[sp]Generally speaking, the treatment interval (up to four hours) of which you spoke would not be inordinately long if one encountered a case of simple joint pain-only decompression sickness (the bends). However, if one is dealing with any type of neurological problems, then one must ever bear in mind that nerves die when the blood supply is blocked. [This is recognized in the general situation when someone gets a stroke. There may be good recovery or there may be very little.] I would certainly plan for the worst-case scenario, that is, neurological DCS.
[sp]When transport times are on the order of hours, there is always the chance that the treatment outcome will be less than expected. It is an unfortunate reality of recreational diving that divers will seek out remote sites that are pristine and untouched since they are remote. Regrettably, the treatment sites are likewise far removed.
[sp]In addition, be certain that one has insurance, such as can be purchased from DAN, since transport to a chamber becomes very uncertain when payment to the carrier is not guaranteed.