There is another site with some good ideas on planning your conversation with your doctor: https://patientrevolution.org/visit-tools. If it were me, I might want to ask the doctor what he is looking for when he wants to observe your husband. Another question might be does your husbands symptoms fit the diagnosis of Orthostatic Hypotension. You might want to write a list of questions you have to take them with you to make sure they all get answered.
How is your husband feeling about waiting until the doctor makes some observations?