Use of Near-Infrared Spectroscopy in the Neonatal Intensive Care Unit

Use of Near-Infrared Spectroscopy in the Neonatal Intensive Care Unit

G. Naulaers (University Hospitals Leuven, Belgium), A. Caicedo (KU Leuven, Belgium) and S. Van Huffel (KU Leuven, Belgium)
Copyright: © 2012 |Pages: 28
DOI: 10.4018/978-1-4666-0975-4.ch004
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Abstract

Near-infrared spectroscopy was first described in 1977 as a non-invasive technique to measure the cerebral oxygenation and cytochrome oxydase. Different techniques have been developed resulting in new instruments that make it possible to measure cerebral oxygenation in a non-invasive way. In this chapter the physiology and pathophysiology in relation to the measurement of cerebral oxygenation are explained and the direct possible clinical use enlightened, with special focus on measurement of ischemic cerebral hypoxia. The measurement of other organs like the liver, the bowel and the peripheral circulation are described. At the end, a short overview of future possible bed-side measurements like functional near-infrared spectroscopy, near-infrared imaging and photoacoustic measurements are given.
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2. Technique Of Near-Infrared Spectroscopy

The relative transparency of biological tissue to light in the near infrared part of the spectrum (700-1000 nm) enables photons to be detected following passage through tissue at distances of up to 8 cm. As the light passes through the head it is attenuated due to a combination of absorption and scattering. Brain contains three changing chromophores that are present in variable concentrations: oxyhaemoglobin, deoxyhaemoglobin and cytochrome oxidase. Attenuation of transmitted light in the brain due to other causes (muscle, bone, bilirubin, ...) will be assumed to be constant over the period of monitoring. Consequently any change in observed attenuation is due to a change in the concentration of these chromophores. Because of safe levels of light input, it is difficult to use source-detectors distances of more than 5 cm (Wolf, 2009) and because of scattering and acquiring enough depth of measurement the minimum interoptode distance will probably be around 1.5 to 2 cm (Faris, 1991). The depth measured with this method is around half of the source-detector distance, so between 1 and 2,5 cm (Choi, 2004). Different techniques are used to measure the cerebral oxygenation.

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