Airway obstruction when coughing

My husband, age 35, has been sick for about three weeks now. It started after a four wheeling trip where there was a lot of dust blowing around. He has had a chronic cough where he will cough up grayish-greenish mucus and he feels a little tightness of the chest probably from some asthma. For the last five days, his cough has become more serious. Many times when he coughs hard he will temporarily not be able to breathe AT ALL! No inhaling, no exhaling for about 10-30 seconds. It's very scary. His airway will then slowly open up, accompanied by a wheezing sound with the sensation of breathing through a straw. He also has difficulty talking for a few minutes after.

He went to visit an urgent care physician who did chest x rays and blood tests. Both came back normal. The doctor prescribed antibiotics, inhalers, breathing treatments, and allergy medication. He has since finished the antibiotics and had been consistently taking the other meds, which seem to help with his overall breathing, but the airway obstruction issue still persists.

My husband describes the airway obstruction as feeling as though his epiglottis is blocking his airway???

My husbands background: Never smoked. No non prescription drugs whatsoever. When in college he interned  as a road construction supervisor exposing him to harsh asphalt chemicals and second hand smoke. He also worked as an engineer in the carbon fibers industry for four year. He then ran a powdered metal facility for three years-again harsh particles to inhale.