Nuisance alarm reductions in a physiological monitor

• US 6,754,516 B2
• Filed: 07/19/2001
• Issued: 06/22/2004
• Est. Priority Date: 07/19/2001
• Status: Expired due to Term

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett Incorporated (Medtronic Plc)
• Inventors: Mannheimer, Paul D.
• Primary Examiner(s): Hindenburg, Max F.
• Assistant Examiner(s): KREMER, MATTHEW J
• Application Number:
  US09/910,700
• Publication Number:
  US 20030018241A1
• Time in Patent Office: 1,069 Days
• Field of Search: 600/309-310, 600/322-326, 600/500-504, 356/39-42
• US Class Current: 600/323
• 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;

automatically establishing a dynamic threshold value, wherein said dynamic threshold value changes in time as the measured value changes in time;

establishing a condition value from a combination of said measured value and said dynamic threshold value, wherein said condition value comprises an integrated product of the extent by which said dynamic threshold value is exceeded by said measured value over a quantity of time said dynamic threshold value is exceeded by said measured value;

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

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 measured 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.

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 comprises 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 comprises a lower threshold value for said measured value and said establishing said dynamic threshold value further comprises:

continuously calculating a baseline value of said measured value; and

computing said 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 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.

11. 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.

12. The method of claim 1 wherein said dynamic threshold value comprises 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; and

computing said upper threshold value by offsetting a value above said baseline value.

13. The method of claim 12 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.

14. 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:

automatically 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 an integrated product of said extent over said quantity of time 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.

15. A pulse oximeter, comprising:

an alarm;

a sensor for measuring a value of a physiological parameter;

a computer usable 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;

automatically establishing a dynamic upper threshold value and a dynamic lower threshold value, wherein said threshold values define a range, and wherein said dynamic upper and said dynamic lower threshold values are related to said baseline of said 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 measured value during said quantity of time;

triggering said alarm when an integrated product of said extent over said quantity of time 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.

16. The apparatus of claim 15 wherein said measured value is an oxygen saturation, and said range comprises a high oxygen-saturation threshold value and low oxygen-saturation threshold value.

17. The apparatus of claim 15 wherein said measured value is a pulse rate, and said range comprises a high pulse rate threshold value and a low pulse rate threshold value.