Medical data display method

• US 5,941,820 A
• Filed: 07/03/1997
• Issued: 08/24/1999
• Est. Priority Date: 01/03/1994
• Status: Expired due to Fees

• Current Assignee: Steven Zimmerman
• Original Assignee: Steven Zimmerman
• Inventors: Zimmerman, Steven
• Primary Examiner(s): Lacyk, John P.
• Assistant Examiner(s): GILBERT, SAMUEL G
• Application Number:
  US08/888,008
• Time in Patent Office: 782 Days
• Field of Search: 128/898, 128/920-925, 600/300, 600/481, 600/515, 600/544-547
• US Class Current: 600/300
• CPC Class Codes: G16H 40/63 for local operation

Abstract

The invention is a method of measuring patient data, determining statistics from the data; determining measures of variation within the data, determining from the measures of variation a measure of homeostasis, modifying control chart limits based on the determined measure of homeostasis and displaying the statistic on the modified control chart. In addition, the control charts are modified as data varies over time in statistically significant groups as determined by the user and the modification of the limits is repeated so that the patient'"'"'s real time change in condition is constantly reflected in modified control charts. Records of the changes in the chart limits and data are maintained for consistency. Patient specific data received from a monitor are thereby modified to reflect the level of consistency in data received. The date include specific biological rhythms such as: pulse, oxygen content in the blood, blood pressure, and other bodily functions capable of being monitored. By determining the amount of consistency (or similarity) within consecutive subgroups of data (auto correlation or serial correlation) significant changes in the body may be identified relative to the time when consistency changes. The data are coordinated by time and subgroup number. The results are applied to control chart data (1) to obtain statistical results comparable to statistically independent control chart data, (2) to correct limits for control chart data, (3) to correct the plotting of data for control charts and (4) to determine when the prior three actions should be taken and for treating and diagnosing patients.

Claims

1. A method of evaluating patient specific data from a medical monitor which measures patient vital signs readable as individual data readings having a value as of a particular relevant time comprising of the steps of:

a) selecting individual data readings;

b) setting a subgroup number as the number of measurements in subgroups;

c) grouping the data readings so that a number of readings equal to the subgroup number are grouped into consecutive subgroups as subgroup data;

d) determining at least one control chart statistic for each of the subgroups;

e) determining a correlation value for correlation between at least two individual data readings;

f) determining at least one control chart limit;

g) determining at least one correcting factor for modifying the at least one control chart limit relative to the correlation value;

h) modifying the at least one control chart limit using the at least one correcting factor to obtain a modified chart limit;

i) displaying the at least one control chart statistic for the patient specific data in conjunction with the at least one modified chart limit.

2. The method of claim 1 wherein each individual data reading is taken at a relevant time, said relevant time being the time when the data readingis taken and wherein the step of selecting individual data readings further comprises (a) associating at least one data reading with the relevant time for that data reading and wherein the step of displaying the at least one control chart statistic for the patient specific data further comprises (a) displaying the at least one control chart statistic data associated with the relevant time associated with the at least one data reading from the subgroup from which the control chart statistic is determined.

3. The method of claim 2 wherein the step of determining a correlation value between at least two individual data readings further comprises the steps of:

a) setting a correlation subgroup number as the number of measurements in subgroups;

b) grouping the data readings so that a number of readings equal to the correlation subgroup number are grouped into consecutive subgroups as subgroup data;

c) determining a correlation value between at least one control chart statistic of one subgroup with the same at least one control chart statistic of another subgroup.

4. The method of evaluating patient specific data of claim 2 wherein the step of determining a correlation value comprises the additional steps of:

(a) determining a first correlation statistic for the at least two consecutive data readings;

(b) determining a second correlation statistic for the at least two consecutive data readings;

(c) determining a ratio of the first correlation statistic to the second correlation statistic as the correlation value.

5. The method of claim 4 wherein the step of determining the second correlation statistic further comprises determining at least one first correlation statistic from the selected group consisting of:

(1) absolute serial difference;

(2) serial difference;

(3) range;

(4) range of first datum between successive subgroups;

(5) variation between averages (averages of the subgroups);

(6) standard deviation within subgroups; and

(7) standard deviation of all data.

6. The method of claim 4 wherein the step of determining a first correlation statistic further comprises determining at least one first correlation statistic from the selected group consisting of:

(1) absolute serial difference;

(2) serial difference;

(3) range;

(4) range of first datum between successive subgroups;

(5) variation between averages;

(6) standard deviation within subgroups; and

(7) standard deviation of all data.

