Method for continuous baroreflex sensitivity measurement
A medical device and method for determining baroreflex sensitivity (BRS) based on one or more respiration cycles. The BRS determination may be performed continuously based on measurements of heart rate, blood pressure, and respiration cycles.
1. A method for calculating a continuous baroreflex sensitivity (BRS) value, comprising:
detecting respiration cycles of a patient;
measuring heart rate of the patient over a first set of respiration cycles;
measuring a pressure metric of the patient over a second set of respiration cycles; and
calculating a BRS value based on the heart rate and pressure measurements, wherein the calculating the BRS value is based on heart rate and pressure measurements taken over different respiration cycles.
2. A method according to claim 1 , wherein the calculating the BRS value is performed for each respiration cycle.
3. A method according to claim 1 , wherein the respiration cycles are detected from the pressure measurement.
4. A method according to claim 1 , wherein the measuring the pressure metric comprises measuring a right ventricular systolic pressure metric.
5. A method according to claim 1 , wherein the calculating the BRS value includes determining a maximum change in the pressure metric over each respiration cycle.
6. A method according to claim 1 , wherein calculating the BRS value includes determining a maximum change in an R-R interval over each respiration cycle.
7. A method according to claim 1 , wherein the heart rate is measured from an ECG signal.
8. An implantable medical device, comprising:
one or more sensors for sensing patient heart rate, blood pressure, and respiration cycles; and
a housing supporting a processor and adapted for implantation in a patient, the processor coupled to the one or more sensors, the processor for calculating continuous baroreflex sensitivity (BRS) for each detected respiration cycle based on the sensed heart rate, blood pressure and respiration cycles, wherein:
the processor compares the BRS calculation against a zone of predetermined BRS thresholds, and
the processor changes at least one zone threshold if the BRS calculation intermittently produces values outside the zone.
9. A medical device according to claim 8 , wherein the respiration cycles and blood pressure are sensed by the same one of the one or more sensors.
10. A medical device according to claim 8 , wherein the processor calculates a trendline of BRS values obtained over multiple respiration cycles.
11. A medical device according to claim 8 , wherein the processor initiates an alarm if the BRS calculation is outside the zone of predetermined BRS thresholds.
12. A medical device according to claim 8 , wherein the processor initiates a treatment if the BRS calculation is outside of the zone of predetermined thresholds.
13. A computer-readable medium programmed with instructions for baroreflex sensitivity (BRS) measurement, the medium comprising instructions for causing a programmable processor to:
detect respiration cycles of a patient;
measure heart rate of the patient over a first set of respiration cycles;
measure a pressure metric of the patient over a second set of respiration cycles; and
calculate a BRS value based on the heart rate and pressure measurements, wherein the calculating the BRS value is based on heart rate and pressure measurements taken over different respiration cycles.
14. A medium according to claim 13 , further comprising instructions to detect a patient circumstance including at least one of patient activity, time of day, and patient posture, and initiate BRS calculation after detection of the patient circumstance.
15. A medium according to claim 14 , further comprising instructions to initiate the at least one of inspiration and expiration cycle detection, heart rate measurement, and pressure measurement after detection of the patient circumstance.
16. A medium according to claim 14 , further comprising instructions to detect a change in the patient circumstance and to halt BRS calculation after detection of the change in the patient circumstance.
17. A medium according to claim 14 , further comprising instructions to halt BRS calculation upon reaching a predetermined time period after initiating BRS calculation.
18. A computer-readable medium programmed with instructions for baroreflex sensitivity (BRS) measurement, the medium comprising instructions for causing a programmable processor to:
determine patient heart rate, blood pressure, and respiration cycles from one or more sensors and
calculate continuous baroreflex sensitivity (BRS) for each detected respiration cycle based on the sensed heart rate, blood pressure and respiration cycles;
compare the BRS calculation against a zone of predetermined BRS thresholds, and
change at least one zone threshold if the BRS calculation intermittently produces values outside the zone.
19. A medium according to claim 18 , further comprising instructions to detect a patient circumstance including at least one of patient activity, time of day, and patient posture, and initiate BRS calculation after detection of the patient circumstance.
20. A medium according to claim 19 , further comprising instructions to initiate the at least one of inspiration and expiration cycle detection, heart rate measurement, and pressure measurement after detection of the patient circumstance.
21. A medium according to claim 20 , further comprising instructions to detect a change in the patient circumstance and to halt BRS calculation after detection of the change in the patient circumstance.
22. A medium according to claim 20 , further comprising instructions to halt BRS calculation upon reaching a predetermined time period after initiating BRS calculation.