Universal/upgrading pulse oximeter

DETAILED DESCRIPTION FIG.
1 illustrates a prior art pulse oximeter 100 and associated sensor 110.
Conventionally, a pulse oximetry sensor 110 has LED emitters 112, typically one at a red wavelength and one at an infrared wavelength, and a photodiode detector 114.
The sensor 110 is typically attached to an adult patient's finger or an infant patient's foot.
For a finger, the sensor 110 is configured so that the emitters 112 project light through the fingernail and through the blood vessels and capillaries underneath.
The LED emitters 112 are activated by drive signals 122 from the pulse oximeter 100.
The detector 114 is positioned at the fingertip opposite the fingernail so as to detect the LED emitted light as it emerges from the finger tissues.
The photodiode generated signal 124 is relayed by a cable to the pulse oximeter 100.
The pulse oximeter 100 determines oxygen saturation (SpO.
sub.
2) by computing the differential absorption by arterial blood of the two wavelengths emitted by the sensor 110.
The pulse oximeter 100 contains a sensor interface 120, an SpO.
sub.
2 processor 130, an instrument manager 140, a display 150, an audible indicator (tone generator) 160 and a keypad 170.
The sensor interface 120 provides LED drive current 122 which alternately activates the sensor red and IR LED emitters 112.
The sensor interface 120 also has input circuitry for amplification and filtering of the signal 124 generated by the photodiode detector 114, which corresponds to the red and infrared light energy attenuated from transmission through the patient tissue site.
The SpO.
sub.
2 processor 130 calculates a ratio of detected red and infrared intensities, and an arterial oxygen saturation value is empirically determined based on that ratio.
The instrument manager 140 provides hardware and software interfaces for managing the display 150, audible indicator 160 and keypad 170.
The display 150 shows the computed oxygen status, as described above.
The audible indicator 160 provides the pulse beep as well as alarms indicating desaturation events