7. The method of claim 4 wherein the step of determining the ratio of correlation statistics further comprises determining a ratio of correlation statistics for the data subgroups.

8. The method of claim 7 wherein the step of determining a ratio comprises the step of making a ratio of an absolute serial difference statistic divided by a standard deviation statistic.

9. The method of claim 4 wherein the step of determining a ratio of correlation statistics comprises the step of preparing a ratio of a serial variation statistic to a total variation statistic.

10. The method of claim 2 wherein the step of determining a correlation value further comprises:

(a) assigning a correlation value for an acceptable level of serial correlation based upon the desired level of homeostasis in the patients condition.

11. The method of claim 2 wherein the step of determining at least one correcting factor further comprises the step of:

(a) setting the value of the correcting factor for an assigned acceptable level of serial correlation so that when acceptable patient specific data is displayed on the control chart it falls within the modified control limits.

12. The method of claim 2 wherein the step of displaying the at least one control chart statistic for the patient specific reading further comprises the step of displaying the value for correlation determined for the patient specific reading for each subgroup data.

13. The method of evaluating patient specific data of claim 1 utilizing patient data from control data from control patients whose treatment was considered successful wherein the step of determining a correlation value comprises the additional steps of:

(a) collecting control data from control patients;

(b) grouping the control data into statistically significant control subgroups of control subgroup size of at least one data point of a size wherein the control subgroup size is statistically significant to the subgroup number of the subgroup of the patient specific data;

(c) Determining at least one control chart statistic for control subgroups of the data identical to the statistics of the patient individual data readings to be examined;

(d) determining a control correlation statistic for the control subgroups of control data;

(e) and wherein determining the at least one correcting factor further comprises determining the correction value relative to the control correlation statistic.

14. The method of claim 13 wherein the control data is from statistically derived hypothetical-patient data as opposed to live patient data.

15. The method of claim 13 wherein grouping by correlation further comprises grouping by the amount of serial correlation in assigned increments of serial correlation.

16. The method of claim 13 wherein the step of determining a correcting factor further comprises performing regression analysis of the statistics determined using the control data.

17. The method of claim 16 wherein the step of performing regression analysis further comprises:

(a) graphing the A-E ratio against corresponding incremental values of serial correlation;

(b) performing a standard regression from the following list of regression analysis linear sum of least squares or non-linear sum of least squares to fit the average A-E ratio to the assigned value of serial correlation for the control data to determine a specific factor in the form of a formula which formula approximates the line formed by graphing the a-e ratio to input serial correlation.

18. The method of evaluating patient specific data of claim 1 wherein the the at least one control chart statistic and at least one control chart limit form a control chart comprised of a chart from the selected group consisting of:

Shewhart process control charts;

the cumulative sum chart, exponential weighted moving average chart, grand mean moving average chart, and continuous hypothesis testing process control chart.

19. The method of claim 1 wherein the step of displaying serial correlation further comprises the step of (a) determining a set of events for redetermination of the correlation value and (b) re-determining the correlation value and correcting factor to obtain a new correcting factor when the set of events for redetermination occurs.

20. The method of claim 19 wherein the step of determining a set of events and re-determining the correlation value further comprises modifying the control limits as a factorof the serial correlation value when there are a selected number of data points falling outside of the modified control limits.

21. The method of claim 20 wherein the selected number of data points are consecutive points falling outside of the modified control limits.

22. The method of claim 19 wherein the step of modifying the control limits further comprises the step of (a) determining an acceptable difference between the average and the control limits and obtaining a factor of that acceptable difference and (b) modifying the correlation value when this acceptable difference is exceeded.

23. The method of claim 19 wherein the set of events is further determined based on a set event not associated with the condition of the patient.

24. The method of claim 1 wherein the at least one control chart statistic of the patient specific data further comprises the average and standard deviation for the patient specific data.

25. The method of claim 1 wherein the step of (b) modifying the value of the control limits in charts where data is displayed by computing a new value for the control chart limits as a factor of the correlation statistic comprises (1) storing correcting factors for different stored serial correlation values (2) matching a stored value with a value for serial correlation determined for the data and (3) computing a new value for the control chart limits as a factor of the selected stored value.

26. The method of claim 1 wherein step f further comprises saving the control chart limit as an unadjusted limit and further compromising the step of displaying the unadjusted limit contemporaneously with the modified chart limit.