Method and apparatus for analyzing heart and respiratory frequencies photoplethysmographically
First Claim
1. A monitoring apparatus for analyzing a frequency of a pulse obtained by measuring blood circulation of a subject photoplethysmographically, said apparatus comprising:
- a) a light source for emitting a light beam toward a surface of said subject,b) a detector unit for detecting a photoplethysmographic (PPG) signal, generated by said light beam and including an AC-component which represents a heart frequency of said subject,c) an electronic amplifying unit for amplifying said detected PPG-signal and outputting an amplified PPG-signal,d) means for separating from said amplified PPG-signal an amplified signal component representing a component of said detected PPG-signal which indicates a respiration frequency of said subject, ande) means for determining the respiration frequency of said subject based on said amplified signal component.
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Abstract
A pulse-frequency analyzing monitor which is provided with an optical sensor and which is intended for measuring photoplethysmographically the blood circulation of a subject, such as a body part of a human being or an animal, includes a light source, preferably a light-emitting diode for infrared light, fibre optics, a detector unit for detecting the alternating voltage, or AC-component of a generated PPG-signal for the purpose of determining the heart frequency of the subject, an electronic amplifying unit and a presentation unit, for instance an oscilloscope of a display unit. The apparatus also includes means for separating from the detected PPG-signal a signal component which indicates the respiration frequency of the subject. The PPG-signal is coupled to a filter, preferably a digital filter, which enables limit frequencies and the degree of amplification to be set. The digital filter may be a component of a microprocessor which is able to eliminate disturbances, for instance disturbances emanating from 50 Hz stray light, in addition to separating signals concerning the heart and respiration frequency of the subject. The invention also relates to a method of carrying out such photoplethysomographic measuring processes.
135 Citations
11 Claims
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1. A monitoring apparatus for analyzing a frequency of a pulse obtained by measuring blood circulation of a subject photoplethysmographically, said apparatus comprising:
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a) a light source for emitting a light beam toward a surface of said subject, b) a detector unit for detecting a photoplethysmographic (PPG) signal, generated by said light beam and including an AC-component which represents a heart frequency of said subject, c) an electronic amplifying unit for amplifying said detected PPG-signal and outputting an amplified PPG-signal, d) means for separating from said amplified PPG-signal an amplified signal component representing a component of said detected PPG-signal which indicates a respiration frequency of said subject, and e) means for determining the respiration frequency of said subject based on said amplified signal component. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of measuring blood circulation of a subject photoplethysmographically by using a light source, a detector unit for detecting a generated PPG-signal including an AC-component representing a heart frequency of the subject, an electronic amplifying unit and a presentation unit, comprising the steps of:
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separating from the detected PPG-signal a signal component indicating a respiration frequency of the object; and determining the respiration frequency of the subject based on said signal component. - View Dependent Claims (11)
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Specification