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

Abstract

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.

Changes in Hematological and Hemorheological Parameters Following Mild COVID-19: A 4-Month Follow-Up Study

“…Typical symptoms are breathlessness, cough, fever, ageusia, and loss of smell; however, there might also be cases with asymptomatic or mild disease courses. Reduced fitness is reported by many patients [ 2 , 3 ], which might be related to impaired oxygen transport and/or release by red blood cells (RBC) [ 4 ]. The SARS-CoV-2 virus has been demonstrated to invade erythroid precursors and progenitors [ 4 ] which can lead to hematopoietic stress, resulting in RBC morphological abnormalities, an inability to respond to cues from the environment, and a premature exit from the bone marrow [ 4 ].…”

“…Reduced fitness is reported by many patients [ 2 , 3 ], which might be related to impaired oxygen transport and/or release by red blood cells (RBC) [ 4 ]. The SARS-CoV-2 virus has been demonstrated to invade erythroid precursors and progenitors [ 4 ] which can lead to hematopoietic stress, resulting in RBC morphological abnormalities, an inability to respond to cues from the environment, and a premature exit from the bone marrow [ 4 ]. Indeed, an altered hematological profile in COVID-19 patients has been observed in the acute phase of the disease, including lower RBC count, mean cellular hemoglobin concentration (MCHC), hemoglobin concentration (hb), and hematocrit (hct) [ 5 ].…”

“…Other findings also indicated reduced mean cellular volume (MCV) and mean cellular hemoglobin (MCH) [ 6 ]. Additionally, an increased red blood cell distribution width (RDW) has been described [ 4 , 7 ]. These alterations are associated with functional changes of the RBC.…”

“…An impaired deformability is discussed to decrease the functional capacity of RBC for oxygen transport and/or release, resulting in tissue hypoxia [ 12 ]. These phenomena have been related to damages of the beta-chain of the hemoglobin or a rising formation of methemoglobin, which might increase the affinity for oxygen of the undamaged hemoglobin [ 4 , 13 ].…”

Evidence associating neutrophilia, lung damage, hyperlactatemia, blood acidosis, impaired oxygen transport, and mortality in critically ill COVID-19 patients

“…In this study, we also show that the oxygen dissociation curve of the ICU-NS group exhibits a right shift when compared with that at standard condition or of the ICU-S groups. Published data on ODC curves stratified per mortality outcome in hospitalized critically ill COVID-19 patients are scarce (reviewed recently in [44]) but the few identified studies suggest that left-shifted ODCs are usually associated with better prognosis [45]. Recently, it has been proposed that ODC in critically ill COVID-19 patients display a left shift when compared with the standard ODC [46], or with patients suffering from hypoxia caused by other respiratory disorders [47].…”