DEFINITELY have a chest x-ray done if there is coughing which isn't easily
traced back to something like a case of influenza which is NOT thought by
your vet to have possibly worsened in pneumonia in that individual.  You
NEED to know up-front if you might be dealing with cardiomyopathy,
pneumonia, pleurosy (very rare but we've had one with it, -- x-rayed and
ultra-sounded), etc.  since these are serious conditions but their damage
(or rate of damage) can be stopped or slowed with RAPID appropriate care.
The vet may also want to do a head x-ray (in case there's a possibility of
a growth in a sinus contributing) or other testing as well.  As you all
should know by now, but which bears repeating -- we are not vets, just
owners with long experience.
[Posted in FML issue 2865]