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Barotrauma/Decompression Sickness Overview

Barotrauma refers to medical problems that arise from the pressure differences between

areas of the body and the environment and is a particular concern for scuba divers.

Certain laws of physics apply to this topic. Boyle's law states that the product of the

multiplication of pressure and volume remains a constant. As the pressure increases, the

volume decreases and vice versa. As you dive deeper when scuba diving, pressure increases

and this volume change in gas-filled spaces and organs within your body accounts for the

distortion and damage to surrounding tissues.

Decompression sickness, or "the bends," is related more to Henry's Law, which

states that more gas will be dissolved in a liquid when the gas is pressurized. Because

of the water pressure, body tissue absorbs nitrogen gas faster as a diver descends

than when ascending to the surface. However, if a diver ascends too quickly,

nitrogen gas bubbles will form in body tissue rather than being exhaled. The nitrogen

bubbles cause severe pain.

External ear squeeze occurs when your ear canal is blocked by something such as

earplugs or earwax. As the water pressure increases while you descend, the air

pocket between the obstruction and the tympanic membrane (eardrum) shrinks.

This can damage the tissue in the ear canal, usually your eardrum.

Middle ear squeeze occurs when you cannot equalize the pressure in your middle

ear. The eustachian tube is a small canal that connects the middle ear to the back

part of the nasal cavities and allows pressure to equalize. When there is a problem

with the tube, the middle ear volume decreases and pulls the eardrum inward,

creating damage and pain. You can try certain maneuvers, called Valsalva

maneuvers, such as yawning or trying to blow with your nose and mouth closed, to

open the tube and equalize the pressure.

Inner ear barotrauma occurs from the sudden development of pressure differences

between the middle and inner ear. This can result from an overly forceful Valsalva

maneuver or a very rapid descent. The result is usually ringing in the ear, dizziness,

and deafness. This injury is less common than a middle ear squeeze.

Less common types of barotrauma include the following. All involve air trapped in an

enclosed area where pressure cannot equalize during descent causing a vacuum

effect where it occurs.

o Sinus squeeze: When air becomes trapped in the sinuses because of

congestion or cold symptoms, a sinus squeeze can occur.

o Face mask squeeze: This occurs if you do not exhale through your nose into

the dive mask while descending (equalizing).

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o Suit squeeze: A dry diving suit tightly encloses an area of skin.

o Lung squeeze: This occurs when you are free-diving, but very few divers can

hold their breath to depths that cause this injury to occur.

o Tooth squeeze: This occurs during an ascent while scuba diving and air

becomes trapped in a filling or cavity.

o Gastric squeeze (aerogastralgia): This occurs when gas swallowed during

diving expands during ascent. This happens more often with novice divers

and causes temporary pain but rarely significant damage.

Barotrauma can occur during ascent also. A reverse squeeze occurs in the middle ear

or sinus when a diver has an upper respiratory infection (cold) and has used nasal

spray to open the breathing passages. As the spray wears off during diving, tissues

swell and cause obstruction, resulting in a pressure difference and damage. During

"bounce diving" the eustachian tube may become inflamed and lead to a middle ear

squeeze.

Pulmonary barotrauma (pulmonary overpressurization syndrome, POPS, or burst

lung) can occur if the diver fails to expel air from the lungs during ascent. As the

diver rises, the volume of the gas in the lung expands and can cause damage if the

excess is not exhaled.

Air embolism is the most serious and most feared consequence of diving.

o While scuba diving, gas bubbles can enter the circulatory system through

small ruptured veins in the lungs.

o These bubbles expand during ascent, following Boyle's Law, and can pass

through the heart to obstruct blood flow in the arteries of the brain or heart.

This most commonly occurs when a diver ascends rapidly because of

air shortage or panic.

The diver then passes out, experiences a stroke, or has other nervous

system complaints within minutes of surfacing.

The brain is affected more than other organs because gas rises, and

most divers are in a vertical position while ascending.

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Decompression sickness (DCS, "the bends") involves gases diffusing into the tissues

and getting trapped there. The diver now has gas bubbles in places where there

should be none. Nitrogen is the usual culprit.

o During descent and while on the bottom, the diver absorbs nitrogen into the

tissues until they reach a pressure balance.

o When the diver ascends at the right rate, the gas diffuses from the tissues.

