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 with mortality approaching 50% if descent is not completed in a timely manner [1]
  • 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

Pathophysiology

  • Multiple pathways but thought to be due to an exaggerated pulmonary artery pressure elevation in response to hypoxia [2] and the following hypothesis:
    • Breakdown of the alveolar/endothelial barrier leading to increased pulmonary vascular endothelial permeability
    • Normal wedge pressure, which distinguishes this pathophysiology from heart failure [3]
    • Increased intra-cranial pressure which can lead to pulmonary edema [4]

Clinical Features

Early

  • Dry cough, decreased exercise performance, prolonged exercise recover time, 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

Differential Diagnosis

High Altitude Illnesses

Pulmonary Edema Types

Pulmonary capillary wedge pressure <18 mmHg differentiates noncardiogenic from cardiogenic pulmonary edema[5]

Evaluation

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

Workup

Evaluation

  • The Lake Louise Consensus Definition of HAPE[6]
    • At least two of the following symptoms:
      • Dyspnea at rest
      • Cough
      • Weakness or decreased exercise performance
      • Chest tightness or congestion
    • As well as two of the following signs:


  • Clinical Severity Grading [7]
Grade HR RR Symptoms
I < 100 < 20 Dyspnea on exertion; can perform light activity
II 110-120 20-30 Dyspnea on slight effort; cannot perform light activity, cough, dyspnea at rest
II 121-140 31-40 Severe dyspnea, recurrent productive cough, wheezing, cyanosis
IV >140 > 40 Stupor, coma, unable to stand/walk, severe cyanosis, blood copious sputum

Expected SpO2 and PaO2 levels at altitude[8]

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)[9]
      • May consider the other medications listed below that are usually used for prevention


Medication Dosing

Nifedipine 30mg ER q12hr (or 20mg IR q8hr) PO

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

  • Slow ascent at a rate no more than 300-350m (1000ft) per day above 2500m (8000ft)[10]
  • 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
  • Dexamethasone 8mg PO BID[11]

See Also

References

  1. ↑ Lobenhoffer HP, Zink RA, et al. High altitude pulmonary edema: analysis of 166 cases. In: Brendel W, Zink RA, editors. High Altitude Physiology and Medicine. New York, NT: Springer-Verlag; 1982. pp. 219–231
  2. ↑ Bärtsch P. High altitude pulmonary edema. Med Sci Sports Exerc. 1999;31(1 Suppl):S23-27.
  3. ↑ Hultgren HN, Lopez CE, Lundberg E, Miller H. Physiologic studies of pulmonary edema at high altitude. Circulation. 1964;29(3):393-408.
  4. ↑ Ducker TB, Simmons RL. Increased intracranial pressure and pulmonary edema. 2. The hemodynamic response of dogs and monkeys to increased intracranial pressure. J Neurosurg. 1968;28(2):118-123.
  5. ↑ Clark SB, Soos MP. Noncardiogenic Pulmonary Edema. In: StatPearls. Treasure Island (FL): StatPearls Publishing; October 1, 2020.
  6. ↑ Sutton JR, Coates G, Houston CS, eds. Hypoxia and Mountain Medicine: Proceedings of the 7th International Hypoxia Symposium, Held at Lake Louise, Canada, February 1991. 1st ed. Pergamon Press; 1992.
  7. ↑ Marticorena E, Hultgren HN. Evaluation of therapeutic methods in high altitude pulmonary edema. Am J Cardiol. 1979;43(2):307-312.
  8. ↑ Gallagher, MD, Scott A.; Hackett, MD, Peter (August 28, 2018). "High altitude pulmonary edema". UpToDate. Retrieved May 2, 2019.
  9. ↑ 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)
  10. ↑ Rosen JM. High Altitude Disease in Adults. www.uptodate.com. Version 14.1:2005. (On line review and treatment guidelines)
  11. ↑ Maggiorini M, Brunner-La Rocca H-P, Peth S, et al. Both tadalafil and dexamethasone may reduce the incidence of high-altitude pulmonary edema: a randomized trial. Ann Intern Med. 2006;145(7):497-506.
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