MOUNTAIN AIR

Permission to use by Seniors Outdoors! obtained from Backpacker Magazine 9-6-00

Text by - Michele J. Morris

What do we mean when we say that mountain air is thin? To understand how it works, you first have to think of air as something that has weight and mass. If that’s hard to grasp, think of the last time you hiked into a headwind. Air couldn’t hit with that kind of force unless it had mass. And anything that has mass has weight. At sea level, there’s about 55 miles of that air weight, or atmospheric pressure, pushing down on you. Fifty-five miles above sea level is space, where there’s no air at all.

So the higher the altitude, the less air there is above pushing down. Scientists measure this air pressure in pounds per square inch, or psi. Less psi results in two things.

· First, the closer our atmosphere gets to space, the more dispersed the oxygen and other gas molecules are because there’s less pressure to keep them concentrated. That means that a cubic foot of air at 18,000 feet contains only about 50 percent as much available oxygen as a cubic foot of air at sea level. (See psi chart below.)

· Second, and even more important, thought, is there’s less pressure to affect you and all the gasses inside your body. So it’s harder for oxygen to get to all the tissures and cells it needs to reach to do its job.

Weather and the latitude you’re at also affect atmospheric pressure, and consequently, the effect on you body at altitude.

· A low-pressure weather front can make you feel as though you’re 500 to 700 feet higher on the mountain than you really are.

· Atmospheric pressure is greatest at the equator and least at the poles. That means that all other things being equal, a 12,000-foot peak in Alaska will seem higher than a 12,000-foot peak in Mexico to your body.

Don’t Be a Statistic

· Women and men have the same incidence of AMS

· Men are more likely than women to get HAPE.

· Fitness has little or no effect; being fit doesn’t help.

· People who live below 3,000 feet may be as much as 3-5 times as likely to develop AMS at moderate elevations (6,000 to 9,500 feet) as those who live above 3,000 feet

· Those who’ve previously experienced AMS may be 2.8 times as likely to experience symptoms again.

· About 2 percent of people who travel to 9,000 feet will develop symptoms of HAPE

· Both HAPE and HACE occur most often in those who ignore AMS symptoms.

The Golden Rules of Altitude

Follow these suggestions developed by the Himalayan Rescue Association, and you’ll be less likely to get sick no matter how high you go.

· Assume that any illness at altitude is altitude illness until proven otherwise.

· Don’t go higher if any AMS symptoms are present.

· If the symptoms are severe, or the person can’t do the heel-toe straight-line walk used in roadside sobriety tests without difficulty, go down.

· Never let anyone with altitude illness be alone.

PSI Chart
Altitude	Symptoms
Sea Level (15 psi)
5,000 Ft. (12 psi)	Significant problems are rare at this height, though people with lung or heart diseases may show some symptoms of AMS
6, 500 Ft.	Mild AMS symptoms–headache, shortness of breath, dizziness, fatigue may appear.
8,000 Ft. (10 psi)	Symptoms of AMS, HAPE, and HACE most commonly appear between 8,000 and 14,000 ft.
14,000 Ft.	The highest most backpackers travel.
16,000-18,000 Ft.	This elevations is the approximate location of basecamps where extreme mountaineer might sleep for several days or weeks to acclimatize before trying for the summit
18,000-29,028 Ft.	The “deathzone,” where even with supplemental oxygen, your body literally begins to die.
*Psi is a column of air one square inch across reaching upward to space, weighs about 15 pounds at sea level.

The Flatlanders Guide to Retch-Free Hiking
Illness	AMS–Acute Mountain Sickness	HAPE–High Altitude Pulmonary Edema	HACE–High Altitude Cerebral Edema
Prevention	From sea level, ascend no farther than 7,000 feet the first day; better yet, spend a day and night at 6,000 feet to acclimatize. Limit subsequent gain to 2,000 feet between sleeping elevations	Same as for AMS. If AMS symptoms are present remain at the same elevation or descent and rest until AMS symptoms disappear	Same as for HAPE
Signs & Symptoms	Headache, lack of energy, insomnia, loss of appetite, nausea, dizziness, shortness of breath, fluid retention, vomiting	Breathlessness at rest, dry cough that may develop into pink froth, bluish lips, nausea or vomiting, headache	Headache, stumbling, inability to perform “sobriety tests,” loss of hand coordination, disorientation, confusion, hallucinations
Usual time of Onset (after Ascent)	2 hours to 4 days	Abrupt onset, usually after second night, though may appear earlier or later	12 hours to 9 days
Likely Altitude	8,000 feet or more	9,000 feet or more	12,000 feet or more
Treatment	Do not go higher until symptoms disappear, or descend 1,500 feet and stay put until symptoms improve. Ibuprofen or aspirin for headache; acetazolamide (Diamox): 125 to 250 milligrams every 6 hours to aid acclimatization; Compazine for nausea	Immediately descent 1,500 to 3,000 feet; minimize exertion and keep warm; supplemental oxygen; nifedipine: 10 milligrams orally every 4 hours until improvement or 10 milligrams orally once, then 30 milligrams extended release every 12 to 24 hours; hyperbaric therapy (pressure chamber)	Immediately descent 1,500 to 3, 000 feet; supplemental oxygen; dexamethasone: 4 milligrams every 6 hours; hyperbaric therapy