However, if the diver ascends too rapidly to allow diffusion, the nitrogen

bubbles will expand in the tissues as pressure decreases.

o Different body parts can be affected, depending on where the bubbles are

located.

Barotrauma/Decompression Sickness Causes

Two different phenomena cause barotrauma:

The inability to equalize pressures

The effect of pressure on an enclosed volume

Decompression sickness is caused by the elevated pressures of the gas mixture

inhaled underwater that diffuse into the body tissues, and then the inadequate

diffusion of the gas from the tissues if the diver surfaces too quickly.

Middle ear squeezes occur because of obstruction of the eustachian tube.

o The most common cause is an upper respiratory infection (cold), creating

congestion.

o Other causes of obstruction include congestion caused by allergies or

smoking, mucosal polyps, excessively aggressive Valsalva attempts, or

previous facial injuries.

Factors that trigger sinus squeezes include a cold, sinusitis, or nasal polyps.

Contributing factors to aerogastralgia (swallowing air) include performing Valsalva

maneuvers with the head down (which allows air swallowing), consuming

carbonated beverages or heavy meals prior to diving, or chewing gum while diving.

Pulmonary barotrauma occurs from the diver holding their breath during ascent,

which allows pressure to rise in the lungs.

o The pressure increase results in rupture.

o Air also may penetrate into the tissue around the lungs.

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The classic description of a dive causing an air embolism is rapidly ascending to the

surface because of panic.

Failure to make recommended decompression stops during ascent usually causes

decompression sickness. Stops are based on diving tables or charts, which factor into

account the depth, duration of the dive, and previous dives completed and give you

guidelines on the proper rate of ascent.

Barotrauma/Decompression Sickness Symptoms

You should consider the signs and symptoms of diving injuries with regard to your overall

dive plan, including what part of the dive you were performing when the problems

occurred.

The history of the dive is very important to medical personnel and should always be

included when assistance is required.

o Barotrauma such as squeezes will commonly occur during descent, and the

symptoms will frequently prevent a diver from reaching the desired depth.

o You will notice symptoms of aerogastralgia, pulmonary barotrauma, air

embolism, and decompression sickness both during and after ascent.

The following are symptoms for specific pressure problems:

External ear squeeze: Pain in your ear canal and blood from your ear

Middle ear squeeze: Ear fullness, pain, eardrum rupture, disorientation, nausea, and

vomiting

Inner ear barotrauma: Feeling that your ear is full, nausea, vomiting, ringing in the

ear, dizziness, and hearing loss

Sinus squeeze: Sinus pressure, pain, or nasal bleeding

Face mask squeeze: "Bloodshot" eyes and redness or bruising of the face under the

mask

Lung squeeze: Chest pain, cough, bloody cough, and shortness of breath

Aerogastralgia (gastric squeeze): Abdominal fullness, colicky pain (severe pain with

fluctuating severity), belching, and flatulence (gas expelled through the anus).

Pulmonary barotrauma: Hoarseness, neck fullness, and chest pain several hours after

diving. Shortness of breath, painful swallowing, and loss of consciousness also may

occur.

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Air embolism: Sudden loss of consciousness within 10 minutes of surfacing. Other

symptoms include paralysis, numbness, blindness, deafness, dizziness, seizures,

confusion, or difficulty speaking. The paralysis and numbness can involve several

different parts of the body at the same time.

Decompression sickness: Rashes, itching, or bubbles under your skin

o Lymphatic obstruction which can cause localized swelling

o Musculoskeletal symptoms include joint pain that worsens with movement

and commonly involves the elbows and shoulders

o Nervous system after-effects include paralysis, sensory disturbances, and

bladder problems, usually the inability to urinate.

o Pulmonary symptoms include chest pain, cough, and shortness of breath.

Symptoms usually appear within 1 hour of surfacing but can be delayed up to 6

hours. In rare instances symptoms may not appear until 48 hours after the dive.

Flying in a commercial aircraft after diving may cause "the bends" to develop in the

airplane because the cabin pressure is less than sea level pressure.

When to Seek Medical Care

Most problems that arise from barotrauma will require medical diagnosis or treatment. The

most important thing the patient can do if they experience barotrauma is to seek medical

attention and avoid future dives until cleared by a doctor.

Some injuries from barotrauma require immediate medical attention, while others can wait

for treatment. In all cases, stop further diving until the patient has been seen by a doctor.

