Externally worn vasovagal syncope detection device

• US 20070070800A1
• Filed: 09/27/2005
• Published: 03/29/2007
• Est. Priority Date: 09/27/2005
• Status: Abandoned Application

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Virag, Nathalie, Vetter, Rolf
• Application Number:
  US11/235,943
• Publication Number:
  US 20070070800A1
• Time in Patent Office: Days
• US Class Current: 365/244
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02116 of pulse wave amplitude A61B5/02225 takes precedence
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• CPC Class Codes: A61B 5/4035 Evaluating the autonomic nervous system
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured

Abstract

A device is worn adjacent to tissue of a patient to detect vasovagal syncope (VVS). The device includes a photoplethysmographic sensor that measures a plethysmographic signal through tissue, and a processor that derives an indicator of an autonomous nervous system (ANS) activity from the plethysmographic signal and estimates a probability that the patient will experience VVS as a function of the indicator.

Claims

1. A device configured to detect vasovagal syncope (VVS), the device comprising:

a photoplethysmographic sensor which is operable to measure a plethysmographic signal; and

a processor to derive an indicator of an autonomous nervous system (ANS) activity from the plethysmographic signal and to estimate a probability of VVS as a function of the indicator.

2. The device of claim 1, wherein the plethysmographic signal is representative of at least one of a heart rate, a heart interval, and a blood pressure.

3. The device of claim 1, wherein the photoplethysmographic sensor comprises:

a radiation source to emit radiant energy; and

a plurality of detectors to detect an intensity of the radiant energy after propagation through a medium.

4. The device of claim 1, wherein the indicator of the ANS activity comprises a value representative of a sympatho-vagal balance.

5. The device of claim 1, wherein the indicator of the ANS activity includes at least one of a cardiac sympathetic nervous activity value and a cardiac parasympathetic nervous activity value.

6. The device of claim 1, and further comprising:

an alarm for providing an output when the probability of VVS exceeds a threshold probability.

7. The device of claim 1, wherein the alarm produces an auditory output.

8. The device of claim 1, wherein the alarm produces a visual output.

9. The device of claim 1, wherein the device includes a wrist strap.

10. A device configured for wearing adjacent to tissue of a patient to detect vasovagal syncope (VVS) in the patient and alert the patient of the VVS, the device comprising:

a light source for transmitting radiant energy into the human tissue;

light detectors for detecting an intensity of the radiant energy after propagation through the human tissue;

a processor for deriving a plethysmographic signal from the detected intensity of the radiant energy, deriving an indicator of an autonomous nervous system (ANS) activity from the plethysmographic signal, and estimating a probability that the patient will experience VVS as a function of the indicator; and

an alarm for providing an output as a function of the estimated probability that the patient will experience VVS.

11. The device of claim 10, wherein the indicator of the ANS activity comprises a measure of sympatho-vagal balance.

12. The device of claim 10, wherein the indicator of the ANS activity includes a measure of at least one of cardiac sympathetic nervous activity and cardiac parasympathetic nervous activity.

13. The device of claim 10, wherein the processor further derives a baseline indicator of ANS activity and stores the baseline indicator of ANS activity in a memory.

14. The device of claim 13, wherein the processor is further configured to compare the indicator to the baseline indicator and to estimate the probability that the patient will experience VVS as a function of the comparison.

15. A method for detecting vasovagal syncope (VVS) in a patient, the method comprising:

directing radiant energy into tissue of the patient;

measuring an intensity of the radiant energy after propagation through the tissue;

deriving a physiological signal from the measurement;

deriving an indicator of an autonomous nervous system (ANS) activity from the physiological signal; and

estimating a probability that the patient will experience VVS as a function of the indicator.

16. The method of claim 15, wherein deriving an indicator of an ANS activity from the physiological signal comprises:

deriving a sympathetic activity indicator from the physiological signal;

deriving a parasympathetic activity indicator from the physiological signal; and

estimating a relative magnitude of the sympathetic activity indicator in comparison to the parasympathetic activity indicator.

17. The method of claim 15, wherein deriving an indicator of an ANS activity comprises:

determining a baseline indicator of the ANS activity; and

comparing the indicator to the baseline indicator.

18. The method of claim 17, wherein determining a baseline indicator of the ANS activity comprises:

commencing a monitoring period in response to a detected posture transition; and

determining the baseline indicator of the ANS activity during the monitoring period.

19. The method of claim 18, and further comprising:

sensing at least one physiological signal during the monitoring period;

generating a measure of the physiological signal as a function of the sensing during the monitoring period;

sensing the physiological signal following the monitoring period; and

normalizing the physiological signal following the monitoring period with respect to the measure.

20. The method of claim 15, and further comprising:

generating an output when the probability that the patient will experience VVS exceeds a threshold probability.