Outdoor Action Guide to High Altitude: Acclimatization

[rlown]

Outdoor Action Guide to High Altitude: Acclimatization and Illnesses

https://www.princeton.edu/~oa/safety/altitude.html

Traveling at high altitude can be hazardous. The information provided here is designed for educational use only and is not a substitute for specific training or experience. Princeton University and the author assume no liability for any individual's use of or reliance upon any material contained or referenced herein. This paper is prepared to provide basic information about altitude illnesses for the lay person. Medical research on high altitude illnesses is always expanding our knowledge of the causes and treatment. When going to altitude it is your responsibility to learn the latest information. The material contained in this article may not be the most current. Copyright � 1995 Rick Curtis, Outdoor Action Program, Princeton University.

High altitude-we all enjoy that tremendous view from a high summit, but there are risks in going to high altitude, and it's important to understand these risks. Here is a classic scenario for developing a high altitude illness. You fly from New York City to a Denver at 5,000 feet (1,525 meters). That afternoon you rent a car and drive up to the trailhead at 8,000 feet (2,438 meters). You hike up to your first camp at 9,000 feet (2,745 meters). The next day you hike up to 10,500 feet (3,048 meters). You begin to have a severe headache and feel nauseous and weak. If your condition worsens, you may begin to have difficulty hiking. Scenarios like this are not uncommon, so it's essential that you understand the physiological effects of high altitude.

What is High Altitude?

Altitude is defined on the following scale High (8,000 - 12,000 feet [2,438 - 3,658 meters]), Very High (12,000 - 18,000 feet [3,658 - 5,487 meters]), and Extremely High (18,000+ feet [5,500+ meters]). Since few people have been to such altitudes, it is hard to know who may be affected. There are no specific factors such as age, sex, or physical condition that correlate with susceptibility to altitude sickness. Some people get it and some people don't, and some people are more susceptible than others. Most people can go up to 8,000 feet (2,438 meters) with minimal effect. If you haven't been to high altitude before, it's important to be cautious. If you have been at that altitude before with no problem, you can probably return to that altitude without problems as long as you are properly acclimatized.

What Causes Altitude Illnesses

The concentration of oxygen at sea level is about 21% and the barometric pressure averages 760 mmHg. As altitude increases, the concentration remains the same but the number of oxygen molecules per breath is reduced. At 12,000 feet (3,658 meters) the barometric pressure is only 483 mmHg, so there are roughly 40% fewer oxygen molecules per breath. In order to properly oxygenate the body, your breathing rate (even while at rest) has to increase. This extra ventilation increases the oxygen content in the blood, but not to sea level concentrations. Since the amount of oxygen required for activity is the same, the body must adjust to having less oxygen. In addition, for reasons not entirely understood, high altitude and lower air pressure causes fluid to leak from the capillaries which can cause fluid build-up in both the lungs and the brain. Continuing to higher altitudes without proper acclimatization can lead to potentially serious, even life-threatening illnesses.

Acclimatization

The major cause of altitude illnesses is going too high too fast. Given time, your body can adapt to the decrease in oxygen molecules at a specific altitude. This process is known as acclimatization and generally takes 1-3 days at that altitude. For example, if you hike to 10,000 feet (3,048 meters), and spend several days at that altitude, your body acclimatizes to 10,000 feet (3,048 meters). If you climb to 12,000 feet (3,658 meters), your body has to acclimatize once again. A number of changes take place in the body to allow it to operate with decreased oxygen.

The depth of respiration increases.
Pressure in pulmonary arteries is increased, "forcing" blood into portions of the lung which are normally not used during sea level breathing.
The body produces more red blood cells to carry oxygen,
The body produces more of a particular enzyme that facilitates
the release of oxygen from hemoglobin to the body tissues.
Prevention of Altitude Illnesses

Prevention of altitude illnesses falls into two categories, proper acclimatization and preventive medications. Below are a few basic guidelines for proper acclimatization.

