Yeah, this is really dependent on whether or not Respira works like every reiatsu based attack in the series. A Reiatsu that's high enough could simply shrug it off, if that were the case. Which would mean that Vasto Lorde Ichigo could probably just walk through it, unfazed.
I can see that being the case, honestly. Which is why I think it would have been useless against Aizen, even if he had gotten to use it directly on him.
That's also true. Going by sheer placement of the Espada, Barragan not being the Primavera should mean that he could be defeated by Stark, which likely means that Stark is strong enough to overcome Respira. Or at least resist it. Who knows though, it could be because of his Camarades. Maybe they don't age, since they're soul fragments. So they could be like Barragan's kyrptonite, essentially.