that gas is dissolved in the surrounding liquid until saturation occurs. Since oxygen is utilized in metabolism, nitrogen, which is metabolically inert, is driven into solution in the circulating fluids of the body (eg, blood and lymph) in increasing amounts with increasing ambient pressure. Conversely, as ambient pressure is decreased, the dissolved gas becomes supersaturated and is released as gas bubbles. The latter two laws account for the indirect effects of pressure and are responsible for decompression sickness, or the bends, to be discussed later.

Because divers spend much of their time in the water, they are subject to the same cutaneous problems of the external ear as are swimmers.

External Otitis

External otitis is very common and needs to be treated in the same fashion as external otitis that does not result as a complication of diving. In mild cases of pruritus, which are indicative of atopic external otitis, treatment can be limited to steroid drops both prophylactically and therapeutically. This is more of a chronic problem and treatment can be administered as needed. The more severe forms may require steroid–antibiotic drops with a wick being placed if the ear canal is completely closed. For severe infections, broad-spectrum antibiotics may be added. The prognosis is excellent and prophylaxis may prevent further infections. The use of acid–alcohol drops before diving and after leaving the water may prevent infection. One should wait until all the symptoms have resolved, the ear canal has returned to normal diameter, and hearing is restored. Prophylactic antibiotic drops may be needed for several weeks after the infection has cleared.

Foreign Bodies

Foreign bodies in the external ear canal, including cerumen, can be driven into the ear canal by the increasing water pressure and can either be lodged at the narrow portion of the canal or driven against the tympanic membrane. If they are lodged at the narrow portion of the ear canal and there is an air-filled space between the foreign body and the tympanic membrane, this air space is subject to Boyle's law, as stated above. The volume of the air space decreases with increasing ambient pressure, producing pain, and hearing loss. There may be hemorrhage in the canal and on the outer surface of the tympanic membrane, and blebs, and edema may be found after the foreign body is removed. Earplugs should never be used while diving unless they have a small vent hole. Treatment is removal of the foreign body and topical antibiotic eardrops.

Although exostoses can occur in divers who are also surfers; those who dive in cold water usually wear a thermal protective hood, which can prevent the formation of exostoses. If they are obstructive, they can be removed surgically.

Etiology

As the diver descends in the water column, the air-filled space of the middle ear is subject to the effects of Boyle's law. With increasing pressure, the volume of the gas in the middle ear reduces proportionately and must be equalized by some technique (see equalizing techniques later in the chapter). Frequent equalization is required near the surface as one descends and less so as the diver achieves greater depth. If equalization is not performed, the volume of the middle ear gas is reduced to the point that the tympanic membrane is retracted severely and fluid or blood (or both) is secreted into the middle ear, reducing the volume and equalizing the pressure. Alternately, the tympanic membrane may rupture.

Because of the unique etiology of diving disorders, the treating physician will see the entire spectrum of middle ear disease from eustachian tube obstruction, occurring rapidly, rather than over an extended period. Because this spectrum is caused by pressure changes, and usually on descent, it is referred to as barotrauma.

Occasionally, middle ear barotrauma can occur with ascent. In this case, the middle ear is equalized at depth, or partially so, and the diver ascends with an obstructed eustachian tube due to rebound rhinitis. The air in the middle ear space increases in volume with a decrease in ambient pressure, and if the middle ear is not vented via the eustachian tube, there will be pain and possible rupture of the tympanic membrane into the external ear canal. Descending to a deeper depth can relieve these symptoms; however, the diver is usually ascending because his/her breathing gas supply is low. Swallowing continually and ascending very slowly may partially relieve the symptoms, but if the gas supply is low, returning to the surface is mandatory. The symptoms, findings, and treatment are the same as for barotrauma of descent.

Prevention

Middle ear barotrauma can be prevented by not diving when there is any condition that might lead to eustachian tube obstruction (including upper respiratory infection or allergy). The diver should be able to easily equalize the middle ear. Prophylactic oral decongestants, short courses of nasal decongestants (no longer than 3 days because of possible rebound rhinitis), and steroid nasal sprays can assist in preventing obstruction.

Clinical Findings

Symptoms of middle ear barotrauma range from a dull feeling in the ear to pain and hearing loss. If a perforation of the tympanic membrane occurs, there will be vertigo with nausea and vomiting caused by the passage of water that is colder than body temperature into the middle ear; this water stimulates the lateral semicircular canal (a caloric stimulation).

Physical findings can be as simple as retraction, erythema and injection, or hemorrhage in the tympanic membrane. More severe findings include serous otitis, hemotympanum, and perforation of the tympanic membrane. Tuning fork tests and audiograms reveal a conductive hearing loss.

