Regulation of plasma volume in male lowlanders during 4 days of exposure to hypobaric hypoxia equivalent to 3500 m altitude

Abstract

Acclimatization to hypoxia leads to a reduction in plasma volume (PV) that restores arterial O 2 content. r Findings from studies investigating the mechanisms underlying this PV contraction have been controversial, possibly as experimental conditions were inadequately controlled. r We examined the mechanisms underlying the PV contraction evoked by 4 days of exposure to hypobaric hypoxia (HH) in 11 healthy lowlanders, while strictly controlling water intake, diet, temperature and physical activity. r Exposure to HH-induced an ∼10% PV contraction that was accompanied by a reduction in total circulating protein mass, whereas diuretic fluid loss and total body water remained unchanged. r Our data support an oncotically driven fluid redistribution from the intra-to the extravascular space, rather than fluid loss, as the mechanism underlying HH-induced PV contraction.

Plasma volume contraction at altitude: where does the plasma go?

“…2017), thus providing a rationale for the study by Schlittler et al . (2021) published in this issue of The Journal of Physiology .…”

“…2017), the data of Schlittler et al . (2021) nonetheless highlights the rapidity of PV contraction in response to hypoxia.…”

Hypoxia research: to control or not to control? That is the question

“…Recently, Schlittler et al . (2021) examined the mechanism(s) underlying the decrease in PV during hypoxia, and chose a laboratory‐based design to remove confounders associated with field expeditions. Eleven healthy participants were exposed to 4 days of normoxia and hypoxia in a randomised order.…”

“…Schlittler et al . (2021) highlighted the importance of water intake in PV regulation, which will affect cardiovascular function, including the baroreceptors response due to a decrease in carotid wall tension, and changes in cardiac function via decreased venous return (i.e. Frank‐Starling) (Stembridge et al .…”

“…Controlled laboratory research may be most appropriate for mechanistic research, where the focus lies on one specific physiological alteration in response to hypoxia. Schlittler et al (2021) highlighted the importance of water intake in PV regulation, which will affect cardiovascular function, including the baroreceptors response due to a decrease in carotid wall tension, and changes in cardiac function via decreased venous return (i.e. Frank-Starling) (Stembridge et al 2019).…”