A novel hybrid reflectance pulse oximeter sensor with improved linearity and general applicability to various portions of the body

The objective of this study was the development of a reflectance pulse oximeter sensor for broader clinical applications, specifically for broader arterial oxygen saturation (SaO/sub 2/) measurement from various body portions. To enhance the reflectance pulse amplitude from any body surface and eliminate the effect of tissue inhomogeneity, the new sensor incorporated ten LED chips for each wavelength mounted symmetrically at the radial separation distance of 7 mm around a photodiode chip. Based on the photon diffusion theory, the wavelength combination, 730/880 nm, was determined to obtain a linear relationship between the reflectance ratio and broader SaO/sub 2/ range from 100% to 30%. The improved linearity of the new sensor was evaluated in dogs (n=5) in comparison to the 665/910 nm conventional wavelength sensor. Additionally, this new reflectance sensor was applied to various body surfaces in healthy human adults (n=30). The relative reflectance pulse amplitudes from the fingertip, forehead, and chest were 1.0, 0.3, and 0.1 as normalized to the fingertip at each wavelength. These results will broaden the application sites of the reflectance pulse oximeter sensor in the hospital and home healthcare.