Manferdelli, Giorgio, Denis J. Wakeham, Keval D. Patel, Eric T. Hedge, Michael G. Leahy, Abel Thomas, James Berry, Tony G. Babb, Peter Hackett, Renie Guilliod, Benjamin D. Levine, Christopher M. Hearon, Jr., and Andrew R. Tomlinson. Relationship between pulse oximetry and arterial oxygen saturation during rest and exercise at extreme altitude. High Alt Med Biol. 00:00–00, 2026. Introduction: Pulse oximetry (SpO 2 ) is commonly used to guide oxygen use, including at high altitude, but its accuracy during severe hypoxemia remains uncertain. This study aimed to compare arterial oxygen saturation (SaO 2 ) and SpO 2 while using graded levels of supplemental oxygen at simulated extreme altitude in a hypobaric chamber. Methods: Four healthy, unacclimatized adults completed rest and 60 Watts of exercise at different flow rates of supplemental oxygen (6, 4, 2, 1, and 0 l/min nominal flow) at 282 mmHg barometric pressure (Pb; equivalent to 8,100 m) and 253 mmHg Pb (equivalent to 8,848 m) with simultaneous measurement of arterial blood gases (radial artery catheter) and SpO 2 (forehead pulse oximetry). Exercise was only performed at 282 mmHg. Results: Across all altitudes and conditions, SaO 2 and SpO 2 demonstrated a very strong correlation (all r 2 ≥ 0.95, p < 0.001), with SpO 2 showing a consistent positive bias (pooled: 1.7% [−4.4% to 7.7%]; 282 mmHg rest: 0.4% [−4.5% to 5.3%]; 282 mmHg exercise: 3.1% [−2.2% to 8.5%]; 253 mmHg rest: 2.9% [4.9% to 10.6%]). The magnitude of the SpO 2 bias was higher when only SaO 2 <70% was considered (pooled: 5.2%). The root mean square error was 2.6 for SaO 2 ≥70% and increased to 6.2 when SaO 2 was <70%. Conclusions: Although SpO 2 represents a precise noninvasive measure for SaO 2 across a wide range of oxygen saturations (70%–100%), SpO 2 has lower precision and accuracy during severe hypoxemia (<70% SaO 2 ).
Srour, MHD Osama, Darla Carvallo-Castañeda, Monica Medina, Gian Huaman, Rafael Marquez, and Katia Bravo-Jaimes.Variability of right ventricular structure and function in infants across different high-altitude regions: ANDES-CHD-ECHO sub-study. High Alt Med Biol. 00:00–00, 2026. Background: Right ventricular (RV) predominance is a normal fetal state that rapidly regresses postnatally at sea level. High-altitude hypobaric hypoxic environment may alter this adaptation process. This study evaluated echocardiographic RV variations in healthy infants across different altitudes in the Peruvian Andes. Methods: This sub-study of the ANDES-CHD cohort included 81 healthy infants from sea level to 4,338 meters (m) in Peru. RV fractional area change (FAC) and indexed RV free wall thickness were measured. Multivariate linear regression assessed the independent effect of altitude, adjusting for relevant confounders. Results: Infants at higher altitudes exhibited a statistically significant reduction in RV FAC compared with sea level (45.5% at sea level vs. 38% at 3,259 m [ p = 0.021] and 4,338 m [ p = 0.006]), though all median values remained within normal physiological ranges. Sixteen percent of infants had an RV FAC < 35%, with no significant difference between high- and low-altitude groups, and no adverse outcome at 12-month follow-up. Indexed RV free wall thickness did not differ significantly across groups. Conclusion: Healthy Andean infants demonstrate a physiological adaptation to high-altitude hypobaric hypoxia characterized by a statistical reduction in RV systolic function without pathological compromise, alongside normal postnatal regression of RV wall thickness.
Marín, Alejandro Ferreiro, María Paula Ferreiro Soria, Karla Sánchez Olivera, Aranza Suárez Ortega, and Luis Martín Garrido García. High-altitude pulmonary edema in children in Mexico City: A case series. High Alt Med Biol. 00:00–00, 2026.—High-altitude pulmonary edema (HAPE) is a potentially life-threatening form of noncardiogenic pulmonary edema caused by hypobaric hypoxia. Although well characterized in adults, pediatric cases remain underrecognized and are frequently mistaken for pneumonia. We describe four pediatric patients aged 7–12 years diagnosed with HAPE at a Private Tertiary Referral Medical Center in Mexico City. One patient developed classic HAPE after ascent from low altitude, and three patients developed reentry HAPE after returning to high altitude following temporary stays near sea level. All patients presented with hypoxemia (SpO 2 77%–93%), respiratory symptoms, bilateral pulmonary infiltrates, absence of fever, and low inflammatory markers. Echocardiography demonstrated elevated or borderline elevated pulmonary artery pressures without structural heart disease. Supplemental oxygen resulted in rapid clinical improvement in all cases. Hospital stay ranged from 2 to 4 days, and none required mechanical ventilation. One patient experienced recurrence shortly after discharge. HAPE should be considered in children presenting with acute hypoxemic respiratory illness after recent ascent to high altitude. The combination of hypoxemia, bilateral infiltrates, low inflammatory markers, and rapid response to oxygen therapy may help distinguish HAPE from infectious pneumonia and facilitate timely treatment.
Chen, Chen, Yang, Li, Xu, Fan, Xu, Zhijuan Liu, and Dong Wu. Distinct etiological and clinical patterns of acute mesenteric ischemia at high altitude: a retrospective comparative study. High Alt Med Biol. 00:00–00, 2026. Background: Acute mesenteric ischemia (AMI) is a life-threatening abdominal emergency, yet evidence regarding its etiology and clinical outcomes in high-altitude populations remains limited. This study aimed to compare the etiology, clinical characteristics, and outcomes of AMI between high- and low-altitude populations in China. Methods: We conducted a retrospective comparative study at two tertiary referral centers in China: People’s Hospital of the Xizang Autonomous Region (PHOXAR; 3,700 m) and Peking Union Medical College Hospital (PUMCH; <100 m). Mesenteric venous thrombosis (MVT) comparisons were restricted to the overlapping period of 2020–2024. Results: Among 186 patients in the high-altitude cohort and 549 in the low-altitude cohort, MVT was more frequent at high altitude (84.9% vs. 61.2%, p < 0.001). 158 high-altitude and 120 low-altitude patients with MVT were compared. Cirrhosis-related (29.1% vs. 11.7%) and erythrocytosis-related MVT (27.2% vs. 1.7%) were more common in the high-altitude cohort, whereas autoimmune disease-related MVT (0.6% vs. 11.7%) and thrombophilia (0 vs. 16.7%) were more frequent in the low-altitude cohort. High-altitude patients had higher hemoglobin/hematocrit, bilirubin, and fibrinogen levels and a higher mean onset-to-admission time (95.4 vs. 30.2 days). They underwent surgery less frequently (29.7% vs. 80.0%, p < 0.001) and had higher in-hospital mortality (26.6% vs. 11.7%, p = 0.004). Mortality was not significantly different among patients admitted within 2 days (31.6% vs. 8.3%, p = 0.111) but remained higher among those admitted after 2 days (25.9% vs. 12.5%, p = 0.012). Male sex, older age, alcohol consumption, smoking, and higher hematocrit, bilirubin, and fibrinogen were independently associated with the high-altitude MVT phenotype. Conclusions: AMI in the high-altitude population was characterized by a marked predominance of MVT, with distinct etiological and clinical profiles and poorer outcomes. These findings highlight the importance of early recognition, timely referral, and improved access to appropriate treatment for AMI in high-altitude settings.
