Tennessee has allowed a small metal device called a vena cava filter that is designed to protect against pulmonary embolisms to be exempt from their sales and use tax as a prosthetic device. The State defines a prosthetic as a device that replaces a missing body part or augments the performance of a natural function. Since the filter augments the function of the pulmonary veins by preventing clots from blocking the veins, it qualifies as a prosthetic device. The intruder system used to place the filter is also exempt as a prosthetic device because any disposable unit that holds and delivers an exempt medical device acts as a single item that qualifies for the prosthetic device exemption. (Revenue Ruling No. 06-15, TN Dept of Rev, May 4, 2006)