Altitude Illness: Acute Mountain Sickness, HACE, HAPE, Prevention, and Treatment Practice Questions

25 multiple-choice questions on Altitude illness: acute mountain sickness, HACE, HAPE, prevention, and treatment for paramedic and EMT students, from Chapter 39 (Environmental Emergencies). Read each question, pick your answer, then tap Show answer to check it and read the explanation.

25 practice questions

1. Altitude illness occurs mainly because at higher elevation:

   1. A. The percentage of oxygen in the air drops
   2. B. Barometric pressure and inspired PO2 fall
   3. C. Nitrogen dissolves into the blood faster
   4. D. Carbon dioxide levels in the air rise
   Show answer

   Answer: B. Barometric pressure and inspired PO2 fall

   The air still contains about 21% oxygen, but lower barometric pressure reduces the partial pressure of inspired oxygen, causing hypoxemia. The oxygen percentage does not change with altitude.

2. High altitude is generally defined as an elevation of about:

   1. A. 1,500 to 3,500 m (4,900 to 11,500 ft)
   2. B. 300 to 900 m (1,000 to 3,000 ft)
   3. C. Above 8,000 m (26,000 ft), the death zone
   4. D. Heights above 150 m (500 ft)
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   Answer: A. 1,500 to 3,500 m (4,900 to 11,500 ft)

   High altitude is 1,500 to 3,500 m, very high altitude 3,500 to 5,500 m, and extreme altitude above 5,500 m. Acute mountain sickness becomes common above about 2,500 m (8,200 ft).

3. The earliest physiologic response to ascending to high altitude is:

   1. A. Increased red blood cell production
   2. B. Increased breathing rate and depth
   3. C. A fall in the resting heart rate
   4. D. Decreased urine output
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   Answer: B. Increased breathing rate and depth

   The hypoxic ventilatory response begins within minutes and raises oxygen levels; red cell production takes weeks. A good ventilatory response helps acclimatization.

4. Acute mountain sickness (AMS) is characterized by:

   1. A. Ataxia with confusion and increasing drowsiness
   2. B. Cough with pink, frothy sputum
   3. C. Chest pain radiating to the left arm
   4. D. Headache with nausea, fatigue, or dizziness
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   Answer: D. Headache with nausea, fatigue, or dizziness

   AMS is a headache plus at least one of GI upset, fatigue, dizziness, or poor sleep after a recent ascent. Ataxia and confusion mean progression to HACE.

5. Symptoms of acute mountain sickness typically begin how long after arrival at a new altitude?

   1. A. 6 to 12 hours
   2. B. 5 to 10 minutes
   3. C. 1 to 2 weeks
   4. D. 3 to 4 weeks
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   Answer: A. 6 to 12 hours

   AMS usually starts 6 to 12 hours after ascent and resolves over 1 to 3 days if the person stops ascending. Immediate symptoms suggest another cause.

6. A skier who flew to a 2,900-m (9,500-ft) resort yesterday has a headache, nausea, and poor sleep. He is alert with a normal gait. The best advice is to:

   1. A. Exercise hard today to speed acclimatization
   2. B. Start nifedipine and descend 3,000 m
   3. C. Rest, avoid ascent, and use analgesics
   4. D. Sleep with a benzodiazepine tonight
   Show answer

   Answer: C. Rest, avoid ascent, and use analgesics

   Mild AMS is treated by not ascending further, rest, fluids, and analgesics such as ibuprofen or acetaminophen, with descent if symptoms worsen. Hard exertion worsens symptoms, nifedipine is a HAPE drug, and benzodiazepines and alcohol depress ventilation during sleep and worsen hypoxemia.

7. A climber with AMS has ataxia when trying to walk heel-to-toe and is confused. This indicates:

   1. A. High-altitude pulmonary edema
   2. B. Mild AMS that will resolve
   3. C. High-altitude cerebral edema
   4. D. Exercise-related hyponatremia
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   Answer: C. High-altitude cerebral edema

   Ataxia and altered mental status mark the progression of AMS to HACE, a life-threatening brain swelling. The heel-to-toe walking test is a simple field screen for ataxia.

8. The most important treatment for HACE is:

   1. A. Rest at the same altitude
   2. B. Oral fluids and ibuprofen
   3. C. Ascent to a higher camp
   4. D. Immediate descent
   Show answer

   Answer: D. Immediate descent

   Descent of 300 to 1,000 m (1,000 to 3,300 ft) is the definitive treatment, supported by oxygen and dexamethasone. Resting at the same altitude allows HACE to progress to coma and death.

