Mij
Senior Member (Voting Rights)
"Blood volume (BV) is among the most tightly regulated variables in the human body and the small variations of only a few percent likely reflect the central role of BV in the maintenance of arterial blood pressure [1]. In turn, changes in blood pressure affect BV, mainly through dynamic plasma volume (PV) modulation, where decreased central venous pressure (CVP) triggers renal release of volume-regulating hormones that promote fluid retention [2-5], while elevations in CVP facilitate renal fluid loss that reduces PV [1, 6]. The potential for CVP to also regulate red blood cell volume (RBCV), however, remains largely unexplored. Members of our group demonstrated that a reduction in CVP—induced by three hours of head-up tilting—increases circulating erythropoietin (EPO) levels in healthy individuals [7] suggesting that a sustained reduction in CVP may promote erythropoiesis.
Changes in RBCV are slower than alterations in PV and typically occur over the course of weeks [8]. Accordingly, we tested whether sleeping in a tilted head-up position for five weeks to reduce CVP during the night would facilitate erythropoiesis and expand RBCV.
For this purpose, nine males (24.2 ± 5.5 yrs.; 85.4 ± 10.8 kg and 188 ± 7 cm) gave oral and written consent to voluntarily participate in the study. The study was approved by the Ethical Committee of Southern Denmark (project ID: S-20240009) and was conducted in accordance with the Helsinki declaration. In a randomized and counterbalanced order, all participants completed five weeks of either six-degree head-up sleeping (HUS) or horizontal sleeping (CON) in their own homes.
Trials were separated by a five-week wash-out period. Sleep quality (scale of 1–10, with 10 being high and 1 being low) and nightly time spent in bed were recorded. For the first (Pre) and last night (Post), as well after one week (1 W) of the respective trials, the participants slept in the laboratory on a mattress identical to the one they were assigned during that specific trial. On these days, before rising from bed, resting systolic and diastolic blood pressure was determined by sphygmomanometry (M3, OMRON, Kyoto, Japan), and a morning forearm vein blood sample was obtained. Plasma for these samples was stored at−20°C and later analyzed for EPO concentrations."
Study
Changes in RBCV are slower than alterations in PV and typically occur over the course of weeks [8]. Accordingly, we tested whether sleeping in a tilted head-up position for five weeks to reduce CVP during the night would facilitate erythropoiesis and expand RBCV.
For this purpose, nine males (24.2 ± 5.5 yrs.; 85.4 ± 10.8 kg and 188 ± 7 cm) gave oral and written consent to voluntarily participate in the study. The study was approved by the Ethical Committee of Southern Denmark (project ID: S-20240009) and was conducted in accordance with the Helsinki declaration. In a randomized and counterbalanced order, all participants completed five weeks of either six-degree head-up sleeping (HUS) or horizontal sleeping (CON) in their own homes.
Trials were separated by a five-week wash-out period. Sleep quality (scale of 1–10, with 10 being high and 1 being low) and nightly time spent in bed were recorded. For the first (Pre) and last night (Post), as well after one week (1 W) of the respective trials, the participants slept in the laboratory on a mattress identical to the one they were assigned during that specific trial. On these days, before rising from bed, resting systolic and diastolic blood pressure was determined by sphygmomanometry (M3, OMRON, Kyoto, Japan), and a morning forearm vein blood sample was obtained. Plasma for these samples was stored at−20°C and later analyzed for EPO concentrations."
Study
