We were in Dingboche when we heard it.
Peaceful Lodge and Restaurant, somewhere in the middle of the night, a couple of rooms down the hall. Though with walls that thin it could have been further. Someone was choking. That was what it sounded like. Frantic, desperate gasps for air, the kind of sound that gets you upright in your sleeping bag with your heart going before your brain has caught up.
Then it stopped. Then it started again.
Eventually it settled, and the building went quiet, and everyone presumably lay there in the dark doing the same arithmetic we were: is that person alright, is someone going to knock on their door, is this something that happens up here, and how would any of us know?
We never found out who it was. We never found out what happened to them the next day.
Here is what we did learn, and it is the thing worth knowing before you sleep above 3,000 meters: that sound is one of the most common experiences on any high trek. It has a name and a mechanism. And there is a version of it that is normal, and a version of it that means you wake your guide immediately.
Why sleep falls apart up high
Sleep at altitude is bad in a way that surprises people who were expecting to be tired enough not to care.
You lie down exhausted after seven hours of walking, and then spend the night surfacing every twenty minutes. Vivid dreams. Waking hot, waking cold, waking for no reason at all. Trips to the toilet in the freezing dark. And in the morning you feel like you were awake the entire night, which is not quite true, but is not far off either.
Part of that is simple. Thin air, cold rooms, a body working harder at rest than it does at home. But the strangest part of it, and the part responsible for that gasping sound, is happening inside your own breathing control.
Your body argues with itself while you sleep
Two systems govern how you breathe. While you are awake they cooperate. At altitude, asleep, they fall out.
The first responds to low oxygen. At 4,400 meters each breath carries a little under 60% of the oxygen it would at sea level, so this system pushes hard: breathe more, breathe deeper, get more in.
The second responds to carbon dioxide, and this is the one that actually runs your breathing while you sleep. When CO2 levels in your blood rise, your brain triggers a breath. It is a beautifully reliable thermostat, and it works without your involvement every night of your life.
The problem is that these two signals give opposite instructions up high.
You breathe hard because oxygen is low. Breathing hard flushes out carbon dioxide. Now CO2 drops below the level your brain uses as its trigger, and the thermostat concludes that no breath is needed. So your breathing slows. Then stops, briefly, for a handful of seconds. Oxygen falls, CO2 climbs back, the alarm goes off, and your body takes a large, urgent, panicked breath to catch up.
That last breath is the sound.
The cycle is called periodic breathing, and it repeats for much of the night: a run of deepening breaths, a tapering off, a pause, then the gasp. From the inside it wakes you with your heart hammering, convinced something is badly wrong. From two rooms away, through a plywood wall, it sounds exactly like someone choking.
It is common above about 2,500 meters and very common above 3,000, on any mountain, in any range. The same chorus plays in the huts on Kilimanjaro, the refugios of the Andes, and tents pitched high anywhere on Earth. On a busy night in a teahouse at Dingboche or Lobuche, it is happening to several people at once.
The part nobody tells you: it does not simply go away
The usual reassurance is that this settles as you acclimatize. That is half right, and the half that is wrong matters.
Your sleep does tend to feel better after the first few nights at a given altitude. But the periodic breathing pattern itself can stick around, and in some people it becomes more pronounced as they acclimatize, because the very adaptation that helps you, a stronger drive to breathe in thin air, is also what feeds the cycle. Climbers who have spent weeks on big mountains still hear it in their tents.
So the honest version is this: expect broken sleep for the first nights at every new altitude, expect it to feel more manageable as the trek goes on, and do not treat the persistence of the pattern as a sign that something is wrong with you.
The line that actually matters
Everything above describes normal. Here is where it stops being normal, and this is the section to remember at 2am in a cold room.
Periodic breathing wakes you, and then it resolves. You sit up, you breathe, within a minute or two you feel fine, and the alarm passes. You are not short of breath while sitting still. You can lie back down.
What does not belong in that category:
Breathlessness at rest that does not settle. If you are sitting upright, awake, doing nothing, and you still cannot get enough air, that is a different problem.
Breathing that gets worse over the night instead of better, especially on a second night at the same altitude.
A cough that develops or worsens, particularly a wet one, or a rattling sound in the chest.
Unusual exhaustion out of proportion to the day, or a sudden drop in how far you can walk.
A headache that keeps building, nausea and vomiting, or a person who seems confused, clumsy, unsteady on their feet, or unlike themselves.
