Pulse oximeter using a virtual trigger for heart rate synchronization

A pulse oximeter comprising:

• oximeter means for generating an oximeter signal corresponding to an absorption of light in a blood flow of a patient;
• means for receiving a heart rate signal having a first frequency corresponding to a heart rate of said patient;
• means for generating a virtual trigger having said first frequency, said virtual trigger being generated independent of any feature of a waveform corresponding to said heart rate of said patient other than said first frequency;
• and
• means for processing said oximeter signal in periods defined by said virtual trigger.

A method comprising the steps of:

• generating a first signal from a periodic physical activity;
• receiving a second signal having a first frequency corresponding to said periodic physical activity;
• generating a virtual trigger having said first frequency, said virtual trigger being generated independent of any feature of said second signal other than said first frequency;
• and
• processing said first signal in periods defined by said virtual trigger.

A method of operating a pulse oximeter comprising the steps of:

• generating an oximeter signal corresponding to an absorption of light in a blood flow of a patient;
• receiving a heart rate signal having a frequency corresponding to the heart rate of said patient;
• generating a virtual trigger having said frequency, said virtual trigger being generated independent of any feature of a waveform corresponding to said heart rate of said patient other than said frequency;
• and
• processing said oximeter signal in periods defined by said virtual trigger.

A pulse oximeter comprising:

• a photodetector for generating an oximeter signal corresponding to an absorption of light in a blood flow of a patient;
• a heart rate frequency generator providing a heart rate frequency;
• a sampling circuit producing digital samples of said oximeter signal for a plurality of periods;
• and
• a processing circuit for generating a virtual trigger having a frequency equal to said heart rate frequency, said virtual trigger being independent of any feature of a waveform corresponding to a heart rate other than a frequency of said heart rate, said virtual trigger defining said plurality of periods, said processing circuit including
• first means for averaging samples in said plurality of periods,
• second means for inhibiting generation of a virtual trigger based on heart rate frequencies greater than a first predetermined frequency and less than a second predetermined frequency,
• third means for inhibiting generation of said virtual trigger based on a heart rate frequency that varies at more than a predetermined rate, and
• fourth means for determining a maximum and a minimum value of said oximeter signal in said periods, including examining all samples in each period.