Treatment

Treatment of middle ear barotraumas consists of oral decongestants, short-term decongestant nasal sprays, and appropriate antibiotics if secondary infection is present. The diver should stay out of the water until the middle ear is healed and the diver can easily equalize the middle ear. If a perforation occurs, one must wait until the perforation heals and the tympanic membrane is intact again. If surgery is required for a nonhealing perforation, the above requirements must be met, usually requiring 3–4 months after surgery.

Divers should not return to diving until all the symptoms and findings have cleared. There should be ease of equalization of both middle ears confirmed by physical examination, tympanometry with a Valsalva maneuver, or both.

There remains controversy among otologists as to if or when divers who have had middle ear surgery can return to diving. The conditions that usually require myringoplasty or tympanoplasty are caused by eustachian tube obstruction. The surgical site and procedure should be completely healed with no evidence of difficulty in equalizing the middle ear. If ancillary conditions (eg, allergy or sinus disease) contributed to the need for middle ear surgery, they should be completely cleared, and if they recur, diving should be avoided.

Inner Ear Barotrauma

Etiology

Two mechanisms have been postulated as causing inner ear barotrauma. As the diver descends with difficulty in equalizing the middle ear space and continues to descend, attempting to forcefully equalize the middle ear, there can be a sudden opening of an obstructed eustachian tube with a rush of air into the middle ear space. This can rupture one of the windows between the middle ear and the inner ear–either the fenestra rotundum (ie, round window) or the fenestra ovalis (ie, oval window)–into the inner ear.

Conversely, if the diver descends with difficulty in equalizing the middle ear space and continues to descend, attempting to forcefully equalize the middle ear, and the eustachian tube does not open, the force is transmitted (as in a Valsalva maneuver) via the spinal fluid, through the cochlear aqueduct to the perilymphatic space of the inner ear. The round or oval windows can rupture into the middle ear.

Prevention

Prevention consists of avoiding situations that require forceful autoinflation of the middle ear, straining, or both.

Clinical Findings

Both mechanisms that cause inner ear barotrauma produce a perilymphatic fistula. The round window is more commonly affected than the oval window, but occasionally both windows rupture.

Symptoms include tinnitus, vertigo with nausea and vomiting, and hearing loss, which occur usually while descending. There may be pain due to a concomitant middle ear barotrauma. There is usually evidence of middle ear barotrauma, but the tympanic membrane may look perfectly normal. The hearing loss is sensorineural, accompanied by nystagmus and a positive fistula test.

Treatment

Treatment includes bed rest with the head of the bed elevated, antivertiginous medication, steroids (60–80 mg of prednisone or similar drugs initially, reducing the dosage over several days), and avoiding coughing, sneezing, and straining. Audiograms should be performed daily, and if there is improvement, continuation of nonsurgical treatment. Most patients recover spontaneously, but if the hearing loss and vertigo persist or worsen after 4–5 days, surgical exploration with repair of the fistula is recommended.

Many otologists trained in diving medicine recommend that the patient does not return to diving, and many divers do return to diving in spite of the physician's recommendation. In addition, there have been no, or limited, recurrences. The diver should have no significant residual hearing loss (especially in speech frequencies), no significant defects in vestibular function, and no abnormalities of the eustachian tube function with ease of equalization; however, he or she should not dive for at least 2 months after complete recovery. Divers should abort any dive in which there is difficulty in equalizing the middle ear. They should be advised that they might be at risk for further damage to the ear if they continue to dive.

Inner Ear Decompression Sickness

Etiology

Decompression sickness follows Dalton's and Henry's laws. As one descends beneath the surface, the metabolically inert gas in the breathing mixture is dissolved in the fluids of the body with increasing pressure until that gas is saturated in solution. As one ascends, the dissolved gas comes out of solution as bubbles and is usually evacuated via the lungs. All divers ascend in a much shorter time than they spend under water; consequently, there is dissolved gas that now becomes supersaturated with decreasing pressure and is released as bubbles. Dive protocols have been created to allow the diver to ascend without the critical amounts of bubbles that produce symptoms of decompression sickness (or the bends).

Clinical Findings

If the diver violates protocols for ascending, or even when they are not violated, the bubbles can produce symptoms. The symptoms vary depending on the location of the bubbles. They can include cutaneous eruptions, pain, neurologic symptoms (including paralysis), and, rarely, death. If the bubbles lodge in the inner ear fluids, symptoms similar to inner ear barotrauma can occur and must be differentiated from that condition.

