Effects of normobaric hypoxic bed rest on the thermal comfort zone

Ursa Ciuha; Ola Eiken; Igor B Mekjavic

doi:10.1016/j.jtherbio.2015.02.001

Effects of normobaric hypoxic bed rest on the thermal comfort zone

J Therm Biol. 2015 Apr-May:49-50:39-46. doi: 10.1016/j.jtherbio.2015.02.001. Epub 2015 Feb 3.

Authors

Ursa Ciuha¹, Ola Eiken², Igor B Mekjavic³

Affiliations

¹ Jozef Stefan International Postgraduate School, Jamova 39, SI-1000 Ljubljana, Slovenia; Biomed d.o.o., Stari trg 4, SI-1000 Ljubljana, Slovenia. Electronic address: ursa.ciuha@gmail.com.
² Swedish Aerospace Physiology Centre, Department of Environmental Physiology, School of Health and Technology, Royal Institute of Technology, Berzelius v. 13, Stockholm, Sweden.
³ Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, Ljubljana, Slovenia.

PMID: 25774025
DOI: 10.1016/j.jtherbio.2015.02.001

Abstract

Future Lunar and Mars habitats will maintain a hypobaric hypoxic environment to minimise the risk of decompression sickness during the preparation for extra-vehicular activity. This study was part of a larger study investigating the separate and combined effects of inactivity associated with reduced gravity and hypoxia, on the cardiovascular, musculoskeletal, neurohumoural, and thermoregulatory systems. Eleven healthy normothermic young male subjects participated in three trials conducted on separate occasions: (1) Normobaric hypoxic ambulatory confinement, (2) Normobaric hypoxic bedrest and (3) Normobaric normoxic bedrest. Normobaric hypoxia was achieved by reduction of the oxygen fraction in the air (FiO2 = 0.141 ± 0.004) within the facility, while the effects of reduced gravity were simulated by confining the subjects to a horizontal position in bed, with all daily routines performed in this position for 21 days. The present study investigated the effect of the interventions on behavioural temperature regulation. The characteristics of the thermal comfort zone (TCZ) were assessed by a water-perfused suit, with the subjects instructed to regulate the sinusoidally varying temperature of the suit within a range considered as thermally comfortable. Measurements were performed 5 days prior to the intervention (D-5), and on days 10 (D10) and 20 (D20) of the intervention. no statistically significant differences were found in any of the characteristics of the TCZ between the interventions (HAMB, HBR and NBR), or between different measurement days (D-5, D10, D20) within each intervention. rectal temperature remained stable, whereas skin temperature (Tsk) increased during all interventions throughout the one hour trial. no difference in Tsk between D-5, D10 and D20, and between HAMB, HBR and NBR were revealed. subjects perceived the regulated temperature as thermally comfortable, and neutral or warm. we conclude that regulation of thermal comfort is not compromised by hypoxic inactivity.

Keywords: Bed rest; Behavioural temperature regulation; Hypoxia; Thermal comfort zone.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adult
Atmospheric Pressure
Bed Rest
Body Temperature Regulation*
Heart Rate
Humans
Hypogravity*
Hypoxia*
Male
Skin Temperature