How to increase cellular oxygen availability in COVID‐19?

Kulow, Vera A.; Fähling, Michael

The Coronavirus Disease-2019 (COVID-19) outbreak is still keeping the world in suspense and challenges humanity on a new level. Infection with the acute respiratory syndrome coronavirus-2 (SARS-CoV-2) impairs oxygen diffusion capacity of the lung and in consequence causes hypoxemia. In 20 - 40 % of COVID-19 cases, patients have alarmingly low oxygen (O2 ) saturation of the blood without being dyspneic, a condition called "silent hypoxia".1 However, hypoxemia leads to severe injuries in diverse organs, particularly those of high oxygen dependency such as the brain, heart or kidney.1 Tissue hypoxia results from an imbalance between O2 consumption and O2 delivery.2 Insufficient oxygen supply forces cells to adapt via multiple physiological processes as has been extensively reported in Acta Physiologica (Oxf.).3-5 In general, but also in the context of COVID-19, the basic understanding of cellular O2 availability represents a major topic.6-8 The final amount of oxygen reaching the cell, or more precisely the mitochondria for oxidative metabolism, is mainly attributed to i) the oxygen carrying capacity of the blood as determined by the haemoglobin (Hb) level, and ii) the ability to release O2 to the tissue as determined by the Hb-O2 affinity. The latter may belong to the physiological knowledge that is underestimated in clinical routine, as indicated by only few investigations in this regard. However, due to the risk of thrombotic events, the issue of Hb-O2 affinity might be of exceptional relevance in COVID-19 and silent hypoxia. Thus, we are wondering whether the modulation of oxygen affinity to haemoglobin may help to improve cellular oxygen availability.