Fig. 4 Evolution of fraction of sickled RBCs under hypoxia. Evolution of fraction of sickled RBCs under hypoxia. Deoxygenation completes in 15 s after the simulations begin. Black line represents the experimental results reported in (24). Red dashed line denotes model prediction with O2 concentration of 2% and variance of HbS distribution of 2.3 g/dl. Blue dashed curve denotes model prediction with O2 concentration of 3.75% and variance of HbS distribution of 0.7 g/dl. Gray lines represent 20 of 5000 sensitivity tests with O2 concentration varying at 3.75 ± 0.01% and the variance of hemoglobin distribution varying between 0.7 ± 0.35 g/dl. Blue area represents SD. Lu Lu et al. Sci Adv 2019;5:eaax3905 Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).