If possible, don't fly or drive to high altitude. Start below 10,000 feet (3,048 meters) and walk up.
If you do fly or drive, do not over-exert yourself or move higher for the first 24 hours.
If you go above 10,000 feet (3,048 meters), only increase your altitude by 1,000 feet (305 meters) per day and for every 3,000 feet (915 meters) of elevation gained, take a rest day.
"Climb High and sleep low." This is the maxim used by climbers. You can climb more than 1,000 feet (305 meters) in a day as long as you come back down and sleep at a lower altitude.
If you begin to show symptoms of moderate altitude illness, don't go higher until symptoms decrease (&quotDon't go up until symptoms go down").
If symptoms increase, go down, down, down!
Keep in mind that different people will acclimatize at different rates. Make sure all of your party is properly acclimatized before going higher.
Stay properly hydrated. Acclimatization is often accompanied by fluid loss, so you need to drink lots of fluids to remain properly hydrated (at least 3-4 quarts per day). Urine output should be copious and clear.
Take it easy; don't over-exert yourself when you first get up to altitude. Light activity during the day is better than sleeping because respiration decreases during sleep, exacerbating the symptoms.
Avoid tobacco and alcohol and other depressant drugs including, barbiturates, tranquilizers, and sleeping pills. These depressants further decrease the respiratory drive during sleep resulting in a worsening of the symptoms.
Eat a high carbohydrate diet (more than 70% of your calories from carbohydrates) while at altitude.
The acclimatization process is inhibited by dehydration, over-exertion, and alcohol and other depressant drugs.
Preventive Medications

Diamox (Acetazolamide) allows you to breathe faster so that you metabolize more oxygen, thereby minimizing the symptoms caused by poor oxygenation. This is especially helpful at night when respiratory drive is decreased. Since it takes a while for Diamox to have an effect, it is advisable to start taking it 24 hours before you go to altitude and continue for at least five days at higher altitude. The recommendation of the Himalayan Rescue Association Medical Clinic is 125 mg. twice a day (morning and night). (The standard dose was 250 mg., but their research showed no difference for most people with the lower dose, although some individuals may need 250 mg.) Possible side effects include tingling of the lips and finger tips, blurring of vision, and alteration of taste. These side effects may be reduced with the 125 mg. dose. Side effects subside when the drug is stopped. Contact your physician for a prescription. Since Diamox is a sulfonamide drug, people who are allergic to sulfa drugs should not take Diamox. Diamox has also been known to cause severe allergic reactions to people with no previous history of Diamox or sulfa allergies. Frank Hubbell of SOLO recommends a trial course of the drug before going to a remote location where a severe allergic reaction could prove difficult to treat.
Dexamethasone (a steroid) is a prescription drug that decreases brain and other swelling reversing the effects of AMS. Dosage is typically 4 mg twice a day for a few days starting with the ascent. This prevents most symptoms of altitude illness. It should be used with caution and only on the advice of a physician because of possible serious side effects. It may be combined with Diamox. No other medications have been proven valuable for preventing AMS.
Acute Mountain Sickness (AMS)

AMS is common at high altitudes. At elevations over 10,000 feet (3,048 meters), 75% of people will have mild symptoms. The occurrence of AMS is dependent upon the elevation, the rate of ascent, and individual susceptibility. Many people will experience mild AMS during the acclimatization process. Symptoms usually start 12-24 hours after arrival at altitude and begin to decrease in severity about the third day. The symptoms of Mild AMS are headache, dizziness, fatigue, shortness of breath, loss of appetite, nausea, disturbed sleep, and a general feeling of malaise. Symptoms tend to be worse at night and when respiratory drive is decreased. Mild AMS does not interfere with normal activity and symptoms generally subside within 2-4 days as the body acclimatizes. As long as symptoms are mild, and only a nuisance, ascent can continue at a moderate rate. When hiking, it is essential that you communicate any symptoms of illness immediately to others on your trip. AMS is considered to be a neurological problem caused by changes in the central nervous system. It is basically a mild form of High Altitude Cerebral Edema (see below).

