Near infrared spectroscopy: methodological principles and clinical application in preterm infants

Neonatal encephalopathy, plausibly related to hypoxia and ischaemia, remains one of the main problems in perinatal medicine. Efforts are necessary to find new non-invasive methods for assessing brain oxygenation. Near infrared spectroscopy (NIRS) provides information on the concentrations of the oxygenated and deoxygenated forms of haemoglobin, as well as of the redox state of cytochrome aa3. Different important variables such as cerebral blood volume and flow, and the responses of these to changes in pCO2, can be derived through haemoglobin measurement. Changes in cytochrome aa3 may provide immediate information on intracellular oxygen utilization. Various studies have shown the feasibility of NIRS in preterm infants. Methodological and technical problems of this method are discussed.