Validation of Air Storage System for Hypoxia Exposure During Exercise

Author(s)

Norberto, Matheus S. ; Torini, Joao Victor G. ; Firmino, Matheus S. ; Papoti, Marcelo

• Document type: Journal article
• Source: HIGH ALTITUDE MEDICINE & BIOLOGY; v. 25, n. 2, p. 7-pg., 2024-03-15.

Abstract

Norberto, Matheus S., Joao Victor G. Torini, Matheus S. Firmino, and Marcelo Papoti. Validation of air storage system for hypoxia exposure during exercise. High Alt Med Biol. 00:000-000, 2024.-Considering the importance of optimizing normobaric hypoxia exposure (i.e., higher delivery capacity), the current study aims to validate a hypoxic air storage system. The study has a cross-over, one-blind randomized design. The air storage is composed of a piping system that directs hypoxic air from a hypoxia generator into nylon bags. Sixteen men (age, 25.4 +/- 4.8 years; height, 174.9 +/- 9.4 cm; weight, 77.1 +/- 17.2 kg) performed three incremental treadmill tests until exhaustion on different days. For test-retest, the subjects repeated two tests in similar hypoxia conditions (H1 and H2; fraction of inspired O-2 [FIO2] = similar to 0.13; reliability analysis), and one time in normoxia (FIO2 = similar to 0.20; condition comparison). Subjects' performance, blood lactate concentration ([La-]), arterial oxygen saturation (SpO(2)), oxygen consumption (VO2), heart rate (HR), and several respiratory-derived variables were evaluated. A comparison was made between the rest, moderate intensity, and exhaustion stages. All variables were compared using the Friedman test with Durbin-Conover post hoc (p < 0.05). The hypoxia test-retest showed no statistical differences for any variable. Time analysis showed similar behavior for SpO(2), HR, and cardiorespiratory variables (p < 0.01) for both conditions. The mean FIO2 at rest and during the incremental treadmill test was higher for normoxia (20.6 +/- 0.2%) than for H1 (13.8 +/- 0.8%) and H2 (13.7 +/- 0.3%) (p < 0.001). The VO2 response was higher in normoxia than during hypoxia exposure at moderate intensity (Normoxia = 43.1 +/- 8.1; H1 = 38.7 +/- 5.7; H2 = 35.8 +/- 8.8 ml.kg(-1).min(-1)) and at the exhaustion stage (Normoxia = 52.7 +/- 12.5; H1 = 41.9 +/- 8.8; H2 = 40.5 +/- 8.9 ml.kg(-1).min(-1)) (p < 0.01). SpO(2) and HR showed excellent intraclass correlation coefficient (ICC) during all moments, whereas VO2, SpO(2), ratio between ventilation and CO2 production (V-E/V-CO2), ratio between oxygen consumption and ventilation (V-E/V-O2), and HR showed moderate or good ICC and coefficient of variation <9% during hypoxia test-retest exercises. Thus, the air storage system showed validity for its application and reliability in the measurements associated. (AU)

• FAPESP's process: 21/02403-1 - Effects of intermittent recovery hypoxia on molecular, metabolic and neuromuscular responses
• Grantee: Matheus Silva Norberto
• Support Opportunities: Scholarships in Brazil - Doctorate