Tumor growth. 4T1 mammary tumor growth (% of initial volume) in control (n = 19), intermittent (n = 24) and daily (n = 9) hyperbaric oxygen (HBO) treated tumors during an 8 day period. Intermittent treatments were given at day 1, 4 and 7. Data represent mean ± SEM. * p < 0.001 compared to control.