Altitude Illness - Pulmonary Syndromes Treatment & Management

The mainstay of treatment is descent for anything other than mild HAPE. Descent to an altitude below that where symptoms started is always effective treatment, but it may not be practical or possible given the topography, weather, the patient's ultimate trekking or climbing goals, or group resources. Accordingly, a descent of 500-1000 m is usually sufficient. As noted above, while case series of treatment of even severe HAPE under expert care in well-equipped settings have been reported, descent for other than mild HAPE cases remains clearly indicated. Selected cases of reascent HAPE and mild HAPE at moderate altitude may be treated with oxygen and strict bedrest. If patients worsen, they must descend.

All of the following treatments are used as an adjunct to descent. Oxygen, if available, is lifesaving and should be administered at 4 L/min by mask or nasal cannula. Nifedipine should be used if descent or oxygen is not available. Nifedipine may help prevent exertional worsening in patients being evacuated on foot. Portable hyperbaric chambers (see image below) can effect a physiologic (simulated) descent when actual descent is not possible or practical. ^[22] End-positive pressure masks are useful in treating HAPE but are poorly tolerated. 

Hyperbaric treatment at 4250 m in a Gamow bag.

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The role of acetazolamide in the treatment of HAPE remains ill-defined but may prove beneficial. Additionally, recent reports give evidence that dexamethasone might have beneficial effect in HAPE as well. While not clearly established, there is little apparent downside risk to using either acetazolamide and dexamethasone in severe HAPE. ^[23]

Inhaled salmeterol (a beta-agonist) has been demonstrated to help prevent acute HAPE in HAPE-susceptible populations. Salmeterol is thought to act by increasing alveolar fluid clearance through pulmonary sodium channels. Although its use in HAPE treatment has not been proven, it is often used in this indication.

Phosphodiesterase inhibitors have also been demonstrated to help prevent acute HAPE in HAPE-susceptible populations. These agents are thought to act by increasing availability of nitric oxide in pulmonary arterial vessels and so result in decreased pulmonary arterial tone and reduced pulmonary hypertension. Although its use in HAPE treatment has not been proven, it is often used in this indication.

Only limited studies provide any evidence that furosemide may be useful with acute HAPE, and it is not without downside risk. Furosemide should be used with substantial caution, if at all, as many patients are intravascularly depleted. Most authors discourage use of furosemide in treating HAPE.

Portable hyperbaric chambers (eg, Gamow, CERTEC, PAC) are widely used among adventure travel/trekking groups and climbing expeditions. These chambers are lightweight, coated fabric bags about 2 m in length and 0.7 m in diameter. The patient is placed inside the bag, which is sealed shut and inflated with a manually operated pump, pressurizing the inside to 105-220 mm Hg above ambient atmospheric pressure. This pressure gradient is regulated by pop-off valves set to the target pressure, and it is fixed depending on the brand of bag in use.

Depending on the elevation, a physiologic (simulated) descent of about 2000 m (7000 ft) may be achieved within minutes. Intermittent pumping is necessary to flush carbon dioxide from the system, unless a chemical scrubber system is used. Patients with severe HAPE may need to have their head elevated to tolerate lying down. Elevation can be accomplished by placing the bag on a rigid surface, such as boards or a wooden bed, and propping up the head end by 0.3-0.5 m (12-20 inches).

In practice, most patients with moderate HAPE tolerate lying flat after reaching the physiologic lower elevation of the pressurized bag. Patients typically are treated in 1-hour increments and then are reevaluated, with additional treatments as indicated. Closely monitor patients for rebound signs and symptoms, which may occur soon after removal from the hyperbaric environment, or they may develop over a period of hours.

For cases of persistent desaturation or dyspnea, administer oxygen to keep oxygen saturation (SaO₂) above 90%.

Consider continuing nifedipine in symptomatic patients. Furthermore, consider dexamethasone, phosphodiesterase inhibitors, and inhaled beta-agonist as conditions indicate.

Emergency departments at altitude must assess the elevation at which the patient's illness occurred and determine whether further descent is necessary.

Admission criteria are as follows:

• Significant arterial oxygen desaturation at rest

• Dyspnea at rest

• Inability to descend

Treatment of moderate-to-severe HAPE after descent consists of bedrest and oxygen ^[24] ; continuation of nifedipine, tadalafil, dexamethasone, inhaled beta-agonist also may be helpful.

Discharge criteria are as follows:

• Normal SaO₂ on room air

• No dyspnea at rest (mild dyspnea with exertion may persist for several days)

Children living at altitude who develop HAPE should undergo screening for diagnosis of underlying cardiopulmonary abnormalities, including pulmonary hypertension.

Recommendations on staged ascents are by and large adequate for the average person, but some persons will still become ill despite a slow, staged ascent. Persons traveling to high altitude should allow adequate time for acclimatization and pay careful attention to symptoms. Helpful guidelines to avoid altitude illness include the following:

• Avoid abrupt ascent to sleeping elevations over 3000 m (10,000 ft).

• Spend 1-2 nights at an intermediate elevation (2500-3000 m) before further ascent.

• Above 3000 m, sleeping elevations should not increase by more than 300-400 m per night.

• When topography or village locations dictate more rapid ascent, or after every 1000 m gained, spend a second night at the same elevation.

• Day hikes to higher elevations, with return to lower sleeping elevations help to improve acclimatization.

• Avoid overexertion.

• Avoid alcohol consumption in the first 2 days at a new, higher elevation; in addition to concerns about respiratory depression and exaggerated sleep hypoxemia, an AMS headache the next morning is all too easily dismissed as a hangover.

Significant abnormalities of pulmonary vasculature (eg, absence of the left pulmonary artery ^[25] ) or pulmonary hypertension are contraindications for going to high altitude.

There is limited evidence to suggest that a low hypoxic ventilatory response (HVR) at low altitudes is a predictor for HAPE at high altitudes. ^[26]

The indication for chemoprophylaxis of HAPE is repeated episodes. Whether one prior episode should encourage prophylaxis is arguable, but demonstrated susceptibility certainly requires caution. Oftentimes, a slower ascent is the only preventive method required. Effective agents for prevention of HAPE include nifedipine and salmeterol. ^{[27, 28, 29]} Those with a history of HAPE should carry nifedipine to use either prophylactically or with the first signs of HAPE. Salmeterol reduced HAPE by 50% in susceptible persons, appears safe, and should be considered for treatment as well, though it has not yet been studied for this indication. Other studies have shown evidence for a prophylactic role in HAPE for dexamethasone, but detailed study of optimal dosing protocol has not been reported. ^{[30, 31]} Oral phosphodiesterase-5 inhibitors (eg, sildenafil, tadalafil) have been found effective for prophylaxis of HAPE, ^{[30, 31, 32, 33]} but they have not yet been studied for treatment.

Outpatient treatment of mild HAPE after descent consists of bedrest. Follow up in 24 hours to check on clearance of HAPE edema.