METHOD AND APPARATUS FOR DETERMINING AT LEAST ONE UNKNOWN DATA OF A BIOLOGICAL FLUID

• US 3,654,445 A
• Filed: 01/08/1970
• Issued: 04/04/1972
• Est. Priority Date: 01/09/1969
• Status: Expired due to Term

• Current Assignee: Peter Ring, Soren Peter Weis Stranddorf, Stig Glerup Mikkelsen
• Original Assignee: Peter Ring, Soren Peter Weis Stranddorf, Stig Glerup Mikkelsen
• Inventors: Mikkelsen, Stig Glerup, Ring, Peter, Stranddorf, Soren Peter Weis
• Primary Examiner(s): Morrison, Malcolm A.
• Assistant Examiner(s): Wise, Edward J.
• Application Number:
  US05/001,332
• Time in Patent Office: 817 Days
• Field of Search: 235/151.3,185,92,151.35 23/253 128/2 374/71
• US Class Current: 205/779
• CPC Class Codes: G01N 33/492 Determining multiple analytes
• CPC Class Codes: G06G 7/58 for chemical processes G06G7/75 takes precedence; for physico-chemical processes; for metallurgical processes
• CPC Class Codes: G06G 7/60 for living beings, e.g. their nervous systems ; for problems in the medical field

Abstract

The invention relates to a method and apparatus for determining at least one unknown parameter of a biological fluid, for example a blood sample. The apparatus comprises equipment for reading known or measured data of the biological fluid into an analog computer-either by using digital or analog values of the known data-and with the analog computer being programmed to process the read-in data to produce therefrom a plurality of variable voltages which represent curves of different configuration in a hypothetical coordinate system and memorizing the magnitude of these voltages when they assume a value equal to a corresponding point of intersection between the curves of the hypothetical coordinate system, and including means for reading out the memorized values in analog or digital form. Specifically, with respect to the biological fluid being a blood sample, the data to be read in are in the form of two correlated values of pH and PCO2 and the method comprises the steps of producing two voltages which vary as a function of time and processing these voltages to assume in time sequence values corresponding to voltage values being analog with the two correlated sets of data and at the same time building up variable voltages which represent curves of a predetermined configuration in the hypothetical coordinate system, points of which are expression of the desired, unknown data, and after comparison memorizing the different voltages when they become equal and reading out the memorized values in analog or digital form.

Claims

1. A method for determining at least one unknown data of a biological fluid of which correlated values of data that can be determined vary according to a substantially linear function, comprising the steps of determining a first and a second correlated set of values of said data, producing a first and a second correlated set of voltages corresponding to the two sets of correlated data and being analog therewith, producing a first and a second voltage both of which vary as a function of time and at one moment assume the value of said first set of analog voltages and at another moment assume the value of said second set of analog voltages, producing a third analog voltage which is relevant to the unknown data, comparing said third analog voltage with the first of said varying voltages, and reading out a value or a function of said third varying voltage when said first varying voltage becomes equal with the third analog voltage.

2. A method according to claim 1, in which said third analog varying voltage is a function of one of said first and second varying voltages.

3. A method as claimed in claim 2, in which the initial values of the voltages which vary as a function of time are adjusted in response to a data of the biological fluid which represents a part of the fluid.

4. A method as claimed in claim 2, in which the ratio between said first and second voltages both of which vary as a function of time is regulated in response to differences between each one of said analog voltages and one of said variable voltages aT different times.

5. A method as claimed in claim 4, in which the differences at different times between the analog voltages corresponding to the data determined and one of the voltages which vary as a function of time are measured and in which the measurement is repeated a number of times and each measurement is used to reduce the differences by changing the ratio between the variable voltages.

6. A method of determining at least one unknown data of a blood sample comprising the steps of determining correlated values of pH and PCO2, the partial pressure of carbon dioxide of said blood sample, producing two sets of correlated voltages analog with said pH and PCO2 values, producing two voltages which vary as a function of time according to a substantially linear function and at different moments assume the values of said two sets of analog voltages, producing a third variable analog voltage which is a non-linear function of at least one of said time varying voltages and represents a plurality of analog values of the base excess in different blood samples, comparing said third voltage with one of said varying voltages, and maintaining the analog value of the base excess when said time varying voltage becomes equal with said third voltage, and reading out the base excess value.

7. A method as claimed in claim 6, in which one of the sets of correlated pH and PCO2 values is a function of the hemoglobin value of the blood sample.

8. A method as claimed in claim 6, in which the initial values of the voltages which vary as a function of time are a function of hemoglobin values of blood.

