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

Authors: Morin Lang *,1, Guillem Vizcaíno-Muñoz *,2, Paulina Jopia 3, Juan Silva-Urra 4 and Ginés Viscor 2

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 submaximal 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 sickness (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 pressure and dyspnea values increased before, during and after the exercise at HA (p <0.01). Also, submaximal 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 cardiorespiratory 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.

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1    Department of Rehabilitation Sciences and Human Movement, Faculty of Health Sciences, University of Antofagasta, Chile; morin.lang@uantof.cl

2    Physiology Section, Department of Cell Biology, Physiology and Immunology, Faculty of Biology, Universitat de Barcelona, Barcelona, Spain; gviscor@eub.edu (G.V.); guillebike96@hotmail.com (G.V.M.) 

3         Occupational Health Department, Institute of Occupational Safety, Copiapó, Chile; paulina.jopia@ist.cl

4     Biomedical Department, Faculty of Health Sciences, University of Antofagasta, Chile; juan.silva.urra@uantof.cl

*    These authors share first authorship 

*    Correspondence: morin.lang@uantof.cl (M.L.)

Walking South America Project

My name is Francesco Magistrali, 42 years old, Italian, Degree in Human Movement from the Catholic University of Milan. Last November I’ve started a project I named ‘Walking South America’, an initiative that required more or less 8 months of preparations. The idea was to cross the South American Continent from the Pacific Ocean to the Atlantic Ocean never using motorised transportation: walking and kayaking across Chile, Argentina and Uruguay. Aside from being a personal challenge, the goals of the project were: collecting data and info about the environment and climate change; interview local people on their cultures and social status; collect micro-plastics’ samples from the waters of Rio Bermejo, a river located in Northern Argentina. All this with a good array of sponsors, media partners and scientific collaborations, the whole expedition being a blend of adventure, physical and mental feat, science, anthropology. 

A Brief Story

I was crossing Uruguay (Leg 2 of expedition) on foot when Covid19 hit the country obliging me to a 2 months lockdown, before eventually finding a flight to run home. Thus, I had to abort the expedition (kayaking Rio Bermejo was supposed to be 3rd and final leg of the journey). But at least I completed Leg 1 successfully and here comes a brief story of it.

After landing in Santiago del Chile with riots and social disorders still hitting the city (and the whole country) I eventually made it to Antofagasta. In a few days I met a bunch of new friends and a good amount of people. Doctor Morin Lang at the University of Antofagasta officially asked me to carry a special heart monitor during my solo trek across the Atacama Desert and the Andes (my planned route) to then share the results with NEXER project. I eventually left the shores of Antofagasta, right in front of the Ocean.

Heading towards a location called La Negra, where I did rendez-vous with Doctor Morin Lang and a team of journalists and film makers. After a last technical check, an interview and a little bit of filming I was finally ready for the off. In front of me the driest desert on Earth, the legendary Atacama. Walking in such a place with no resupplies is impossible. You can’t travel only with a backpack. For this scenario, the solution was a aluminum two wheeled cart that I’d pull using a small dayback as a harness. This way I managed to carry 50 litres of water and at least 40 days of food, plus all my equipment. First week I followed a big paved road that leads to one of the most important copper mines of Chile, La Escondida. Fifty degrees centigrade around noon, strong winds, the sun like a laser but a lot of support and pure kindness from the truck drivers that always helped me providing water and snacks! Something I didn’t expect to happen. From La Escondida on, the road ends and it’s pure off road tracks that I had to follow on my way to Paso Socompa, a high altitude mountain pass that is located right on the border between Chile and Argentina. Officers both on the Chilean and Argentinean side were extremely warm when I got there. I actually spent one day of rest with the small team of militaries on the Argentinean side.

From that point on it’s been pure ‘altiplano’. I knew I was going to come across a few communities before reaching the city of Salta, but I was ready to spend many a days with no humans in sight since I left the Police Station at Paso Socompa. I didn’t come across any person during one entire week since the pass. I’m used to that from past expeditions, but all that time with nobody in sight is still quite unusual for the modern man. Days were long, alone and in the middle of nowhere. Nothing extreme, since I was safely following well marked tracks, but still I was by myself, totally immersed in my inner trip, in a constant meditation state, walking all day, pulling my heavy burden loaded with water, food and gear. All uphill stretches were hard and slow to negotiate. But I was well prepared, fit and extremely motivated to reach Salta in Argentina. 

 I managed to reach the city in exactly one month of walking since I left Antofagasta, taking into account only a few days of rest at Socompa and in a couple of villages that I came across in the last part of the journey. In Salta, with a perfect timing, I made rendez-vous with Doctor Morin Lang. She came from Antofagasta so that I could return the heart monitor and all the data saved in it.

I’ll never forget the desert and the mighty Andes. It’s amazing places and circumstances that leave a mark in one’s life.