9. The drug used to treat HACE is:

   1. A. Dexamethasone
   2. B. Acetaminophen
   3. C. Morphine
   4. D. Nifedipine
   Show answer

   Answer: A. Dexamethasone

   Dexamethasone, typically 8 mg followed by 4 mg every 6 hours, reduces cerebral edema. Nifedipine lowers pulmonary artery pressure and is used for HAPE, not HACE.

10. Acetazolamide helps prevent acute mountain sickness by:

    1. A. Reducing cerebral edema the way a steroid does
    2. B. Increasing ventilation through mild acidosis
    3. C. Dilating the pulmonary arteries directly
    4. D. Increasing red blood cells within hours
    Show answer

    Answer: B. Increasing ventilation through mild acidosis

    Acetazolamide causes bicarbonate excretion and a mild metabolic acidosis that stimulates breathing, speeding acclimatization. Dexamethasone, not acetazolamide, works by reducing edema.

11. A climber 2 days after reaching 4,200 m (13,800 ft) is short of breath at rest, coughing, and has crackles. SpO2 is 68%. The most likely diagnosis is:

    1. A. High-altitude pulmonary edema
    2. B. Acute mountain sickness
    3. C. High-altitude cerebral edema
    4. D. Spontaneous tension pneumothorax
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    Answer: A. High-altitude pulmonary edema

    Dyspnea at rest, cough, decreased exercise tolerance, crackles, and severe hypoxemia out of proportion to the setting define HAPE. HACE causes ataxia and confusion rather than primary lung findings.

12. HAPE is classified as:

    1. A. Cardiogenic edema from heart failure
    2. B. An infectious pneumonia
    3. C. An asthma-like bronchospasm
    4. D. Noncardiogenic pulmonary edema
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    Answer: D. Noncardiogenic pulmonary edema

    Hypoxic pulmonary vasoconstriction is uneven, raising pressure in some capillaries and causing leakage despite normal heart function. Diuretics and nitrates aimed at heart failure are not the treatment.

13. The earliest sign of HAPE is often:

    1. A. Pink, frothy sputum on coughing
    2. B. Central cyanosis and coma
    3. C. Reduced exercise tolerance
    4. D. Wheezing at rest
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    Answer: C. Reduced exercise tolerance

    A climber who falls behind the group and needs longer to recover is the early clue, followed by dry cough and dyspnea at rest. Frothy sputum and cyanosis are late findings.

14. The treatment of choice for HAPE is:

    1. A. Furosemide and continued ascent
    2. B. Descent with supplemental oxygen
    3. C. Bed rest at the current altitude
    4. D. Antibiotics for presumed pneumonia
    Show answer

    Answer: B. Descent with supplemental oxygen

    Descent and oxygen rapidly reduce pulmonary artery pressure and reverse HAPE; nifedipine can help when descent is delayed. Furosemide may cause dangerous volume depletion and is not recommended.

15. When descent is impossible because of weather, a climber with HAPE can be treated with oxygen and:

    1. A. Furosemide to clear the fluid
    2. B. Acetazolamide by mouth
    3. C. A portable hyperbaric bag
    4. D. Large IV fluid boluses
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    Answer: C. A portable hyperbaric bag

    A portable hyperbaric chamber pressurized by foot pump simulates a descent of about 1,500 to 2,000 m. It buys time but does not replace actual descent. Diuretics can worsen volume depletion and are not recommended, acetazolamide helps prevent AMS but does not treat HAPE, and large fluid boluses add to the lung edema.

16. Which person is at greatest risk of acute mountain sickness?

    1. A. One with prior AMS ascending quickly
    2. B. A fit runner who ascends over a week
    3. C. A person who lives at a high altitude
    4. D. One taking acetazolamide as directed
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    Answer: A. One with prior AMS ascending quickly

    Rapid ascent and a history of altitude illness are the strongest risk factors, and physical fitness does not protect. Living at altitude and acetazolamide lower the risk.

17. Above 3,000 m (9,800 ft), a common guideline for preventing altitude illness is to:

    1. A. Ascend 2,000 m per day to limit exposure
    2. B. Sleep at the highest point reached that day
    3. C. Skip rest days to finish the climb sooner
    4. D. Raise sleeping altitude 500 m a day at most
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    Answer: D. Raise sleeping altitude 500 m a day at most

    Increasing sleeping elevation by no more than about 500 m (1,600 ft) per day, with a rest day every 3 to 4 days, allows acclimatization. "Climb high, sleep low" means sleeping lower than the highest point reached.