Air embolism is life threatening and requires immediate attention. Planning ahead is

important.

Know the location of the nearest emergency facility and recompression (hyperbaric)

chamber before you dive.

Bring emergency phone numbers with you on the dive. A phone can be the best

immediate life saving tool.

The Divers Alert Network (DAN) at Duke University maintains a list of recompression

facilities and can be reached around the clock at (call local EMS first, then DAN):

o (919) 684-8111 (collect)

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o 800-446-2671 (toll free)

o 1-919-684-9111 (Latin America Hotline)

If a diver collapses within 10 minutes of diving, suspect air embolism and seek help

immediately. Most U.S. communities have an emergency access number (911). Find

out in advance if such a number is available and how to activate emergency medical

services when diving in a foreign country. A diver who has collapsed requires oxygen

and emergency life support. Lay the person flat and keep the diver warm until help

arrives.

Decompression sickness also requires immediate attention, but its symptoms may not

appear as quickly as those of air embolism.

Information on recompression chambers is important and generally can be obtained

through the emergency medical system (911 in the U.S.).

Divers with complaints consistent with decompression sickness should seek

attention through their doctor or a hospital's emergency department.

Pulmonary barotrauma and lung squeeze will require attention in an emergency

department in most instances because the studies required to evaluate the symptoms and

determine the possible treatment must be performed in the hospital environment.

A doctor can evaluate and treat ear squeezes and sinus squeezes initially and refer the

patient to a specialist if required.

Evaluation may require a dive history.

Ear squeezes require an examination to ensure the eardrum has not ruptured.

The diver needs immediate medical attention if they lose consciousness, show paralysis, or

exhibit stroke symptoms within 10 minutes of surfacing.

You or your diving buddy should contact an ambulance through 911 or the local

emergency phone numbers.

Symptoms of chest pain and shortness of breath may occur minutes to hours after a

dive. These require emergency department evaluation.

o If the symptoms are severe enough, contact an ambulance. Otherwise, have

someone drive the patient to the hospital, but do not drive yourself.

o These symptoms can be dive-related or could be caused by another

condition, such as a heart attack. This will be sorted out in the hospital.

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Decompression sickness, or "the bends,” may require an emergency department to

control pain and arrange for recompression services using specialized equipment

that is available only at regional centers that specialize in barotrauma.

Dizziness or pain from a squeeze may require emergency attention as well. When in

doubt, contact a doctor or a local emergency department for advice.

Exams and Tests

The doctor will gather information about the dive and perform a standard physical exam,

paying particular attention to the areas of pain and nervous system.

Depending on the patient's condition, they may be referred immediately to a recompression

(hyperbaric) chamber or may undergo further testing.

The patient's vital signs will be taken, measuring blood pressure, pulse, breathing

rate, and temperature.

Doctors probably will do a pulse oximetry - an instrument that measures the level of

oxygen in the blood - using a sensor on a finger or earlobe.

The most common initial treatments may be oxygen (through a face mask or a tube

near the nose) and intravenous fluids.

Air embolism and decompression sickness usually will require recompression treatment and

repeated physical examinations. After treatment, the doctor may recommend a specialized

imaging study (CT scan or MRI) to further evaluate any neurological problems.

Chest pain and shortness of breath associated with pulmonary barotrauma may require an

electrocardiogram (ECG) and a chest x-ray.

The doctor will inspect the patient's ear canal and eardrum if they have an ear squeeze,

looking for physical signs that can range from no visible problems to a small amount of

bleeding to eardrum rupture to heavy bleeding.

Any hearing loss or dizziness will probably require referral to an otolaryngologist (ear, nose,

and throat specialist) or audiologist (hearing specialist). They will test the patient's hearing

and balance systems to determine if they have suffered any inner ear problems.

Barotrauma/Decompression Sickness Treatment

The most serious diving complications - air embolism and decompression sickness - will

require recompression therapy in a hyperbaric chamber. These hyperbaric chambers may be

freestanding or associated with a local hospital. The chamber itself is typically made of thick

metal plates with windows for observation. On the outside there are many pipes and valves.

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The chamber is usually large enough to accommodate more than one person. Medical

personnel may come into the chamber with the patient or stay outside, watch through the

window, and communicate by intercom, depending on the severity of the illness. While

inside the chamber, one may experience loud noises or cold as the pressures change. Similar

to diving, one will need to do Valsalva maneuvers to clear the ears while being pressurized.

