PODCAST Altitude Illness Myths with Dr. Andrew Luks
Season 6 | Episode 7
Joe McIntrye (Host): Welcome to another episode of the Merck Manuals Medical Myths podcast. On this show, we set the record straight on today's most talked about medical topics and questions. I'm your host, Joe McIntyre, and on this episode we're heading for the mountains. Literally, if you've ever taken a ski trip, gone hiking in Colorado or even flown into a high altitude city, you've probably heard warnings about altitude sickness. But is it really something only out-of-shape travelers get? Can you power through it if you're tough enough? And does chugging water or skipping caffeine make a difference? There's a lot of misinformation about altitude sickness, and getting the facts wrong can actually put people at serious risk. To help us separate myths from medicine, we're joined by Dr. Andrew Luks, a board-certified physician and professor of pulmonary and critical care medicine at the University of Washington School of Medicine. We'll discuss what altitude illness actually is, how to spot it early, and what really works when it comes to prevention and treatment. Dr. Luks, thanks for joining us.
Dr. Andrew Luks: Great. Thanks very much for having me.
Host: Of course, of course. So maybe you can start with a bit of an explainer. What exactly is altitude illness and how does it differ from just feeling winded at high elevations?
Dr. Luks: Acute altitude illness refers to a series of problems that people can develop anywhere from the first one to five days after getting up to certain elevations at high altitude, and it can range from mild illness to potentially really serious life-threatening problems. It's a little different than being winded with physical exertion at high altitude in the sense that being winded with physical exertion is something that's going to happen to nearly everyone upon ascent to high elevation just simply because of the lack of oxygen in the environment. Exercise is more difficult than it is at sea level regardless of whether you're in good shape or not particularly good shape. So that's going to happen to everyone, but the acute altitude illnesses are only going to happen to a select number of individuals who get up to high elevations.
Host: Is there a specific altitude where people generally start to feel the effects of altitude sickness? I'm based in Philly and we're pretty much at sea level, so I don't get to experience it that often, but what is that altitude if there is one?
Dr. Luks: So there is generally thought to be a threshold that if you travel above that altitude, you're at risk for developing acute altitude illness, and that threshold is generally about 8,000 feet or higher for the majority of people. There are some folks who are extremely susceptible to acute altitude unless you might actually get sick at lower elevations around like 6,000 to 8,000 feet. But it's also important to remember that the response to high altitude varies significantly from person to person. And so while the average person is at risk once they get up above 8,000 feet in elevation, some people don't get sick until they get up above 10 or about 12,000 feet in elevation and some people just won't have any problems at all. Regardless of how high it is that they're going.
Host: Are there different types of altitude illness and how severe can they really get?
Dr. Luks: Yeah, there are actually three specific forms of what's referred to as acute altitude illness. The first is acute mountain sickness or AMS for short. The second is high altitude, cerebral edema or HACE for short. And then the third is high altitude pulmonary edema or HAPE for short. So acute mountain sickness is by far the most common problem that happens to people who travel to elevations of 8,000 feet and above. And on average it's the least severe of all three problems. In general, people who are developing AMS, they have a headache plus one or two other symptoms such as the fact that they're profoundly fatigued. They have this kind of persistent lightheadedness or dizziness, they're sick to their stomach, maybe even vomiting in some cases. High altitude cerebral edema or HACE refers to a swelling of the brain. And because the brain resides within a fixed space that's defined by the cranium, when the brain swells, it has nowhere to go.
So the pressure builds up within the cranium and that leads to neurologic dysfunction. And in the early phases of high altitude cerebral edema, what you have are people are starting to the more confused they may have problems with what we refer to as ataxia or clumsiness. So they're having a little, like if you ask them to walk, for example on a straight line heel to toe, they would have trouble doing that or they have trouble coordinating other types of activities. And as cerebral edema gets worse, so the neurologic problems will get worse, so people can become very sleepy and difficult to arouse, and eventually if it's not recognized and treated properly, they can lapse into a coma. High altitude pulmonary edema is a really different problem altogether. What HAPE involves is a fluid buildup the lungs, and when that fluid builds up in the air sacks of the lungs, it makes it difficult to move oxygen from the environment through the lungs into the bloodstream.
