Extracorporeal
oxygenators are artificial devices that substitute for anatomical lungs by delivering
oxygen to, and extracting
carbon dioxide from, blood. They were first conceptualised by the English scientist Robert Hooke (1635-1703) and developed into practical extracorporeal
oxygenators by French and German experimental physiologists in the 19th century. Indeed, most of the extracorporeal
oxygenators used until the late 1970s were derived from von Schroder's 1882 bubble
oxygenator and Frey and Gruber's 1885 film
oxygenator. As there is no intervening barrier between blood and
oxygen, these are called 'direct contact'
oxygenators; they contributed significantly to the development and practice of cardiac surgery till the 1980s. Membrane extracorporeal
oxygenators introduce a gas-permeable interface between blood and
oxygen. This greatly decreased the blood
trauma of direct-contact extracorporeal
oxygenators, and enabled extracorporeal
oxygenators to be used in longer-term applications such as the intensive
therapy of
respiratory distress syndrome; this was demonstrably beneficial for neonates but less so for older patients. Much work since the 1960s focused on overcoming the gas exchange handicap of the membrane barrier, leading to the development of high-performance microporous hollow-fibre
oxygenators that eventually replaced direct-contact
oxygenators in cardiac theatres.