Methods and systems for determining physiological information based on a correlation sequence

A processing module of a pulse oximeter for processing physiological information of a subject, wherein the processing module comprises a pulse oximetry processor configured to:

• receive a physiological signal derived from an output of a detector of a pulse oximetry sensor, wherein the detector detects light attenuated by the subject;
• calculate a correlation sequence corresponding to multiple lag values based on the physiological signal, wherein the correlation sequence comprises a correlation sequence value corresponding to each of the multiple lag values;
• for at least one lag value of the multiple lag values:
• determine at least one threshold value corresponding to the at least one lag value of the multiple lag values, wherein the at least one threshold value varies as a predetermined function of lag values,
• compare the correlation sequence value corresponding to the at least one lag value to a corresponding one of the at least one threshold value,
• determine whether the correlation sequence value exceeds the corresponding threshold value, and
• determine whether the correlation sequence value corresponds to a peak;
• identify a particular lag value of the multiple lag values when the correlation sequence value corresponding to the particular lag value exceeds the corresponding threshold value and corresponds to a peak;
• determine a physiological rate of the subject based on the identified particular lag value;
• and
• display the physiological rate of the subject on a display.

A method for processing physiological information of a subject, comprising:

• receiving, using a pulse oximetry processor, a physiological signal derived from an output of a detector of a pulse oximetry sensor, wherein the detector detects light attenuated by the subject;
• calculating, using the pulse oximetry processor, a correlation sequence corresponding to multiple lag values based on the physiological signal, wherein the correlation sequence comprises a correlation sequence value corresponding to each of the multiple lag values;
• for at least one lag value of the multiple lag values:
• determining, using the pulse oximetry processor, at least one threshold value corresponding to the at least one lag value of the multiple lag values, wherein the at least one threshold value varies as a predetermined function of lag values,
• comparing, using the pulse oximetry processor, the correlation sequence value corresponding to the at least one lag value to a corresponding one of the at least one threshold value,
• determining, using the pulse oximetry processor, whether the correlation sequence value exceeds the corresponding threshold value, and
• determining, using the pulse oximetry processor, whether the correlation sequence value corresponds to a peak;
• identifying, using the pulse oximetry processor, a particular lag value of the multiple lag values when the correlation sequence value corresponding to the particular lag value exceeds the corresponding threshold value and corresponds to a peak;
• determining, using the pulse oximetry processor, a physiological rate of the subject based on the identified particular lag value;
• and
• displaying the physiological rate of the subject on a display.

A non-transitory computer-readable medium for use in processing physiological information of a subject, the non-transitory computer-readable medium comprising:

• computer program instructions recorded thereon for causing a pulse oximetry processor to:
• receive a physiological signal derived from an output of a detector of a pulse oximetry sensor, wherein the detector detects light attenuated by the subject;
• calculate a correlation sequence corresponding to multiple lag values based on the physiological signal, wherein the correlation sequence comprises a correlation sequence value corresponding to each of the multiple lag values;
• for at least one lag value of the multiple lag values:
• determine at least one threshold value corresponding to the at least one lag value of the multiple lag values, wherein the at least one threshold value varies as a predetermined function of lag values,
• compare the correlation sequence value corresponding to the at least one lag value to a corresponding one of the at least one threshold value,
• determine whether the correlation sequence value exceeds the corresponding threshold value, and
• determine whether the correlation sequence value corresponds to a peak;
• identify a particular lag value of the multiple lag values when the correlation sequence value corresponding to the particular lag value exceeds the corresponding threshold value and corresponds to a peak;
• determine a physiological rate of the subject based on the identified particular lag value;
• and
• display the physiological rate of the subject on a display.