Any of those, at any hour, is a wake your guide situation. Not in the morning. Then. High altitude pulmonary edema and high altitude cerebral edema both progress, both can develop fast, and both are much more survivable when someone competent starts making decisions early. Descent is the answer that works, and your guide is the person who knows how to organize it from where you are standing.
This is worth reading up on properly before you go rather than trying to remember it in the dark. Our guide to what altitude does to your body breaks down AMS, HAPE and HACE, what each one looks like, and why descent is the answer to all three.
The uncomfortable truth of our Dingboche night is that a room full of people, including us, heard something alarming and did nothing, because none of us knew which category it belonged to. Almost certainly it was periodic breathing and the person went on to have an ordinary trek. But we did not know that at the time, and we could not have known.
Learn the difference before you go. Then you get to be the person who knocks on the door, or the person who confidently goes back to sleep.
What actually helps
There is no trick that makes altitude sleep good. There are things that make it less bad.
Ascend slowly, and pay attention to sleeping altitude. Your sleeping height matters more than the highest point you touch during the day. Standard guidance above about 3,000 meters is to keep the increase in sleeping altitude modest from night to night and to build in rest days as you go higher. Walking high during the day and coming back down to sleep is one of the oldest and most effective habits in the mountains, and it is why good itineraries look inefficient on paper. If your trek plan looks fast compared to the standard schedule, that is worth a conversation with your operator before you book, not after you arrive.
Skip the alcohol, especially early. A beer at 4,000 meters is not the same beer it was at home. Alcohol suppresses breathing during sleep, which is the last thing you need on a night when your breathing control is already unstable.
Do not self medicate to sleep. Sedatives can blunt the drive to breathe, and the drive to breathe is doing important work up there. If you are worried about sleep, that is a conversation to have with a travel medicine doctor before you leave, along with any discussion of medication. It is not something to sort out on the trail with whatever a fellow trekker offers you from their bag.
Drink, but sensibly. You lose more fluid than you expect through hard breathing in dry air. You will also be up in the night regardless, so most people find their own balance between hydration and the cold walk to the toilet.
Get warm before you get in the bag. Being cold fragments sleep further. A hot drink, dry base layers to sleep in, and a bottle of hot water in the bag are teahouse standards for a reason.
And set your expectations before you fly. This is the one that costs nothing and helps most. People who know that broken sleep and 2am gasping are normal features of altitude handle them far better than people who lie awake at Dingboche wondering whether they are dying. Half of what makes that night frightening is not knowing. Our complete trek preparation guide covers the rest of what to sort out before departure.
Where fitness fits, and where it does not
Being fit does not protect you from altitude illness. That is worth stating plainly, because it is one of the most persistent misunderstandings in trekking. Fit people get altitude sick. Marathon runners get evacuated. Your body’s response to thin air runs on a different system than your training does. A faster marathon time does not speed up acclimatization.
What training does give you is reserve. Arriving with legs and lungs that can handle a long day means the trek itself costs you less, and you have more left over on the nights when sleep does not come. It also means the days after a bad night are survivable rather than miserable, which on a two week trek is the difference between finishing well and grinding. We’ve written a full guide to high altitude training for trekkers that covers how to build that reserve, and if you live at sea level, our honest guide to altitude training without altitude covers what actually works from flat ground.
That reserve is what our 8-Week Trekking Fitness Plan is built for. It will not acclimatize you. Nothing you do at home will. But it will get you to the mountain with something in the tank.
Back in Dingboche
We still think about that night. Not because anything dramatic happened, but because of how ordinary the whole thing was in hindsight, and how frightening it felt at the time.
Someone a few rooms away had a rough night at 4,400 meters, and probably got up the next morning, ate their porridge, and walked to Lobuche with everyone else. We hope so. We never saw who it was, and we have thought about it every time we have slept high since.
Go up slowly. Learn the difference between the breathing that is normal and the breathing that is not. And when it happens to you, and at some point it will, you will recognize it for what it is instead of lying there in the dark doing the arithmetic we did. If the EBC trek is the trip in your calendar, our essential tips for Everest Base Camp cover the rest of that walk.
This article is for awareness only and is not medical advice. It cannot diagnose anything and it is not a substitute for a professional. Speak to a doctor or travel medicine specialist about your own situation before any high altitude trip, and take altitude symptoms on the mountain to your guide immediately.
