This article focuses on information related to the physiologic aspects of the TCI mechanical left ventricular assist device (LVAD). The two types of LVADs designed by ThermoCardiosystems, Inc., Woburn, Massachusetts, are discussed, but most of the information provided relates to the pneumatic TCI LVAD. The structure and function of the two LVADs, including device similarities and differences, are discussed first. Then physiologic, device, and treatment variables that influence the nursing care of patients requiring the pneumatic TCI LVAD are presented. Pneumatic console operator role and qualifications used at Sharp Healthcare and suggestions for future nursing research involving the TCI LVAD are provided.