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Your physician will explain the procedure to you and offer you the opportunity to ask any questions that you might have about the procedure.
Generally, no prior preparation, such as fasting or sedation, is required.
Your physician may give you specific instructions about smoking and consuming caffeine. You may be asked to refrain from smoking for at least two hours before the test, as smoking causes blood vessels to constrict. You may also be asked to refrain from consuming caffeine in any form for about two hours prior to the test.
Based upon your medical condition, your physician may request other specific preparation.