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Porters have accompanied trekkers and climbers to high altitude since the earliest expeditions in the Himalayas. As the existing body of knowledge on high-altitude medicine expands, the focus remains on trekkers or climbers. And published literature on medical problems in the large porter population remains sparse. It is well known that porters working at high altitude in the Nepal Himalayas are often lowland dwellers and are as prone to high-altitude illnesses such as acute mountain sickness, high-altitude pulmonary edema, and high-altitude cerebral edema as the trekkers are. Other illnesses such as diarrhea, respiratory illnesses, and infections also occur in this population. In this review, studies reporting these findings will be discussed along with the local context of socioeconomic barriers to adequate health care for these porters. [ABSTRACT FROM AUTHOR]

Humans have populated the Tibetan plateau much longer than the Andean Altiplano. It is thought that the difference in length of occupation of these altitudes has led to different responses to the stress of hypoxia. As such, Andean populations have higher hematocrit levels than Himalayans. In contrast, Himalayans have increased circulation to certain organ systems to meet tissue oxygen demand. In this study, we hypothesize that cerebral blood flow (CBF) is higher in Himalayans than in Andeans. Using a MEDLINE and EMBASE search, we included 10 studies that investigated CBF in Andeans and Himalayans between 3,658 and 4,330 m altitude. The CBF values were corrected for differences in hematocrit and arterial oxygen saturation. The data of these studies show a mean hematocrit of 50% in Himalayans and 54.1% in Andeans. Arterial oxygen saturation was 86.9% in Andeans and 88.4% in Himalayans. The CBF in Himalayans was slightly elevated compared with sea-level subjects, and was 24% higher compared with Andeans. After correction for hematorit and arterial oxygen saturation, CBF was ∼20% higher in Himalayans compared with Andeans. Altered brain metabolism in Andeans, and/or increased nitric oxide availability in Himalayans may have a role to explain this difference in brain blood flow. [ABSTRACT FROM AUTHOR]

Cerebral autoregulation is impaired in Himalayan high-altitude residents who live above 4,200 m. This study was undertaken to determine the altitude at which this impairment of autoregulation occurs. A second aim of the study was to test the hypothesis that administration of oxygen can reverse this impairment in autoregulation at high altitudes. In four groups of 10 Himalayan high-altitude dwellers residing at 1,330, 2,650, 3,440, and 4,243 m, arterial oxygen saturation (Sao2), blood pressure, and middle cerebral artery blood velocity were monitored during infusion of phenylephrine to determine static cerebral autoregulation. On the basis of these measurements, the cerebral autoregulation index (AI) was calculated. Normally, AI is between zero and 1. AI of 0 implies absent autoregulation, and AI of 1 implies intact autoregulation. At 1,330 m (Sao2 = 97%), 2,650 m (Sao2 = 96%), and 3,440 m (Sao2 = 93%), Al values (mean ± SD) were, respectively, 0.63 ± 0.27, 0.57 ± 0.22, and 0.57 ± 0.15. At 4,243 m (Sao2 = 88%), AI was 0.22 ± 0.18 (P < 0.0005, compared with AI at the lower altitudes) and increased to 0.49 ± 0.23 (P = 0.008, paired t-test) when oxygen was administered (Sao2 = 98%). In conclusion, high-altitude residents living at 4,243 m have almost total loss of cerebral autoregulation, which improved during oxygen administration. Those people living at 3,440 m and lower have still functioning cerebral autoregulation. This study showed that the altitude region between 3,440 and 4,243 m, marked by Sao2 in the high-altitude dwellers of 93% and 88%, is a transitional zone, above which cerebral autoregulation becomes critically impaired. [ABSTRACT FROM AUTHOR]

Baniya, Santosh, Christopher Holden, and Buddha Basnyat. Reentry high altitude pulmonary edema in the Himalayas. High Alt Med Biol. 18:425-427, 2017.-Reentry high altitude pulmonary edema (HAPE), a subset of HAPE, is a well recognized, life-threatening illness documented almost exclusively in the North and South Americans, who live at high altitude (>2500 m) and return to their homes after a brief sojourn of days to months at lower altitude. This phenomenon has not been reported in Sherpas or other people of Tibetan origin in Nepal or India. And it has rarely been reported from Tibet. In this study we document a case of reentry HAPE in Manang region (3500 m) of Nepal in a 7-year-old Nepali boy of Tibetan ancestry who fell ill when he ascended to his village (Manang, 3500 m) from Besisahar (760 m) in 1 day in a motor vehicle after spending the winter (December to March) at Besisahar with his family. With more motorable road access to high altitude settlements in the Himalayas, reentry HAPE may need to be strongly considered by healthcare professionals in local residents of high altitude; otherwise life-threatening complications may ensue as in our case report. [ABSTRACT FROM AUTHOR]