Chronic dyspnea could be due to many causes like heart failure, interstitial lung diseases,anaemia...Is that an episodic dyspnea or chronic continuous dyspnea..if it is episodic, could be due to the history of allergies also ...if he is a chronic smoker,it might be due to COPD ...and history of any pedal edema or periorbital edema or generalised edema need to be known.. Advised to get an x ray chest PA view, 2d echo,ECG,Hb,LFT,RFT..if everything is normal can go for PFT for further evaluation..

Is the cough associated with sputum, any exacerbating factors? Was he a smoker. Is he on any anti hypertensives, as they can also cause cough, as allergic history is there, has he taken any medication for that.? What is the range of BP

Pl consult.

Consult a pulmonologist with detailed history and get Evaluated Allergic airway disease should be ruled out

some antihypertensive medications are known to cause the cough..plus gerd can be there because of gall bladder surgery..that can also worsen his cough..kindly check and connect here

Get his cbc , chest xray and igE level , consult a pulmonologist . Start syp rapitus 10ml three times a day for 7 days meanwhile