DEVICE FOR OBTAINING AN INDICATOR OF A MICROCIRCULATORY CONDITION

Abstract

The invention relates to a device (1) and a method for obtaining an indicator of the microcirculatory condition of a patient. the device (1) comprises at least one sensor (2) for measuring data indicative of an arterial blood oxygen level, at least one sensor (3) for measuring data indicative of a tissue oxygen level and a control unit (4) for determining a measure of microcirculation, in particular changes in tissue perfusion on the basis of the tissue oxygen level and the arterial blood oxygen level.

Claims

1-17. (canceled)

18. A device for obtaining an indicator of microcirculatory condition of a patient, comprising: at least one sensor for measuring data indicative of a tissue oxygen level, at least one sensor for measuring data indicative of an arterial blood oxygen level; and a control unit for determining changes in tissue perfusion.

19. The device according to claim 18, wherein the control unit has at least one input for receiving a measured or estimated tissue oxygen level value, at least one input for receiving a measured or estimated arterial blood oxygen level value, and at least one output interface for outputting an indicator of a microcirculatory condition of a patient based on the received inputs.

20. The device according to claim 18, wherein the sensor for measuring data indicative of a tissue oxygen level is a first sensor element and the sensor for measuring data indicative of an arterial blood oxygen level is a second sensor element different from the first sensor element.

21. The device according to claim 20, wherein the second sensor element comprises a pulsoximetric sensor adapted for measuring the arterial blood oxygen level by optical detection of oxygen saturation.

22. The device according to claim 21, wherein the device comprises at least one further sensor adapted for measuring data indicative of a carbon dioxide level, a pH-level and/or a temperature.

23. The device according to claim 20, wherein the first sensor element comprises a transcutaneous measurement sensor.

24. The device according to claim 23, wherein the transcutaneous measurement sensor is adapted for heated transcutaneous measurement.

25. The device according to claim 18, wherein the sensor for measuring data indicative of an arterial blood oxygen level and/or the sensor for measuring data indicative of a tissue oxygen level are adapted for continuous and/or intermittent and/or alternating measurements.

26. The device according to claim 18, wherein the sensor for measuring data indicative of an arterial blood oxygen level and the sensor for measuring data indicative of a tissue oxygen level are arranged in a common housing.

27. The device according to claim 18, wherein the sensor for measuring data indicative of an arterial blood oxygen level and/or the sensor for measuring data indicative of a tissue oxygen level are adapted to be placed on a part of the skin.

28. The device according to claim 18, wherein the control unit is adapted for determining an indicator of a microcirculatory condition of a patient based on the difference between a first and a second oxygen level, the ratio of a first and a second oxygen level and/or an index based on a first and a second oxygen level.

29. The device according to claim 18, wherein the control unit is adapted for collecting, storing and processing time dependent data.

30. The device according to claim 29, wherein the control unit is adapted for determining changes in tissue perfusion on a predetermined and/or selectable timescale.

31. The device according claim 18, wherein the control unit is connected or connectable to an output device, such as a monitor or a display for displaying the measure of microcirculation.

32. The device according to claim 18, wherein the control unit is adapted for indication of an arterial partial pressure of oxygen PaO.sub.2, and/or the control unit is adapted for indication of a transcutaneous partial pressure of oxygen PtcO.sub.2.

33. A method for obtaining an indicator of tissue perfusion, comprising: providing an arterial blood oxygen level of a patient; providing a tissue oxygen level of the patient; and determining a measure for microcirculation on the basis of the tissue oxygen level and the arterial blood oxygen level.

34. The method according to claim 33, wherein the measure for microcirculation is determined in septic patients.

35. The method according to claim 33, comprising: measuring an arterial blood oxygen level for pulsoximetric determination of an oxygen saturation; and measuring a tissue oxygen level.

36. The method according to claim 35, wherein the arterial blood oxygen level is measured by optical detection, and/or the tissue oxygen level is measured by a transcutaneous measurement.

37. The method according to claim 33, wherein the arterial blood oxygen level is provided by pulsoximetric detection using two or more wavelengths.

38. The method according to claim 33, comprising providing further data indicative of a carbon dioxide level, a pH-level and/or a temperature.

39. The method according to claim 38, wherein data indicative of a carbon dioxide level, a pH-level and/or a temperature are provided for correcting a pulsoximetric detection of the arterial blood oxygen level.

