by David Page
• Obesity
• Female gender
• Advanced age
• Alcohol
• Cold environment
• Exertion at pressure
• Fatigue
• Repeated dives
When breathing compressed air at increased pressure, oxygen is utilized by the body but nitrogen, which makes up 80 percent of ambient air, remains in the tissues. The deeper the dive, the higher the content of nitrogen in the tissues. Obese people absorb even more inert (not used by the body) gas because nitrogen is five times more soluble in fat than in water.
As the diver ascends from the depths, gas tension in tissues (particularly of nitrogen) rises because the pressure on the diver decreases. If the pressure is reduced too quickly—that is, if the diver ascends from a long, deep dive without decompression stops—gas bubbles may form in the tissues, and a number of complications may occur:
• Gas bubbles may block arteries and veins and impair the function of organs.
• Gas bubbles may form in cells and rupture tissues.
• Gas bubbles may form in closed spaces with no ability to expand and cause tissue damage from increased compartment pressure.
• Gas bubbles may form in the blood and cause blood elements to coagulate inappropriately and cause a variety of tissue damage.
Decompression sickness is usually divided into two types or patterns according to severity:
1. Type I decompression sickness (pain only)
• Joint pain (mild or severe)
• Itchy skin
• Rash (large flat plaques, sometimes reddish)
• Local swelling
2. Type II decompression sickness (serious)
• Spinal cord "hit": gas bubbles obstruct arteries to spinal cord, cause ischemia, tissue death, paralysis, incontinence of urine or feces; priapism (uncontrolled erection)
• Cerebral involvement: headache, blurred or double vision, dizziness, personality changes, convulsions
• Cardiovascular collapse: air hunger, rapid pulse, blood pressure drop (shock)
• Type I symptoms that occur while still under pressure
Both types of symptoms begin to appear within fifteen to thirty minutes of surfacing, and the more severe form can progress to death within hours. Fifty percent of all decompression sickness cases appear within the first hour and over 90 percent become manifest within six hours. Professional and avid sports divers may develop hearing loss and vertigo from inner ear decompression sickness where hemorrhage and repeated attempts at healing affect the semicircular canals and nerves. Divers with extensive experience often have x-rays that show islands of dead bone here and there from previous bubble damage.
Decompression sickness is called the bends because of the prominence of joint pain. Bubbles form in tight joint tissues and create various degrees of pressure. Pain occurs most commonly in the shoulders and elbows with bending and extending the joint. In the severe forms, any tissue may be involved. For example, all parts of the brain may be hit, often simultaneously, resulting in anything from memory loss to incoordination and loss of balance.
Treatment for decompression sickness centers on recompressing the victim. Depending on the location of the accident and support capabilities, this may be done by submerging once more and resurfacing slowly or by transporting the victim to a decompression chamber. Other support measures in treating decompression sickness include steroids to reduce brain swelling, blood thinners to reduce likelihood of blood clot formation, IV fluids for hydration, bladder catheterization for spinal hits and supplemental oxygen.
Barotrauma
This group of pressure-related problems occurs because gas-filled spaces in the body were not equilibrated with the outside (ambient) pressure during submersion. If we ignore minor problems such as excessive face mask pressure and cramps from squeezed gut gas, two common forms of barotrauma are seen:
1. Middle ear barotrauma
2. Pulmonary barotrauma
Middle ear barotrauma is the most commonly seen diving problem and must be solved before the diver gets too deep. Between the back of the throat and the middle ear inside the temporal bone lies the connecting eustachian tube. Its slitlike end in the throat must be opened in order for changing ambient pressure to be transferred to the middle ear cavity where the tube ends. This is accomplished by moving the jaw, yawning, swallowing or squeezing the nose and blowing gently. If not performed
properly, symptoms appear. These include ear pressure, then pain and rupture of the ear membrane with pain relief. This is followed by vertigo (dizziness), if underwater, when cold water stimulates the middle ear.
Conditions that aggravate middle ear problems by making it more difficult to open the eustachian tube include cigarette smoking, allergies, upper respiratory infections and occasionally throat polyps. If you have a character with the flu who dives, he may blow out his eardrum and resurface in pain, or he may become dizzy and disoriented and nearly drown.
Ear problems in the diver may be simple or complicated. It's the writer's call. Maybe you just want to annoy someone in your story.
On the other hand, pulmonary barotrauma is serious business. The lungs contain mostly air, and any failure to exhale on the way up from a dive will result in rupture of lung tissue as the gas expands. There's more. Gas may come out of body fluids in the mediastinum (the space between the lungs) and cause a variety of symptoms. The following list contains most of the symptoms experienced by a diver suffering from mild or severe pulmonary barotrauma:
• Shortness of breath
• Chest fullness
• Coughing up blood
• Chest pain
• Change in the voice
Physical findings in pulmonary barotrauma are variable and depend on what injury has occurred:
• Diminished breathing sounds on one side (as heard through a stethoscope)
• Crepitus in the neck (crepitus is caused by gas bubbles collecting in tissues; the tissue feels squishy like rolling cellophane)
• Arterial air embolism (bubble in the blood stream); may cause a heart attack or stroke just as a clot would in someone with arteriosclerosis and clot emboli; symptoms are strokelike paralysis or severe chest pain
In general, lung damage while descending is called lung squeeze, while barotrauma during the ascent is termed burst lung. Air embolism is the most problematic aspect of burst lung, followed by pneumothorax (collapsed lung) and surgical emphysema—a condition where gas fills the chest and travels up into the neck. It can even fill the heart sac.
