What Causes Sudden Chocking Sensation Followed By Severe Coughing?

My husband will all of a sudden start choking. He may go 10 seconds or more without breathing. When he finally starts coughing, the cough will last a minute or so but then he is fine. He is a smoker and has been diagnosed with emphysema. What causes this and is it related to emphysema? It will happen just all of a sudden.