HAPE EVALUATION

HAPE is life threatening and early diagnosis is critical. The international diagnostic criteria for HAPE are a combination of two signs and two symptoms. The symptoms are dyspnea at rest, cough, decreased exercise tolerance or weakness, and chest tightness or congestion. The earliest symptoms are commonly decreased exercise tolerance and dyspnea at rest. Signs include crackles or wheezing in at least one field. Central cyanosis, tachycardia, and tachypnea.

Risk factors for HAPE include pulmonary arterial hypertension, previous history of HAPE (50-60% risk of recurrence after a first HAPE episode), pulmonary infection, PFO, and use of respiratory depressants. HAPE presents in isolation from AMS/HACE in 50% of cases and will often present on the second night of higher sleeping altitude exposure.3 Development of disease after 4 days of stable altitude exposure is unusual. Disease progression can present as fever, increasing tachycardia, tachypnea, fatigue, productive cough, hypoxia/cyanosis, and hypoxic encephalopathy. Physical exam findings can include rales, particularly in the right mid-lung fields. SpO2 readings will be lower than expected for a given elevation. Differential diagnoses to consider include asthma, chronic obstructive pulmonary disease, heart failure, bronchitis, myocardial infarction, pneumonia, pulmonary embolism, pneumothorax, and trauma.3,17

HAPE PREVENTION

Mission planning, pre-acclimatization strategy, nutrition, and hydration are discussed above for all HAI and will mitigate incidence and severity of HAPE. Identify those at high risk of developing HAPE, particularly those with risk factors for HAPE participating in aggressive ascent profiles with limited pre-acclimatization.

Slow ascent rate is more critical for those at high risk of HAPE. These individuals should ascend no faster than 350M sleeping elevation per night.

Nifedipine: For individuals at high risk of HAPE, prophylaxis with nifedipine extended- release formulation 30mg orally every 12 hours or immediate-release formulation 20mg orally every 8 hours, beginning on the day of ascent is recommended. Prophylaxis should be continued for 7 days at maximum altitude and can be discontinued upon descent.3,17

Phosphodiesterase inhibitors: For individuals at high risk of HAPE who are not candidates for nifedipine, prophylaxis with tadalafil 10mg orally every 12 hours or sildenafil 50mg orally every 8 hours, beginning on day of ascent is recommended. Do not use phosphodiesterase inhibitors in combination with nifedipine due to risk of hypotension. Prophylaxis should be continued for 7 days at maximum altitude and can be discontinued upon descent.3,17,38

Dexamethasone: There is weak evidence showing benefit of dexamethasone in preventing HAPE and the mechanism is poorly understood. Thus, if patients are at high risk of HAPE and are not candidates for nifedipine or a phosphodiesterase inhibitor, consider prophylaxes with dexamethasone 8mg orally every 12 hours, beginning on day of ascent. Prophylaxis should continue until at a stable altitude for two days.3,17,38

Acetazolamide: No robust data exists supporting the use of acetazolamide in HAPE prevention; however, the physiologic response to acetazolamide and acclimatization likely leads to a benefit in reducing severity of HAPE.17,39 Patients at risk of HAPE are probably also at risk of severe AMS/HACE. Thus, patients at high risk for HAPE should be on prophylactic acetazolamide. See AMS prevention recommendation.

Salmeterol: Inhaled salmeterol has been shown to decrease HAPE risk up to 50% in susceptible individuals. The studies utilized 250mcg doses which are not standard. Inhaled salmeterol should not be used for HAPE prevention.

HAPE TREATMENT

Descent: HAPE leads to high mortality and morbidity; thus, descent to lowest possible altitude in the most expeditious manner should be of the highest priority until symptoms fully resolve. Individuals suffering from HAPE should descend using as little exertion to themselves as possible, ideally via vehicle. If they must walk themselves, then remove any burdening load.4,17

Oxygen: If available, oxygen should be given continuously, titrating to an SpO2>90%. Rapid evacuation should not be delayed for oxygen therapy.

Portable hyperbaric chambers: See PHC recommendation for HACE.4,17,40

Nifedipine: In cases when evacuation to lower altitude is prolonged or unavailable, patients should be treated with nifedipine. Treatment dose of nifedipine is identical to prophylactic dose. If immediate evacuation is available, then nifedipine is not indicated.3,17,41

Phosphodiesterase inhibitors: In cases where the patient is not a candidate for nifedipine, consider treating with tadalafil or sildenafil at the prophylactic dose. See phosphodiesterase inhibitor recommendation for HAPE prevention.