40. The method according to claim 38, wherein data indicative of a carbon dioxide level, a pH-level and/or a temperature, are provided by measuring data indicative of a carbon dioxide level, a pH-level and/or a temperature.

41. A computer program for loading into a computer and/or for running on the computer, wherein the computer program is adapted for carrying out a method according to claim 33.

Description

[0116] The invention is further explained with reference to preferred embodiments and the following drawings which show:

[0117] FIG. 1: A schematic representation of a first example of a device;

[0118] FIG. 2: a schematic view on a sensor head of a second example for a device;

[0119] FIG. 3: a schematic cross-sectional view of the sensor head of FIG. 2;

[0120] FIG. 4: a schematic representation of a third example of a device;

[0121] FIG. 5: a schematic cross-sectional view of the sensor head of the third example of a device;

[0122] FIG. 6a: a first schematic representation of an O.sub.2 level;

[0123] FIG. 6b: a second schematic representation of an O.sub.2 level.

[0124] FIG. 1 shows a schematic representation of a first example of a device 1 for for obtaining an indicator of a microcirculatory condition of a patient. The device 1 comprises a first sensor 3 for measuring data indicative of a tissue oxygen level and a second sensor 2 for measuring data indicative of an arterial blood oxygen level.

[0125] The second sensor 2 for measuring data indicative of an arterial blood oxygen level is a second sensor element 12 and the first sensor 3 for measuring data indicative of a tissue oxygen level is a first sensor element 13, in this example different from the first sensor element 12.

[0126] The device 1 comprises a further additional sensor 5 adapted for measuring data indicative of a carbon dioxide level, a pH-level and/or a temperature, in particular for correcting the pulsoximetric detection of the arterial blood oxygen level.

[0127] The first sensor element 13 and the second sensor element 12 are arranged in a common housing 6 forming a sensor head 8.

[0128] The device 1 comprises a control unit 4 for determining a measure of microcirculation, in particular changes in tissue perfusion, on the basis of the tissue oxygen level and the arterial blood oxygen level.

[0129] The device 1 comprises an additional sensor 5 for measuring data indicative of a further parameter, such as the temperature, the carbon dioxide level, the pH-value of the blood and/or another blood parameter, in particular for correcting the arterial blood oxygen level and/or the tissue oxygen level.

[0130] The sensor head 8 may be connected to a device base 9 by a cable 10. The control unit 4 may be arranged in the device base 9.

[0131] The control unit 4 is connected to an output device 7, such as a monitor or a display for displaying the measure of microcirculation. The output device 7 may also be arranged in the device base 9.

[0132] The sensor head 8 comprises a contact face 11 which is directable towards a measuring site. In this case, the measuring site is an area on the skin of a patient.

[0133] The device 1 shown in FIGS. 2 and 3 allows a combined measurement of the arterial oxygen saturation (SpO.sub.2) and of the transcutaneous O.sub.2 partial pressure (PtcO.sub.2).

[0134] For the measurement of the arterial oxygen saturation, the device 1 in this alternative embodiment according to FIG. 2 comprises a second sensor 17 adapted for measuring the arterial blood oxygen level by pulsoximetric detection, hence a pulse oximetric measurement system which includes, among other things, a two-color light-emitting diode 22 (LED) as well as a photodetector 23. The two-color light-emitting diode 22 includes two light-emitting diodes 22a, 22b disposed closely next to one another and arranged in a common housing, with the one light-emitting diode 22a for example having a wavelength of approximately 660 μm (red) and the other light-emitting diode 22b for example having a wavelength of approximately 890 μm (infrared).

[0135] The device 1 has a surface 15 over which, in the embodiment shown, a membrane 50 is arranged and there between a thin layer of electrolyte 51. This membrane 50 is placed on the skin at a point of the human body which has a good blood flow, for example at a finger, at the forehead or at the earlobe. The light transmitted by the two light emitting diodes 22a, 22b radiates through the electrolyte 51 located above the light emitting diodes 22a, 22b and through the membrane 50 and is conducted into the body part, not shown, with a good blood flow and is scattered there and partly absorbed. The light reflected by the body part is measured using the photodetector 23. The signal measured by the photodetector 3 is supplied to a control unit 4.

