Asthma is quite common in cats. My Wellington has always had it and Bonaparte has what are almost asthmatic attacks from tim to time, though the vet can't hear anything. The only real way to tell is with an Xray of the bronchial tubes, though if the cat has regular coughing fits with its head down and stretched out, and wheezes at other times, then it could well have it. And watch for the circumstances - different factors bring it out in different cats - cold weather, wet weather, dust, etc. there are various treatments - one of the most common is prednisone, taken in gradually reduced dosages till the condition is under control, then the minimum possible for the rest of its life. Sometimes a young cat will grow out of it, as sometimes an older cat will suddenly develop it. But ask your vet and take the cat for a full examination if you really think it is possible - it is a life-threatening condition and my sister's cat died of it a few years ago.