Respiratory disease monitoring system

• US 6,450,957 B1
• Filed: 07/07/2000
• Issued: 09/17/2002
• Est. Priority Date: 08/02/1999
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Nishida, Yoshifumi, Yanai, Kenichi, Yoshimi, Tomohisa
• Primary Examiner(s): Winakur, Eric F.
• Assistant Examiner(s): Kremer, Matthew J.
• Application Number:
  US09/612,557
• Time in Patent Office: 802 Days
• Field of Search: 600/322-324, 600/534-536, 600/587, 600/595, 600/309
• US Class Current: 600/309
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/113 occurring during breathing
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/4818 Sleep apnoea
• CPC Class Codes: A61B 5/6887 mounted on external non-worn devices, e.g. non-medical devices
• CPC Class Codes: A61B 5/6892 Mats

Abstract

A respiration monitoring system monitors the state of disorder of the respiratory system of a sleeping patient based on the detection of respiratory body movement without the need of putting sensors directly on the patient'"'"'s body. The system includes weight sensors that produce weight signals attributable to the patient'"'"'s respiratory body movement. From weight signals having a frequency band of respiration, a respiratory body movement signal is produced, and the fall of blood oxygen saturation which occurs at obstructive apnea of the sleeping patient is determined based on the variation pattern of the amplitude of respiratory body movement signal. The occurrence and frequency of the fall of blood oxygen saturation are displayed on a display unit.

Claims

1. A respiratory disease monitoring system comprising:

a detection means which detects body movement of a patient caused by respiration during sleep, wherein the detection means extracts a signal within a frequency band corresponding to a patient'"'"'respiratory rate as a respiratory body movement signal;

a determination means which determines a fall of blood oxygen saturation during an obstructive sleep apnea based on a variation pattern of the body movement detected by the detection means, wherein the determination means recognize, as the fall of blood oxygen saturation, a peak of a maximum amplitude out of peaks of a plurality of waves included in the respiratory body movement signal; and

an indication means which indicates the fall of blood oxygen saturation.

2. A respiratory disease monitoring system according to claim 1, wherein the determination means determines the fall of blood oxygen saturation based on a body movement variation pattern where the body movement stays below a predetermined level for a predetermined time length and thereafter exceeds the predetermined level.

3. A respiratory disease monitoring system according to claim 1, wherein the detection means includes a plurality of weight sensors arranged beneath, inside or on a surface of a sleeping pad, the sensors producing weight signals representing weights applied to the sensors.

4. A respiratory disease monitoring system according to claim 3, wherein the detection means extracts detection signals having a frequency band of human respiration from weight signals of weight sensors, said detection signals indicative of the respiratory body movement.

5. A respiratory disease monitoring system according to claim 4, wherein the determination means determines the fall in blood oxygen saturation based on the variation pattern of the amplitude of the respiratory body movement signal.

6. A respiratory disease monitoring system according to claim 5, wherein the determination means includes:

an envelope waveform producing means which produces an envelope waveform which connects peaks of the respiratory body movement signal; and

a waveform recognition means which recognizes a virtually triangular characteristic waveform that correlates with the fall in blood oxygen saturation and counts frequency of the fall of blood oxygen saturation based on frequency of the appearance of the characteristic waveform.

7. A respiratory disease monitoring system according to claim 6, wherein the indication means indicate the frequency of the fall in blood oxygen saturation in time series.

8. A respiratory disease monitoring system according to claim 4, further comprising a respiration frequency calculating means which calculates the respiration frequency of the sleeping patient based on the respiratory body movement signal, the indication means indicating the respiration frequency of the patient and the fall in blood oxygen saturation.

9. A respiratory disease monitoring system according to claim 3, wherein the detection means includes:

a reference sensor selecting means which selects as reference sensor a weight sensor that produces a weight signal having a largest amplitude in a respiration frequency band;

a weight sensor designating means which designates in-phase weight sensors that produce weight signals substantially in-phase with the weight signal produced by the reference sensor and opposite-phase weight sensors that produce weight signals substantially opposite in phase to the weight signal produced by the reference sensor; and

a respiratory body movement signal producing means which produces a summed respiratory body movement signal based on the weight signal produce reference signals produced sensor and the weight signals produced by the sensor and the weight signals produced by at least one of the in-phase weight sensors and the opposite-phase weight sensors.

10. A respiratory disease monitoring system according to claim 9, wherein the respiratory body movement signal producing means produces a summed respiratory body movement signal by summing the weight signal produced by the reference sensor and the substantially in-phase weight signals, or by summing the weight signal produced by the reference sensor and an inverted version of the substantially opposite-phase weight signals.

11. A respiratory disease monitoring system comprising:

a detection device having a plurality of sensors disposed under a sleeping area of a patient, each of said sensors outputting signals representative of a force exerted on each said sensor by said patient, wherein the detection device extracts a signal within a frequency band corresponding to a patient'"'"'s respiratory rate as a respiratory body movement signal; and

a processing unit which processes each said signal to calculate a fall of blood oxygen saturation during an obstructive apnea, said processing unit calculating said fall in blood oxygen saturation based on a variation pattern of said signals from said plurality of sensors, wherein said processing unit recognizes, as the fall of blood oxygen saturation, a peak of a maximum amplitude out of peaks of a plurality of waves included in the respiratory body movement signal.

12. A respiratory disease monitoring system according to claim 11, wherein a detection device determines the fall of blood oxygen saturation based on a body movement variation pattern where the respiratory body movement stays below a predetermined level for a predetermined time length and thereafter exceeds the predetermined level.

