GSTM1 and COVID-19: The aim of this study was to determine whether RBCs from hospitalized COVID-19 subjects demonstrated altered features (or impaired compensation) relevant to O2 homeostasis, i.e., hematological parameters, altered O2 transport characteristics (i.e., Hb–O2 affinity/cooperativity), impaired rheology, and/or altered release of vasoactive compounds, i.e., a diminished hypoxic vasodilatory reflex.