The Basics of Altitude: A Primer on AMS, HACE, & HAPE
Altitude has been on my mind a lot recently; my colleagues and I at the American Mountaineering Museum are putting the final touches on a new exhibit called Thin Air: Altitude and Oxygen. It will open at the Museum this month.
I awoke Tuesday morning to a sad story in my inbox about a University of Arizona student, Morgan Boisson, who died near Rongbuk Monastery, at the foot of the Tibetan side of Mount Everest, on October 20, 2009.
Boisson was on a study abroad program in Nanjing, China, and traveled to Rongbuk with classmates on a a 10 day tour in Tibet.
Judging from the article I read and the symptoms described, Boisson was died from HAPE, or High Altitude Pulmonary Edema. And, sadly, he was not the first to die this way at Rongbuk, nor will he probably be the last.
We tend to think of severe altitude sickness like HAPE, and it's equally dangerous cousin, HACE (High Altitude Cerebral Edema), as something that only effects climbers. When we're "just trekking" or - like Boisson and the thousands of others who travel in Tibet each year – visiting the high country in a vehicle, we rarely give much thought to the effects of high altitude and the accompanying hazards.
But, these are major dangers for climbers, trekkers, tourists, and anyone traveling to altitude. In fact, Telluride's Institute for Altitude Medicine (IFAM), estimates that altitude sickness costs the Colorado ski industry upward of $200 million each year!
Thus, it's always a good idea to know the basics of HAPE and HACE – and even the more benign AMS, or Acute Mountain Sickness – and to have some tricks up your sleeve to deal with it if it hits a companion, or you.
For today, let's talk a bit about HAPE. I'll write later on about HACE if people are interested.
To begin, keep in mind I am not a doctor, and I don't even play one on TV. But, I do play one in the mountains quite often, treating clients and fellow travelers and local people we encounter along the way. Anyone wanting to know all the in-depth analysis of AMS, HAPE, and HACE should read articles available online at IFAM and the Altitude Research Center. That said, the following are some rules of thumb for altitude, and the things I look for in my clients – and in myself – whenever I travel to altitude.
HAPE, although very dangerous, is fairly rare, especially in travels below 15,000 feet. But, it does occur. IFAM tabulated only 150 cases over a 3 year period in Colorado's Summit County, and estimates that only about 1 in 10,000 skiers develops HAPE during their travels to the high country.
However, in my travels to mountains around the world, I've seen it a lot. From 10,000 foot Camp Muir on Mount Rainier to the 19,000 foot Garganta Camp on Nevado Huascaran in Peru to climbers dying high on the North Side of Everest, HAPE occurs all over the place, and is never a nice thing.
In general, the first signs of possible HAPE, and the ones I am on the lookout for in the mountains, are:
- A sudden and marked decline in ability to "keep up"
- Inability to catch one's breath, even when at rest
- Unnaturally elevated heartrate, even when at rest
- "Rails" or rattling/wheezing/crackling sound in the lungs
If you see these symptoms in yourself or your teammate, it's time to act. While it may not be HAPE, these are generally telltale signs, and the symptoms will progress rapidly downward if HAPE is indeed at play.
If a pulse-oximeter is on hand, it can be used and, in the case of HAPE, will show a decreased oxygen saturation level in the patient. Without a pulse-ox, oxygen saturation can be "guesstimated" by looking for a bluish, somewhat ashen look to the skin and a blue-gray look to the lips and nail beds.
For most trips in the mountains, however, we'll need to decide and act fast. And, in my opinion, it's always best to be conservative with HAPE and HACE, and err on the side of caution. So, how do we treat HAPE?
Seriously…go down, and go down now! The only true treatment for HAPE – and HACE – is to descend. And the rule of thumb is to descend at least 3000 feet.
But, what if descent is not an immediate option due to injury, weather, or other factors? Then, it's time for alternate plans which have hopefully been thought out in advance.
If oxygen is available, it should be administered at a high flow rate (i.e., 6-8 liters per minute). If a Gamov Bag or Portable Altitude Chamber is on hand, it should be used immediately. And, Nifedipine can be administered to help you buy some time as well. (Nifedipine, in layman's terms, reduces pulmonary arterial pressure and helps slow the leakage of blood and fluid into the lungs.
Again, though, the only true treatment for High Altitude Pulmonary Edema is descent.
Here's a classic example: in 1998 on Huascaran in Peru, Jason Edwards, Maximo Henostroza, and I rescued Miguel Tello from high on the mountain. When we found him at 19,000 feet, he was ashen, hypothermic, wheezing, unconscious, and had an oxygen saturation of about 40%. Diagnosing hypothermia, HAPE, and HACE, we administered drugs accordingly and began immediate descent, with concurrent monitoring. After the textbook 3000 feet of descent, Miguel was responsive and moving in our makeshift litter. He made a full recovery, but may well have passed away high in the Andes if we hesitated in our descent.
So, next time you head for the hills, be prepared. HAPE and HACE are rare, but they do occur, and they do kill. Know your body. Know your treatment options. And, have plans at the ready to deal with these ailments if they occur.
Let me know via the comments if this was even remotely interesting to people. If so, I'll write something up about HACE as well. And, if not, I'll drift on to other topics!