I watched a program on the discovery channel (or national geographic) recently on a study doing the same thing as yourselves. The scientists wanted to find methods to predict who would be susceptible and who would not. It was done in the alps, so search and rescue could get to them quickly incase of emergency (and yes it was needed). Firstly a study was done on the ground and then they went high up (lower altitudes than yourselves though with little acclimitisation)on foot and spent about a week in a well heated cabin. I can't remember what the results were, but it seems like the possible long term effect is death. One of the candidates (who they had predicted would be susceptible) got extremely ill, and noone realised because he didn't come to complain to the scientist he was feeling poorly, eventhough the expedition leader did check on everyone several times during the night. In the end the candidate had to be airlifted off the mountain, and he recovered fairly quickly on the ground. The doctors thought he would have died had he stayed up on the mountain for much longer.
Very interesting program, and if i can find the name of it i'll post it here.