The patient will be closely monitored and be given specific instructions while they are in the

chamber.

Other injuries can be managed at the hospital or doctor's office. All conditions will require

avoidance of diving until improved.

The patient may need to be transported to another location for hyperbaric

treatments. This may include low-level flights in an aircraft to minimize further

pressure changes.

"Treatment tables" will determine the length of treatment and treatment steps.

These tables take into account the depth, time of dive, decompression stops, and

previous dives performed. The hyperbaric specialist will recommend which table to

use.

The hyperbaric chamber will increase the air pressure to make any gas bubbles

inside the tissues smaller and to allow them to go away properly to avoid injury.

Pulmonary barotrauma may result in a collapsed lung (pneumothorax). If this occurs, the

doctor must first determine how much of the lung has collapsed. If the collapse is relatively

small the patient can be treated with supplemental oxygen and observation. Larger ones

require that air be withdrawn from the body.

Depending on the amount of air in the cavity, the doctor could use a needle or a

hollow tube to withdraw air from the cavity.

The needle will withdraw small amounts of air, and then the patient will be observed

for at least 6 hours.

Larger collapses require a catheter, or chest tube, to be placed in the chest wall and

remain for a few days until the lung that has been damaged can heal.

Doctors must insert this tube through the skin into the chest cavity by doing a small

surgical procedure. Local anesthetics reduce and generally eliminate any pain

associated with this procedure.

The tube is attached to a flutter valve or suction to promote air escape from the

inappropriate space.

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Self-Care at Home

There is no special treatment for face mask and suit squeezes. They usually go away in a few

days.

Aerogastralgia symptoms usually clear up on their own and do not require attention unless

the abdominal discomfort continues to worsen and does not go away in a few hours.

Pain from ear or sinus squeezes can be treated with over-the-counter pain relievers, such as

acetaminophen (Tylenol), ibuprofen (Motrin, Advil), or naproxen (Aleve). The patient should

visit a doctor to exclude possible serious ear injuries.

Medications

Sinus squeezes usually require oral and nasal decongestants. Antibiotics are usually

recommended for a squeeze involving the frontal sinuses. Pain medication may also be

prescribed.

Ear squeezes also require decongestants, both oral and long-acting nasal types. Antibiotics

may be given if the patient had a rupture, a previous infection, or the diving occurred in

polluted waters. Pain medication also may be prescribed.

Next Steps

Follow-up

Doctors will recommend follow-up based on the diagnosis.

Make sure everything has healed and the patient has received clearance before diving

again.

Prevention

The best prevention against barotrauma is to plan and prepare for your dive properly.

Make sure you are in good health with no upper respiratory or sinus problems.

Obtain the proper training and always use the buddy system (never dive alone).

Check that your equipment is in good working order.

Know the local emergency phone numbers in advance and have a means of

contacting help, for instance, with a cellular phone. (The location of the nearest

recompression facility could be very important in a problem such as air embolism.)

Newer "dive computers" designed to maximize safety can be used and may allow

longer diving times and fewer or shorter decompression stops. They provide

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information similar to the original diving tables but are more precise. Be certain you

are familiar with their use before depending on them.

Avoid flying in a plane within 24 hours of diving to reduce the risk of "the bends"

occurring unexpectedly in the lower air pressure of an airplane cabin.

Outlook

Most people recover from their diving accidents and are able to participate in future dives.

Air embolism can be the most devastating complication from a diving accident. The

initial problems that occur can be very dramatic. Appropriate measures, including

recompression, must be taken quickly to minimize disabilities. Recovery rates for

people reaching a recompression chamber have been 66%-90%.

Decompression sickness can also generally be treated effectively and result in very

good recovery rates when recompression is performed, even several days after the

initial onset.

Pulmonary barotrauma associated with a collapsed lung (pneumothorax) may

require several days in the hospital if a chest tube is placed. There is always a risk of

recurrence once a diver has a collapsed lung. Complete recovery will usually take

several weeks to months.

Mild ear squeezes usually take about 1-2 weeks to recover. More significant ones,

typically associated with eardrum rupture, may take longer. Depending on the

severity and amount of damage, surgery may be recommended.