Basic Treatment of AMS

The only cure is either acclimatization or descent. Symptoms of Mild AMS can be treated with pain medications for headache and Diamox. Both help to reduce the severity of the symptoms, but remember, reducing the symptoms is not curing the problem. Diamox allows you to breathe faster so that you metabolize more oxygen, thereby minimizing the symptoms caused by poor oxygenation. This is especially helpful at night when respiratory drive is decreased. Since it takes a while for Diamox to have an effect, it is advisable to start taking it 24 hours before you go to altitude and continue for at least five days at higher altitude. The recommendation of the Himalayan Rescue Association Medical Clinic is 125 mg. twice a day (morning and night). (The standard dose was 250 mg., but their research showed no difference for most people with the lower dose, although some individuals may need 250 mg.) Possible side effects include tingling of the lips and finger tips, blurring of vision, and alteration of taste. These side effects may be reduced with the 125 mg. dose. Side effects subside when the drug is stopped. Contact your physician for a prescription. Since Diamox is a sulfonamide drug, people who are allergic to sulfa drugs should not take Diamox. Diamox has also been known to cause severe allergic reactions to people with no previous history of Diamox or sulfa allergies. Frank Hubbell of SOLO in New Hampshire recommends a trial course of the drug before going to a remote location where a severe allergic reaction could prove difficult to treat.

Moderate AMS

Moderate AMS includes severe headache that is not relieved by medication, nausea and vomiting, increasing weakness and fatigue, shortness of breath, and decreased coordination (ataxia). Normal activity is difficult, although the person may still be able to walk on their own. At this stage, only advanced medications or descent can reverse the problem. Descending even a few hundred feet (70-100 meters) may help and definite improvement will be seen in descents of 1,000-2,000 feet (305-610 meters). Twenty-four hours at the lower altitude will result in significant improvements. The person should remain at lower altitude until symptoms have subsided (up to 3 days). At this point, the person has become acclimatized to that altitude and can begin ascending again. The best test for moderate AMS is to have the person "walk a straight line" heel to toe. Just like a sobriety test, a person with ataxia will be unable to walk a straight line. This is a clear indication that immediate descent is required. It is important to get the person to descend before the ataxia reaches the point where they cannot walk on their own (which would necessitate a litter evacuation).

Severe AMS

Severe AMS presents as an increase in the severity of the aforementioned symptoms, including shortness of breath at rest, inability to walk, decreasing mental status, and fluid buildup in the lungs. Severe AMS requires immediate descent to lower altitudes (2,000 - 4,000 feet [610-1,220 meters]).

There are two other severe forms of altitude illness, High Altitude Cerebral Edema (HACE) and High Altitude Pulmonary Edema (HAPE). Both of these happen less frequently, especially to those who are properly acclimatized. When they do occur, it is usually with people going too high too fast or going very high and staying there. The lack of oxygen results in leakage of fluid through the capillary walls into either the lungs or the brain.

High Altitude Pulmonary Edema (HAPE)

HAPE results from fluid buildup in the lungs. The fluid in the lungs prevents effective oxygen exchange. As the condition becomes more severe, the level of oxygen in the bloodstream decreases, and this can lead to cyanosis, impaired cerebral function, and death. Symptoms include shortness of breath even at rest, "tightness in the chest," marked fatigue, a feeling of impending suffocation at night, weakness, and a persistent productive cough bringing up white, watery, or frothy fluid. Confusion, and irrational behavior are signs that insufficient oxygen is reaching the brain. One of the methods for testing yourself for HAPE is to check your recovery time after exertion. If your heart and breathing rates normally slow down in X seconds after exercise, but at altitude your recovery time is much greater, it may mean fluid is building up in the lungs. In cases of HAPE, immediate descent is a necessary life-saving measure (2,000 - 4,000 feet [610-1,220 meters]). Anyone suffering from HAPE must be evacuated to a medical facility for proper follow-up treatment.

High Altitude Cerebral Edema (HACE)

HACE is the result of swelling of brain tissue from fluid leakage. Symptoms can include headache, loss of coordination (ataxia), weakness, and decreasing levels of consciousness including, disorientation, loss of memory, hallucinations, psychotic behavior, and coma. It generally occurs after a week or more at high altitude. Severe instances can lead to death if not treated quickly. Immediate descent is a necessary life-saving measure (2,000 - 4,000 feet [610-1,220 meters]). There are some medications that may be prescribed for treatment in the field, but these require that you have proper training in their use. Anyone suffering from HACE must be evacuated to a medical facility for proper follow-up treatment.