9. A method as claimed in claim 8, in which the voltages which vary as a function of time are compared in time sequence with the voltages which are analog with pH and PCO2 and deviations, if any, are used to change the ratio between said variable voltages as well as the initial values thereof.

10. A method as claimed in claim 9, in which the comparison and change of ratio as well as initial values of the variable voltages is repeated until the deviations between the variable voltages and the voltages analog with pH and PCO2 are below predetermined limits.

11. A method as claimed in claim 10, in which the comparisons and changes are repeated a further plurality of times after the deviations have been found to be below the predetermined limits.

12. A method as claimed in claim 6, in which the actual value of pH of the blood sample is measured and a corresponding analog voltage is produced and the variable voltages are adjusted to correspond to a value of PCO2 which enables the analog value of the actual PCO2 to be determined.

13. In an apparatus for determining at least one unknown data of a biological fluid of which correlated values of data which can be determined vary according to a substantially linear function, comprising in combination means for producing a first and a second correlated set of voltages corresponding to two sets of correlated data and being analog therewith, means for producing a first and a second voltage both of which vary as a function of time and at one moment assume the value of said first set of analog voltages and at another moment assume the value of said second set of analog voltages, means for producing a third varying analog voltage which is relevant to the unknown data, means for comparing said third analog voltage with the first of said varying voltages, and means for reading out a value or a function of said third analog voltage when said first varying voltage becomes equal with said third analog voltage.

14. Apparatus as claimed in claim 13, further comprising means for adjusting the initial values as well as the ratio between the voltages which vary as a function of time.

15. Apparatus as claimed in claim 13, further comprising means for comparing in time sequence the voltages which vary as a function of time with the analog voltages and means for adjusting The initial values of as well as the ratio between the variable voltages in response to the comparison.

16. Apparatus as claimed in claim 13, wherein said first and second varying voltage producing means comprises a voltage source, a pair of integrators in operative connection with the voltage source and responsive to said correlated voltage set generating means, two outputs from said pair of integrators, a function generator operable to produce said third voltage connected to one of said two outputs, an output of the function generator, a limit sensor connected with the output of said function generator and the other output from said pair of integrators and wherein said reading out means includes means for maintaining a value of said third voltage or a function thereof when it becomes equal to said second output voltage.

17. In an analog computing apparatus for determining at least one unknown data of biological fluid of which correlated values of data that can be determined vary according to a substantially linear function and of which a first and a second set of correlated values are determined, comprising in combination:

first means for reading in a first and a second set of correlated voltages being analog with two sets of correlated data each representing abscissa and ordinate respectively of each of two spaced points in a hypothetical coordinate system, second means for producing two voltages which vary as a function of time and in sequence assume the values of said first set of read-in voltages and the values of said second set of read-in voltages symbolizing a substantially straight line through said two points of the hypothetical coordinate system, third means for producing at least a third analog voltage relevant to the unknown data, fourth means for comparing said third analog voltage with one of said variable voltages corresponding to finding the point of intersection between said substantially straight line in the hypothetical coordinate system and a curve therein corresponding to said third voltage and fifth means for reading out a value of at least one of said variable voltages or a function thereof when the value of the first variable voltage is equal with said third voltage.

18. Apparatus as claimed in claim 17, further comprising sixth means for comparing in time sequence the voltages which vary as a function of time with the analog voltages and means for adjusting the initial values of as well as the ratio between the variable voltages in response to the comparison.

19. Apparatus as claimed in claim 17, wherein said second means comprises a voltage source, a pair of integrators in operative connection with the voltage source and responsive to said first means, two outputs from said pair of integrators, a function generator operable to produce said third voltage connected to one of said two outputs, an output of the function generator, a limit sensor connected with the output of said function generator and the other output from said pair of integrators and wherein said fifth means includes means for maintaining a value of said third voltage or a function thereof when it becomes equal with said second output voltage.

20. In analog computing apparatus for determining at least one unknown data of a blood sample of which correlated values of pH and PCO2, the partial pressure of carbon dioxide, are determined, comprising in combination:

means for reading in a first and a second set of correlated voltages being analog with two sets of correlated values of pH and PCO2 each representing the abscissa and ordinate respectively of each of two spaced points in a hypothetical coordinate system, means for producing two voltages which vary as a function of time and in sequence assume the values of said first set of analog voltages and the values of said second set of analog voltages symbolizing a substantially straight line through said two points of the hypothetical coordinate system, means for producing at leaSt a third analog voltage which varies as a function of time and represents the base excess of blood, means for comparing said third voltage with the first of said variable voltages corresponding to finding the point of intersection between said substantially straight line in the hypothetical coordinate system and a curve therein, which represents the base excess, and means for reading out the value of the base excess when the value of the first variable voltage is equal with said third voltage which represents the base excess.