Treatment of air embolism and surgical emphysema involves recompression or hyperbaric oxygen treatment. A pneumothorax requires the surgical placement of a chest tube, just as with chest trauma.
Nitrogen Narcosis ("Rapture of the Deep")
In the mid-1800s, symptoms were first noted in divers that were variously attributed to claustrophobia, impure air mixtures and high partial pressures of oxygen. It wasn't until 1935 when the great diving researcher A. R. Behnke and his associates properly attributed these peculiar symptoms to the effects of nitrogen excess. As deep diving systems evolved, helium was substituted for nitrogen as the inert gas in the breathing mixture, commonly referred to as heliox.
A spectrum of mental aberrations are seen in nitrogen narcosis, all of which rapidly disappear when the victim returns to one atmosphere, or sea level. The picture has often been compared to alcohol intoxication: For each added atmosphere of depth (thirty-three feet), the effect is much like another martini. The aberrations include the following:
• Higher functions are affected first, including judgment, memory, ability to concentrate and reason.
• Euphoria occurs early, but panic and terror are occasionally seen.
• Symptoms are aggravated by cold, alcohol, drugs and anxiety or fear.
• Not all divers react the same.
• Symptoms become worse as the depth increases.
• Symptoms
occur within minutes of reaching depth and don't usually progress.
Prevention is the best course of action and only requires the diver to perform nondecompression dives to eighty or one hundred feet for twenty minutes or less. The U.S. Navy Decompression Tables are designed to instruct the diver on how long to remain at specific depths without undergoing decompression. Decompression stops are various depths at which one halts to breathe in order to let the lungs blow off nitrogen now coming out of the body fluids. But the tables aren't perfect. If the diver sticks to shallow dives, say forty feet or less, she can stay there for extended periods of time.
Other diving problems that can arise are sinus barotrauma, diving suit squeeze, marine animal attacks, coral cuts and drowning.
It doesn't get much better up on the mountain.
Altitude Sickness
An illness at altitude is altitude illness until proven otherwise.
—Stephen Bezruchka, M.D.
Other than denizens of high altitude, people who periodically go to the mountains fall into two categories:
1. Inexperienced travelers
2. Risk-taking adventurers
Millions of people travel to high altitudes each year, often doing so on rushed schedules as weekend climbers, thrill seekers or as part of an impromptu outing with little preparation. There meanders in the wake of these thrill seekers a vapor trail of disrespect for the high mountain environment. For some novice climbers, it is a cavalier conviction of immortality; for others, it's just plain ignorance.
A new, belligerent term has wedged itself into the young adventurer's lexicon. The term is extreme. People speak of extreme skiing or climbing, and they seek out other extreme experiences like plunging down a vertical waterfall in a kayak or plummeting from a bridge with an elastic cord tied to one's body. Somewhere along the path to hightech, no-boundaries living we seem to have discarded our senses. Injury or death may be the price one pays when one searches through risk taking for insightful messages in the e-mail of one's soul.
Like scuba diving, mountain climbing demands effort and physical conditioning with a significant additional factor thrown into the risk equation. The world of these activities is unfriendly. Beyond physical exertion and its effect on the person's heart, coronary arteries and general health, the diver and climber find themselves exercising vigorously in a hostile world of oxygen deprivation. And it all takes place at some distance from appropriate medical help.
Altitude conceals within its magical vistas a significant threat to anyone who has not undergone acclimation. Before climbing into the rare atmosphere of high altitude medicine, we must organize ourselves and sort out the illnesses to which your characters may fall prey. Twenty-five percent of all folks who ascend to high altitude develop some manifestations of altitude illness.
The major activities that take people to high altitudes include:
• Serious mountain climbing
• Trekking
• Skiing
• Mountain biking
• Sight-seeing
Mountain activities of all sorts have become a growth industry, and peaks in several parts of the world are favorites, including those in the states of Utah, Colorado, Washington, New Mexico and Wyoming and Central and South America, as well as the traditionally sought-after peaks of the Himalayas. Few casual climbers prepare adequately, and therein lies the dilemma. Your characters may be irresponsible weekend adventurers or serious climbers or trekkers who simply run out of luck.
Either way you need to know the sorts of feelings and symptoms they might experience.
The illnesses described here are not unique. And although three major illnesses are described separately, they have common features and often appear together in the same victim. All of these diseases are tied together by the same physiological knot: lack of oxygen. Doctors call it hypoxemia.
