Welcome to the community Rory but sorry you have the need to join us!
Unfortunately, boost doesn't have enuf O2 to abort even 1 hit for most folks.
Many of us ditch the doc and O2 suppliers and put our own welding oxygen rig together.....cost is around $400 for a large (48" tall x 9" diameter) cylinder, a weld ox regulator from harbor freight......and the Clustero2kit from our sister site.......refills (exchange) runs me $21.
Dallas Denny