Reentry High Altitude Pulmonary Edema in the Himalayas

A 7-year-old Nepali boy of Tibetan ancestry fell ill when he ascended to his village (Manang, 3500 m) from Besisahar (760 m) in 1 day in a motor vehicle. He together with his family had spent the winter (December to March) at low altitude at Besisahar. In Manang he complained of difficulty in breathing and intermittent cough after the journey, but his parents ascribed this to the rough ride on a bumpy road. The boy's dyspnea increased overnight and during the following day, prompting his parents to take him to the local village health post where he was diagnosed with influenza-like illness and was managed symptomatically with simple cough medicines. His symptoms worsened again over night. The next morning (day 3 since ascending to Manang village) his parents sought help at the Himalaya Rescue Association (HRA) aid post in Manang, which is primarily tasked with the prevention and treatment of altitude related illnesses in the region. In addition to the breathlessness he now had a severe headache and had vomited twice overnight. He had no significant past medical history. The parents said that last year they had come up the same road with a similar ascent profile with no untoward events. In years past, before the construction of the road, they said they would trek up to Manang from Besisahar which would take several days.

On presenting to the HRA aid post, the patient was observed to be minimally responsive with globally reduced tone. Work of breathing was markedly increased with a respiratory rate of 55 breaths per minute, chest wall retraction, use of accessory muscles, and nasal flare. Oxygen saturation measured by portable saturation probe was 44%. Chest auscultation revealed good air entry, which was equal bilaterally, but with crepitations throughout the lung fields. Heart rate was 150 beats per minute, and temperature was 35.7°C. He was diagnosed with reentry high altitude pulmonary edema (HAPE) (Scoggin et al., 1977; Hultgren and Marticorena, 1978) and high altitude cerebral edema (Basnyat and Murdoch, 2003) and was treated with high-flow oxygen and 3 mg of dexamethasone. A helicopter rescue was organized to fly him to Kathmandu (1300 m).

In Kathmandu, the treating doctor found him to have improved markedly. He was oriented appropriately, his vital signs were within normal limits, and he was ambulating with a normal gait. His oxygen saturation was 94% in room air with bilateral crepitations. His blood count, routine urine, creatinine, and liver function tests were normal. The chest X-ray revealed heterogeneous opacities in the lower and mid zones bilaterally (Fig. 1). He was discharged to his hotel in Kathmandu with no medicines and followed up after 2 days. In his follow-up consultation he was noted to have normal vesicular breath sounds with no added sounds and his repeat chest X-ray was normal (Fig. 2). He continued to do well and we last followed up a month ago.

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FIG. 1.

Chest X-ray of the patient at Kathmandu after helicopter evacuation. The X-ray reveals heterogeneous opacities in the lower and mid zone bilateral lung fields.

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FIG. 2.

Follow-up chest X-ray after 72 hours in Kathmandu reveals resolution of the opacities.

HAPE is a medical emergency due to a noncardiogenic form of edema with elevated pulmonary artery pressures often seen in trekkers, mountaineers, and pilgrims who ascend (usually >3000 m) too high too fast (Basnyat and Murdoch, 2003). The pathophysiological mechanism of HAPE is primarily thought to be mechanical with patchy smooth muscle constriction of the pulmonary vasculature triggered by hypobaric hypoxia (Basnyat and Murdoch, 2003). Unlike, in the case of pneumonia where opacities or consolidation may remain for weeks on the chest X-ray, the prompt disappearance of the patchy opacities in our patient's chest X-ray within days is in keeping with HAPE (Zafren et al., 2009).

Reentry HAPE, which is a subset of HAPE, is a well-recognized life-threatening illness documented so far almost exclusively in the North and South Americas when people, who live at high altitude (>2500 m), return to their homes after a brief sojourn of days to months at a lower altitude setting (Scoggin et al., 1977; Hultgren and Marticorena, 1978; Niermeyer et al., 2009).

Reentry HAPE as described in our patient has not been reported in Sherpas or other people of Tibetan origin in Nepal or India. There has been only one report from Tibet (Wu, 2004). Children seem to be more susceptible to reentry HAPE than adults (Hultgren and Marticorena, 1978). A few explanations have been put forward to explain the lack of reentry HAPE in the Himalayan highlanders. Sevringhaus (1971) postulated that chronic hypoxia of high altitude causes increased muscularization of the pulmonary arterioles. This generates excessive pulmonary arteriole pressure on reascent to high altitude to which children may seem more predisposed to. Due to poorer adaptation to high altitude by the Andean native in comparison to the Tibetan-origin highlanders (Moore, 2001), this phenomenon may be more commonly seen in the South Americans. Another explanation suggests that reentry HAPE may be due to change in blood volume because prolonged exposure to high altitude results in increased blood volume (Wu, 2004). When the high altitude resident descends to lower altitude there is decrease in red cell mass resulting in compensatory rise in plasma volume which may predispose to pulmonary edema on return to high altitudes.

We suggest that another explanation for the rarity of this illness in Himalayas relative to that in South America (e.g., Peru where this phenomenon is well described) (Hultgren and Marticorena, 1978) is that historically a lack of roads in the high altitude Himalayas has largely prevented rapid reentry for high altitude residents sojourning after a temporary stay at lower altitudes. Lack of such roads may have previously protected children from reentry HAPE since rapid reascent is known to be an important risk factor in this disease. Now road building in the region, including the road recently completed from Besisahar to Manang, along which this patient traveled, may contribute to an increased prevalence of reentry HAPE (Reisman et al., 2017).

In addition, health workers at high altitudes in Nepal where reentry HAPE is unknown may select an alternate diagnosis as clearly happened in our patient. This may easily lead to a fatal outcome, as may have happened in this case had it not been for the prompt diagnosis and treatment by the HRA aid post doctors. Proper awareness regarding reentry HAPE in Himalayan high altitude natives needs to be created in high altitude population in this region, including in high altitude health workers. In this way, proper diagnosis and treatment with oxygen and rest or, if necessary, descent can be carried out promptly for effective treatment of reentry HAPE.