Oxygen depletion upon FLASH irradiation of aqueous solutions (containing BSA 5%w/w). (a) Changes in pO2 upon application of a series of FLASH exposures, each delivering 20 Gy. (b) Reduction in oxygen upon application of FLASH at different dose rates at a fixed total dose of 20 Gy. No statistically significant difference was found between the dose rates used here, using ANOVA, with Tukeýs multiple comparison test, p-value< 0.05, for n=5. (c) Reduction in oxygen as a function of the total dose at a fixed dose rate (300 Gy/s).