Great question. Intuitively, the time in chamber for each treatment might be based on the ATA available. So if it is, say, 1 hour 50 minutes with 2 ATA, one might want treatment to last 2 or more hours at 1.3 to 1.5 ATA. Personally, if there was a 1.3 ATA treatment available locally I would go for it.
I just finished 35 of 40 2ATA HBOT sessions that I had to travel 450 miles round trip for. Fortunately I was able to stay with my son who lives a 20 minute walk from the facility.
I plan on doing the remaining 5 sessions next month but at a facility 200 miles roundtrip from me. What I wonder about is if there is any drop off in effectiveness when the treatments are discontiguous. My 35 treatments were over a 13 1/2 week period because I suffered a pneumothorax after a bad fall and had to postpone treatment for a month while it healed. My remaining 5 will be after a 7 week hiatus.
I had two reasons to seek hyperbaric therapy. First was to counter the effects of IMRT on my prostate and pelvic lymph nodes and hopefully overcome radiation proctitis symptons. The second reason was to counter some negative effects on my right leg after a total knee replacement wounding. A side benefit was to experience the rejuvenating effects (anti-aging?) of the treatment.
Time will tell more but at this point in time I have not had a resolution of my radiation proctitis symptoms, my right leg has more "life" in it now but with room for more improvement and the anti-aging effects will be subtly expressed as I continue to age using future blood tests as a barometer.
I just received my first "electro-acupuncture" treatment for "overactive bladder" so I am hopeful that I will see improvement over the next several treatments. Fortunately, that clinic is only 70 miles round trip!
Best wishes to you.

Thank you for your input! I am told my insurance will not cover 1.3 ATA chamber sessions I would have to pay out of pocket. Please let me know if your treatments took care of the problems. I am leaning towards the local facility because the costs of the stay away from home exceeds the out of pocket costs. Thats why I was wondering if the 1.3 ATA would be enough to take care of my situation.

I did a quick Google search on 1.3 HBOT and it looks like it is an effective pressure to achieve benefits.
https://www.google.com/search?client=safari&rls=en&q=1.3+ATA+HBOT+effectiveness&ie=UTF-8&oe=UTF-8
I would appeal the decision of the insurance company and get your physician involved. Fight them tooth and nail! Give them/him/her some of the info from the above link. In my case, my radiation oncologist gave me a referral to the HBOT clinic and they took it from there to get insurance approval with no problem. The clinic was part of a hospital so they deal with insurance companies all the time.

HBOT is not 100% effective but does have high percentage effectiveness. In my case it did not take care of my problem yet (I have 5 more sessions next month) so I might be one of the folks who keep it from being 100% effective.
Good luck.

I think it is the clinic that is giving me a run around about the insurance. I have Medicare and a supplemental insurance. I have called Medicare because it is the primary. They told me they can not find anything that says there is a difference between mild chamber and hard chamber. The clinic I think is a privately owned and sounds like they only want to deal with cash customers. I can rent a in home chamber for 1300, dollars a month which would be a 1.5ATA. That is not including the oxygen concentrator. From what I have found in researching a person can possibly do 2 sessions a day. That is why I am trying to find out if a 1.3 to 1.5 chamber will be effective. The cost of the clinic treatments which consist of 40 treatments for 1 hour a day is over 4000. dollars out of pocket. To rent one is a lot cheaper. Also I can purchase a 1.3 chamber for less than 7000. I have done a lot of research on my condition and everything I have found says I would definitely benefit from it. But have to keep in mind them treatments were done in a hard chamber with 2.0 ATA or higher with 100 percent oxygen. Thanks again for your input.