Review: Near-infrared brain and muscle oximetry: from the discovery to current applications

"In the early 1960, Norris introduced near-infrared (NIR) spectroscopy (700-2500 nm) as an analytical technique for agricultural products. In 1977, Jöbsis founded in vivo medical NIR spectroscopy reporting that the relatively high degree of transparency of brain tissue in the NIR spectral window (700-1000 nm) enables safe real-time non-invasive detection of regional haemoglobin oxygenation using transillumination spectroscopy. In order to place the current medical NIR spectroscopy in its proper perspective, this article provides a snapshot of the roots of the discovery and the early years of medical NIR spectroscopy research and development. Starting in 1992 the opportunity of measuring quantitatively, by different NIR spectroscopy techniques, regional oxy-haemoglobin saturation by NIR oximetry, it is possible to monitor brain\/muscle reserve capacity following tissue oxygen extraction in different pathophysiological conditions. This review article reports the status of the current commercial oximeters (including wireless instrumentation) and their main clinical and physiological applications. In the last decade, NIR spectroscopy brain oximetry has obtained significant clinical relevance as suggested by the over 10,000 instruments sold and the high number of the related scientific publications. The most relevant clinical application is represented by the evaluation of cerebral oxy-haemoglobin saturation during adult cardiac surgery and cardiopulmonary bypass. Many commercial oximeters are presently available. However, their relatively poor precision and the lack of standardization amongst the different instruments suggest that further technological advances are required before NIR spectroscopy oximetry can be adopted more widely under the “guide lines” of regulatory authorities."