I took Calvin to his doggie daycare today for a playdate and one of the employees heard Calvin cough when he was pulling towards the door..(He LOVES this place), anyway, he said I may have damaged his trachea when he was pulling on walks. I told him I stopped using the choke chain after about 2 walks because it was clear that he was not going to stop pulling..and got him a gentle leader and have used it ever since. Then he said maybe he has kennel cough which I vaccinated him for. I will be devistated if I have somehow hurt him and/or his trachea. Has anyone had any experience with this? What does kennel cough sound like? He goes to this daycare once a week for 4 hours. They require all dogs to have the bordatella vaccine...So how could it be that? Help?