Other Medications for Altitude Illnesses

Ibuprofen is effective at relieving altitude headache.
Nifedipine rapidly decreases pulmonary artery pressure and relieves HAPE.
Breathing oxygen reduces the effects of altitude illnesses.
Gamow Bag (pronounced ga� m�f)

This clever invention has revolutionized field treatment of high altitude illnesses. The bag is basically a sealed chamber with a pump. The person is placed inside the bag and it is inflated. Pumping the bag full of air effectively increases the concentration of oxygen molecules and therefore simulates a descent to lower altitude. In as little as 10 minutes the bag can create an "atmosphere" that corresponds to that at 3,000 - 5,000 feet (915 - 1,525 meters) lower. After a 1-2 hours in the bag, the person's body chemistry will have "reset" to the lower altitude. This lasts for up to 12 hours outside of the bag which should be enough time to walk them down to a lower altitude and allow for further acclimatization. The bag and pump weigh about 14 pounds (6.3 kilos) and are now carried on most major high altitude expeditions. Bags can be rented for short term trips such as treks or expeditions.

Cheyne-Stokes Respirations

Above 10,000 feet (3,000 meters) most people experience a periodic breathing during sleep known as Cheyne-Stokes Respirations. The pattern begins with a few shallow breaths and increases to deep sighing respirations then falls off rapidly. Respirations may cease entirely for a few seconds and then the shallow breaths begin again. During the period when breathing stops the person often becomes restless and may wake with a sudden feeling of suffocation. This can disturb sleeping patterns, exhausting the climber. Acetazolamide is helpful in relieving the periodic breathing. This type of breathing is not considered abnormal at high altitudes. However, if it occurs first during an illness (other than altitude illnesses) or after an injury (particularly a head injury) it may be a sign of a serious disorder.

Sources:

Mountain Sickness, Peter Hackett, The Mountaineers, Seattle, 1980.
High Altitude Illness, Frank Hubble, Wilderness Medicine Newsletter, March/April 1995.
The Use of Diamox in the Prevention of Acute Mountain Sickness, Frank Hubble, Wilderness Medicine Newsletter, March/April 1995.
The Outward Bound Wilderness First Aid Handbook, J. Isaac and P. Goth, Lyons & Burford, New York, 1991.
Medicine for Mountaineering, Fourth Edition, James Wilkerson, Editor, The Mountaineers, Seattle, 1992.
Gamow Bags - can be rented from Chinook Medical Gear, 34500 Hwy 6, Edwards, Colorado 81632, 970-926-9277. http://www.chinookmed.com
Additional Reading:

Altitude Illness Prevention & Treatment, Steven Bezruchka, The Mountaineers, Seattle, 1994.
Going Higher, Charles Houston, Little Brown, 1987.
High Altitude Sickness and Wellness, Charles Houston, ICS Books, 1995.
High Altitude Medicine and Physiology, Ward Milledge, West, Chapman and Hall, New York, 1995.
This article is written by Rick Curtis, Director, Outdoor Action Program. This material may be freely distributed for nonprofit educational use. However, if included in publications, written or electronic, attributions must be made to the author. Commercial use of this material is prohibited without express written permission from the author. Copyright � 1998 Rick Curtis, Outdoor Action Program, Princeton University.

Trying to keep my nephew safe. I know the signs.

[gdurkee]

Very good overview. I'd add a couple of things for recognizing HAPE. Many of the cases I've seen happen on day 3. They're sometimes masked on day 2 if the person travels to low elevation (< 9,000) then > 10,000 for day 3, when the acute symptoms often happen. At night, the person will describe feeling more comfortable with the upper body elevated and might need more pillow/jacket. This is because of fluid in the lungs and the need to pool it at the bottom of the lungs to breathe better. It's rare to hear any gurgling breath sounds. The person is almost always significantly slower than the rest of the party, needing to stop and breathe heavily often, bending over with a pack on to do so. Resting pulse is >100 and respiration >20. A very typical case will be someone who hikes maybe 50 - 100 steps then has to stop, bends over and breathes for a minute or so, then continues. Stop! Figure out what's going on and if you suspect HAPE, descend immediately. You really need to get down to 8,000 feet or so but also evaluate that possibility vs. calling for immediate help. As the article says, this doesn't go away.

On the very off chance you have a stethoscope, you can sometimes (but not always!) hear crackles on the right side under the armpit (where the thoracic wall is thinnest). I've heard crackles/rales in only 30% of cases. Go with symptoms you see. It still happens that a passing doctor without experience will diagnose as pneumonia. Ignore them.

