Heart-lung machines are key components of cardiac surgery. Their main purpose is to replace cardiopulmonary functions during surgical interventions in the open heart. While today’s heart-lung machines are robust and reliable devices, their early versions were highly precarious assemblages. When US surgeon John H. Gibbon, Jr. (1903–1973) started to develop the heart-lung machine in the 1930s, minor factors such as the irregular flow of blood through the tubes and vessels of machine and organism could quickly result in death. In fact, throughout all the stages of its development – from Gibbon’s early animal experiments to his successful cooperation with IBM following World War II – the heart-lung machine required meticulous strategies to control the blood flow. Based on new archival evidence, this paper reconstructs the development of the corresponding control systems, situating them within the material culture of their time. It argues that Gibbon’s work crucially relied on devices of and evolved from media technology: Gibbon started out by adopting instruments from telegraphy systems, but increasingly incorporated electronics derived from radio research laboratories. As a result, it will become clear that the heart-lung machine evolved within complex intersections between academic medicine, industrial research, and amateur radio.