So people will start having a lot of respiratory problems. The earliest thing that you see in high altitude pulmonary edema is a person who early on in the trip might not have had any difficulty keeping up with their group and with the physical exertion that they're doing at high elevation, but all of a sudden they're starting to fall behind. They can't keep up, they're needing more frequent rest breaks. On those rest breaks, it's taken a long time for them to recover. They may even have a dry cough in some situations. And as that gets more severe, that breathlessness becomes present with much simpler activities like walking on flat ground, going to the bathroom or changing their clothing. And then in the most severe cases, these people are just out of breath. At rest, the color looks terrible. They often have cyanosis or bluish discoloration of their lips and their fingertips, and they can even develop a lot of confusion as well if their blood oxygen levels are severely low. And then another concerning sign you'll see in these cases is that cough, which in the early phases of HAPE may just be dry. In these more severe stages, people are coughing up this pink, frothy looking sputum, and that's a kind of harbinger of the fact that they're in a really dangerous situation.
Host: Yeah, some of these are pretty scarier here. So are there any early warning signs that people should look out for as they think about altitude sickness or how to avoid it if they're in high elevation?
Dr. Luks: As I mentioned before, I mean the most common problem that people are going to develop when they get up to high elevation is they're going to develop acute mountain sickness. It's way more common than either HACE or HAPE. So people need to be on the lookout for that. And the harbinger of that is that they develop a headache and they're otherwise just not feeling great following ascent. If you develop a headache following ascent to high elevation, it's time to kind of dial back things, stay put in elevation and start thinking about whether this could be altitude illness or something else. The warning signs, it's something more severe is going on would be in the case of HACE that all of a sudden what was just a headache is now starting to include other signs of neurologic dysfunction. So the person's confused, they're asking the same questions over and over again.
They don't know where there are, they may be hallucinating. And then if you see someone who's kind of staggering around or looking clumsy on their feet, that's a particularly concerning sign. And then high altitude pulmonary edema can be a little bit hard to tease out in the early stages because as we mentioned at the very beginning of the podcast, everyone who goes up the high elevation and exerts themself is going to feel really out of breath, whether they're in great shape or not in particularly good shape. It's just a feature of exercise when you first get up to high elevation. But the key thing when people are having kind of the normal breathlessness at high elevation is that when they stop and take a break within just 30 seconds to a minute, they feel fine again, their breathing feels good, they're able to talk at a normal conversational pace.
When the group is ready to go, they're ready to shoulder their pack and head on their way, and they're not having trouble keeping up with the rest of the group. What's going on in HAPE is different. They're needing more frequent breaks, they're having trouble keeping up. And it's on those breaks, they're not recovering within 30 seconds to a minute, it's taking much longer. And even when the group is ready to go and head off again, they're like, wait, wait, I need more time. And then certainly if anyone's having a lot of breathlessness with very simple activities, and that's a clear sign, that's something's going on.
For each of those stages, whether it's a simple headache or as it gets more severe, maybe at each stage, what should someone do if it's just a headache? Should they sit down and relax as it gets more severe? Should they go to the hospital? Maybe tell our listeners what they should do at each of those intervals of symptoms there?
Yeah, I think the response kind of depends to some extent on where you are. Are you in a well-resourced resort community like one of the ski resort areas in Colorado or are you trekking around in some remote valley in Nepal or Karu, for example? But a general principle is that if someone's developing signs and symptoms of acute mountain sickness, they should really stop ascending in elevation. They should stay put. They should try to rehydrate themselves to get rid of any element of dehydration, which can look and feel a lot like AMS. They should take some ibuprofen or acetaminophen to try to treat the headache, maybe something for nausea. And generally, if all you have is AMS stopping ascending and doing those conservative measures is going to be sufficient for most people. And then due time the symptoms are going to resolve and they should be good to continue on again.
But the key principle is don't go any higher in elevation. If someone's developing signs of high altitude cerebral edema or high altitude pulmonary edema, those are things that definitely warrants a much more immediate attention. If someone's in a well-resourced ski resort community or even often the far reaches of the mountains, like in the Nepal for example, there are some areas on the trekking circuit where there are medical clinics like in the village of Periche on the Everest base camp circuit or the village of Manang on the Annapurna circuit. Someone needs to get to those health facilities promptly. If you are in a more remote setting far, far away from any medical resources, the most important thing is to send those people down to a lower elevation. And how far you descend, it's really as far as you can get in a safe manner. And a key principle about descending in those situations is never send the person who's ill down alone, they should go with someone who can accompany them. You can imagine if someone had high altitude cerebral edema that was developing and you send them down on the trail alone, if they're staggering around, they could easily trip and fall and cause much more serious problems in addition to the HACE.
Host: You mentioned a little bit earlier that pretty much everybody is susceptible to this, but do younger or healthier people have an advantage or is kind of everyone equally at risk?
