You havent shared for how long he has been suffering from this. neither have you shared any investigation reports
Next Steps
TC,DC, CHEST XRAY PA VIEW, if any abnormality is seen then treatment accordingly.if no abnormality then get a spirometry done. which will decide upon the need of inhaler medications if any ( ICS +LABA)
Health Tips
Consult a pulmonologist who'll guide you with your dad's therapy. Wish him speedy recovery.