Method and apparatus for detecting optical pulses

Apparatus for calculating the amount of a blood constituent from the blood flow characteristics of a patient comprising:

• means for photoelectrically detecting an absorption signal corresponding to the absorption of light measured at two or more wavelengths in the patient's tissue including periodic changes caused by periodic arterial pulses in the blood flow characteristics and aperiodic changes unrelated to the patient's heartbeat;
• means for electrically detecting an ECG signal corresponding to the patient's ECG waveform corresponding to the periodic electrical heart activity of the patient;
• means for selecting a first time-measure of the absorption signal including a maximum and minimum amplitude change in absorption;
• means for selecting a second time-measure of the ECG signal including components corresponding to the occurrence of the heartbeat;
• means for correlating the ECG signal and the absorption signal by multiplying the first time-measure of the absorption and the second time-measure of the ECG signal together to form a waveform product and thereafter shifting the time-measure of the absorption signal backwards in time relative to the time-measure of the ECG signal and multiplying the shifted and unshifted waveforms together to identify a maximum waveform product corresponding to the product of the ECG signal corresponding to the occurrence of the heartbeat and the maximum amplitude of the absorption signal;
• means for processing the absorption signal and the determined correlation to identify the periodic changes in the absorption signal associated with the determined maximum waveform product likely to correspond to arterial pulses in the patient's blood flow characteristics;
• and
• means for calculating the amount of the blood constituent from the identified periodic changes in the absorption signal.

A method for calculating the amount of a blood constituent from a patient's blood flow characteristics including aperiodic information corresponding to artifacts and periodic information corresponding to arterial pulses, comprising:

• detecting a set of first signals representing the absorption of light measured at two or more wavelengths of light in the patient's tissue including detected information corresponding to changes in absorption as a result of changes in the blood flow characteristics;
• detecting a second signal representing the occurrences of a selected portion of the ECG waveform of the patient;
• processing the first and second signals to enhance the periodic information contained in each individual signal whereby the first signals are processed in a repetitive manner, one discrete portion at a time, and the occurrence of a selected portion of the patient's ECG waveform in the second signal initiates processing of a discrete portion of the first signals;
• and
• calculating the amount of blood constituent using the enhanced periodic information in the processed portions of the first signals.

Apparatus for calculating the amount of a blood constituent from a patient's blood flow characteristics including arterial pulses and artifacts comprising:

• means or photoelectrically detecting a set of first signals representing the absorption of light measured at two or more wavelengths in the patient's tissue including detected information corresponding to changes in absorption as a result of changes in the blood flow characteristics;
• means for detecting a second signal representing the occurrences of a selected portion of the patient's ECG waveform;
• means for processing the first and second signals to enhance the periodic information contained in each individual signal whereby each occurrence of a selected portion in the second signal initiates processing of a discrete portion of the first signals so that the information in the first signals are processed in a repetitive manner;
• and
• means for calculating the amount of blood constituent using the enhanced information in the processed portions of the first signals.