Acute Mountain Sickness (AMS)
Two quick points to remember about AMS: The symptoms are much like a hangover, and they vary in degree from mild to moderate to very severe. (You don't know what a hangover feels like? It's possible, I suppose.)
There's an interesting irony here. Many people travel to extreme mountain heights to experience a "natural high." What do they get for their dollars? A garden variety hangover! The following is a classification of symptoms of acute mountain sickness.
Symptoms of mild AMS:
• Headache
• Loss of appetite
• Insomnia
• Nausea
• Uneasy feeling of fatigue Symptoms of moderate AMS:
• Repeated vomiting
• Decreased urine output
• Persistent headache Symptoms of severe AMS:
• Loss of balance
• Lethargy to unconsciousness
• Cyanosis (blue discoloration) of lips, fingernails
The two other diseases that are seen at altitude are really a part of severe acute mountain sickness rather than isolated problems. The target organs—the lungs and the brain—are affected in the same manner. Each organ becomes wet. This increased tissue fluid, or edema, results from excessively low oxygen levels in the inspired air and the resultant insult to sensitive brain and lung cells.
High Altitude Pulmonary Edema (HAPE)
The lung failure seen at altitude is caused by "leaky membranes," or a break in the barrier that usually keeps fluid out of the air spaces. It's like heart failure in the elderly patient, but instead of pump failure causing excessive pressure buildup in the lung capillaries, it's the capillary membrane that is affected by hypoxemia. Fluid leaks out of the capillary into the air sacs and "internal drowning" begins.
Occurring more often in males, HAPE is seen at moderate altitudes in ski resorts and often doesn't appear until the day after exposure to altitude. Normally, at sea level, the amount of air and blood flow to the lungs are equally matched and blood oxygenation proceeds effectively. In HAPE (as well as in most sick ICU patients on ventilators), there is a mismatch between air exchange and regional blood flow to the lungs. Blood oxygen levels may drop precipitously.
People with early high altitude pulmonary edema become symptomatic in subtle ways. As the following complaints escalate, the victim becomes more aware of the growing discomfort. Findings in early HAPE include:
• Fatigue
• Inability to perform at usual exercise level
• Dry cough
• Increased heart rate
As the illness progresses, symptoms become more bothersome and severe HAPE mimics lung failure from any cause.
• Shortness of breath at rest (without exercise)
• Productive cough (moderately large amount of sputum)
• Cyanosis of fingernails, lips, etc.
• Severe weakness
• Loss of balance, which may suggest associated cerebral edema
• Sudden death may occur
The profile of that individual who is at highest risk of developing high altitude pulmonary edema is:
• Male gender
• Overweight
• Poor physical condition
• Rapid ascent to altitude
High Altitude Cerebral Edema (HACE)
Just as lack of oxygen (hypoxemia) is toxic to lung tissue, the same kind of effect occurs with brain cells, and as a consequence they swell and function poorly. Some experts think HACE is the worst consequence of acute mountain sickness, the endstage of the hypoxemic insult. Whatever the exact cause of the swelling, brain cells are impaired and the person affected demonstrates a variety of symptoms. Because even young people can have small strokes, or TIAs (transient ischemic attacks), at altitude, it's important to pay attention to any of these symptoms:
• Change in behavior—victim does peculiar things
• Inability to make reasonable decisions
• Severe persistent headache
• Vomiting
• Loss of balance
• Lethargy possibly leading to coma
There is an interplay between high altitude cerebral edema and pulmonary edema. If you survey the symptoms, it becomes clear that they blend together and may also be confused with other potential issues. A partial list of possible associated problems includes dehydration, alcohol or drug abuse, severe exhaustion, hypothermia or worsening of a known medical condition.
Treatment of High Altitude Illnesses (HAPE or HACE) Mild acute mountain sickness may be treated by:
• Remaining at same altitude for a day or two in order to undergo acclimation
• Moderate exercise at same altitude
• Over-the-counter pain medication
• Diamox (acetazolamide) with prior OK by physician; acts like a water pill to cause fluid loss and also acts on the brain to decrease HACE symptoms
Severe acute mountain sickness must be treated by:
• Immediate descent at least 1,500 to 3,000 feet (avoid trap of delaying descent or cancelling evacuation plans if victim demonstrates some improvement)
• Administering oxygen
• Physician-directed use of steroids (dexamethasone)
• Use of hyperbaric chamber after descent or portable hyperbaric "bag" at altitude if available
A less serious altitude problem described by Dr. Michael Weidman is hemorrhage into the retina of the eye. Seldom associated with blindness, it occurs in folks sleeping above 15,000 feet and usually resolves spontaneously after a week or two regardless of altitude. Sometimes, though, the victim "sees spots," and blindness has occurred.
Prevention of Acute Mountain Sickness
A few basic common sense principles ought to be followed by anyone traveling to high altitude:
• Forget adhering to a tight schedule; make time for a safe ascent!
• Stay warm; dress in layers.
• Practice deep breathing regularly.
• Watch each other for changes in behavior.