The light still shines, but not that brightly? The current status of perinatal near infrared spectroscopy.

Efforts have been made to find new, non-invasive methods for assessing tissue oxygenation and haemodynamics, particularly in the brain of the fetus and the newborn infant. Near infrared spectroscopy (NIRS) is a developmental technique that provides just such a method, allowing calculation of variables such as cerebral blood flow and cerebral blood volume. It can also measure peripheral oxygen consumption. This review is based on our long experience of using NIRS. Basic principles, techniques, validation, and clinical applications are highlighted. Although more than two decades have passed since its introduction, NIRS remains very much a developmental technique, despite technical progression. A great deal more research is required for NIRS to become a routine clinical tool.