No idea? It's your senario, feel free to fill in the blanks. You indicate an intercept with a ground ambulance, I have to assume they have the patient. The time required to land, tranfer care, transport, land, and hand off the patient in your senario v.s. transport 30 minutes via ground is pretty much the same. The flight crew has nothing more to offer this patient other than speed. I do a fair amount of mixed gas diving, never been 400 but been close to 300, in very cold, dark north atlantic water. I appreciate the urgency, but disagree air transport has a significant advantage over ground in the senario as stated.