Remember that you probably won't see all of these symptoms but will likely see a couple of them -- exhaustion hiking, high pulse and respiration especially.

I've seen a fair amount of HAPE but a very few HACE. The latter will sometimes present with a major unremitting headache; lack of coordination, maybe slurring speech, sleeping long periods and difficulty waking the person up (which also happens with advanced HAPE).

Both of these are medical emergencies and can go downhill really, really fast from the recognizable moderate stages. I'd strongly recommend finding someone with a SPOT or InReach or Sat phone (if you don't have one) and call for help. My last case was a 17 year old male who showed mild symptoms of AMS at the Bullfrog junction (coming up from Vidette). Family camped at Charlotte that night and his symptoms became much worse. They decided to hike out (without coming by the ranger station!). The boy collapsed halfway to Kearsarge when I was called (party passing with a Sat phone). I would estimate he was hours from dying. You could hear the classic gurgling breathing from 10 feet away on approach. Older books give that as a primary symptom but if it's that far advanced, you've missed a lot.

george

[Jimr]

I would go as far to say that audible gurgling = standing at death's door. You're literally drowning in your own fluid.

I've had two hiking partners who experienced AMS on our trip. The first was my Hapkido instructor. We base camped at North Lake campground to acclimate, then hit Desolation Lake the next day. He mentioned a headache once, but is not one to complain (martial artists suck it up and move through pain). I think this type of personality is the most difficult in these situations because they do not reveal what they are feeling.

Once we hit Deso Lk., I started dinner and he didn't want any. He said he felt a bit nauseous and feverish. I felt his forehead and it was slightly warm, but not alarming. The nausea had me concerned. I told him I wanted him to keep me posted on exactly how he was feeling and if thing improved or worsened. I told him I would much rather abort and bring him out of Paiute Pass than to continue on over Alpine Col. and have symptoms go south without an easy exit point. His symptoms improved, but he suffered with a headache throughout the trip.

I took my son on a trip over Paiute pass a few years ago and we base camped at N. Lake campground to acclimate. On the way up, he complained of a headache and, as George described, once he hit around 10K, his energy bonked and after 10 steps or so, would be bent over trying to catch up on his breath. We camped short of the pass and Paiute Lk. He was able to eat and felt better during the afternoon and evening hours, so I thought he was just in mild mountain sickness. He could not get warm during the night. We were cowboy camping, so I pulled out the tent and rocked it over us like a comforter. He still could not get warm, so I put up the tent in the darkness and got him into it. We had decided to bail on the trip, but we would do a quick dayhike to Muriel Lk. since we were so close to him viewing the interior, then we would pack up and head out.

On the way to Muriel, after crossing the pass, I mentioned to him the Master Shuman had problems with elevation when I took him as well (above story). When I mentioned nausea, my son spoke up and said he had been nauseous much of the night and sometimes felt like puking. It was then I realized how all of the pieces fit together and that he was suffering from AMS. We turned around, packed up and got down the mountain.

[rlown]

I'm never afraid to bail on a trip if someone has symptoms that worsen. I demand everyone drinks their water, and/or electrolytes on the trip up, and maybe an aspirin or 2 that first night. We had a party of 3 CDFW women doing a trout survey at Puppet Lk one year, and one of their members didn't come out of the tent the next day due to an extreme headache. They packed her up and went right out the shortest distance; Pine Creek. I've had to bail myself a couple times. That first night at altitude is so important as I age.

[balance]

Thanks rlown

Living at sea level, it takes several days at altitude in the Sierra Nevada for my breathing and heartrate to somewhat normalize. Other than getting winded more easily, I've never had any AMS symptoms during the day. No headaches, nausea, nothing, even when going from sea level on a hard climb to over 12,000' on the first day. Staying hydrated makes a difference.

However, sometimes at night I go to sleep feeling fine, then all hell breaks loose, as noted in the original post:

Cheyne-Stokes Respirations

Above 10,000 feet most people experience a periodic breathing during sleep known as Cheyne-Stokes Respirations. The pattern begins with a few shallow breaths and increases to deep sighing respirations then falls off rapidly. Respirations may cease entirely for a few seconds and then the shallow breaths begin again. During the period when breathing stops the person often becomes restless and may wake with a sudden feeling of suffocation. This can disturb sleeping patterns, exhausting the climber. This type of breathing is not considered abnormal at high altitudes.

