Mastering Medical
USMLE Step 1 · Respiratory

High-altitude pulmonary edema vs High-altitude cerebral edema

How to tell High-altitude pulmonary edema and High-altitude cerebral edema apart when a board question makes them look alike.

Fastest separator

HAPE is lungs: dyspnea, cough, crackles, hypoxemia; HACE is brain: ataxia and altered mental status.

Side by side

High-altitude pulmonary edemaHigh-altitude cerebral edema
Key clue

Altitude-triggered noncardiogenic pulmonary edema with dyspnea, cough, severe fatigue, hypoxemia, crackles, and reduced exercise tolerance.

Altitude-triggered brain edema with severe headache, ataxia, confusion, altered mental status, hallucinations, or coma.

Mechanism

Hypoxic pulmonary vasoconstriction becomes uneven and raises capillary pressure, causing pulmonary edema at altitude.

Hypoxia and impaired acclimatization promote cerebral edema and neurologic dysfunction.

Labs and tests

Cough, crackles, low oxygen saturation, dyspnea at rest, and chest findings point HAPE; descent and oxygen are definitive.

Ataxia and altered mental status after ascent points HACE; descent, oxygen, and dexamethasone are key.

The trap

Both are high-altitude emergencies and can coexist, so do not let dyspnea hide a neurologic exam.

The repair move

For altitude illness, decide whether the first dangerous organ is lung or brain, then descend.

Try a free question

Core

A climber at high altitude develops severe dyspnea, cough, reduced exercise tolerance, hypoxemia, and crackles without primary neurologic findings. Which altitude illness is most likely?

Show answer and explanation

Answer: A. High-altitude pulmonary edema. HAPE is high-altitude pulmonary edema with hypoxemia, dyspnea, cough, crackles, and reduced exercise tolerance; descent and oxygen are key.

Why the other choices are tempting

  • B. HACE is neurologic altitude illness with ataxia and altered mental status.
  • C. Acute mountain sickness alone causes headache/nausea/fatigue without frank pulmonary edema.
  • D. PE can cause hypoxemia and dyspnea but is not specifically triggered by ascent with crackles.
  • E. Viral pneumonia is infectious and not defined by high-altitude physiology.

Flashcards

Tap a card to flip it.

What is the fastest separator for High-altitude pulmonary edema vs High-altitude cerebral edema?

HAPE is lungs: dyspnea, cough, crackles, hypoxemia; HACE is brain: ataxia and altered mental status.

What clue should make you choose High-altitude pulmonary edema?

Altitude-triggered noncardiogenic pulmonary edema with dyspnea, cough, severe fatigue, hypoxemia, crackles, and reduced exercise tolerance.

Quick answers

What is the fastest way to tell High-altitude pulmonary edema from High-altitude cerebral edema?

HAPE is lungs: dyspnea, cough, crackles, hypoxemia; HACE is brain: ataxia and altered mental status.

What is the key clue for High-altitude pulmonary edema?

Altitude-triggered noncardiogenic pulmonary edema with dyspnea, cough, severe fatigue, hypoxemia, crackles, and reduced exercise tolerance.

What is the key clue for High-altitude cerebral edema?

Altitude-triggered brain edema with severe headache, ataxia, confusion, altered mental status, hallucinations, or coma.

What is the common trap with High-altitude pulmonary edema vs High-altitude cerebral edema?

Both are high-altitude emergencies and can coexist, so do not let dyspnea hide a neurologic exam.