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Middle Ear Squeeze

Barotrauma

Joseph Kaplan, MD, MS, FACEP, Attending Physician, Department of Emergency Medicine, Martin Army Community Hospital, Fort Benning, Georgia Marshall E Eidenberg, DO, Staff Emergency Physician, Via Christi Regional Medical Center

Updated: Sep 29, 2009

Introduction

Background

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Diving as a profession can be traced back more than 5000 years, yet diving-related disease was not described until Paul Bert wrote about caisson disease in 1878. Symptoms of caisson disease were noted among bridge workers after finishing their shifts underwater and coming back to the surface. These symptoms included dizzy spells, difficulty breathing, and sharp pain in the joints or abdomen. The caisson workers often noted that they felt better while working. This was usually attributed to their being rested at the beginning of the shift as opposed to being tired when the workday was through. The workers would often have severe back pain that left them bent over, which is how caisson disease earned the nickname "the bends."

Diving barotrauma can present with a variety of manifestations, from ear or mouth pain and headaches to major joint pain, paralysis, coma, and death. As a result of the wide variety of presentations, these disorders must be considered in any patient who has recently been exposed to a significant change in barometric pressure. The 3 major manifestations of barotrauma include the following: (1) sinus or middle ear effects, (2) decompression sickness (DCS), and (3) arterial gas emboli.

Barotrauma has also reportedly been caused by an airbag rupturing during deployment, forcing high-pressure gas into a person's lungs. It has also reportedly been associated with rapid ascent in military aircraft and with pressure changes associated with space exploration. The most current research in barotrauma has been dealing with ventilator-associated barotrauma and barotrauma prevention.

Recently, there has been a significant rise in articles dealing with combat-associated barotrauma. These articles deal mainly with blast injury patterns and ballistics. This is an extensive subject and is not covered in this article.

Pathophysiology

Injuries caused by pressure changes are generally governed by the Boyle and Henry laws of physics.

The Boyle law states, "For any gas at a constant temperature, the volume of the gas will vary inversely with the pressure," or P1 X V1 = P2 X V2. Pressure rises by 1 atmosphere for every 33 ft (10 m) of seawater depth. This means that a balloon (or lungs) containing a volume of 1 cubic foot of gas at 33 ft of seawater depth will have a volume of gas of 2 cubic feet at the surface. If this air is trapped, as occurs when a person holds his or her breath during rapid ascent, it expands with great force against the walls of that space (reverse squeeze). During rapid ascent, incidents of pneumothorax and pneumomediastinum as well as sinus squeeze and inner ear injuries can occur. Sinus squeeze occurs with eustachian tube dysfunction, which may result in inner ear hemorrhage, tearing of the labyrinthine membrane, or perilymphatic fistula.

The Henry law states that the solubility of a gas in a liquid is directly proportional to the pressure exerted upon the gas and liquid. Thus, when the cap is removed from a bottle of

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soda pop, the soda begins to bubble as gas is released from the liquid. In addition, when nitrogen in a diver's air tank dissolves in the diver's fatty tissues or synovial fluids at depth, nitrogen will be released from those tissues as the diver ascends to a lower pressure environment. This occurs slowly and gradually if the diver ascends slowly and gradually, and the nitrogen enters the bloodstream to the lungs and is exhaled. However, should the diver ascend rapidly, nitrogen exits tissues rapidly and forms gas bubbles. Once bubbles are formed, they can affect tissues in many ways. They can simply obstruct blood vessels leading to ischemic injury. This can be devastating when occurring in critical areas in the brain. The bubbles can also form a surface to which proteins in the bloodstream can cling, unravel, and begin a clotting/inflammatory cascade. This cascade can lead to endothelial breakdown and permanent tissue damage.

Decompression sickness

Decompression sickness (DCS) usually results from the formation of gas bubbles, which can travel to any part of the body, accounting for many disorders. A gas bubble forming in the back or joints can cause localized pain (the bends). In the spinal cord or peripheral nerve tissues, a bubble may cause paresthesias, neurapraxia, or paralysis. A bubble forming in the circulatory system can lead to pulmonary or cerebral gas emboli.

Some gases are more soluble in fats. Nitrogen, for example, is 5 times more soluble in fat than in water. Approximately 40-50% of serious DCS injuries involve the central nervous system (CNS). Women may be at an increased risk of DCS because they have more fat in their bodies. DCS also may occur at high altitudes. Those who dive in mountain lakes or combine diving with subsequent flying are at increased risk as well.

