Woah, nice, thanks for all that research! Yeah, it looks pretty much just how you described it. So, my statement, "no research backs it up" was wrong - there was research in the 70s and 80s that DID indicate it, so there WAS evidence. Thus, this is a case of "Old ideas in the process of getting overturned... maybe" and not "people doing it without science backing it up".
I don't have access to UpToDate here (because they recently skyrocketed their prices so my school is switching), so I only read emedicine.
EDIT: I can only read the abstracts, and nothing from the 70s article, so this input is limited. That said, the 80s article seemed to look at all aspiration pneumonias (most of which was are caused by chronic aspiration), while my professor's point was specifically about one-time aspiration (i.e. aspirating vomit). I did not make that distinction clear in my OP. So, you're right, though I wanted to defend my professor, because I think his point might still stand, though my post did not present the full story. I'd look more into the research, but I probably won't find the time. Yvain's a real trooper for wading through all those articles.
Today I Learned in Medical School:
Doctors have medical myths too! According to my prof, many doctors believe that aspiration (having stuff go down into the lungs) causes anaerobic pneumonia, but that is rarely the case. He says that myth is often taught resident-to-student, but it isn’t actually backed up by any research, and isn’t true. The kicker - if the doctor would stop to think about it, it should jump out as unintuitive – it would take some serious changes inside the *lung* to make an *anaerobic* infection – an infection of bacteria that thrive in areas with no oxygen. In reality it takes frequent aspirations over a long period of time to block off an area of the lungs.
I think the moral of this story (though this just may be preaching to the choir here at LW) – all people, be they doctors or kindergarteners, don’t usually check facts they’re taught, especially when being taught by an authoritative teacher. Unless they’re lead to discover/derive a fact themselves, they usually assimilate it into their network of beliefs as a brute fact – “carbon has four valence electrons,” “don’t end a sentence with a preposition,” “in 1492 Columbus discovered America.”
Now, you frequently don’t have enough time to “learn it the hard way” or derive an answer yourself. If I had to read every single research publication that populated the facts in my textbooks, I might not ever graduate. However, it is important to remember that you’ve taken shortcuts for most of your education (and religion/lack thereof, and life in general) – and if some fact ever later strikes you as being odd, look into it. Otherwise, we’re just playing the telephone game.