I agree. That the study has some flaws doesn't mean there isn't other good information out there to recommend against using the Sawyer extractor. I've read varying accounts on the effectiveness of the device. I wonder if some of the variables I mentioned are factors in that.

As for the whole circulation question, one of the things I read some time ago made the point that letting the poison circulate has the potential benefit of dilution. The more the poison is allowed to spread and dilute, the weaker its effect in those areas to which it has spread. The reality may simply be that for every person and bit combination that somewhat different treatments may be optimal.