18. The leading cause of death from altitude illness is:

    1. A. Severe acute mountain sickness
    2. B. High-altitude pulmonary edema
    3. C. High-altitude retinopathy
    4. D. Peripheral edema
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    Answer: B. High-altitude pulmonary edema

    HAPE is the most common cause of altitude-related death, often because the climber continues ascending. HACE is also lethal but less common.

19. A patient with suspected HACE is ataxic and drowsy at a mountain hut. Oxygen is available, but helicopter evacuation is several hours away. You should give oxygen and:

    1. A. Nifedipine in place of dexamethasone
    2. B. Sedation so that the patient can rest
    3. C. Dexamethasone while arranging descent
    4. D. Acetazolamide and wait at the hut
    Show answer

    Answer: C. Dexamethasone while arranging descent

    Dexamethasone reduces cerebral edema and is given in addition to oxygen and descent or evacuation. Sedatives depress breathing and mask the neurologic exam.

20. Nifedipine is used for HAPE because it:

    1. A. Lowers pulmonary artery pressure
    2. B. Reduces swelling in the brain
    3. C. Increases the breathing drive
    4. D. Removes fluid through the kidneys
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    Answer: A. Lowers pulmonary artery pressure

    Nifedipine, a calcium channel blocker, reduces pulmonary vasoconstriction and pulmonary artery pressure. Acetazolamide increases breathing drive; it does not treat established HAPE.

21. A 62-year-old with COPD plans to travel by train to 3,500 m (11,500 ft). He is at increased risk mainly because:

    1. A. Thin air raises the work of each breath
    2. B. His drive to breathe falls at altitude
    3. C. His red blood cell count falls at altitude
    4. D. His baseline hypoxemia worsens at altitude
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    Answer: D. His baseline hypoxemia worsens at altitude

    Chronic lung disease leaves less reserve, so lower inspired oxygen pressure causes more severe hypoxemia. People with significant cardiopulmonary disease may need supplemental oxygen at altitude. Thinner air lowers rather than raises airway resistance, the hypoxic drive to breathe rises rather than falls, and altitude increases red cell production over time.

22. A trekker with mild AMS at 3,800 m (12,500 ft) wants something to help him through the night. Which should he avoid?

    1. A. Acetaminophen for his headache
    2. B. Benzodiazepine sleeping pills
    3. C. Ibuprofen for his headache
    4. D. Oral rehydration fluids
    Show answer

    Answer: B. Benzodiazepine sleeping pills

    Benzodiazepines and other sedative hypnotics, like alcohol, depress the drive to breathe. At altitude this worsens the low oxygen levels and periodic breathing that already occur during sleep, and it can turn AMS into something worse; sedation also hides the confusion of early HACE. Acetaminophen and ibuprofen are the recommended analgesics for AMS headache under the WMS 2024 guideline. Fluids to stay normally hydrated are appropriate, although overhydration does not prevent or treat AMS. If sleep is the main problem, acetazolamide, which improves breathing at night, is the usual choice. (WMS 2024 acute altitude illness update.)

23. A trekker with HAPE should be carried down rather than walked down if possible because exertion:

    1. A. Raises pulmonary pressure and worsens edema
    2. B. Raises his core body temperature too much
    3. C. Uses up glucose needed for the brain
    4. D. Causes nitrogen bubbles to form in blood
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    Answer: A. Raises pulmonary pressure and worsens edema

    Exertion increases cardiac output and pulmonary artery pressure, worsening HAPE, so minimizing effort during descent helps. Nitrogen bubbles relate to diving, not altitude illness.

24. A person who descends to treat AMS or HACE should descend about:

    1. A. 10 to 30 m (33 to 100 ft)
    2. B. As far as the next nearby tent site
    3. C. Down to sea level in each case
    4. D. 300 to 1,000 m (1,000 to 3,300 ft)
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    Answer: D. 300 to 1,000 m (1,000 to 3,300 ft)

    Descent of 300 to 1,000 m usually brings improvement, and descent continues until symptoms resolve. Small drops of a few meters make no physiologic difference.

25. A climber on a mountain has had a headache, now with vomiting, ataxia, and SpO2 of 72%. She also has cough and crackles. You should suspect:

    1. A. Mild AMS alone
    2. B. Both HACE and HAPE
    3. C. HACE with no lung edema
    4. D. HAPE with no brain edema
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    Answer: B. Both HACE and HAPE

    HACE and HAPE often coexist, and hypoxemia from HAPE can worsen cerebral edema. Treatment combines descent, oxygen, dexamethasone, and possibly nifedipine. Her ataxia points to HACE and her cough, crackles, and low SpO2 to HAPE, so neither condition alone explains the picture, and ataxia excludes mild AMS.