When a Patronus confronts a Dementor, the protective Patronus spell appears to be a solid shield. Thinking about a combined Dark Wizard/Dementor attack against Harry made me wonder if physical contact from a wizard would affect the effect of a Patronus spell, so I'm asking if JKR establishes whether or not the spell could be influenced by contact with people.
Does physical contact by a person with a cast Patronus shield negatively influence the effectiveness of the Expecto Patronum spell?