[0136] The device 1 shown moreover includes a first sensor 19 adapted for transcutaneous measurement, hence an electrochemical measuring device, for the measurement of the transcutaneous oxygen partial pressure (PtcO.sub.2 measurement), with this measuring device 19 preferably including a micro-pH electrode 24 as well as an Ag/AgCl reference electrode 25. The transcutaneous partial pressure of oxygen is, in this example, measured potentiometrically in that the pH of the thin layer of the electrolyte solution 51 is measured which is in communication with the skin via the hydrophobic membrane 50 which has good gas permeability. A change in the pO.sub.2 value at the skin surface effects a pH change of the electrolyte solution. The pH is measured in that the potential is measured between the miniature pH electrode 24 and a reference electrode 25. The micro-pH electrode 24 is conductively connected via the electrical inner deflector 16 to the control unit 4.

[0137] The device 1 comprises a heating element 26 and a temperature sensor 27.

[0138] FIG. 4 shows a schematic representation of a third example of a device 1 for for obtaining an indicator of microcirculatory condition of a patient.

[0139] A second sensor 2 for measuring data indicative of an arterial blood oxygen level, a so called blood oxygen sensor, a first sensor 3 for measuring data indicative of a tissue oxygen level, a so called tissue oxygen sensor, an additional sensor 5, a housing of a processor or control unit 4 and an output device 7 are arranged in a common housing 6.

[0140] Preferably the housing allows every combination, integration and separation of components.

[0141] The second blood oxygen sensor 2 may be formed by a pulse oximeter and may comprise two parts 2a, 2b (see FIG. 5).

[0142] The first tissue oxygen sensor 3 may be a transcutaneous measurement device.

[0143] The additional sensor 5 may detect temperature, transcutaneous CO.sub.2 and/or may comprise an input for external values.

[0144] The control unit 4 may provide a calculation of PaO.sub.2 from a measured Sp0.sub.2 value.

[0145] The output device 7 may comprise a display for showing a digital or analogue output.

[0146] FIG. 5 shows a schematic cross-sectional view of the sensor head 8 of the third example of a device 1.

[0147] The sensor head 8 is placed in contact to the skin 103 of a patient.

[0148] A first sensor 3 for measuring data indicative of a tissue oxygen level, a so called tissue oxygen sensor, an additional sensor 5, a first part 2a and a second part 2b of a second blood oxygen sensor 2 are arranged in a common housing 6. A housing of a processor or control unit 4 and an output device 7 (see FIG. 4), not shown in this figure, may also be arranged in the housing 6.

[0149] The sensor head 8 is connected to an output connection 20, which may establish a connection to an external processor or controller and which may act as a power supply.

[0150] Accordingly, the device 1 for obtaining an indicator of microcirculatory condition of a patient, comprises at least one first sensor 3 for measuring data indicative of a tissue oxygen level, in particular a skin oxygen level, and at least one second sensor 2 for measuring data indicative of an arterial blood oxygen level and a control unit 4 (see FIGS. 1 and 4) for determining changes in tissue perfusion.

[0151] The control unit 4 in particular has at least one input for receiving a measured or estimated arterial blood oxygen level value, at least one input for receiving a measured or estimated tissue oxygen level value, and at least one output interface for outputting an indicator of a microcirculatory condition of a patient based on the received inputs, not explicitly shown in the figures.

[0152] The skin 103 is permeated with arteries 101 and capillaries 102.

[0153] Blood supply in the arterioles and/or capillaries 102 may be impaired in a septic condition consequently significantly less oxygen diffuses to the skin surfaces, which may be detected by a transcutaneous measurement.

[0154] Blood supply in the skin arteries 101 remains unimpaired during sepsis. By using pulse oximetry the arterial oxygen saturation Sp0.sub.2 can be measured and then the corresponding partial pressure PaO.sub.2 may be calculated. The partial pressure PaO.sub.2 may be compared to the transcutaneously measured oxygen tension PtcoO.sub.2.

[0155] FIGS. 6a and 6b show representations of O.sub.2 levels in the skin S and in the blood B.

[0156] FIG. 6a shows that in a normal condition the oxygen level in the skin corresponds to the oxygen level in the blood.

[0157] To the contrary, as shown in FIG. 6b, the oxygen level in the skin S is much lower than the oxygen level in the blood B in a septic condition.