Our son would go through this at different stages. Beyond the distracting and making the time a special time for doing things he liked, I think it is important to make it clear that he has to do it and that I will wait for him to be ready. So if he was fussying and fighting, I'd say "you seem to be having a hard time. You must do your nebulizer and your vest." And then I'd do one of a few things: say, "I'll wait until you are ready" and turn off and not engage at all until he was quite and then I'd start up and immediately do something fun and give lots of over the top attention. If he tried to get up, I'd say "no, we can't play until we're done with your treatments," pick up, etc. Sometimes I'd say instead "I'll give you two minutes for a break" and then when it was over say something like "okay, now let's do X," and start the fun thing and start up again. And then if it was lots of breaks and lots of fussying I'd say after when we would want to do something, "Oh, I'm sorry. You took so long with your vest, we don't have time to do X now." Or I'll say "oh, I'm sorry, I don't have enough energy to do X because you were so icky while we were doing your treatments." I think the distraction is great but the matter of fact expectation that they will do it and stopping when the fighting starts (so they don't get the extra attention then), helps. fwiw.