Thanks for your question on Health Care Magic.
I can understand your concern.
Since he is active smoker, possibility of either
bronchitis or
lung infection is very high because fever, cough,
oxygen need etc are seen in both.
So better to
consult pulmonologist and get done
1. Clinical examination of respiratory system
2. Chest x ray
3. PFT (Pulmonary Function Test).
Chest x ray is needed to rule lung infection.
PFT is must for the diagnosis of bronchitis.
He may need antibiotics, inhaled bronchodilators and inhaled corticosteroid (ICS).
Smoking cessation should be done first.
So better to consult pulmonologist and discuss all these.
Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks.