Cerebral blood flow in Andean children and adolescents living above 5000m

A number of indigenous populations have resided at high-altitude for generations, resulting in various phenotypical adaptations promoting successful high-altitude adaptation. While many of these adaptations have been investigated in adults, little is known regarding how children residing at high-altitudes adapt, particularly with regards to the cerebrovasculature. Under hypoxic environments, compensatory changes in cerebral blood flow (CBF) are necessary to couple oxygen delivery to metabolic demand in the face of reduced oxygen availability. In this study, we aimed to evaluate regional and global cerebral blood flow (CBF) in Andean children and adolescents living in the highest city in the world at 5100m. Eighteen Andeans (ages 6-17years) living in La Rinconada, Peru (5100m) were compared to sex, age, size, and maturity matched high-altitude Sherpa (3800m) living in the Khumbu valley of Nepal (n=18) and lowlanders (44m) living at sea-level in Cardiff, Wales (n=18). Volumetric measurements of CBF were assessed using duplex ultrasound of the internal carotid, and vertebral arteries to assess regional and global CBF. End-tidal gases and oxygen saturation were measured in all groups while hemoglobin concentration was assessed in Andeans. Despite Andeans living under a more severe hypoxic environment, global CBF was similar between Andeans (687.01±138.49ml/min), Sherpa (711.27±110.27ml/min) and lowlanders (704.88±59.23ml/min). In contrast, vertebral artery blood flow was 24% lower in Andeans (72.93±31.60ml/min) compared to lowlanders (96.09±19.23ml/min). The similar global CBF in Andean children might be achieved through elevated hemoglobin concentration. However, lower posterior perfusion in Andeans requires further investigation to determine whether it represents an adaptive or maladaptive response.