Shortness of breath as possible side effect of Zolpidem tartrate?

I have been taking Zolpidem tartrate for about 2 years. In the beginning now and again, in the last few months half a 10mg tablet every night. For years I have suffered from occasional asthma and a general, but mild shortness of breath, due to having only half a lung and a heart valve replacement. Co-inciding with the regular taking of the sleeping tablet, I have noticed an increased and severe shortness of breath, which does not seem to be like the usual asthma problem. Is it possible this is connected to taking Zolpidem?
I am also taking other medications, i.e.
hypertension = Karvezide
colesterol = Simvar
stomach acid = Omeprazole
heart = Sotacor or Sotalol
Also could there perhaps be an interaction between the various medications to cause the increased breathing problem??
So far, I have been unable to get any professional advice on the matter. I would be grateful if you could provide me with some answers.