I'm HIV specialist board certified in FP. I just had an emergency on Emirates flight 3/23/11 from MEL-DXB. Woman with syncopal episode. They had her supine in the galley & were giving her oxygen. But when she sat up she'd get nauseous & lightheaded. I did hx & found out she had had similar episodes in past. The crew was great, had nice equipment & satellite hook-up. We were about 4-hours out, so they were concerned they didn't have enough O2 for 12-hour flight, and we reached a point where there wasn't really an airport close to divert to (Indian Ocean I'm guessing). She was better after 1-2 hours without O2 & we laid her down in 4 Y seats & she did fine. I didn't have my license, but did give them an blank Rx with my name/office on it.
But I have had others: AKL-LAX woman with abdominal pain (REALLY in the middle of nowhere with no airport close). Woman fainting going to bathroom (CLUNK). A guy with abdominal pain just before take-off (interesting we went back to gate, but the guy's checked luggage was left on the plane. Several pax in 1st were concerned, asked me if guy was really sick, and 3-4 other pax deplaned because of security concern).