Physiological responses at rest and exercise to high altitude in lowland children and adolescents

Abstract

During the last decades, the number of lowland children exposed to high altitude (HA) has increased drastically. Several factors may influence the development of illness after an acute HA exposure on children an adolescent population such as altitude reached, ascent velocity, time spent at altitude and, specially, their age. The main goal of this study was to evaluate the resting cardiorespiratory physiological and submax-imal exercise responses under natural HA conditions by means of the six-minute walking test (6MWT). Secondly, we aimed to identify the signs and symptoms associated to acute mountain sick-ness (AMS) onset after acute HA exposure in children and adolescents. Forty-two children and adolescents, 18 boys and 24 girls, aged from 11 to 15 years old participated on this study, which was performed at sea level (SL) and during the first 42 hours at HA (3,330 m). Lake Louise score (LLS) was recorded to evaluate the evolution of AMS symptoms. Submaximal exercise tests (6MWT) were performed at SL and HA. Physiological parameters such as heart rate, systolic and diastolic blood pressure, respiratory rate, and arterialized oxygen saturation were measured at rest and after ending exercise test at the two altitudes. After acute HA exposure, participants showed lower arterial oxygen saturation levels at rest and after submaximal test compared to SL (p <0.001). Resting heart rate, respiratory rate and diastolic blood pressure presented higher values at HA (p <0.01). Moreover, heart rate, diastolic blood pres-sure and dyspnea values increased before, during and after the exercise at HA (p <0.01). Also, sub-maximal exercise performance decreased at HA (p <0.001). The AMS incidence at HA ranged from 9.5% to 19%, with mild to moderate symptoms. In conclusion, acute HA exposure in children and adolescent produces an increase in basal cardi-orespiratory parameters and a decrement in arterial oxygen saturation. Moreover, cardiorespiratory parameters increase during submaximal exercise at HA. Mild to moderate symptoms of AMS at 3,330 m and adequate cardiovascular responses to submaximal exercise do not contraindicate the ascension of children and adolescents to that altitude, at least for a limited time.