What is altitude sickness? Are there different types?
Altitude sickness is a spectrum of disease. The most common form is acute mountain sickness. It generally is related to people who aren’t acclimatized, meaning they typically are not people living in Denver or higher altitudes. Typically, people have to ascend 8,000 feet above sea level — which is roughly the elevation of Summit County — or more to get mountain sickness. People can very easily get to these altitudes in Colorado when they visit the mountains.
Another type of altitude sickness is high altitude pulmonary edema (HAPE). It affects a very small minority of people who travel to a high altitude — around the 1% range.
How common is acute mountain sickness?
It's not that common for Coloradans because we’re acclimatized, but Coloradans who ascend too quickly may get it. Probably less than 10% of residents who travel from Denver up to a Summit County altitude or higher would experience it.
Someone who lives in a state that is closer to sea level and travels to Colorado is much more likely to experience it. For example, if a person living in Chicago flies into Denver and immediately travels to Summit County to go skiing the next day, about 25% of people in that scenario will get acute mountain sickness.
What is altitude sickness caused by?
In general, it is caused by hypoxia, which is low oxygen levels. But the different types of altitude sickness have some different pathways that they’re generated by.
We think that acute mountain sickness is somehow related to a combination of blood vessel dilation and minor swelling in the brain related to low oxygen levels. That is the most cogent theory we have.
High altitude pulmonary edema only happens in a small minority of patients, and it has two mechanisms. One mechanism is that we have proteins that remove fluid that has accumulated in our lung’s air sacs to keep them dry and functioning properly. The proteins use a lot of energy to do this, so when we get to low oxygen levels, the body stops the proteins from doing this to conserve energy. This causes us to not empty our lungs as well as we should, and we call that subclinical pulmonary edema. For most people, it’s very mild and they hardly even notice it, potentially experiencing a slight shortness of breath as they go higher in altitude.
But when this is combined with the second mechanism — which is when the blood vessels in our lungs constrict exuberantly when exposed to low oxygen levels — it is a double whammy that can lead to pressure building up in the lungs, damage to the capillaries, and a leakage of fluid and blood in the lung’s air sacs.
How can someone recognize altitude sickness? What are signs of it?
For people with acute mountain sickness, a headache is the number one symptom. It can be difficult to differentiate a headache due to mountain sickness from a headache related to being dehydrated, so it’s important to stay hydrated. You may also experience insomnia, decreased appetite, and low energy levels. People with acute mountain sickness typically experience symptoms during the first day at altitude. Most of the time, it’s very mild.
People with high altitude pulmonary edema usually experience symptoms on the second or third day at altitude, because it takes a few days to develop. They typically experience shortness of breath, exhaustion, coughing, and sometimes they may cough up bloody sputum. A mild version of these symptoms may lead someone to think they just have a cold, but if they experience moderate or severe symptoms, they will need medical attention.
If someone suspects they have altitude sickness, what should they do?
Generally, if a person suspects they have acute mountain sickness and their symptoms are mild, then they can stay at that altitude and the symptoms will go away in a day or two. Oftentimes, medications like ibuprofen will be fine to manage the headache. Make sure to stay hydrated, limit alcohol intake, and get plenty of sleep and rest.
If a person appears to be confused, stumbling, falling, or showing mental status changes, that may indicate they have a more severe form of altitude sickness, and they need to be medically evaluated.
Similarly, if a person experiences shortness of breath and coughing, and those symptoms progress — and if they are coughing up anything that has a trace of blood in it — then they need to be medically evaluated.
What are some ways people can better adjust to a higher altitude? For instance, if someone has a ski trip planned, what steps can they take to reduce the odds of getting altitude sickness?
If someone is traveling from another state to Colorado, we recommend they acclimatize at an intermediate altitude for a day. For example, if someone is flying into Colorado from Chicago, they may want to consider staying in Denver for a day to get their body used to being at 5,000 feet above sea level before they travel up to the mountains.
If you know you are prone to acute mountain sickness, another recommendation is to not stay in the resorts that have you sleep high on the mountains. The lower altitude you sleep at, the less likely you are to get mountain sickness. They can also pick a lower altitude ski resort.
For people who’ve experienced severe symptoms of acute mountain sickness during a previous trip, I recommend they talk with their primary care doctor about potentially getting preventative medications to prevent mountain sickness.
What would you most like for people to know about altitude sickness?
It’s manageable, and very few people get severely ill. If you suspect something is not right and your symptoms are getting worse, go get evaluated by a medical provider.
For people who have previously visited Colorado and got altitude sickness, they may think that they can’t come back here again. That’s not true. It just means that they have to change their ascent pattern, not come up the mountain as quickly, and talk with their doctors about preventative medications. They can definitely come back and have a successful and fun vacation — they just have to prepare a bit more.