21. Apparatus as claimed in claim 20, further comprising means for reading in actual pH and reading out actual PCO2.

22. Apparatus as claimed in claim 20, further comprising means for adjusting the initial values of the variable voltages to assume values corresponding to the analog value of the contents of hemoglobin in the blood sample.

23. Apparatus as claimed in claim 22, further comprising means for reading out the analog value of the hemoglobin.

24. Apparatus as claimed in claim 20, further comprising means for reading in the analog value of the hemoglobin.

25. Apparatus as claimed in claim 20, further comprising means for changing the ratio between the two voltages which vary as a function of time in response to the actual oxygen saturation of the blood sample.

26. In an analog computing apparatus for determining at least one unknown data of a blood sample of which a first and a second set of correlated values of pH and PCO2, the partial pressure of carbon dioxide, are determined comprising in combination:

first means for reading in a first and a second set of correlated analog voltages corresponding to said two sets of correlated values each representing abscissa and ordinate respectively of each of two spaced points in a hypothetical coordinate system, second means for producing two voltages which vary as a function of time and in sequence assume the values of said first set of read-in voltages and the values of said second set of read-in voltages symbolizing a substantially straight line through said two points of the hypothetical coordinate system, third means for producing a non-linear function of at least one of said variable voltages symbolizing the base excess curve of a Siggaard Andersen nomogram, fourth means for comparing the first of said variable voltages with said non-linear function corresponding to finding the point of intersection between said substantially straight line and said base excess curve in the hypothetical coordinate system, and an analog memory for maintaining the value of said non-linear function or a function thereof when the first one of said variable voltages is equal with said non-linear function voltage.

27. Apparatus as claimed in claim 26, further comprising an additional analog memory and an interconnected calculation network for calculating and maintaining the analog values of data representative of the said straight line in the hypothetical coordinate system.

28. Apparatus as claimed in claim 27, wherein said network comprises a network for calculating actual base excess BEact by means of the formula BEact BE100 + K'"'"''"'"' . Hb (100-SO2/100) where BE100 is the base excess for 100 percent saturation of the blood with O2, Hb is hemoglobin in grams per 100 mls. and SO2 is the actual oxygen saturation of the blood sample and K'"'"''"'"' is a constant.

29. Apparatus as claimed in claim 27, wherein said network comprises a network for calculating the actual bicarbonate ABC by means of the formula log ABC pHa - K + log ( Alpha . PCO2a) where Alpha is the solubility coefficient of carbon dioxide in blood plasma and K is a constant, whereas pHa is the actual pH value of the blood sample and PCO2a is the actual value of PCO2 in the blood sample.

30. Apparatus as claimed in claim 27, wherein said network comprises a network for calculating the buffer base by means of the formula BB BE100 + K3 + K4 . Hb where BE100 is the base excess for 100 percent saturation of the blood with oxygen, Hb is hemoglobin in grams per 100 ml. and K3 and K4 are constants.

31. Apparatus as claimed in claim 27, said network comprising means for calculating the actual base excess BEact by means of the formula BEact BE100 + K'"'"''"'"' . Hb . (100 -SO2/100) where BE100 is the base excess for 100 percent saturation of the blood with oxygen, Hb is hemoglobin in grams per 100 ml, SO2 is the actual oxygen saturation of the blood sample and K'"'"''"'"' is a constant and means for changing said substantially straight line such that this line will correspond to the actual base excess value.

32. Apparatus as claimed in claim 27, wherein said network comprises further comprising means for calculating the base excess of fully oxygenated blood, BE100 by means of the formula BE100 BEact - K'"'"''"'"' . Hb . (100 - SO2/100) where BEact is the actual base excess, Hb is hemoglobin in grams per 100 ml., SO2 is the actual oxygen saturation of the blood sample and K'"'"''"'"' is a constant and means for changing said substantially straight line such that this line will correspond to the base excess value of fully oxygenated blood.

33. Apparatus as claimed in claim 26, further comprising means coupled to said second means for changing the ratio Delta L between the voltages which vary as a function of time by means of the formula Delta L (K1/K2 - BE100). (100 SO2) .F(Hb) in which F(Hb) is a function of the hemoglobin content of the blood sample, BE100 is the base excess for 100 percent saturation of the blood with oxygen, SO2 is the actual oxygen saturation of the blood and K1 and K2 are constants.