Nuisance alarm reductions in a physiological monitor

• US 20030018241A1
• Filed: 07/19/2001
• Published: 01/23/2003
• Est. Priority Date: 07/19/2001
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett Incorporated (Medtronic Plc)
• Inventors: Mannheimer, Paul D.
• Granted Patent: US 6,754,516 B2
• Time in Patent Office: Days
• US Class Current: 600/300
• CPC Class Codes: A61B 2560/0276 Determining malfunction
• CPC Class Codes: A61B 5/02455 provided with high/low alarm devices
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• 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: G08B 21/02 Alarms for ensuring the safety of persons

Abstract

A method and apparatus for controlling alarms in a medical diagnostic apparatus where an alarm is generated when a measured value for a physiological parameter is outside a specified range. The method continuously calculates a baseline value, and establishes dynamic thresholds that are related to and continuously track the baseline value. The method determines the amount of time the measured value is past the dynamic threshold, and the amount by which the threshold is passed. Alarms are triggered based upon a combination of the amount of time and the amount by which the threshold is passed. Preferably, the combination is an integral or some function of an integral.

Claims

1. A method for controlling an alarm in a medical diagnostic apparatus, said apparatus monitoring a measured value, said method comprising:

measuring a value of a physiological parameter;

establishing a dynamic threshold value;

establishing a condition value from a combination of said measured value and said dynamic threshold value; and

triggering an alarm when said condition value exceeds a predetermined level.

2. The method of claim 1 wherein said dynamic threshold value tracks said measured value.

3. The method of claim 1 wherein said dynamic threshold value changes continuously in time with changes in time of said measured value.

4. The method of claim 1 wherein said dynamic threshold value changes in time at a rate less than the rate at which said measured value changes in time.

5. The method of claim 1 wherein said dynamic threshold value comprises a lower alarm limit for said measured value.

6. The method of claim 1 wherein said dynamic threshold value comprises an upper alarm limit for said measured value.

7. The method of claim 1 wherein said dynamic threshold value is one of a lower limit and an upper limit for said measured value, and where said lower limit and said upper limit define a range.

8. The method of claim 1 wherein said dynamic threshold value is one of a lower threshold value and an upper threshold value for said measured value and said establishing said dynamic threshold value further comprises:

continuously calculating a baseline value of said measured value;

computing an upper threshold value by offsetting a value above said baseline value; and

computing a lower threshold value by offsetting a value below said baseline value.

9. The method of claim 8 wherein said baseline value is continuously calculated using a filter selected from the group consisting of a low-pass filter, a running median filter, an infinite impulse filter and a finite impulse filter.

10. The method of claim 1 wherein said condition value comprises an extent by which said dynamic threshold value is exceeded by said measured value.

11. The method of claim 1 wherein said condition value comprises a quantity of time said dynamic threshold value is exceeded by said measured value.

12. The method of claim 1 wherein said condition value comprises

an extent by which said dynamic threshold value is exceeded by said measured value, and

a quantity of time said dynamic threshold value is exceeded by said measured value.

13. The method of claim 12 wherein said condition value comprises an integral of said extent over said quantity of time.

14. The method of claim 1 wherein said measured value is an oxygen saturation, and said dynamic threshold value is one of a high oxygen-saturation threshold value and low oxygen-saturation threshold value.

15. The method of claim 1 wherein said measured value is a pulse rate, and said dynamic threshold value is one of a high pulse rate threshold value and a low pulse rate threshold value.

16. The method of claim 1 further comprising:

monitoring said alarm when a measured value for said physiological parameter is outside a fixed range;

establishing a fixed upper threshold value and a fixed lower threshold value, wherein said fixed threshold values define said fixed range;

determining a quantity of time said measured value is outside said fixed range;

determining a measure of the amount by which said fixed range is exceeded by said value during said quantity of time; and

triggering said alarm when a combination of said quantity of time and said amount exceeds a second predetermined level.

19. The apparatus of claim 18 wherein said combination comprises an integral of said extent over said quantity of time.

20. The apparatus of claim 18 wherein said measured value is an oxygen saturation, and said threshold value is one of a high oxygen-saturation threshold value and low oxygen-saturation threshold value.

21. The apparatus of claim 18 wherein said measured value is a pulse rate, and said threshold value is one of a high pulse rate threshold value and a low pulse rate threshold value.

17. A method for controlling an alarm in a pulse oximeter apparatus, said apparatus monitoring said alarm when a measured value for a physiological parameter is outside a specified range, comprising:

establishing a dynamic upper threshold value and a dynamic lower threshold value, wherein said threshold values define said range, and wherein said dynamic upper and said dynamic lower threshold values are related to a continuously calculated baseline value;

determining a quantity of time said measured value is outside said range;

determining a measure of the extent by which said range is exceeded by said value during said quantity of time;

triggering said alarm when a combination of said quantity of time and said extent exceeds a predetermined level;

further monitoring said alarm when a measured value for said physiological parameter is outside a fixed range;

establishing a fixed upper threshold value and fixed lower threshold value, wherein said fixed threshold values define said fixed range; and

triggering said alarm when said measured value exceeds said fixed range by a second predetermined value.

18. A medical diagnostic apparatus, comprising:

an alarm;

a sensor for measuring a value of a physiological parameter;

a computer useable medium having computer readable code embodied therein for managing said alarm, said computer readable code configured to execute functions, comprising;

calculating a baseline of said value;

establishing a continuously tracking threshold value, wherein said threshold value follows said baseline;

comparing said value of a physiological parameter to said threshold value;

monitoring said alarm when said value of a physiological parameter exceeds said threshold;

determining a quantity of time where said value of a physiological parameter exceeds said threshold;

determining a measure of the extent said threshold is exceeded by said value during said quantity of time; and

triggering said alarm when a combination of said quantity of time and said extent exceeds a predetermined level.