Nocturnal decrease of arterial oxygen content—hidden stimulus for erythropoietin secretion at altitude

Q1Q1To the Editor: In their investigation in male mountaineers in the Andes, Tannheimer et al.1 showed that arterial oxygen saturation (SaO2) during undisturbed night sleep increased from a nadir during the first half to a higher value during the second half and a maximum in the morning after wake-up. The difference diminished with acclimatization and ascent from 3050 m to 5630 m of altitude during 19 days but remained significant. Unfortunately, the time of day was not communicated.Revista Nacional - Indexad

The oxygen dissociation curve of blood in COVID-19–An update

An impressive effect of the infection with SARS-Co-19 is the impairment of oxygen uptake due to lung injury. The reduced oxygen diffusion may potentially be counteracted by an increase in oxygen affinity of hemoglobin. However, hypoxia and anemia associated with COVID-19 usually decrease oxygen affinity due to a rise in [2,3-bisphosphoglycerate]. As such, COVID-19 related changes in the oxygen dissociation curve may be critical for oxygen uptake and supply, but are hard to predict. A Pubmed search lists 14 publications on oxygen affinity in COVID-19. While some investigations show no changes, three large studies found an increased affinity that was related to a good prognosis. Exact causes remain unknown. The cause of the associated anemia in COVID-19 is under discussion. Erythrocytes with structural alterations of membrane and cytoskeleton have been observed, and virus binding to Band 3 and also to ACE2 receptors in erythroblasts has been proposed. COVID-19 presentation is moderate in many subjects suffering from sickle cell disease. A possible explanation is that COVID-19 counteracts the unfavorable large right shift of the oxygen dissociation curve in these patients. Under discussion for therapy are mainly affinity-increasing drugs

Commentaries on viewpoint : physiology and fast marathons

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Intravascular hemolysis and mean red blood cell age in athletes

More and more municipalities and parking companies are willing to provide occupancy information to drivers. Information provision to drivers can potentially be beneficial in decreasing cruising. In crowded urban areas the ratio of cruising cars can raise up to thirty percent of all traffic. While most cities provide drivers with information on the occupancy rates of off-street parking facilities, information on single on-street parking places was non-existing until recently. The aim of this paper is to study the impact of bottom-up information provision on performance for on-street parking places under heterogeneous conditions. Using an agent-based simulation, performance is compared between a bottom-up vehicle-to-vehicle communication strategy and a strategy that combines parking sensors and vehicle-to-vehicle communication. In the latter approach on-street parking places are all equipped with sensors capable of disseminating their status. The results show that using a sensor-based strategy, search time is decreased for informed cars, especially under spatially heterogeneous conditions. Furthermore, the results point out that, under most conditions, informed cars outperform regular cars in terms of walking distance

Die Hypoferritinämie des Sportlers ist kein sicheres Indiz für Eisenmangel [High Serum Ferritin Levels Have Low Sensitivity for Iron Deficiency in Athletes]

Iron deficiency is commonly diagnosed by serum ferritin [sFer] determination, iron deficiency anaemia from reduced mean cellular volume (MCV). [sFer] shows a high variance if inflammation or liver dysfunction are present. Athletes often present with hypoferritinaemia. This study was designed to evaluate the relation of total body haemoglobin mass (tHb) which is commonly elevated in athletes to [sFer]. In the present study 56 trained (TR), 72 moderately trained (MT) and 31 untrained (UT) male individuals were investigated for peak oxygen uptake (VO2max), serum iron, [sFer] soluble transferrin receptor [sTfr], serum erythropoietin [EPO], haemoglobin concentration [Hb] haematocrit (Het), MCV blood volume (BV), and plama volume (PV). TR and UT individuals differed significantly in VO2max, tHb, PV, and BV (all p<0.01). [sFer] correlated negatively with tHb (r=-0.31,p<0.05), BV (r=-0.38,p<0.05) and max (r=-0.54,p<0.01) but not with EPO, [Fe], [sTfr], MCV, [Hb], Het, and PV. Since a negative correlation of [sFer] and tub was found, an iron storage shift from the reticuloendothelial system (RES) to the erythroid system could have occurred. This is only pathological if functional iron deficiency occurs, as suggested by increased [sTfr]. Possible causes of functional iron deficiency are gastrointestinal microhaemorrhage, menstrual blood loss and EPO-doping. True iron deficiency should be treated by dietary means or iron supplementation. Iron misuse instead has severe side-effects and uncritical addition of iron to the athlete's nutrition should be avoided