13. A respiratory disease monitoring system according to claim 11, wherein:

said processing unit selecting a reference sensor that produces a reference signal having a largest amplitude in a respiration frequency band;

a first portion of said sensors producing signals within a phase range of said reference signal, a second portion of said sensors producing a weight signal outside of said range, said range being substantially in phase with said signal generated by said reference sensor; and

said processing unit producing a summed respiratory body movement signal based on the reference signal, signals from said first portion of sensors and signals from said second portion of said sensors.

14. A respiratory disease monitoring system according to claim 13, wherein said processing unit sums signals from said first portion, an inverted version of signals from said second portion, and said reference signal to generate said summed respiratory body movement signal.

15. A respiratory disease monitoring system according to claim 13, wherein the processing unit determines the fall in blood oxygen saturation based on the variation pattern of the amplitude of the respiratory body movement signal.

16. A respiratory disease monitoring system according to claim 15, wherein the determination means includes:

said processing unit connects peaks of the respiratory body movement signal to generate an envelope wave form; and

said processing unit determines a fall in blood oxygen saturation by identifying a virtually triangular characteristic waveform that correlates with the fall in blood oxygen saturation and counts a frequency of the fall of blood oxygen saturation based on a frequency of the appearance of the characteristic waveform.

17. A method for monitoring a respiratory disease of a patient, comprising the steps of:

sensing a weight of a patient at a plurality of positions under a sleeping area of said patient to generate a plurality of weight signals from said plurality of positions;

detecting, as a respiratory body movement signal, a signal within a frequency band corresponding to a patient'"'"'s respiratory rate from the plurality of weight signals; and

calculating a fall of blood oxygen saturation during an obstructive apnea based on a wave of a maximum amplitude out of a plurality if waves included in an envelope waveform of a respiratory body movement signal.

18. The method as claimed in claim 17, wherein said calculating step comprises:

selecting a reference signal having a largest amplitude in a respiration frequency band;

selecting a first portion of said signals being within a phase range of said reference signal, said range being substantially in phase with said reference signal;

selecting a second portion of said signals being outside of said phase range of said reference signal; and

summing a respiratory body movement signal based on said reference signal, signals from said first portion of sensors and signals from said second portion of said sensors.

19. The method as claimed in claim 18, wherein said summing step comprises:

summing signals from said first portion, an inverted version of said signals from said second portion and said reference to generate said summed respiratory body movement signal.

20. A respiratory disease monitoring system comprising:

a detection means which detects the body movement of a patient caused by respiration during sleep, wherein the detection means extracts a signal within a frequency band corresponding to a patient'"'"'s respiratory rate as a respiratory body movement signal;

a determination means which determines a fall of blood oxygen saturation during an obstructive apnea based on a variation pattern of the body movement detected by the detection means, wherein the determination means further comprises,

an envelope waveform producing means which produces an envelope waveform which connects peaks of the respiratory body movement signal; and

a waveform recognition means which recognizes a characteristic waveform that correlates with the fall in blood oxygen saturation in the envelope waveform,

wherein a determination means counts the frequency of the fall of blood oxygen saturation based on a frequency of the appearance of the characteristic waveform; and

a display means which displays the fall of blood oxygen saturation.

21. A respiratory disease monitoring system comprising:

a detection means which detects body movement of a patient caused by respiration during sleep, wherein the detection means extracts a signal within a frequency band corresponding to a patient'"'"'s respiratory rate as a respiratory body movement signal;

a determination means which determines a fall of blood oxygen saturation during an obstructive apnea based on a variation pattern of the body movement detected by the detection means, wherein the determination means comprises a waveform recognition means which recognizes a characteristic waveform, which correlates with the fall in blood oxygen saturation, in peaks of a plurality of waves included in the respiratory body movement signal and wherein the determination means counts a frequency of the fall of blood oxygen saturation based on a frequency of the appearance of the characteristic waveform; and

a display means which displays the fall of blood oxygen saturation.

22. A respiratory disease monitoring system comprising:

a detection device having a plurality of sensors disposed under a sleeping area of a patient, each of said sensors outputting signals representative of a force exerted on each said sensor by said patient; and

a processing unit which processes each said signal to calculate a fall of blood oxygen saturation during an obstructive apnea, said processing unit calculating said fall in blood oxygen saturation based on a variation pattern of said signals from said plurality of sensors, wherein,

said processing unit selecting a reference sensor that produces a reference signal having a largest amplitude in a respiration frequency band;

a first portion of said sensors producing signals within a phase range of said reference signal, a second portion of said sensors producing a weight signal outside of said range, said range being substantially in phase with said signal generated by said reference sensor; and

said processing unit producing a summed respiratory body movement signal based on the reference signal, signals from said first portion of sensors and signals from said second portion of said sensors.

23. A respiratory disease monitoring system according to claim 22, wherein said processing unit sums signals from said first portion, an inverted version of signals from said second portion, and said reference signal to generate said summed respiratory body movement signal.

24. A respiratory disease monitoring system according to claim 22, wherein the processing unit determines the fall in blood oxygen saturation based on the variation pattern of the amplitude of the respiratory body movement signal.

25. A respiratory disease monitoring system according to claim 24, wherein the determination means includes:

said processing unit connects peaks of the respiratory body movement signal to generate an envelope wave form; and

said processing unit determines a fall in blood oxygen saturation by identifying a virtually triangular characteristic waveform that correlates with the fall in blood oxygen saturation and counts a frequency of the fall of blood oxygen saturation based on a frequency of the appearance of the characteristic waveform.