Dr. Luks: I generally approach it as everyone is equally at risk. You'll see some studies in the medical literature that have tried to tease out whether the susceptibility to acute altitude illness varies with age, but I think there's a lot of methodological problems with those studies, and I wouldn't rely on them and use that to counsel people to ascend at different rates or do different things to prevent these problems when traveling to high altitude. So I think everyone needs to be treated equally in this regard. And I think a really important thing for people to understand is I think one of the myths that's out there is that if you're in great physical shape, you're the triathlete, the marathon runner, the ultra distance runner, you're protected against one of these three forms of acute altitude almost. And that's just wrong. The average person who's in middling shape is going to have the same susceptibility as the great athlete. And I think to some extent this makes couch potatoes the world quite happy because they see these people who usually would be putting them the shame running and hiking up the trails, and now they're doubled over and having the same symptoms of acute altitude almost. Or maybe they're doing fine while this great athlete has actually doubled over and having problems.
Host: Yeah, I think we hear about that a lot with mostly with sports in Denver or in Mexico City where there's cities with higher elevation that it does impact, especially visiting teams or visiting people who are not used to that high elevation. Even if you're a world-class athlete, you could be impacted by this.
Dr. Luks: That's absolutely correct. If you live at low elevation and you ascend too quickly to high elevation, you're at risk for the same problems regardless of your state of physical fitness.
Host: Does this impact people with asthma or COPD more? Are they more at risk?
Dr. Luks: Yeah, this is a question that's come up quite a bit, and people have thought about this not only with regards to asthma and COPD, but other common medical conditions like hypertension, diabetes, heart disease, for example. And I think in the end, the risk of developing the acute altitude illnesses themselves doesn't differ based on what your underlying medical history is. So in other words, having asthma or COPD does not necessarily predispose to developing the three forms of acute altitude illness. Now that doesn't mean that you can't get into trouble with your asthma or your COPD or your diabetes when traveling at high elevation. Problems can certainly develop with each of those and other diseases at high elevation, but I don't think the risk of acute altitude illness itself, in other words, the risk of developing AMS, HACE or HAPE is different based on whether or not you have those medical problems.
Host: Does drinking lots of water, making sure you're super hydrated, does that have any real impact on preventing the impacts of elevation on your body?
Dr. Luks: So I actually think it's this issue about drinking lots of fluids at high elevation and the fact dehydration predisposes to AMS is another one of these myths that persists out there amongst the lay public. It turns out that the risk of dehydration is actually pretty high when you get up to high elevation. And that's for a couple of reasons. The first is we urinate more upon ascent to high elevation. And then the second thing is we have a lot more of what's referred to as insensible fluid losses from the body. So the humidity goes down a lot as you go up into elevation. So it's easy to lose more of your body's fluid through sweating. We're also breathing a lot more at high elevation, so we're losing a lot of moisture through our respiratory tract. And so because of all those problems, it's really easy to become dehydrated at high altitude, particularly if you're performing physical activity.
And then the problem is that the symptoms of dehydration are pretty similar to the symptoms of acute mountain sickness. People can have a headache, they feel punky and they have no energy at all. And so you feel the same, but it's really a different problem. So by drinking an adequate amount of fluids, what you're trying to do is to prevent dehydration, whose symptoms are going to mimic those of AMS and prevent the confusion of am I sick because of the altitude and therefore I need to descend. Or do I simply just need to drink some more fluids? I'm going to be fine. And I think what you really want to avoid doing when traveling to high altitude is overdoing it on the amount of fluids. I think sometimes people with that myth in the back of their mind, they just drink tons and tons of fluids way more than they need to. And I think what you really should be doing is drink to thirst, right? And if you're urinating with a moderate frequency and your urine looks relatively clear, you're generally doing pretty good on keeping up with your hydration. There's no need to overdo it.
Host: Speaking of consuming too many liquids, what impact does drinking alcohol have when you're at altitude?
Dr. Luks: Alcohol is something people need to pay attention to at high elevation. I think as in regular life, moderate consumption is probably going to be okay. What I think you want to avoid, particularly in the early stages of a trip to high altitude is really high levels of alcohol consumption, particularly at night. You really just don't want to tie it on and go on a big binge of alcohol. And the reason are a couple of fold. One is alcohol increases the risk of dehydration, which can make people feel poor in and of itself, and again, make you think maybe I have acute altitude illness. And then the other risk for people when they drink very heavily is that quite often they have a hangover in the morning. And guess what? A hangover is going to feel a lot like acute altitude illness and may prompt someone to descend to lower elevation to deal with that problem when in fact that wasn't going to be necessary. I think the other concern about drinking heavy amounts of alcohol, particularly at night before people go to bed, is alcohol can suppress your respirations. And by decreasing your breathing at night, it's going to decrease the oxygen levels in your blood during sleep, which can kind of spark along some of these acute altitude illnesses. A glass of alcohol is fine and anything in moderation at high elevations generally need be okay, but I think you really need to avoid the heavy consumption.
