Hi tnt, that's a perfectly reasonable question, and I'll try to answer it.
In their original paper, Eissenberg and colleagues trialed e-cigarettes on 'naive' smokers - i.e. smokers who had never used an e-cigarette before. They measured nicotine blood levels after the smokers had puffed on an e-cigarette as if they were puffing on a cigarette. This was compared to the levels of smokers who had just smoked a tobacco cigarette.
On this site, there was a long discussion in which Eissenberg took part (it got pretty heated!). ECF members held that the comparison wasn't valid; that vapers tend to puff for longer and over longer periods of time. Eissenberg is now conducting similar research to see what the effect is on experienced vapers, so as to gain a better understanding of how e-cigarettes really work with respect to this specific (and valid) research question - i.e. nicotine blood levels.
It would, therefore, be of great benefit to all of us for anyone who is able to get to their lab to take part.
Is this lab at Boston University? I'd love to take part in this! I need more info. Where can I get it?