The compliant membrane 234 is preferably made of a compliant elastomeric or flexible material, such as a thermoplastic elastomer sold under the trademark C-Flex by CPT (Consolidated Polymeric Technologies, Inc.), silicone rubber, urethane, Mylar, Nylon, PEBAX, or any other material that will form a compliant wall membrane which will move sufficiently in response to blood pressure within the devi