Effect of Human Splenic Contraction on Variation in Circulating Blood Cell Counts

Abstract

1. The human spleen sequesters 200-250 mL densely packed red blood cells. Up to 50% of this viscous blood is actively expelled into the systemic circulation during strenuous exercise or simulated apnoea (breath-hold) diving. The contribution of splenic contraction to changes in the circulating volume of red blood cells (RBCV), as well as the venous concentration of white blood cells (WBC) and platelets (PLT), was investigated following repeated breath-hold apnoeas. 2. Eighteen trained apnoea divers and 18 intact and six splenectomized subjects without diving experience repeated five maximal apnoeas with face immersion in cold water, with 2 min intervals between successive attempts. Venous blood samples were taken before and between consecutive apnoeas, as well as at 0, 10 and 20 min after the last breath hold. Arterial pressure, heart rate and transcutaneous partial pressure of oxygen and carbon dioxide were monitored continuously. 3. Plasma protein concentration decreased by 5.8, 2.2 and 9% in apnoea divers, untrained and splenectomized subjects, respectively, indicating an expansion of plasma volume. The RBCV and venous concentration of WBC, corrected for changes in plasma volume, increased in both trained apnoea divers (4.9+/-1.0 and 14.9+/-3.1%, respectively) and intact subjects (1.7+/-0.8 and 7.2+/-1.8%, respectively), whereas in splenectomized subjects there was no change in RBCV and a delayed increase in WBC concentration. Furthermore, an initial lymphocytosis detected during repeated breath holds in divers and intact subjects was completely absent in splenectomized subjects. None of the groups showed significant changes in PLT concentrations. The well-recognized diving response to apnoea (bradycardia and increased blood pressure) was seen during all breath-hold attempts in all subjects. 4. Repeated breath-holds (apnoeas) contribute to increased RBCV and venous blood concentrations of WBC through splenic contraction.

Does breath-holding increase the risk of a thrombotic event?

“…This report focuses on the data obtained, but not analysed in our previous study [8]. In that previous report on the impact of breath hold on hematological parameters we failed to analyse the changes in MPV (observing unchanged platelet count).…”

“…We previously showed that spleen is a major source of freshly recruited lymphocytes and circulating red blood cells, which can be mobilized by breath-holding [8]. The finding of unchanged total platelet count was surprising, since the spleen contains approximately one-third of the total body platelets [2,10].…”

Human Physiology in Extreme Heat and Cold

“…The human spleen sequesters 200-250 mL densely packed red blood cells and it is accepted that it has the capacity to release them into the systemic circulation during times of stress, as seen in hypothermia, by contracting the spleen [27]. The consequence of that process is increasing blood's oxygen transport and its viscosity.…”

“…The consequence of that process is increasing blood's oxygen transport and its viscosity. Spleen contraction seems to be mediated by α-adrenoreceptors [27]. Blood viscosity seems to increase 2% per degree Centigrade drop in temperature [19].…”

The Effect of Brief Exercise on Circulating CD34+ Stem Cells in Early and Late Pubertal Boys

“…One such depot for some stem cells might be the spleen (21). Indeed, in humans, as in other mammals, brief exercise and other stresses do lead to splenic contraction and release of red and white cells into the circulation (29,30).…”