DCS is classified into 2 types. Type I is milder, is not life threatening, and is characterized by pain in the joints and muscles and swelling in the lymph nodes. The most common symptom of DCS is joint pain, which begins mildly and worsens over time and with movement. DCS type II is serious and life threatening. Manifestations may include respiratory, circulatory, and, most commonly, peripheral nerve and/or CNS compromise.

Arterial gas embolism (AGE) is the most dangerous manifestation of DCS type II. AGE occurs after a rapid ascent, when a gas bubble forms in the arterial blood supply and travels to the brain, heart, or lungs. This is immediately life threatening and can occur even after ascent from relatively shallow depths. However, AGE can also occur from iatrogenic causes.

Patients with a patent foramen ovale (up to 30% of the population) are at higher risk of gas passing from a right-to-left shunt and causing CNS injuries.

Frequency

United States

The average risk of severe (type II) DCS is 2.28 cases per 10,000 dives. The number of minor (type I) injures is not known because many divers do not seek treatment. Risk of DCS is increased in divers with asthma or pulmonary blebs. Risk of DCS type II is increased 2.5

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times in patients with a patent foramen ovale. Deaths due to DCS in military aircraft have been reported to occur at a rate of 0.024 per million hours of flight time. Rates of decompression incidents for civilian aviation average about 35 per year, and less than half are significant.

International

No information is available on the incidence of diving barotrauma worldwide. The Australian defense force has averaged 82 incidents per million hours of flying time.

Race

No significant differences in the incidence of dive-related injuries have been associated with race.

Sex

Because of a generally greater percentage of body fat, females have a theoretically higher incidence of barotrauma injuries than males. However, no data support this hypothesis.

Age

Although no direct correlation exists with age and frequency of barotrauma, the most common group affected ranges between 21 and 40 years. However, direct correlation does exist between age and residual effects of barotrauma, which significantly rises after age 50 years.

Clinical

History

Patients with DCS present with a history of diving, generally within 24 hours of the onset of symptoms. Patients may also have a recent history of occupational pressurization or depressurization. For example, this occurs with aircraft mechanics who must test aircraft windows by working in pressurized aircraft. Air emboli have also occurred in mechanics who maintain training altitude chambers. Recently, military operations involving troops traveling from ground level to high-altitude environments in a relatively short time and operations involving soldiers doing strenuous activities at higher altitudes have resulted in many cases of DCS. Recent studies have indicated that aerobic exercise either prior to a dive or during decompression stops may decrease the post dive gas bubble formation.[1,2 ]

Sinus squeeze o Patients usually present with complaints of facial or oral pain, nausea,

vertigo, or headache. o Other important information to gather includes any history of recent upper

respiratory infections, allergic rhinitis, sinus polyps, and sinus surgeries and whether the pain worsened during descent or ascent.

Middle ear squeeze

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o Patients often have a history of sudden vertigo, nausea, tinnitus, ear pain, deafness, or headache.

o They may have a history of previous diving ear injury or a history of previous or current ear infection.

Decompression sickness type I o Patients often have a history of recent diving followed by a flight home. They

may complain of slowly progressing pain or numbness in their limbs or back. o Patients present with joint, muscle, or back pain that worsens over time. The

pain worsens with motion but is always present. The pain may range from mild (tickles) to severe (the bends).

o Patients may have a history of previous decompression illness and multiple dives in the same day and frequently have not followed the dive tables closely. New dive computers that offer more "bottom time" do so by modifying the US Navy dive tables and possibly place divers at an increased risk for DCS injuries. Divers should be questioned as to the method of computing bottom and ascent times with safety stops. This information should be recorded as part of the medical record.

Decompression sickness type II o DCS type II usually presents sooner than DCS type I. o Patients may present with shortness of breath (the chokes), chest pain,

severe headache, altered mental status, and shock. They also may complain of dizziness or weakness. Patients may rapidly deteriorate without emergent intervention.

o Essential history to ascertain includes time since dive ended, the dive profile, when the symptoms began, and prior medical history. The dive profile consists of prior dives that day, depth of dive, bottom time, decompression stop depth, and length of stop.

o Diver should be asked about his or her prior dive category. o Inquiry should be made specifically about previous decompression injuries,

pulmonary blebs, Marfan syndrome, asthma, congenital pulmonary illnesses, HIV status, chronic obstructive pulmonary disease (COPD), lung tumors, histiocytosis X, cystic fibrosis, pregnancy, and any prior pulmonary injuries or surgeries.

