Ascent to high altitude (> 3000 m height above sea level or m.a.s.l) exposes people to hypobaric atmospheric pressure and hypoxemia, which provokes mountain sickness and whose symptoms vary from the mild acute mountain sickness to the life-threatening, high-altitude pulmonary edema (HAPE). This study analysed the risk factors underlying HAPE in dwellers and travellers of the Ecuadorian Andes after sojourning over 3000 m height. A group of HAPE patients (N = 58) was compared to a NO HAPE group (N = 713), through demographic (ethnicity, sex, and age), red blood cell parameters (erythrocytes counts, hematocrit, median corpuscular volume, median corpuscular haemoglobin, and median corpuscular haemoglobin concentration (MCHC)), altitude (threshold: 3000 m.a.s.l.), and health status (vital signs) variables. Analysis of Deviance for Generalised Linear Model Fits (logit regression) revealed patterns of significant associations. High-altitude dwellers, particularly children and elder people, were HAPE-prone, while women were more tolerant of HAPE than men. Interestingly, HAPE prevalence was strongly related to an increment of MCH. The residence at middle altitude was inversely related to the odds of suffering HAPE. Ethnicity did not have a significant influence in HAPE susceptibility. Elevated MCHC emerges like a blood adaptation of Andean highlanders to high altitude and biomarker of HAPE risk.

Background Ascent to high altitude (> 2500 m) exposes people to hypobaric atmospheric pressure and blood hypoxemia. It provokes a syndrome whose symptoms vary from the mild acute mountain sickness (AMS) to the life-threatening, high-altitude pulmonary edema (HAPE). This study analyzed the risk for developing high-altitude sickness in a group of HAPE patients (n = 59), which was contrasted against a group of AMS patients (n = 240) as the NO HAPE group, after sojourning above 4,000 m height. The objective of this retrospective was to analyse the factors contributing to the HAPE prevalence among travellers and dwellers of the Ecuadorian Andes. Methods AMS and HAPE groups were compared through demographic (ethnicity, sex, and age), environmental (permanent residence altitude and recent stay at sea-level), health status (vital signs), and blood analysis variables. The Cramer´s V, simple logistic regression(SLR), and multiple logistic regression(MLR) analyses revealed patterns of significant associations. Results Analyses revealed that high-altitude indigenous residents were HAPE-prone, while mestizos living at sea level only had AMS. Blood pressure played a role in HAPE risk. Women were more tolerant to HAPE than men. Among indigenes, HAPE prevalence significantly rose after sojourning at sea level, a phenomenon called “reentry HAPE”. Conclusions In Andean indigenes, HAPE could be produced by a poor adaptation to high altitude, a high haemoglobin, and a blunted reactivity of blood pressure to environmentally-induced hypoxia. All the above gives support to the complex gene-environment interactions in the progress of HAPE, which may give some clues about of the etiopathogenesis of non-cardiogenic edema.

Ascent to high altitude (> 3,000 m height above sea level or m.a.s.l) exposes people to hypobaric atmospheric pressure and blood hypoxemia, which provokes mountain sickness and whose symptoms vary from the mild acute mountain sickness to the life-threatening, high-altitude pulmonary edema (HAPE). This study analysed the risk factors underlying HAPE in dwellers and travellers of the Ecuadorian Andes after sojourning over 3,000 m height. A group of HAPE patients (N = 58) was compared to a NO HAPE group (N = 713), through demographic (ethnicity, sex, and age), red blood cell parameters (erythrocytes counts, hematocrit, median corpuscular volume, median corpuscular haemoglobin, and median corpuscular haemoglobin concentration or MCHC), altitude (threshold: 3,000 m.a.s.l.), and health status (vital signs) variables. Analysis of Deviance for Generalised Linear Model Fits (logit regression) revealed patterns of significant associations. High-altitude dwellers, particularly children and elder people, were HAPE-prone, while women were more tolerant of HAPE than men. Interestingly, HAPE prevalence was strongly related to an increment of MCH. The residence at low altitude was inversely related to the odds of suffering HAPE. Ethnicity did not have a significant influence in HAPE susceptibility. Blood adaptation of Andean highlanders to high altitude and its probable impact on HAPE was discussed.