NCT04106401

Intravascular Volumes in Hypoxia During Antarctic Confinement

Alterations in Total Red Blood Cell Volume and Plasma Volume During a One-year Confinement in Antarctica: Effect of Hypoxia

• Status: Unknown
• Phase: N/A
• Study type: Interventional
• Enrollment: 24 (estimated)
• Sponsor: Ecole Nationale des Sports de Montagne · Academic / Other
• Sex: All
• Age: 18 Years – 65 Years
• Healthy volunteers: Accepted

Summary

This study evaluates the effect of hypoxia on blood volumes during Antarctic winter-over confinement. Half of the participants will be evaluated during sea-level winter-over confinement, while the other half will be examined during high-altitude hypoxia winter-over confinement.

Detailed description

INTRODUCTION: Short-term space flight induces an alteration of circulating blood volumes, termed "space flight anemia" and characterized by a decrease in total red blood cell volume (RCV) and plasma volume (PV). This haematological alteration is likely to persist during a long-term space mission and impact the astronauts' health, however this question remains unexplored. During a long-term space mission, the use of hypobaric hypoxia is considered for technical reasons, however the safety of hypoxia must first be verified because this environmental condition causes substantial physiological changes, in particular changes in blood volumes that may interact with the haematological effects of microgravity. OBJECTIVE: using the Antarctic confinement model as a high-fidelity terrestrial analogue for long-duration space missions, the investigators hypothesize that 1) sea level confinement reduces blood volume by simultaneously decreasing RCV and PV, and 2) chronic hypoxia offsets the decrease in RCV and exacerbates the decrease in PV induced by confinement. METHODS: blood volumes will be measured via the carbon-monoxide rebreathing method, repeatedly in two groups of participants, overwintering either at Dumont d'Urville (sea level) or Concordia (altitude 3200 m). The blood viscosity will also be measured, as well as the markers of erythropoiesis and iron metabolism. PERSPECTIVE: Documenting if some degree of hypoxia during long-duration confinement may be beneficial or unfavorable in terms of blood volume regulation is potentially relevant information for the astronauts' health and safety during long-duration space missions.

Conditions

• Hypoxia
• Confinement

Interventions

Type	Name	Description
OTHER	carbon-monoxide rebreathing	Inhaled carbon monoxide (CO) administrated as a bolus into a rebreathing circuit serves as a marker to tag circulating hemoglobin molecules and to calculate total hemoglobin mass (Hbmass). The change in blood CO concentration from pre- to postadministration (delta carboxyhemoglobin concentration) and the dose of administrated CO allows for Hbmass determination. The other blood compartments (total red blood cell volume, plasma volume and total blood volume) are derived from Hbmass, hematocrit and/or hemoglobin concentration.
OTHER	venous blood sampling	venous blood sampling at rest to evaluate blood viscosity, erythropoiesis and iron metabolism
OTHER	physical activity monitoring	recording of physical activity by actimetry
OTHER	apnea-hypopnea index and nocturnal oxygenation	recorded by ambulatory sleep recording device
OTHER	24-hour blood pressure	recorded by ambulatory device

Timeline

• Start date: 2019-09-27
• Primary completion: 2022-12-31
• Completion: 2022-12-31
• First posted: 2019-09-27
• Last updated: 2022-09-13

Locations

1 site across 1 country: France