Host: Now you mentioned preparing too much with hydration. Are there any other common mistakes that travelers make when preparing for a ski trip, hike, climb at a high altitude, anything that you've heard over and over again?
Dr. Luks: The biggest mistake that people make is related to the main risk factor for developing one of the three main forms of acute altitude illness. So the main reason that people get sick when they go to high elevation is pretty simple. It's that they go too high, too fast. And by too high, too fast, I don't mean that their hiking pace is too quick on the trail. It means that the rate at which they're increasing the elevation at which they're staying or sleeping is far too great for what their body can tolerate at high elevation. So in terms of people planning their trips, the biggest mistake they make is that they go too high too quickly at the beginning. And I can give you a couple examples of this. So say Joe, you're going to be flying out to a ski resort area in Colorado. So a big mistake for you would be to fly into Denver, drive up to Vail, and that afternoon, think I'm going to go hit the gondola chair and get up to 13,000 feet in elevation to get in a couple of runs.
Whereas the better approach would've been, huh, I think I'm going to go from Denver to Vail, but I'm going to hang out that day and just chill in the lodge or my Airbnb and just sit tight, let my body acclimatize to the elevation the next day, I'll start going up to higher elevations and maybe hit the highest elevation from my ski trip on the second or third day as my body starting to acclimatize. In another setting, I think when people are trekking at high elevation, it's important to pay attention to the altitude at which they're sleeping and raising that sleeping altitude at an appropriately slow rate. And what's generally recommended is once you get above about 2,500 to 3,000 meters in elevation, so roughly like 8,500 to 10,000 feet in elevation, you shouldn't increase the elevation at which you're sleeping by more than about 300 to 500 meters or about a thousand to 1,500 feet per night.
And every three to four days you want to throw in a rest day and stay at the same elevation for at least a second night. And the purpose of all this is just to give your body time to adjust to the environment to do what we call acclimatize, which markedly reduces the risk of acute altitude illness. So in a trekking situation or a climbing situation, a big mistake that people often make is that they just do that too quickly. So they decide, ah, it only took us three hours to get to this camp. There's four hours of daylight left. We should just push on and go another thousand feet higher. And by doing that too much, they increase the risk of acute altitude illness. But, I think it's also important to recognize that while these guidelines are out there for what people should do, as I mentioned earlier, the risk of acute altitude illness varies significantly from person to person.
And the people who really need to be the most cautious are the people who are what we refer to as altitude naive. They've never been at high elevation before. They don't know how their body's going to respond. So in their situations, it's worth it to just kind of take it slow plan, a slow ascent profile, give your body time to acclimatize. But for people who spend a lot of time going to the mountains and in particular going up to high elevations, these people start to learn their personal tolerances and they know what their body's able to tolerate. So through repeated trips to the mountains, someone may learn, yeah, I can actually go and sleep at 11,000 feet on my first night at high elevation coming from sea level, and I tend to do just fine. And I know that if I get up to thousand feet or higher, that's when I start having problems.
So that person can deviate from the general guidelines that are out there, but it's based on knowing their body and how their body responds. I think where the challenge often comes in is if you're traveling as part of a larger group and you don't know everyone's personal tolerances of the hypoxia at high altitude. You really need the plan for the slowest people in the group or for the unknown of some people who had never been at high elevation before. Because if you say, well, I do great, so you're going to be fine and you should just come along with me, that approach may not be good for that other person and they may end up getting pretty sick.
Host: All great tips for acclimating to elevation here. What about prevention? Is there a way to physically train yourself to prevent it? I know there are some tools or some exercise things out there that limit your oxygen. Do those actually work? Can you actually physically train to prevent this?
