In reply to:

Sedation will also sedate the cilia, the little hairs of the cells lining the lungs, which act as an escalator to move bacteria and gunk (technical term) up and out.

Now that's the kind of inside information I knew we'd eventually get around to hearing about! Thanks, Zed. The sleeping pill statement was extremely puzzling--and the open-mouth theory just didn't strike me as being quite plausible since I doubted that all who took sleeping pills automatically slept with their mouths open. But your points make more sense, and this point about the sedated cilia is fascinating.