High Altitude Pulmonary Edema (HAPE) is when the lungs fill up with fluid as a result of the body adapting to high elevation. It occurs vary rarely below 8,000 feet. The reason the lungs fill up with fluid is a bit complex, and I am not a doctor, but the basic idea is the pulmonary artery (from the heart to the lungs) contracts a bit as people go up in elevation. In a few rare cases, people have only one pulmonary artery. These people are susceptible to HAPE below 8,000 feet.

For some reason, the younger you are, the more likely you are to get HAPE. Being well-conditioned is no defense against HAPE. It is thought that people who are susceptible to HAPE have pulmonary arteries that contract more than average.

As the pulmonary artery contracts, the pressure in the alveoli (the capillaries in the lungs) goes up. From osmotic pressure, some fluid goes from the alveoli into the lungs. As the lungs fill with fluid, it becomes harder and harder to breathe. After a while, coma and death can result. Descent is the best solution, although oxygen can help the symptoms when descent is impossible.

I have always been a bit slow at high altitude. At first, I put it down to the lack of oxygen. I remember some odd breathing sounds when I was over 10,000 feet for a weekend. I never got headaches worse than headaches that I sometimes get while hiking. I have never felt nauseated. So I never thought that I was susceptible to any high altitude illnesses.

Well, one day I went on yet another backpack over 10,000 feet. The first night we drove in, and slept around 9,200 feet. The next day, we backpacked to 11,200 feet. The next day we were supposed to go on a hike, and perhaps climb a peak or two. The distance and elevation gain of the hike was well within by abilities. We started off, and I didn't feel so well. I also happened to have a pulse-watch with me, and I was very familiar with my pulse while exercising at different intensities. I was breathing quite rapidly, and feeling very tired. My pulse was around 100-110, which is pretty low for me. My resting pulse is around 40, and my pulse while exercising heavily can stay above 160 for hours at a time. So I knew that I wasn't exercising heavily. It was a very puzzling situation. After a short rest, I decided that hiking was a bad idea, and I returned to camp. I had a mild headache. I could see my fingernail beds were slightly bluish.

I took some aspirin. I didn't feel much better after a few hours, and fearing that I was having some mild altitude problems, I took some Diamox. I had taken Diamox before, and happened to be carrying it in my huge first aid kit. Well, it had its primary effect, and that was to make me urinate quite a bit. Fortunately, we were close to a large lake, so there was no shortage of drinking water... After a few hours, I started feeling a little better.

I went to sleep that evening, and I didn't sleep well. I woke up around midnight, hearing the oddest sound while I was breathing. It sounded like a paper bag being crumpled up. I recalled hearing that sound before, but never quite so clearly. In all the mountaineering medicine books I have read they described rales as sounding like a paper bag being crumpled up, and described the sounds as 'unmistakable'. I thought the unmistakable part was a cop-out to avoid describing the sound in more detail. I was wrong.

Now I knew what I had. I had HAPE! I knew that if I went back to sleep, I would get more de-oxygenated, and that the condition would get worse. I didn't really feel like sleeping anyway, as I have read many books about high altitude expeditions, and people dying of high altitude illness in their sleep. I did have one more drug to try, and that was Dexamethasone. Diamox and Dexamethasone have been the drugs of choice for HAPE. So I figured since I had HAPE, I should take some Dexamethasone. While I was at it, I think I took another Diamox.

Now in retrospect, this was pretty silly. But I know more now that I knew then. Neither Diamox nor Dexamethasone will reverse the symptoms of HAPE.

I woke my friend in the tent, and carefully explained the situation. I decided the best course of action was to hike down immediately. So I packed up my backpack and all my gear. I was there with some more friends. While packing, they woke up. I explained the situation to them, and they agreed that hiking down was the best thing to do. I had each of them put their ear against my chest so that they could hear the rales first hand. One friend insisted on accompanying me. I said this wasn't necessary, but they insisted. So we headed down.

It took about 5 hours for us to do about 5 miles. It was quite dark. I am very used to hiking in the dark, and I never use a flashlight, although I often carry one. I typically hike two times each week for several hours in the dark. This time, it seemed darker. The sky seemed overcast, and I really couldn't see well enough to hike safely. So I took out my trusty Petzel micro headlamp, and used it to hike. The really scary thing is that I knew that poor night vision is one of the first signs of low blood oxygen.

After we got to the cars (9,200) feet, I was feeling a little better, despite having little sleep. We drove down to 4,000 feet, and I was feeling much better. I had a large breakfast. I had to wait about 6 hours for the rest of the people to show up. I could still hear the rales, but my blood was saturated, because I my fingernail beds were pinkish. After a few days the rales went away as the fluid was re-absorbed.

As the Harvard med student said, "You should realize that HAPE is one of those things doctors don't really understand, no matter what anybody tells you. I'd stick with Diamox prophylaxis."

Source: http://www.weasel.com/hape.html: