Comparison Between Pressure Swing Adsorption and Liquid Oxygen Enrichment Techniques in the Atacama Large Millimeter/Submillimeter Array Facility at the Chajnantor Plateau (5,050 m).

Ivan Lopez,Silvia Riquelme,Reinaldo Aravena,Daniel Soza,Rodrigo Calderon-Jofré,Alicia Morales,Fernando A Moraga

doi:10.3389/fphys.2021.775240

Abstract

The Chilean workforce has over 200,000 people that are intermittently exposed to altitudes over 4,000 m. In 2012, the Ministry of Health provided a technical guide for high-altitude workers that included a series of actions to mitigate the effects of hypoxia. Previous studies have shown the positive effect of oxygen enrichment at high altitudes. The Atacama Large Millimeter/submillimeter Array (ALMA) radiotelescope operates at 5,050 m [Array Operations Site (AOS)] and is the only place in the world where pressure swing adsorption (PSA) and liquid oxygen technologies have been installed at a large scale. These technologies reduce the equivalent altitude by increasing oxygen availability. This study aims to perform a retrospective comparison between the use of both technologies during operation in ALMA at 5,050 m. In each condition, variables such as oxygen (O2), temperature, and humidity were continuously recorded in each AOS rooms, and cardiorespiratory variables were registered. In addition, we compared portable O2 by using continuous or demand flow during outdoor activities at very high altitudes. The outcomes showed no differences between production procedures (PSA or liquid oxygen) in regulating oxygen availability at AOS facilities. As a result, big-scale installations have difficulties reaching the appropriate O2 concentration due to leaks in high mobility areas. In addition, the PSA plant requires adequacy and maintenance to operate at a very high altitude. A continuous flow of 2–3 l/min of portable O2 is recommended at 5,050 m.

Highlights

High altitude is a geographical condition where barometric pressure and inspired partial pressure of oxygen (PiO2) are reduced with altitude
A similar oxygenation pattern was observed in both the procedures to increase oxygen concentration (PSA or liquid oxygen) inside Array Operations Site (AOS) rooms
Our results demonstrate that both the oxygen production procedures (PSA or liquid oxygen) effectively increase the fraction of inspired oxygen (FiO2) at very high altitudes, protecting the health of the workers as noted by the increase in oxygen saturation and reduced heart rate (HR)

Summary

Introduction

High altitude is a geographical condition where barometric pressure and inspired partial pressure of oxygen (PiO2) are reduced with altitude. We know that this exposure model is associated with acute mountain sickness, sleep disorders, polycythemia, pulmonary hypertension, and an acute increase in arterial pressure (Ministry of Health Chile, 2014, available at https://www.minsal.cl/sites/default/files/guia_ hipobaria_altitud.pdf). These symptoms are present each time workers arrive at their high altitude worksite and do not disappear over time (Richalet et al, 2002; Moraga et al, 2014, 2018). In regard to environmental oxygenation, the oxygen equivalent must be below 3,000 m with permanent control of temperature, relative humidity, and room ventilation (Ministry of Health Chile, 2014, available at https://www.minsal.cl/sites/default/files/ guia_hipobaria_altitud.pdf)

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