What Causes Difficulty In Breathing In An Elderly Person?

Hello. I am calling concerning my mother who is 73 years old. She had surgery on May 18th 2017 which consisted of fusing three lower disks in her spine together. She is still healing from that but has had different issues lately. She is congested and is having a hard time breathing. She has been to the hospital on numerous occasions concerning this and they've done xrays, catscans, ekgs, etc... with nothing to show whats going on. My question is this I do feel she has some paranoia going on due to the meds she was on and the symtoms she is having but she was a HEAVY smoker before this surgery and hasn't had one cigarette since the beginning of May, which I am thankful for...... but could her smoking menthol cigarettes and then quitting be part of the reason for her congestion. She is constantly having Vicks vapor rub by her bed smelling in and putting it on her nose. I didn't know if the menthol in the cigarettes could have been something that helped her breathing.
Sincerely
A concerned daughter