Since you seem to be offline, ill leave a response here which we can discuss later on.
the first thing which should be excluded as a cause is asthma. If his lungs are clear and he does not have any productive cough, then asthma should be considered as a cause. It can develop at any age and can cause dry cough as well as shortness of breath in many elderly patients. This can be diagnosed on a simple clinical examination as well as with spirometry. This is one thing which would have been excluded by his doctor, you can ask him and if he hasnt he can do so now.
Secondly, since i dont know about his cardiac history i would like to rule out cardiac causes for his symptoms as well. This means that in some cases collection of fluid inside his lungs due to a decreased pumping action by the heart can lead to shortness of breath as well as cough. This would also cause in most cases shortness of breath on lying down and at night, however it is not compulsory. A simple echocardiogram can rule out heart issues along with blood tests like BNP.
Another cause for chronic cough in patients like your father can be due to GERD which is acid reflux. This can cause a metallic taste in his mouth as well as burning in the chest. however many patients present with just dry cough. This can be easily treated by simple lifestyle adjustments like raising the head of the bed, cutting back on caffeine etc and also by using drugs like OTC omeprazole.
Now if you can give me some more information i may be able to give you more insight into what else can be excluded in your fathers case.
Do you have any more questions?
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