The Good Morning Britain presenter — who shares an update on her husband’s long battle with the coronavirus in new ITV documentary Caring For Derek — revealed Draper, 54, underwent oxygen and pressure tests to check he would be able to cope with the 16 hour flight.
Garraway, 54, told GMB: "It's all come about because of the first documentary. This is a doctor who works in the US who has been working for 30 years on clinical trials before COVID came about.
"I can't say too much about it because I'm bound not to. When he saw the documentary he had already started helping people with the impacts of COVID and he saw Derek and said, 'I can help this man.'"
She added: "We are about less than a quarter of the way through this treatment.
"If this works it will be world hope that we get. It will help not just sufferers of Long COVID but all sorts of conditions.
"He is a very extreme case so he's useful as a trial, because if he can make progress with Derek he can help lots of other people."
The TV presenter flew Draper to the doctor's medical centre in Monterrey, Mexico, which was the easiest for them to travel to.
She said: "We hadn't really taken him out of the house at this point, and so it was very difficult to get him abroad...
'You get signs and flickers that he's absolutely there.'
Kate tells @susannareid100 and @richardm56 that in the gaps between the periods of fatigue that Derek experiences, he is '100% there'.
Watch Caring For Derek, tonight on @ITV at 9pm. pic.twitter.com/b6EPuNNAzM
— Good Morning Britain (@GMB) February 22, 2022
"I want to say thank you to British Airways. Obviously, we funded our own trip, but they gave us so much support, as they do to so many people who need it, and they're a wonderful team."
Draper, 54, is bed-bound after contracting coronavirus in March 2020 and has been left with significant brain injuries.
He returned to the family home — where he lives with Garraway and children Darcey, 15, and Billy, 12 — in April 2021 and requires round-the-clock care.
Garraway revealed: "You get signs and flickers that he's absolutely there. Then you then get periods of extreme brain fog, and it's unclear if that is just fatigue, brain fatigue or the effects of Long COVID.
"But in the gaps in between he's 100 per cent Derek Draper."
Caring For Derek airs at 9pm on Tuesday 22 February on ITV.
Watch: Kate Garraway says her MBE was not for caring for Derek Draper