Research show that the improvements in blood flow take 40 to 80 sessions. I think it is the amount of cumulative time spent in the chambers that matters, not the pressure and oxygen level. The rest time between sessions is likely important.

There is no strong evidence that the HBOT sessions affect PCS recovery. The studies have often focused on observing improved capillary growth. Anecdotal reports are often used to promote HBOT. The Boussi-Gross et al. study left a lot of questions. This study showed no benefit. http://journals.lww.com/headtraumare...sistent.2.aspx

Just be careful with the finances and expectations. One could spend a small fortune for a small benefit.