RESPIRATORY WAVEFORM ANALYZER

• US 20100249631A1
• Filed: 03/30/2010
• Published: 09/30/2010
• Est. Priority Date: 03/30/2009
• Status: Active Grant

• Current Assignee: Nihon Kohden Corporation
• Original Assignee: Nihon Kohden Corporation
• Inventors: AOKI, Toshiki, UKAWA, Teiji, DAINOBU, Hidetoshi, ECHIGO, Masahiro
• Granted Patent: US 9,955,899 B2
• Time in Patent Office: Days
• US Class Current: 600/532
• CPC Class Codes: A61B 5/0836 Measuring rate of CO2 production
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/746 Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis
• CPC Class Codes: G01N 33/497 of gaseous biological material, e.g. breath

Abstract

A respiratory waveform analyzer, operable to analyze a respiratory waveform, which is generated based on a temporal change of a concentration of a component in respiratory gas of a subject, includes: a respiratory gas concentration generator which generates a concentration signal based on an output signal from a sensor that is placed to measure the concentration of the component; a flatness calculator which calculates a flatness indicative of flat degree of the respiratory waveform based on a temporal change of the concentration signal; and a reliability calculator which calculates a reliability of the respiratory waveform based on the flatness and the concentration signal.

Claims

1. A respiratory waveform analyzer, operable to analyze a respiratory waveform, which is generated based on a temporal change of a concentration of a component in respiratory gas of a subject, the respiratory waveform analyzer comprising:

a respiratory gas concentration generator which generates a concentration signal based on an output signal from a sensor that is placed to measure the concentration of the component;

a flatness calculator which calculates a flatness indicative of flat degree of the respiratory waveform based on a temporal change of the concentration signal; and

a reliability calculator which calculates a reliability of the respiratory waveform based on the flatness and the concentration signal.

2. The respiratory waveform analyzer according to claim 1, wherein the flatness is a function of an accumulated value which is obtained by accumulating degree of a difference in a time interval over a plurality of the time intervals, based on the concentration signal.

3. The respiratory waveform analyzer according to claim 2, wherein the degree of the difference is an absolute value of the difference.

4. The respiratory waveform analyzer according to claim 2, wherein the degree of the difference is obtained by raising the difference to the power of the even number.

5. The respiratory waveform analyzer according to claim 1, wherein the reliability calculator calculates the reliability based on the flatness which is calculated at a timing by the flatness calculator, and the concentration signal at the timing.

6. The respiratory waveform analyzer according to claim 5, further comprising:

an effective concentration detector which detects a value of the concentration signal at a timing when the reliability that is calculated in a predetermined concentration detecting time period is maximum, as an effective concentration in the concentration detecting time period.

7. The respiratory waveform analyzer according to claim 6, wherein the effective concentration detector accumulates the reliability in the concentration detecting time period to obtain an accumulated value in the concentration detecting time period, and detects the effective concentration in the concentration detecting time period when the accumulated value exceeds a predetermined reliability.

8. The respiratory waveform analyzer according to claim 7, wherein the concentration detecting time period is a time period corresponding to one cycle of the respiratory waveform.

9. The respiratory waveform analyzer according to claim 8, further comprising:

a weighted average processor which, when a plurality of the effective concentrations are detected, weights each of the effective concentrations in accordance with degree of the accumulated value in the corresponding concentration detecting time period, and averages the weighted effective concentrations, to calculate a weighted average value.

10. The respiratory waveform analyzer according to claim 9, further comprising:

a display that displays at least one of a number at which the effective concentration detector detects the effective concentration in a time period, and the weighted average value calculated by the weighted average processor.

11. The respiratory waveform analyzer according to claim 6, wherein

the respiratory gas concentration generator includes:

a respiratory gas concentration detector which converts the analog output signal from the sensor to a digital respiratory gas signal; and

a respiratory gas concentration calculator which generates a respiratory waveform signal based on the respiratory gas signal from the respiratory gas concentration detector,

the concentration signal is the respiratory waveform signal, and

when a value of the respiratory gas signal is a value or greater, which indicates that the concentration of the component is high, the effective concentration detector detects the effective concentration in the concentration detecting time period.

12. The respiratory waveform analyzer according to claim 11, further comprising:

a concentration detection value corrector which corrects the respiratory waveform signal corresponding to the respiratory gas signal, in accordance with a ratio of the respiratory gas signal to a predetermined reference value.

13. The respiratory waveform analyzer according to claim 1, further comprising:

a respiratory airway adaptor in which the respiratory gas of the subject flows; and

a liquid detector which detects a liquid in the respiratory airway adaptor.

14. A respiratory waveform analyzer, operable to analyze a respiratory waveform, which is generated based on a temporal change of a concentration of a component in respiratory gas of a subject, the respiratory waveform analyzer comprising:

a respiratory gas concentration detector which converts a analog output signal from a sensor that is placed to detect the concentration of the component, to a digital respiratory gas signal;

a respiratory gas concentration calculator which generates a respiratory waveform signal based on the respiratory gas signal from the respiratory gas concentration detector; and

a concentration detection value corrector which corrects the respiratory waveform signal corresponding to the respiratory gas signal, in accordance with a ratio of the respiratory gas signal to a predetermined reference value.

15. A respiratory waveform analyzer, operable to analyze a respiratory waveform, which is generated based on a temporal change of a concentration of a component in respiratory gas of a subject, the respiratory waveform analyzer comprising:

a respiratory airway adaptor in which the respiratory gas of the subject flows, the respiratory airway adaptor provided with a sensor that measures the concentration of the component to output a signal;

a respiratory gas concentration generator which generates a concentration signal based on the signal output by the sensor, the concentration signal indicating degree of the concentration; and

a liquid detector which detects a liquid in the respiratory airway adaptor based on the concentration signal.

16. The respiratory waveform analyzer according to claim 15, wherein

the liquid detector compares a value of the concentration signal with at least one preset value and detects the liquid in the respiratory airway adaptor based on comparison result.

17. The respiratory waveform analyzer according to claim 15, wherein

the sensor receives a signal light and a referential light which are different from each other in an absorption property of the component, and

the liquid detector calculates attenuance based on receiving intensities of the signal light and the referential light and detects the liquid in the respiratory airway adaptor based on the attenuance.

18. The respiratory waveform analyzer according to claim 16, wherein

the liquid detector outputs an attention arousing signal when the comparison result reaches an attention arousal level, and

the liquid detector outputs an alarm signal when the comparison result reaches an alarm level.

19. The respiratory waveform analyzer according to claim 18, wherein

the liquid detector determines that the comparison result reaches the attention arousal level or the alarm level based on one of a difference between the value of the concentration signal and the preset value, number of times at which the value of the concentration signal is larger than the preset value, a time period during which the value of the concentration signal is larger than the present value, number of times at which the value of the concentration signal is smaller than the preset value and a time period during which the value of the concentration signal is smaller than the present value.

20. The respiratory waveform analyzer according to claim 15, wherein

the liquid detected by the liquid detector is a water.