Pulse photometer

A pulse photometer comprising:

• a memory storing instructions;
• a processor configured to execute the instructions;
• an emitter that emits first light beam of a first wavelength, a second light beam of a second wavelength, a third light beam of a third wavelength, and a fourth light beam of a fourth wavelength;
• and
• a detector that outputs a first intensity signal in accordance with a first intensity of the first light beam that transmitted through or reflected from a living tissue of a subject, a second intensity signal in accordance with a second intensity of the second light beam that is transmitted through or reflected from the living tissue of the subject, a third intensity signal in accordance with a third intensity of the third light beam that is transmitted through or reflected from the living tissue of the subject, and a fourth intensity signal in accordance with a fourth intensity of the fourth light beam that is transmitted through or reflected from the living tissue of the subject,
• wherein the processor executing the instructions stored in the memory is configured to implement functions of:
• a first signal separator that separates a first signal component of a first observed signal pair made of two of the first to fourth intensity signals from a first noise component of the first observed signal pair;
• a second signal separator that separates a second signal component of a second observed signal pair made of two of the first to fourth intensity signals excluding a combination of the first to fourth intensity signals in the first observed signal pair from a second noise component of the second observed signal pair;
• a third signal separator that that separates a third signal component of a third observed signal pair made of two of the first to fourth intensity signals excluding combinations of the first to fourth intensity signals in the first and second observed signal pairs from a third noise component of the third observed signal pair;
• a first determining section that determines whether a first difference between a first signal absorbance ratio of the first signal component and a first noise absorbance ratio of the first noise component is equal to or larger than a first predetermined value;
• a second determining section that, when it is determined that the first difference is smaller than the first predetermined value, determines whether a second difference between a second signal absorbance ratio of the second signal component and a second noise absorbance ratio of the second noise component is equal to or larger than a second predetermined value;
• a third determining section that, when it is determined that the second difference is smaller than the second predetermined value, determines whether a third difference between a third signal absorbance ratio of the third signal component and a third noise absorbance ratio of the third noise component is equal to or larger than a third predetermined value;
• and
• a concentration calculating section that,
• when it is determined that the first difference is equal to or larger than the first predetermined value, calculates a concentration of a light absorption material in blood of the subject based on a fundamental frequency of the first signal component,
• when it is determined that the first difference is smaller than the first predetermined value and the second difference is equal to or larger than the second predetermined value, calculates the concentration of the light absorption material in blood based on a fundamental frequency of the second signal component, or
• when it is determined that the first difference is smaller than the first predetermined value, the second difference is smaller than the second predetermined value, and the third difference is equal to or larger than the third predetermined value, calculates the concentration of the light absorption material in blood based on a fundamental frequency of the third signal component.

A method of controlling a pulse photometer, the method comprising:

• emitting a first light beam of a first wavelength, a second light beam of a second wavelength, a third light beam of a third wavelength, and a fourth light beam of a fourth wavelength;
• outputting a first intensity signal in accordance with a first intensity of the first light beam that transmitted through or reflected from a living tissue of a subject, a second intensity signal in accordance with a second intensity of the second light beam that is transmitted through or reflected from the living tissue of the subject, a third intensity signal in accordance with a third intensity of the third light beam that is transmitted through or reflected from the living tissue of the subject, and a fourth intensity signal in accordance with a fourth intensity of the fourth light beam that is transmitted through or reflected from the living tissue of the subject,
• separating a first signal component of a first observed signal pair made of two of the first to fourth intensity signals from a first noise component of the first observed signal pair;
• separating a second signal component of a second observed signal pair made of two of the first to fourth intensity signals excluding a combination of the first to fourth intensity signals in the first observed signal pair from a second noise component of the second observed signal pair;
• separating a third signal component of a third observed signal pair made of two of the first to fourth intensity signals excluding combinations of the first to fourth intensity signals in the first and second observed signal pairs from a third noise component of the third observed signal pair;
• determining whether a first difference between a first signal absorbance ratio of the first signal component and a first noise absorbance ratio of the first noise component is equal to or larger than a first predetermined value;
• determining whether a second difference between a second signal absorbance ratio of the second signal component and a second noise absorbance ratio of the second noise component is equal to or larger than a second predetermined value;
• when it is determined that the first difference is smaller than the first predetermined value and the second difference is smaller than the second predetermined value, determining whether a third difference between a third signal absorbance ratio of the third signal component and a third noise absorbance ratio of the third noise component is equal to or larger than a third predetermined value;
• and
• calculating a concentration of a light absorption material in blood of the subject based on a fundamental frequency of the first signal component, the concentration of the light absorption material in blood based on a fundamental frequency of the second signal component, or the concentration of the light absorption material in blood based on a fundamental frequency of the third signal component in response to determining that the first difference is smaller than the first predetermined value and determining that the second difference is smaller than the second predetermined value.

A method of controlling a pulse photometer, the method comprising:

• emitting a first light beam of a first wavelength, a second light beam of a second wavelength, a third light beam of a third wavelength, and a fourth light beam of a fourth wavelength;
• outputting a first intensity signal in accordance with a first intensity of the first light beam that transmitted through or reflected from a living tissue of a subject, a second intensity signal in accordance with a second intensity of the second light beam that is transmitted through or reflected from the living tissue of the subject, a third intensity signal in accordance with a third intensity of the third light beam that is transmitted through or reflected from the living tissue of the subject, and a fourth intensity signal in accordance with a fourth intensity of the fourth light beam that is transmitted through or reflected from the living tissue of the subject;
• separating a first signal component of a first observed signal pair made of two of the first to fourth intensity signals from a first noise component of the first observed signal pair;
• separating a second signal component of a second observed signal pair made of two of the first to fourth intensity signals excluding a combination of the first to fourth intensity signals in the first observed signal pair from a second noise component of the second observed signal pair;
• separating a third signal component of a third observed signal pair made of two of the first to fourth intensity signals excluding combinations of the first to fourth intensity signals in the first and second observed signal pairs from a third noise component of the third observed signal pair;
• determining whether a first difference between a first signal absorbance ratio of the first signal component and a first noise absorbance ratio of the first noise component is equal to or larger than a first predetermined value;
• when it is determined that the first difference is smaller than the first predetermined value, determining whether a second difference between a second signal absorbance ratio of the second signal component and a second noise absorbance ratio of the second noise component is equal to or larger than a second predetermined value;
• when it is determined that the second difference is smaller than the second predetermined value, determining whether a third difference between a third signal absorbance ratio of the third signal component and a third noise absorbance ratio of the third noise component is equal to or larger than a third predetermined value;
• and
• calculating:
• when it is determined that the first difference is equal to or larger than the first predetermined value, a concentration of a light absorption material in blood of the subject based on a fundamental frequency of the first signal component,
• when it is determined that the first difference is smaller than the first predetermined value and the second difference is equal to or larger than the second predetermined value, the concentration of the light absorption material in blood based on a fundamental frequency of the second signal component, or
• when it is determined that the first difference is smaller than the first predetermined value, the second difference is smaller than the second predetermined value, and the third difference is equal to or larger than the third predetermined value, the concentration of the light absorption material in blood based on a fundamental frequency of the third signal component.