I always have clogged up nasal passages almost all my life. I sometimes I think the difficulty of breathing through my nose will cause an attack although I can't say it ever has. I actually have no idea what causes my attacks, they are so random and I am a positive thinker. My panic attacks have become a lot more frequent lately. One thing I noticed though is that no matter how stuffy my noise is before an attack it is always clear during a panic attack or quickly becomes clear. Has anybody else ever noticed this? In fact during the worst part of my last attack when I could not swallow between taking breaths I had drainage from my noise going down the back of my throat. I know many of the reasons for most of my bodies symptoms like tightness, numb fingers, racing heart and so on. But I have not found any explanation behind my nasal passages becoming clear. I don't even see this change being mentioned. Has anybody else noticed this and do you understand why this body change happens? Am I alone on this one lol?
When your heart race increases and you are in a fight of flight response I believe the blood vessels constrict and reduce inflammation, which is a potential reason for this. I notice my sinuses clear when I get up and move around and I suffer from seasonal allergies.
I also experience the draining in the back of my nose frequently, and I do believe there is some hormonal shifts during a panic attack. I am aware cortisol blood levels increase during such an episode. Having said this though, I am not a health professional so I cannot guarantee what I say is true for your case.
I am sorry to hear you are suffering with panic attacks though. I hope you find some relief in this post though. Take care of yourself 
Kyle