This has hit me hard, and caused some bad nights. Waking up in the middle of the night with panic, anxiety, feelings of suffocation. Fortunately I've developed a regimen to deal with this. Drink some water, say a little prayer, and walk around. Why walk around? Through research I've learned this burns up the excess adrenaline that's released into your body, triggered by that feeling of suffocation. I've come to realize that if worse comes to worse while I might not get a lot of sleep, I won't die, which is good to know. There's a way to deal with it. So far so good.

I've also noticed that being in a mummy bag can initiate a sort of claustrophobia/breathing issue stress feedback loop. So I cut the zipper off a sleeping bag and use it as a quilt. I'm more comfortable with that.

Haven't tried Diamox yet. I try to take a night to acclimatize at the trailhead, which seems to help. But my experience with Cheyne-Stokes respiratory problems is highly unpredictable. Sometimes it happens at 8,000', then sometimes it doesn't show up even with a fast and hard East side hike to high altitude on the first day. Very annoying.

Peace.

[rlown]

My friend, I think, suffers from that type of issue and altitude-induced panic. He gets out of the tent regardless of how cold it is and sits outside most of the night in his fleece and rain gear. This next trip, i'm requesting that he take a ground cloth and sleep outside the tent with his sleeping bag zipper unzipped. I wouldn't be happy if someone on my trip suffered just outside the tent without using the sleeping bag in some manner to stay warm.

As my doctor was no help, I get to figure out how I deal with the meds for high blood pressure on this trip. I have a plan. That part is all on me. And gdurkee, I do have a stethoscope. No, I don't carry it with me on trips, but it is fun to listen to ones own heart/lungs or that of a pet.

[gdurkee]

I did snow surveys for years with a guy who snorted like a walrus all night. Worse, he often had Cheynes Stokes breathing. It's never clear if something actually works, but he started taking melatonin and the symptoms seemed (?!) to reduce. Maybe worth trying... .

[rlown]

I'm on Metoprolol (heart rate) and lisinopril (actually works for the BP.) I'm half dosing the Metoprolol at the beginning of this trip. I really need the pulse rate. I already half dose the Lisinopril as it made me faint a few times. I'm good with the approach. If too much info, I don't care. Most here are of my age.

[sambieni]

What is view of diamox?

I actually used it for 2nd time ever last week to get assist me w/ Onion Valley. I know my body by now; it can handle up to 9K, maybe 10K, reasonably well, but over that it needs 3-4 days to feel right. I had a short trip and wanted to be prepared. So I tried it; I let my hiking partner know that I have struggled w/ elevation gain in the past so be prepared to shorten/abort trip with first day over Kearsarge. 2-3 days leading up to the trip were nothing but anxiety inducing, partially just me, but a lot I dedicate to the pills. I was urinating a lot; as expected, but also just felt odd taking it. However, day of the hike, when we set out to trek up to Keasarge, my body handled it well. I am convinced Diamox was the reason; it sorta just opened up my breathing and adjustment as intended. This was my second time taking; years back prepping for Ecuador where we were landing at Quito at 10K and up to 14K 48-72 hours later. I don't recall the nerves and weird energy prior to taking it as i did this time around. I would not storngly recommend, but there may be hikes/moments that it becomes a necessary option/lift for you hike.

I am reminded of my time trekking Kilimanjaro. I never really had headache on the 5 1/2 day approach. But that final night camping around 15K or so; it came on strong. We set off at midnight to summit at dawn. It was a brutal up, tons of nausea, etc. I just kept pushing as a dumb 23 year old would do. My time on the summit is still a major fog/haze. I was wobbly and walked w/ really weak legs/almost drunken. I was super light headed. After 15-30 minutes at summit, once we turned around and headed down, however, I instantly felt amazing. I was literally running/sliding down the mountain. Pretty sure my nearly 40 year old self would not have pushed through that hike - or advised others to do the same - to the summit; glad I was young when I did it.

[rlown]

Consult your doctor. If you or anyone in your party has an altitude issue, you come right back down.