Haemoglobin Oxygen Affinity in Patients with Severe COVID-19 Infection.

During critical care, at least until the late stage of the disease, severely ill COVID-19 patients may have relatively well preserved lung compliance but remain severely hypoxaemic. A recent theoretical study suggested a direct interaction between COVID-19 viral proteins and haemoglobin (Hb) that could lead to a loss of oxygen carrying capacity. As national guidelines strongly support a restrictive transfusion strategy in the critically ill, any right-shift in the Hb O2 affinity curve could contribute to the hypoxaemia and be potentially harmful. We have measured Hb O2 affinity curves from severely ill COVID-19 patients and, in comparison to age- and sex-matched controls, find no evidence for a shift in O2 affinity that would support any change in clinical management.