HAPE and HACE: Warning Signs and What to Do

High-altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE) are the two severe forms of altitude illness, and the response to both starts with the same word: descend. HAPE is fluid on the lungs, with breathlessness that is out of proportion to effort and, later, at rest. HACE is swelling affecting the brain, with confusion, drowsiness and loss of balance. Both can become life-threatening within hours, and both are far more likely to be survived when they are recognised early and the person goes down, with oxygen if available.

This guide is for trekkers and their partners, not a substitute for medical training. It sets out the warning signs as the CDC and the UK's NHS describe them, what to do on a Nepal trek where the nearest road may be days away, and how the pieces of the system, the guide, the Himalayan Rescue Association posts and the helicopter, fit together. It follows our altitude sickness basics, which covers mild altitude sickness and prevention, and it assumes you have read the acclimatisation schedule.

How severe illness differs from a bad headache

Mild altitude sickness usually shows up 6 to 10 hours after arriving at a higher altitude, according to the NHS, with headache, reduced appetite, nausea or vomiting, tiredness, dizziness and poor sleep. Mild symptoms usually improve within one to three days if you rest at the same altitude. The NHS advice is not to go higher until you feel better, and, if symptoms are worsening or have not improved after a day, to descend about 300 to 1,000 m.

HAPE and HACE are different in kind. The NHS lists the serious signs: confusion, poor balance or coordination, hallucinations, breathlessness at rest, coughing up frothy or bloody spit, blue or grey lips or skin, and being very drowsy or hard to wake. Anyone with these needs to go down straight away and needs urgent help.

HACE: the brain

The CDC Yellow Book describes HACE as altered mental status, ataxia, confusion and drowsiness. Ataxia means loss of coordination: a trekker who staggers, cannot walk in a straight line or cannot fasten their own jacket. The CDC notes that coma may follow within 12 to 24 hours of the onset of ataxia if it is untreated. Seizures and focal neurological signs are rare and should prompt a search for another cause.

What this looks like on a trek is often not dramatic. A person is quieter than usual, irritable, unreasonable, slow to answer or oddly clumsy. Companions notice before the patient does, because the illness impairs judgement. That is why partners matter: a partner who knows how you normally behave is the best early-warning system.

What to do:

1. Descend immediately, even at night, if it is safe to travel with a headlamp and a companion. Do not wait for morning.
2. Give oxygen if a lodge, clinic or guide has it.
3. The CDC lists dexamethasone as treatment: 8 mg once, then 4 mg every 6 hours. It is a prescription drug and a guide or doctor should direct it. It treats the swelling, it does not replace descent.
4. If descent is not possible, oxygen or a portable hyperbaric device plus dexamethasone can be lifesaving, according to the CDC, but this is a stopgap while evacuation is arranged.

HAPE: the lungs

The early signs of HAPE, in the CDC's words, are chest congestion, cough, exaggerated breathlessness on exertion and reduced exercise performance. It can progress to breathlessness at rest and bloody sputum, and rales, a crackling sound in the lungs, are present in most cases. A partner may hear a wet cough or a rattle with each breath.

The key sign is breathlessness that is out of proportion to what you are doing. If you are struggling for breath while resting, or cannot keep up with a walking pace you managed yesterday, treat it as an emergency until proven otherwise. The CDC says that SpO2 in HAPE is often 50 to 70 percent. A pulse oximeter can help, but treat the reading as supporting information only, and do not use a normal-looking number to override your own judgement and your guide's.

What to do:

1. Descend urgently and with as little exertion as possible. Help the person walk slowly or arrange a porter, a horse or a helicopter. The CDC stresses oxygen, urgent descent and minimal exertion.
2. Give oxygen if available. The CDC says mild HAPE with access to oxygen may be managed with oxygen for 2 to 4 days and bed rest at altitude, but that is a clinician's decision in a setting with oxygen, not a plan for a teahouse.
3. The CDC lists nifedipine, 30 mg sustained-release every 12 hours, as an adjunct for people especially susceptible to HAPE, used with descent and oxygen. It is not a substitute. The CDC states plainly that descent and oxygen are far more effective than medication.

Who is at risk

Anyone can develop either condition at altitude. Risk rises with fast ascent, previous episodes, exertion and a lack of rest days, which is why the standard rule matters. Above 3,000 m the Wilderness Medical Society guidance, as the CDC cites it, is to gain no more than 500 m of sleeping altitude per night and add an extra night for every 1,000 m. The NHS adds a rest day at the same altitude every 3 to 4 days at 3,000 m or more.

Climbing on the day you feel unwell is the most common mistake. On the Everest Base Camp route the plan takes you from Dingboche (4,410 m) to Lobuche (4,940 m) to Gorak Shep (5,164 m), where lodges are far from any road and the walk down to the clinic at Pheriche (4,371 m) is long. On the Annapurna Circuit, Thorong Phedi (4,540 m) is the last stop before the 5,416 m pass; a person who is unwell there should go down to Manang (3,540 m) rather than up. See rest days on Everest and the Circuit.

Help on the trail

The Himalayan Rescue Association runs seasonal aid posts at Pheriche on the Everest route and at Manang on the Annapurna Circuit, with daily altitude talks. Our HRA clinics guide explains what they can and cannot do. A volunteer clinic is not a hospital. If a clinician says "descend" you descend.

Your guide is the second line. A guide who has seen altitude illness will check on you each morning and evening, and you should tell them symptoms honestly rather than "toughing it out". If you are trekking without a guide, agree with your partners in advance who will make the decision to go down and how you will communicate it. Our partners guide covers the conversation.

Evacuation and insurance

Many trekkers who need to descend can walk or be assisted down a few hundred metres, which can be enough. When they cannot, helicopter evacuation is the route out, and it is arranged through your insurer or agency, not through the lodge. Before you travel, check that your policy covers trekking to the highest altitude of your route and helicopter evacuation, ask what the insurer needs from you to start a rescue and carry the policy number and emergency contact on paper and on your phone. Our cost guide lists insurance among the lines people forget.

Practical habits that save lives

• Report symptoms early and honestly. The sentence "I have a headache and I'm a bit dizzy" is enough to trigger a rest.
• Never leave an unwell person alone. Someone with HACE may not realise how ill they are.
• Do not ascend with symptoms. The NHS says to stay put until you feel better.
• Descend if worse or no better after a day. That is the NHS line, and it is conservative on purpose.
• Drink water and avoid alcohol. The NHS recommends staying hydrated and avoiding alcohol while ascending.
• Know your partner's baseline. Ask them to do the same for you.

When a normal day is not normal

A normal acclimatising day includes mild breathlessness on climbs, a slightly poorer sleep and perhaps a mild headache that eases with rest. Breathlessness at rest, a cough that gets wetter, loss of balance and unusual confusion are not on that list. Our guide to what normal looks like day by day at altitude lays out the contrast against the Everest plan.

This article is general information and not medical advice. Ask a doctor or a travel clinic about your own risk and about medicines before you travel.