Method and apparatus for determining physiological characteristics

A method for determining the blood oxygen saturation level of a subject, said subject having a tissue region and a heart, comprising;

• passing first and second lights through said subject's tissue region, said first light being substantially in a red light range and said second light being substantially in an infrared light;
• detecting the light absorbed by said tissue region and providing a first signal corresponding to said absorbed light;
• processing said first signal to provide a second signal corresponding to at least one red light signal component and a third signal corresponding to at least one infrared light signal component, each of said first and second signals including a noise component;
• detecting the electrical potential generated by said subject's heart and providing an ECG signal corresponding to said electrical potential, said ECG signal including a plurality of first r-wave components corresponding to first r-wave events;
• processing said first, second and ECG signals to provide a first waveform, said first waveform having a reduced level of said noise component, said first waveform including a plurality of quasi-stationary heartbeat spaces;
• processing said first waveform and said ECG signal to provide a second waveform, said second waveform including said plurality of quasi-stationary heartbeat spaces and a plurality of second r-wave events substantially corresponding to said first r-wave events;
• and
• processing said third signal and said second waveform to provide a fourth signal, said fourth signal substantially corresponding to the blood oxygen saturation level of said subject.

An apparatus for determining the blood oxygen saturation level of a subject, comprising:

• an oximeter sensor arrangement coupled to said subject for acquiring a first blood oxygen signal, said first blood oxygen signal having an artifact component;
• an ECG detector coupled to said subject for acquiring an ECG signal, said ECG signal including a plurality of first r-wave components substantially corresponding to first r-wave events;
• first processing means for processing said first blood oxygen signal and said ECG signal to provide a first waveform, said first waveform having a reduced level of said artifact component, said first waveform including a plurality of quasi-stationary heartbeat spaces;
• second processing means for processing said first waveform and said ECG signal to provide a second waveform, said second waveform including said plurality of quasi-stationary heartbeat spaces and a plurality of second r-wave events substantially corresponding to said first r-wave events;
• and
• third processing means for processing said first blood oxygen signal and said second waveform, said third processing means being adapted to provide a second blood oxygen signal substantially corresponding to the blood oxygen saturation level of said subject.

An apparatus for determining the blood oxygen saturation level of subject, said subject having a tissue region and a heart, comprising;

• a plurality of light means for passing first and second lights through said subject's tissue region, said first light being substantially in a red light range and said second light being substantially in an infrared range;
• a photo detector adapted to detect the light absorbed by said tissue region, said photo detector being further adapted to provide at least a first signal corresponding to said absorbed light;
• a demodulator in communication with said photo detector, said demodulator being adapted to provide a second signal corresponding to at least one red light signal and a third signal corresponding to at least one infrared signal in response to said first signal, each of said second and third signals including a noise component;
• an ECG detector adapted to detect the electrical potential generated by said subject's heart, said ECG detector being further adapted to provide an ECG signal corresponding to said electrical potential, said ECG signal including a plurality of first r-wave components corresponding to first r-wave events;
• a data acquisition device in communication with said demodulator and ECG detector, said data acquisition device including first processing means for processing said second, third and ECG signals to provide a first waveform, said first waveform having a reduced level of said noise component, said first waveform including a plurality of quasi-stationary heartbeat spaces, and second processing means for processing said first waveform and said ECG signal to provide a second waveform, said second waveform including said plurality of quasi-stationary heartbeat spaces and a plurality of second r-wave events substantially corresponding to said first r-wave events;
• and
• a correlation canceler for processing said second waveform and said third signal to provide a SpO2 signal, said SpO2 signal substantially corresponding to the blood oxygen saturation level of said subject.