Importance

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Abstract

A improved pulse oximeter comprises first and second light-emitting diodes that apply red light and infrared light, respectively, to a living tissue including the arterial blood, a photodiode for detecting optical outputs as produced after the red and infrared light of two wavelengths issuing from light-emitting diodes have been absorbed by the living tissue, a first computing unit that computes the ratio between the pulsating components of light absorbance .PHI. for the two wavelengths due to the arterial blood on the basis of the dc components and pulsating components of the respective wavelengths that are obtained from the reception outputs of the photodiode, a correction circuit that not only detects the degree of fluctuation in the absorbance ratio .PHI. as produced from the first computing unit but which also holds the pulsating components of the respective wavelengths when they are stable and which, if there is a fluctuation in the absorbance ratio .PHI., computes a corrected absorbance ratio .PHI.' using the pulsating components of the respective wavelengths that were held at the stable time and the dc components of the respective wavelengths at the present time, and a second computing unit 16 for computing the oxygen saturation of arterial blood on the basis of the absorbance ratio .PHI.' as produced from the correction circuit. This pulse oximeter permits the intended measurement to be continued consistently even if there occurs noise due to body movements and yet it is capable of measurements with good response.

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First Claim