Are You High?

I put a lot of thought into the content included in our first aid courses, and there's a reason we don't talk about high altitude illnesses (HAI)—we don't have the mountains.  For the most part, HAIs don't occur under 2500 meters (about 8200ft) and the tallest mountain in New England doesn't come close. New Hampshire's Mountain Washington—while having some of the most extreme weather on the planet--tops out at 6288ft (about 1900m). The tallest mountain east of the Mississippi is Mount Mitchell, in North Carolina, at 6,683ft above sea level (about 2000m), so unless you're heading west or to other parts of the world, altitude shouldn't cause problems.

That being said, I did just take a quick CME (continuing medical education) course, on HAIs so let's discuss the topic while the info is fresh in my mind.

At higher elevations, the air pressure is less than at lower elevations which makes the O2 content less as well. The combination of the two make it harder for the body's tissues to get the oxygen it needs. When dipping your toes in the ocean's at Maui's Makena Beach State Park, the O2 content is about 20%, but at the top of the island's Haleakalā National Park (elevation 10,023ft), the oxygen content would be about 14%.

We could spend days and days discussing the chemical and biologic processes involved here, but let's just summarize it in the fact that gas exchanges in our bodies is highly dependent on pressure gradients. Higher oxygen pressures in the air makes oxygen go into the lungs, cross into the blood, and into the cells, while the higher pressure of carbon dioxide in the cells follows the opposite course to the lungs and out into the air. When the pressure and content of oxygen is less than is optimal, the body can and will make changes, but some people adapt faster than others, and some people have medical conditions that make it harder to adapt. People who live at higher elevations typically have already adapted which is why the population of places like Winter Park, Colorado (pop.1033, elevation 9000ft, O2 15%), aren't all walking around gasping for air. 

For people who don't live at high altitude, the process of adapting to high altitude is called "acclimatization," and biological responses such as increasing production of red blood cells can take weeks, while some other changes to the acid-base balance are more immediate.  

The best approach to prevent HAIs is to ascend slowly, but that's not always possible. That makes sense if you're taking weeks to climb K2, but if you're flying in from Providence, Rhode Island (10ft) to ski for a week at Vail, Colorado (8,200ft), you're going to be in and out.

So what are the High Altitude Illnesses (HAIs) anyway? 

There is a generalized cluster of symptoms that's called Acute Mountain Sickness (AMS) and can manifest within 6-12hrs of arrival at elevation (but can take up to 5 days). AMS typically includes a headache and goes from mild, moderate to severe depending on the additional symptoms of nausea, vomiting, fatigue, weakness, dizziness, and/or lightheadedness, as graded on the 2018 Lake Louise Acute Mountain Sickness Score.

AMS isn't usually serious, but it can certainly ruin a trip. Most symptoms can be treated with rest, fluids, and medications (for headaches and nausea). Supplemental oxygen may help, but people shouldn't go any higher until symptoms improve, and if symptoms do not improve or worsen,  descent to lower elevations is recommended.

And while AMS might make you feel like you're dying, two other HAIs could actually kills you. High-Altitude Cerebral Edema (HACE) and High-Altitude Pulmonary Edema (HAPE) are true emergencies for which rapid descent is critical. 

HACE, swelling of the brain, is usually a progression of AMS where after about 2 days of being at elevation the person is now confused or otherwise has decreased levels of consciousness with VERY unsteady walking. Unrecognized, this can lead to coma and death.

People who develop HAPE, fluid in the lungs, may or may not have had AMS, but will usually start by having a dry cough and shortness of breath with exertion. Symptoms can progress to worsening cough, fast heart rate, fast respiratory rate, worsening shortness of breath, and abnormal lung sounds. Again, treatment is descent, but supplemental oxygen is important and certain medications may be helpful as well. 

As a temporizing measure, portable hyperbaric chambers can be used to simulate lower elevations, and this video has a great demonstration of how the Gamow bags work.

If you're ever going to be visiting somewhere with high elevations, it might be worth talking with your primary care provider, as some medical conditions and medications can make the altitude more problematic and there could be prescriptions to help make the transition easier.

And you may have wondered why I discussed HAPE and HACE, but not HAFE. Well, I'm too mature for that. 

Anyway, it's possible to have effects of altitude at lower elevations than 8000ft, but less likely. Which is a shame because that just means I'm out of shape when slogging up Mt Burke. 

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