Reducing Nuisance Alarms

• US 20090247848A1
• Filed: 03/06/2009
• Published: 10/01/2009
• Est. Priority Date: 03/31/2008
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Baker, Clark R. JR.
• Granted Patent: US 8,792,949 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• 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: G16H 40/63 for local operation
• CPC Class Codes: G16H 40/67 for remote operation

Abstract

Embodiments disclosed herein may describe systems and methods for reducing nuisance alarms using probability and/or accuracy of a measured physiological parameter, such as the pulse rate or SpO2 measurement generated by a pulse oximeter. Embodiments may include methods for adjusting a predetermined alarm threshold based on the probability distribution of the estimated pulse rate and/or oxygen saturation of a patient'"'"'s blood.

Claims

1. A method for generating an alarm indicating that a physiological parameter has exceeded a predetermined threshold, the method comprising:

calculating a probability distribution of an actual value of the physiological parameter based at least in part upon data;

identifying the predetermined threshold associated with the physiological parameter; and

generating the alarm based at least in part upon the predetermined threshold and the probability distribution.

2. The method of claim 1 further comprising:

calculating an estimated value of the physiological parameter based at least in part upon data;

calculating an adjusted threshold based at least in part upon the predetermined threshold and the probability distribution; and

comparing the estimated value of the physiological parameter to the adjusted threshold.

3. The method of claim 1 further comprising:

calculating, based at least in part upon the probability distribution, a confidence interval for the actual value of the physiological parameter; and

comparing the confidence interval to the predetermined threshold.

4. The method of claim 3 further comprising:

retrieving a confidence level; and

calculating, based at least in part upon the probability distribution, the confidence interval for the physiological parameter using the retrieved confidence level.

5. The method of claim 4, wherein the retrieved confidence level is selected from 99%, 98%, 97.5%, 95%, 90% and a user-selected value.

6. The method of claim 2, wherein calculating the probability distribution further comprising:

calculating an accuracy of the estimated value based at least in part upon the data.

7. The method of claim 6, wherein calculating the probability distribution further comprising:

calculating the probability distribution of the actual value of the physiological parameter based at least in part upon the accuracy and the estimated value.

8. The method of claim 7, wherein calculating the probability distribution further comprising:

retrieving, based at least in part upon the accuracy and the estimated value, a confidence limit value from a set of predetermined confidence limit values; and

comparing the confidence limit value to the predetermined threshold.

9. A method for generating an alarm indicating that a physiological parameter has exceeded a predetermined threshold, the method comprising:

calculating a first estimated value of the physiological parameter and a first accuracy of the first estimated value based at least in part upon data;

determining that the first estimated value of the physiological parameter exceeds the predetermined threshold; and

delaying generating the alarm based on the first accuracy.

10. The method of claim 9 further comprising:

calculating a delay time period based at least in part upon a comparison of the first accuracy to a previously determined accuracy associated with a previously estimated value of the physiological parameter.

11. The method of claim 10 further comprising:

after the delay time period, calculating a second estimated value of the physiological parameter based at least in part upon new data; and

if the second estimated value of the physiological parameter still exceeds the predetermined threshold, generating the alarm.

12. The method of claim 9 further comprising:

determining that the first accuracy exceeds a predetermined accuracy range.

13. The method of claim 9 further comprising:

after a predetermined time period, calculating a second estimated value of the physiological parameter and a second accuracy of the second estimated value based at least in part upon new data;

determining that the second accuracy does not exceed the predetermined accuracy range and the second estimated value of the physiological parameter exceeds the predetermined threshold, generating the alarm.

14. The method of claim 12, further comprising:

prior to calculating the first estimated value,

calculating a third estimated value of the physiological parameter and a third accuracy of the current estimated value from data;

determining that the third estimated value of the physiological parameter does not exceed the predetermined threshold; and

setting the third accuracy as the predetermined accuracy range.

15. A pulse oximeter comprising:

an oxygen saturation module capable of calculating an estimated value of pulse rate or oxygen saturation of a patient'"'"'s blood from information received from a sensor;

an accuracy module capable of calculating the accuracy of the estimated value;

an alarm module capable of generating an alarm based at least in part upon the estimated value and a predetermined alarm threshold; and

wherein the alarm module is capable of delaying the generation of an alarm based at least in part upon the accuracy of the estimated value.

16. The pulse oximeter of claim 15, further comprising:

a probability distribution module capable of calculating a probability distribution of an actual value of the oxygen saturation of a patient'"'"'s blood based at least in part upon information received from the sensor; and

wherein the alarm module is further capable of calculating an adjusted threshold based at least in part upon the probability distribution and the predetermined threshold and generating an alarm based at least in part upon the adjusted threshold.

17. The pulse oximeter of claim 16, further comprising:

a processor capable of executing software applications; and

wherein at least one of the modules is a software application capable of being executed by the processor.

18. The pulse oximeter of claim 16, further comprising:

a memory capable of storing one or more of the predetermined threshold, the adjusted threshold, at least one estimated value of oxygen saturation of a patient'"'"'s blood;

at least one accuracy associated with an estimated value, the probability distribution, and a delay time period calculated based on at least one accuracy of an estimated value.