From the CAA's own website
Class 2
(b) Chronic obstructive airways disease
Applicants with only minor impairment of pulmonary function may be assessed as fit.
He DOES require oxygen at home ; we all do ! Presumably not out of a cylinder, and breathed from a mask, though !
Seriously ; COPD would have to be pretty bad to render someone unfit for class 2. Low level (not 8k cabin alt), minimal exertion, etc. If he does not look or sound distressed to you, on the ground, the chances are he is OK.