Inner ear decompression sickness is not a common problem with recreational divers who breathe gas mixtures principally containing nitrogen and oxygen (air and some mixtures with a higher content of oxygen and less nitrogen). It occurs more frequently in technical, commercial, and military divers who breathe gases that contain helium as one of the inert components. It is caused by gas bubbles being lodged in the fluids of the inner ear; these bubbles occur and enlarge on ascent.

Symptoms of tinnitus, hearing loss, severe vertigo with nausea and vomiting, ataxia, and syncope usually occur 10 minutes or longer after ascent from the dive. There is the absence of tympanic membrane and middle ear barotrauma; however, the hearing loss is sensorineural and nystagmus is present.

Differential Diagnosis

Differentiating inner ear barotrauma and inner ear decompression sickness can usually be made by the history of the dive (Table 57–1). If there is doubt as to the differential diagnosis, patients should be treated for inner ear decompression sickness because it is the more severe condition and patients can be left with persistent vertigo and ataxia if this condition remains untreated.

Treatment

Treatment is recompression in a chamber, breathing 100% oxygen. Careful adherence to decompression schedules and ascent rates is the only prevention, but, as stated above, this condition can occur even if proper adherence to decompression schedules is followed.

Vertigo is a common symptom of diving injuries and has many causes common to the diving environment, including unequal vestibular stimulation (Table 57–2), unequal vestibular responses (Table 57–3), and central causes (Table 57–4).

Barodontalgia

Barodontalgia is a condition producing dental pain on descent or ascent. It is caused by poor fillings, air pockets beneath the fillings, dental abscesses, or pressure-induced fluid leakage around the dentin of the tooth. It may be implosive on descent or explosive on ascent, occasionally forcing a filling, inlay, or crown to be extruded. This condition is rare and if dental pain in the upper teeth is a presenting symptom, one must first consider maxillary sinus barotrauma.

Facial Nerve Baroparesis

Facial nerve baroparesis can occur. The facial nerve can be dehiscent of bone as it passes through the middle ear space. If there is extreme pressure due to inadequate equalization of the middle ear, temporary ischemia of the exposed portion may lead to palsy. It is usually selflimited, but can be repetitive.

TMJ Symptoms

Although not a true barotrauma condition, temporomandibular joint (TMJ) symptoms may occur. Novice divers have a tendency to bite down hard on their scuba mouthpieces, occasionally biting through the mouthpiece. The pain produced can mimic otologic conditions unless recognized. The ear examination is usually normal, and there is tenderness in the TMJ just in front of the tragus of the external ear. There may be teeth marks on the scuba mouthpiece.

The ostia of the paranasal sinuses are normally open unless obstructed by disease or anatomic deformities. Air freely exchanges between the nose and the sinus cavities. As long as this occurs, barotrauma of the paranasal sinuses does not occur. However, sinus barotrauma is very common, as are acute and chronic diseases of the sinuses. Pre-existing allergy, acute infections, obstruction by polyps, or a deviated nasal septum can contribute to the inability of the sinuses to adequately aerate. The frontal sinuses are the most commonly involved, followed by the maxillary sinuses, the ethmoid sinuses, and, rarely, the sphenoid sinuses.

The symptoms, findings, and treatment are the same as for sinusitis. Pain, increasing with depth while descending, is the most significant symptom. Barodontalgia is a very rare condition. Maxillary sinus pain can mimic dental pain, and one must consider maxillary sinus barotrauma if the diver complains of upper dental pain.

The diagnosis is confirmed by radiographic examination, and diving should be withheld until there is complete clearing of the sinuses. The treatment of chronic nasal conditions is essential and the correction of anatomic abnormalities is sometimes necessary.

Hearing loss is a common symptom in diving. At the scene of the diving accident, the examiner can frequently determine, with the use of tuning forks, whether the hearing loss was due to some interference with the conductive mechanism or to some damage to the sensory or neural pathway. Table 57–5 lists some of the causes of hearing loss that might occur in divers.

Any condition that either prevents a diver from adequately equalizing the middle ear spaces and sinuses or puts the diver at risk if the condition was to occur under water must be recognized. Some conditions are controversial, and new evidence is helping to resolve the controversies. Several otolaryngologic conditions should preclude returning to diving. These include (1) a tympanic membrane perforation, (2) the presence of pressure-equalizing tubes in the tympanic membrane, (3) a radical or modified radical mastoidectomy (the lateral semicircular canal is exposed to water in the mastoid cavity, producing a caloric response), (4) any vertiginous condition that might occur under water, (5) the inability to inflate the middle ear, (6) chronic refractory sinusitis, (7) tracheotomy or tracheostoma, and (8) any condition that makes it impossible to hold a scuba regulator in the mouth. As noted previously, there is controversy with regard to inner ear barotrauma. Patients who have undergone stapes surgery have been advised not to return to diving. However, there is an increasing body of evidence that allows these individuals to dive safely (see references).

