High altitude pulmonary edema

Background
  • Also known as HAPE
  • Noncardiogenic pulmonary edema due to increased microvascular pressure in the pulmonary circulation
  • Most lethal of the altitude illnesses
  • Occurs in <1/10,000 skiers in Colorado; 2-3% of Mt. McKinley climbers
  • Typical patient is strong and fit; may not have symptoms of altered mental status before onset of HAPE
  • Most commonly noticed on the second night at a new altitude

Risk Factors
  • Heavy exertion
  • Rapid ascent
  • Cold
  • Excessive salt ingestion
  • Use of a sleeping medication
  • Preexisting pulmonary hypertension
  • Preexisting respiratory infection (children)
  • Previous history of HAPE

Clinical Features

Early
  • Dry cough, decreased exercise performance, dyspnea on exertion, localized rales
  • Resting SaO2 is very low for the expected altitude but patients often appear clinically better than their saturation (aids in diagnosis)
  • Easily desaturates with exertion

Late
  • Dyspnea at rest, marked weakness, productive cough, cyanosis, generalized rales
  • Cough generates pink, frothy sputum
  • Tachycardia and tachypnea correlate with severity of illness
  • Altered mental status and coma (from severe hypoxemia)

Differential Diagnosis
  • Asthma
  • Bronchitis
  • CHF
  • COPD
  • MI

High Altitude Illnesses

Pulmonary Edema Types
  • Pulmonary capillary wedge pressure <18 mmHg differentiates noncardiogenic from cardiogenic pulmonary edema[1]

Cardiogenic pulmonary edema

Noncardiogenic pulmonary edema

Evaluation
Chest x-ray of HAPE showing characteristic patchy alveolar infiltrates with right middle lobe predominance.

Workup

Evaluation
  • Clinical diagnosis

Expected SpO2 and PaO2 levels at altitude[2]
Altitude SpO2 PaO2 (mm Hg)
1,500 to 3,500 m (4,900 to 11,500 ft) about 90% 55-75
3,500 to 5,500 m (11,500 to 18,000 ft) 75-85% 40-60
5,500 to 8,850 m (18,000 to 29,000 ft) 58-75% 28-40

Management
High altitude management algorithm.
  • Immediate descent is treatment of choice - minimize exertion
  • If cannot descend use combination of:
    • Supplemental O2 - An oxygen concentrator is often used at high altitude ski resorts after the patient is titrated down to nasal cannula. A portable oxygen tank is used for ambulation. Can completely resolve the pulmonary edema within 36-72hr
    • Hyperbaric bag - (e.g. Gamow Bag). Should not delay descent, if possible.
    • Keep patient warm (cold stress elevates pulmonary artery pressure)
    • Use expiratory positive airway pressure mask
    • Nifedipine 30mg ER q12hr (or 20mg normal-release q8hr)[3]
      • May consider the other medications listed below that are usually used for prevention

Disposition
  • Admission
    • Warranted for severe illness that does not respond immediately to descent
  • Discharge
    • Progressive clinical and X-ray improvement and a PaO2 of 60mmHg or SaO2>90%
  • May re-ascend in 2-3 days if mild-moderate symptoms resolved that only required descent as the intervention

Prevention
  • Nifedipine 20mg q8hr or 30mg ER q12hr while ascending is effective prophylaxis in patients with prior episodes of HAPE
  • Tadalafil 10mg BID 24hr prior to ascent OR Sildenafil 50mg q8hr
  • Salmeterol 125 mcg inhaled BID
  • Acetazolamide 125mg BID for prevention of hypoxia

See Also
  • High Altitude Medicine

References
  1. Clark SB, Soos MP. Noncardiogenic Pulmonary Edema. In: StatPearls. Treasure Island (FL): StatPearls Publishing; October 1, 2020.
  2. Gallagher, MD, Scott A.; Hackett, MD, Peter (August 28, 2018). "High altitude pulmonary edema". UpToDate. Retrieved May 2, 2019.
  3. Luks AM, McIntosh SE, Grissom CK, et al. Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness: 2014 Update. Wilderness & Environmental Medicine. 2014(25): S4–S14)
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