Confusion and hallucinations are unlikely to be caused by a stroke. Stroke are almost always associated with some type of specific neurologic loss of function - such as weakness or numbness of one side of the body, visual loss, language dysfunction, etc. Confusion and hallucinations are almost always caused by something called "encephalopathy". The risk factos for encephalopathy include 1)age, 2)pre-existing memory trouble, 3)co-existing medical conditions. Your father, being 79, with several medical problems, is more likely suffering from encephalopathy. Treatment of his lung issue is most likely to provide the best relief of the problem.