Arterial gas embolism o AGE usually occurs shortly after ascending very rapidly, often from fairly

shallow depths. People may be described to scream suddenly and lose consciousness. Onset of AGE often occurs within a few minutes of surfacing. Patients who experience AGE often die before reaching a medical facility. Air emboli have also recently been noted to occur iatrogenically in association with central venous monitoring during surgical procedures. Case reports have shown AGE occurring secondary to occupational rapid decompression in both aircraft maintenance and altitude-chamber maintenance personnel.[3 ]

o Obtaining a history from these patients can be difficult because they often present with altered mental status or are in shock.

o Witnesses often report that divers experience a sudden or immediate loss of consciousness or collapse, usually within minutes of surfacing.

o Ask the patient or dive partner about a history of patent foramen ovale.

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Abdominal compartment syndrome:[4 ]Divers can develop large amounts of intraperitoneal extraluminal gas, which can compress the intraperitoneal organs. This can lead to venous compression of these organs and secondary compartment syndrome.

Physical

The physical examination should be tailored to the patient's history.

Perform a general physical examination on all patients, with initial emphasis on ears, sinuses, and neck as well as on the pulmonary, cardiovascular, and neurologic systems. AGE often presents with signs and symptoms of acute stroke.

Inspect and palpate the extremities, and test range of motion in all joints. Sinus squeeze

o Inspect nasal mucosa for polyps, hemorrhage, or lesions. o Palpate and transilluminate sinuses to inspect for hemorrhage. o Percuss upper teeth with a tongue blade to inspect for severe sinus

tenderness. Ear squeeze

o Carefully inspect the tympanic membrane (TM), looking in particular for the following signs:

Amount of congestion around the umbo Percent of TM involvement Amount of hemorrhage noted behind eardrum Evidence of TM rupture

o Palpate the eustachian tube for tenderness. o Test the patient's balance and hearing. o Evaluate the TM on the Teed scale:

Teed 0 - No visible damage, normal ear Teed 1 - Congestion around the umbo, occurs with a pressure

differential of 2 pounds per square inch (PSI) Teed 2 - Congestion of entire TM, occurs with a pressure differential

of 2-3 PSI Teed 3 - Hemorrhage into the middle ear Teed 4 - Extensive middle ear hemorrhage with blood bubbles visible

behind TM; TM may rupture Teed 5 - Entire middle ear filled with dark (deoxygenated) blood

Decompression sickness type I o Inspect for swelling or effusion in the affected joint. o Test for range of motion both actively and passively. o Palpate the affected area for crepitus and compartment tightness. o Evaluate neurovascular status by performing a complete neurologic

examination. The examination should include testing motor and sensory functions, cerebellar function, and mental status. The findings from this examination must be recorded and used as a baseline to determine improvement in postdive chamber treatment.

Decompression sickness type II

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o Evaluate cardiovascular and pulmonary systems. o Note neck vein distention or petechiae on the head or neck. o Palpate the skin for crepitus. o Auscultate the lungs and heart for decreased breath sounds, muffled heart

tones, or heart murmurs. o Evaluate neurologic status, including gross motor, sensory, and cerebellar

examinations. Tandem walking (heel to toe, with eyes closed) is an excellent method of evaluation.

o Document Glasgow Coma Scale and Mini Mental State Examination. Arterial gas embolism: Use the same examination used for decompression sickness

type II.

Causes

The causes of DCS are related to predisposing medical or genetic factors, as listed above, and to diver error. Diver error includes the following practices:

Multiple daily dives Poor adherence to the dive tables Breath holding (most common scenario for pulmonary barotrauma) Rapid ascent - This can occur from relatively shallow depths. For example, pilots

undergoing rapid ascent while performing underwater escape training after flight may experience DCS.

Flying or traveling to high altitudes within 24 hours after diving Occupational causes - These causes include rapid depressurization by maintenance

workers and mechanics after working in pressurized aircraft cabins. Reports of altitude chamber mechanics who have depressurized too quickly while working on the altitude chambers have also been documented. Pilots and crewmembers performing high-altitude air drops on military missions and special-operations soldiers involved in such missions have also reported instances of DCS.