The evidence for high flow nasal cannula devices in infants.

High flow nasal cannula (HFNC) devices deliver an adjustable mixture of heated and humidified oxygen and air at a variable flow rate. Over recent years HFNC devices have become a frequently used method of non-invasive respiratory support in infants and preterm neonates that is generally popular amongst clinicians and nursing staff due to ease of use and being well tolerated by patients. Despite this rapid adoption relatively little is known about the exact mechanisms of action of HFNC however and only recently have data from randomised controlled trials started to become available. We describe the features of a modern HFNC device and discuss current knowledge about the mechanisms of action and results of clinical studies in preterm neonates and infants with bronchiolitis. We also highlight future areas of research that are likely to increase our understanding, inform best clinical practice and strengthen the evidence base for the use of HFNC.