What are the typical longterm effects of an O2 saturation of 40-50%?

My 20-year-old son was recently hospitalized with an unknown infection. The doctors so far suspect "septic influenza". He had cpr 3 times and is currently on a ventilator. His oxygen saturation is now in the low 90s, but he spent about 14 hours with a saturation on 40-45%. Assuming he will recover, what long-term effects can we expect from this?