Dr. Luks: There's two types of prevention I think to think about in this regard. There's prevention that you might do before your trip and then there's prevention that you can do on your trip itself. So for prevention on a trip itself, by far the most important thing slowing down the rate of ascent. And as I mentioned before, if you're getting up above about 8,500 to 10,000 feet in elevation, you want to make sure that you're not increasing your sleeping elevation by more than about a 1,000 to 1,500 feet per night and throwing in those rest days every couple of days. And the reality is, if you're trekking, the villages are not laid in at night a thousand foot intervals. So occasionally you have to make a 2,000 foot jump in your sleeping elevation. There's no way to avoid that, but you build in a rest day before or the end so the average ascent rate over that early period of your trip fits what the guidelines are saying. Another important preventive step for people once they're out there is sometimes it's indicated to use pharmacologic prophylaxis and are they use take medications in order to prevent acute altitude illness. And the main thing that people use is a medicine called acetazolamide take 125 milligrams twice a day, and that's very effective at reducing the risk of acute altitude illness. There are some other alternatives out there for people who don't tolerate acetazolamide, but in general, it's a well tolerated effective medication, but people have had high altitude pulmonary edema in the past or HAPE, then they should be using a medication called Nifedipine. It's a calcium channel blocker, which reduces the blood pressures in the lungs and interferes with the processes that are causing the fluid buildup.
But if someone's never had HAPE before, then there'd be no reason for them to use Nifedipine. So the average person, if they're going to use pharmacologic prophylaxis, it's going to be with acetazolamide. In terms of things that people can do before heading off on a trip, there's not a ton that's going to be feasible for the average person who's planning a ski trip to Colorado. I do think it is important to get in good physical shape, particularly if your trip is going to involve a lot of physical activity like hiking or climbing or back backcountry ski touring, not because it's going to protect you against acute altitude illness, but as I mentioned before, physical work is difficult when you get up to high elevation. And so the better shape you're in, the better you're going to be able to tolerate the physical challenges of exercising at high altitude.
I think what's becoming more popular these days, particularly amongst people who are climbing at very high elevation, so these are peaks like Denali or Aconcagua or some of the 8,000 meter peaks like Mount Everest or K2, some people are starting to use these devices known as hypoxic tents to do a strategy that's often referred to as pre acclimatization. So what they're doing is in the weeks leading up to their eventual climbing expedition, they are exposing themselves to hypoxic conditions inside these tents. And the way that the majority of people are using it is they have this tent that fits over their bed in the room in which they sleep, and during the night they're sleeping in hypoxic conditions, simulating high elevations. And if you do that for a sufficient number of hours per night over a sufficient number of weeks ahead of an expedition, that can actually lead to some lasting acclimatization that helps 'em when they're on the mountain.
Some people are actually using this for exercise training as well. Training either using a mask over their face and they're breathing a hypoxic gas mixture or exercising in some large cubicle or even in an entire room that's been outfitted to provide these hypoxic conditions. These systems are somewhat expensive. If you're going to be doing a ski tour and just your regular family ski trip for a week to Colorado, do you really want to spend four weeks sleeping at night in one of these tents? I'm pretty sure your significant others not going to appreciate that. And so I think for the average person doing the standard high altitude trip that most people do, these tents are probably not necessary. But I think for people who are doing bigger, more committing expeditions at the extremists, at elevation, they're totally worth considering.
Host: Dr. Luks, this has been fantastic so far. If there's one thing you want to leave our listeners with or one myth you'd love to see disappear for good, anything that comes to mind as we close out here?
Dr. Luks: I think that there was one message I wanted to leave for people as they're planning trips to high elevation. It's to understand that the phrase I often use is the altitude wins. So if you're traveling at high altitude and you feel sick and you have headache and the other classic symptoms of acute mountain sickness, or you're developing some early signs of cerebral edema or pulmonary edema, you have to listen to your body and do the appropriate things to manage these problems. The altitude doesn't care how strong of mind you are, how strong of heart you are, and how much time and money you've invested in endeavor. If you're sick, it's only going to get worse if you try to go higher in elevation. So you have to stay put, maybe descend, but most importantly have to listen to your body and treat the problems accordingly.
Host: Dr. Luks, this has been a fantastic conversation. Really, really appreciate your time. If our listeners are looking for more information about altitude sickness, where should they go?
Dr. Luks: I think there's some good resources out there that people can look at. So the Wilderness Medical Society has published guidelines for the prevention diagnosis and treatment of acute altitude illness, which are relatively easy to access. There are also some pretty good resources out there in the internet from the UIAA medical condition, which puts out a similar set of guidelines. So I think with some good searching, people are able to find some useful resources that are out there. And then of course, they can always look at merckmanuals.com as well.
Host: Dr. Luks, thank you so much for joining us on the Merck Manuals Medical Myths podcast. As we close out, I'll let you leave our listeners with the final word.
Dr. Luks:Sounds great. I appreciate you having me today. And just remember that medical knowledge is power and people should pass it on.
