Hello and welcome to Just Answer. I am a licensed veterinarian and would be happy to answer your questions.
Is this his rate at rest? How long has it been that way? Is he breathing with his mouth open?
When is the last time Jones was examined by your vet? Do you remember if they listened to his chest then?
An increased respiratory rate at rest can be a sign of various conditions. Heart disease with fluid build up in the chest cavity is one of the most common. The fluid can build up outside of the lungs and compromise lung space along with an enlarged heart. Pain can sometimes be a cause of an increased heart rate, but usually not to that extent. Metabolic changes due to organ dysfunction that leads to an acidic state in the blood can be another cause, but usually the affected pet would not be feeling very well so there would be other signs. His being overweight most likely does limit his ability to expand his chest normally to inhale fully, but should not be causing any changes in his breathing at rest.
I don't think his previous changes noted with his kidneys are related. Even if his kidney function has deteriorated some, I wouldn't expect it to have any bearing on his breathing. I would make sure to have your vet examine him as soon as you can get him in so that a proper diagnosis can be made. Good luck and please let me know if you have any further questions.