JPWO2021099216A5

JPWO2021099216A5 -

Info

Publication number: JPWO2021099216A5
Application number: JP2022527822A
Authority: JP
Publication date: 2023-09-29

Claims

A method of obtaining a filtered capnography signal by suppressing a spectral background signal within an optical absorption signal, the method comprising:
obtaining an optical absorption signal from the subject over a range of wavelengths, said optical absorption signal determining the proportion of said optical signal that is absorbed as it passes through a breathing adapter containing a sample of breathing air under investigation; wherein the optical absorption signal has a spectral background signal;
separating a second harmonic signal from the optical absorption signal;
identifying a period of the spectral background signal;
sampling a plurality of wavelength components of the second harmonic signal, the step of sampling the second harmonic signal comprising:
obtaining a sample of a second harmonic signal at a center wavelength of the second harmonic signal, the center wavelength exhibiting maximum carbon dioxide absorption; and obtaining a sample of a second harmonic signal, the eccentric wavelength and the center wavelength being separated by a half-integer multiple or a non-zero integer multiple of the period of the spectral background signal;
having a step and
A method comprising: generating a filled capnography signal based at least in part on a combination of addition or subtraction of the obtained samples of the second harmonic signal.

Obtaining samples of the second harmonic signal at the center wavelength is performed over a first time period, and obtaining samples of the second harmonic signal at the eccentric wavelength is performed over a second time period. 2. The method of claim 1 , wherein the first time period and the second time period are equal in length.

The step of sampling the second harmonic signal further comprises obtaining a plurality of samples of the second harmonic signal at a plurality of eccentric wavelengths of the second harmonic signal, the plurality of eccentric wavelengths and the center 3. A method according to any preceding claim, wherein the wavelengths are separated by a multiple of the period of the spectral background signal.

Obtaining samples of the second harmonic signal at the center wavelength is performed over a first time period, and obtaining samples of the second harmonic signal at the plurality of eccentric wavelengths is performed over a second period of time. 4. The method of claim 3 , wherein the method is performed over a period of time, and the first and second time periods are of equal length.

The method includes:
separating a third harmonic signal from the optical absorption signal;
sampling a plurality of wavelength components of the third harmonic signal, the step of sampling the third harmonic signal comprising:
obtaining a sample of the third harmonic signal at a center wavelength of the third harmonic signal; and obtaining a sample of the third harmonic signal at an eccentric wavelength of the third harmonic signal, the eccentric wavelength and the center wavelength are separated by a multiple of a period of the spectral background signal, and further comprising: generating a wavelength correction for the center wavelength and the eccentric wavelength. 5. The method according to any one of 1 to 4 .

6. A method according to any one of claims 1 to 5 , wherein the method is for use in processing optical absorption signals obtained from a respiratory cycle of a subject.

7. The method of claim 6 , wherein a period of the spectral background signal is identified during an inspiratory phase of the respiratory cycle.

8. A method according to claim 6 or 7 , wherein the period of the spectral background signal is identified by averaging over multiple respiratory cycles.

9. A method according to any one of claims 1 to 8 , wherein the method further comprises the step of obtaining a distinct background signal, and the period of the spectral background is identified from the distinct background signal. .

10. A computer program comprising computer program code means adapted to implement a method according to any one of claims 1 to 9 when the computer program is run on a computer.

A system for obtaining a filtered capnography signal by suppressing a spectral background signal in an optical absorption signal, the system comprising a processor, the processor comprising:
obtaining an optical absorption signal from the subject over a range of wavelengths, said optical absorption signal representing the proportion of said optical signal that is absorbed as it passes through a breathing adapter containing a sample of breathing air to be investigated; the optical absorption signal has a spectral background signal;
separating a second harmonic signal from the optical absorption signal;
identifying a period of the spectral background signal;
sampling a plurality of wavelength components of the second harmonic signal; sampling the second harmonic signal;
obtaining a sample of a second harmonic signal at a center wavelength of said second harmonic signal, said center wavelength exhibiting maximum carbon dioxide absorption; and a second at an eccentric wavelength of said second harmonic signal. obtaining a sample of a harmonic signal, the eccentric wavelength and the center wavelength being separated by a half-integer multiple or a non-zero integer multiple of the period of the spectral background signal;
have that, and
A system adapted to generate a filled capnography signal based at least in part on a combination of addition or subtraction of the obtained samples of the second harmonic signal.

The system includes:
A processor according to claim 11 ,
a tunable laser light source adapted to generate a laser light signal modulated over a range of wavelengths, the processor configured to separate the second harmonic signal using a frequency of modulation of the light source as a reference; wavelength tunable laser light source, which is further adapted to
an optical fiber communicating with the wavelength tunable laser light source;
a respiratory adapter having a cavity adapted to be connectable to a subject's airway, the adapter communicating with the optical fiber such that the laser light signal enters the cavity;
12. The system of claim 11 , comprising a photodetector in communication with the cavity of the respiratory adapter and adapted to receive the laser light signal transmitted through the cavity.

to align the period of the spectral background with the maxima and minima of the second harmonic signal;
13. The system of claim 11 or 12 , wherein one or more of: a modulation depth of the light source; and a dimension of the breathing adapter are adjusted to thereby adjust the spectral background period.