His breathing has become increasingly difficult.
He has to breathe through his mouth.
He is short of breath, even when he is not exercising, he is breathless.
His cough is more like wheezing.
His cough is dry, producing no phlegm.
He has coughed up blood.
He caught a cold and got a stuffed / stuffed up nose and a sore throat.
He coughs up a lot of phlegm （thick spit）.
He has a feeling of tightness in the chest or a feeling that he is suffocating.