Spectral dependence of absorption sensitivity on concentration of oxygenated hemoglobin: pulse oximetry implications

Abstract

Abstract. The sensitivity analysis indicates that the effective absorption coefficient is most sensitive to the concentration of oxygenated hemoglobin in spectral bands centered at 700 and 960 nm. We find that the highest temporal modulation due to heart function for a thick sample, like an arm, is at 940 nm, a significant shift from 710 nm measured for a finger. The most favorable spectral region for a thick transmission sample, such as a forearm, is the domain defined by intervals ½900 nm ≤ λ 1 ≤ 1000 nm and ½650 nm ≤ λ 2 ≤ 720 nm. We evaluated five near-infrared light-emitting diodes (LEDs) for their potential applications in oximetry. The LED with peak emission at 930 nm emits well in this spectral region. Here the temporal noise is low, and the effective absorption coefficient is strongly dependent on the concentration of the oxygenated hemoglobin. High-quality saturation results are obtained through the forearm during a short measurement (30 s).

Detection of Differentiated Tissue with Pulse Thermography

“…[5] The obvious advantage of the detection of abnormal tissue in-vivo with IR radiation is its human-friendliness. Additionally, the living tissue is may be probed within the so-called therapeutic spectral interval, encompassing red to near IR [6], permitting transmission of illuminating radiation up to the point where a boundary between two optically/ physically different materials is encountered. Fig.…”

An applicable approach for extracting human heart rate and oxygen saturation during physical movements using a multi-wavelength illumination optoelectronic sensor system

“…Pulse oximeters are non-invasive devices designed to measure SpO 2 %. Haemoglobin is the oxygen-transport metalloprotein in the red blood cells [17] and as the light absorption of oxy-haemoglobin (HbO 2 ) is different from that of deoxyhaemoglobin (Hb) at different wavelengths of the spectral window, then, from a ratio of the absorptions at two different wavelengths, SpO 2 % can be determined. Figure 2 Figure 2.1 Absorption spectra of HbO 2 and Hb [18] As tissues in the body generally contain water, they generally absorb light more strongly in the longer wavelength IR region [3] , whereas melanin is known to absorb more light at shorter wavelengths [2] .…”

Tissue characterization with ballistic photons: counting scattering and/or absorption centres

“…In the future, we plan to use a Nd:YAG laser, with nominally 100−W output power at 1.064 μm. Around 1 μm tissue is more transparent to the radiation than in the visible [30]. The output beam of this laser has been characterized for its power density as a function of position and power level [31].…”