Electronic processor for pulse oximeters

An apparatus for calculating arterial oxygen concentration using an electrical signal generated by a probe, comprising:

• at least one demodulator coupled to the probe for converting the electrical signal to digital data;
• a controller coupled to the at least one demodulator for processing the digital data to calculate the arterial oxygen concentration;
• and
• a control signal generator coupled to the controller and a drive circuit for driving a source of electromagnetic radiation in the probe, the control signal generator for generating a drive signal for the drive circuit, the drive signal being generated without intervention by the controller after the control signal generator is initialized by the controller;
• wherein the control signal generator also generates a gating signal for gating the electrical signal to facilitate synchronous detection, the gating signal being generated without intervention by the controller after the control signal generator is initialized by the controller;
• wherein the at least one demodulator comprises an analog-to-digital converter having a dynamic range, and the electrical signal has an amplitude range, the dynamic range being sufficient to cover the amplitude range without clipping, thereby eliminating a need to manipulate the amplitude range of the electrical signal.

An apparatus for calculating arterial oxygen concentration using a first electrical signal generated by a probe, comprising:

• at least one demodulator coupled to the probe for converting the first electrical signal to digital data;
• an interface coupled to the demodulator for receiving the digital data and generating interrupts when a plurality of samples of the digital data has been received;
• a buffer memory coupled to the interface for storing the digital data;
• and
• a controller having a controller memory, the controller being coupled to the buffer memory, the controller transferring the digital data from the buffer memory to the controller memory in response to the interrupts, the controller for processing the digital data to calculate the arterial oxygen concentration.

An apparatus for calculating arterial oxygen concentration using a first electrical signal generated by a probe, comprising:

• at least one demodulator coupled to the probe for converting the first electrical signal to digital data, said demodulator including
• an analog switch coupled to the probe for intermittently switching the first electrical signal to ground, thereby generating a switched electrical signal,
• a filter coupled to the analog switch for filtering the switched electrical signal, thereby generating a filtered electrical signal, and
• an analog-to-digital converter coupled to the filter for converting the filtered electrical signal to the serial digital data;
• an interface coupled to the demodulator for receiving the digital data and generating interrupts when a first amount of the digital data has been received;
• a buffer memory coupled to the interface for storing the digital data;
• and
• a controller having a controller memory, the controller being coupled to the buffer memory, the controller transferring the digital data from the buffer memory to the controller memory in response to the interrupts, the controller for processing the digital data to calculate the arterial oxygen concentration.

A method for calculating arterial oxygen concentration using a first electrical signal generated by a probe, the first electrical signal comprising a plurality of phases, each phase corresponding to a period during which a particular type of electromagnetic radiation is being received by a sensor in the probe, the method comprising the steps of:

• sampling each phase of the first electrical signal a plurality of times, thereby generating a plurality of samples for each phase;
• converting the samples from each phase to first digital data;
• averaging the first digital data from each phase, thereby generating average digital data for each phase, and increasing a signal-to-noise ratio for each phase;
• generating second digital data for each phase from the average digital data;
• and
• calculating the arterial oxygen concentration by analyzing the second digital data.

An apparatus for calculating oxygen concentration using a first electrical signal generated by a probe, the first electrical signal comprising a plurality of phases, each phase corresponding to a period during which a particular type of electromagnetic radiation is being received by a sensor in the probe, the apparatus comprising:

• a demodulator for receiving the first electrical signal and sampling each phase a plurality of times, thereby generating a plurality of samples for each phase, the demodulator converting the samples from each phase to first digital data;
• a logic circuit coupled to the demodulator for filtering the first digital data from each phase, thereby generating filtered digital data for each phase and increasing a signal-to-noise ratio for each phase, the logic circuit generating second digital data from the filtered digital data;
• and
• a controller coupled to the logic circuit for calculating the arterial oxygen concentration by analyzing the second digital data;
• wherein at least three phases of at least one first electrical signal cycle comprise a first phase corresponding to a first electromagnetic radiation, a second phase corresponding to a second electromagnetic radiation, and a third phase corresponding to ambient background radiation, and wherein the logic circuit is for subtracting the filtered digital data for the third phase from the filtered digital data for the first phase to produce second digital data for the first phase, and subtracting the filtered digital data for the third phase from the filtered digital data for the second phase to produce second digital data for the second phase.