Temporary contraindications include (1) any acute or chronic otolaryngologic infection until resolved, (2) healed tympanic membrane perforations until they meet the criteria noted previously, (3) external otitis until cleared, (4) impacted cerumen, (5) middle ear barotrauma until resolved, (6) chronic nasal obstruction, (7) any acute sinus trauma until healed with no dehiscence of bone, (8) orthodontic appliances, and (9) current major dental therapy until completed.

Middle ear and sinus barotrauma are the most common injuries associated with exposure to increasing and decreasing pressure. Descent in the water adds approximately one-half pound of pressure for each foot of descent and diminishes a similar amount on ascent. According to Boyle's law, as the pressure increases on descent, the volume of a gas in an enclosed space decreases proportionately. As the pressure decreases on ascent, the volume of the gas increases proportionately. On descent, it is imperative that all enclosed air-filled spaces be equalized actively or passively. On ascent, the increasing gas volume usually vents itself naturally. As noted previously, the greatest pressure and volume changes occur closest to the surface.

For equalization to be effective, the diver should be free of nasal or sinus infections or allergic reactions. The lining of the nose, throat, and eustachian tubes should be as normal as possible. If this is the case, the following techniques are effective in reducing middle ear and sinus squeeze.

1. 1. Before descent and neutrally buoyant, with no air in the buoyancy compensator, the diver's ears should be gently inflated with one of the methods listed below. This gives the diver a little extra air in the middle ear and sinuses as he or she descends.

2. 2. The diver's descent should be feet first, if possible. This allows air to travel upward into the eustachian tube and middle ear, a more natural direction. A descent or anchor line should be used.

3. 3. The diver should inflate gently every 2 ft for the first 10–15 ft and less frequently as he or she descends more deeply.

4. 4. Pain is not acceptable. If there is pain, the diver has descended without adequately equalizing.

5. 5. If the diver does not feel the ears opening, he or she should stop, try again, and perhaps ascend a few feet to diminish the surrounding pressure. The diver should not bounce up and down, but should try to tilt the ear that is not opening upward.

6. 6. If the diver is unable to equalize, the dive should be aborted. The consequences of descending without equalizing could ruin an entire dive trip and, more important, produce permanent damage and hearing loss.

7. 7. If the diver's physician agrees, decongestants and nasal sprays may be used before diving to reduce swelling in the nasal and sinus passages, as well as in the eustachian tube.

Decongestants should be taken 1–2 hours before descent; they generally last from 8 to 12 hours. Nasal sprays should be taken 30 minutes before descent and usually last about 12 hours. Caution should be taken when using over-the-counter nasal sprays, since repeated use can cause a rebound reaction with a worsening of congestion and a possible reverse block on ascent.

1. 8. If at any time during the dive the diver feels pain, has vertigo (the “whirlies”), or notes sudden hearing loss, the dive should be aborted. If these symptoms persist, the diver should not dive again until consulting a physician.

2. 9. Equalizing techniques may be used.

The following techniques can be used by the diver to equalize the volume of gas in the middle ear.

1. Passive: This technique requires no effort.

2. Valsalva: The diver can increase nasopharynx pressure by holding the nose and breathing against a closed glottis (throat).

3. Toynbee: The diver swallows with mouth and nose closed. This technique is especially good for ascent.

4. Frenzel: This technique involves the diver's using the Valsalva technique while contracting the throat muscles with a closed glottis.

5. Lowry (Valsalva plus Toynbee): The diver holds the nose closed, gently trying to blow air out of the nose while swallowing. This technique is the easiest and best method to use after it is practiced.

6. Edmonds: The diver juts the jaw forward and then performs the Valsalva technique, the Frenzel technique, or both. This method is very effective.

7. Miscellaneous: Miscellaneous techniques include swallowing and wiggling the jaw. These techniques are especially good for ascent.

[Diving Medicine Online]

http://www.scuba-doc.com/

The Divers Alert Network, maintained at Duke University, has a 24 hour number with trained medical personnel available to deal with diving accident problems: (800) 446–2671. They can refer you to the nearest recompression chamber and to the nearest physician trained in diving medicine who can handle your questions.