DEVICE FOR OBTAINING AN INDICATOR OF A MICROCIRCULATORY CONDITION

Abstract

The invention relates to a device (1, 1′) and a method for obtaining an indicator of microcirculatory condition of a patient. The device (1, 1′) comprises at least one first sensor (13) for measuring data indicative of first carbon dioxide levels, in particular tissue carbon dioxide levels, at least one second sensor (12) for measuring data indicative of second carbon dioxide levels, in particular transcutaneously measured arterial blood carbon dioxide levels, and a control unit (4) for determining a measure of microcirculation, in particular changes in tissue perfusion, preferably in septic patients, on the basis of the tissue carbon dioxide level and the transcutaneously measured arterial blood carbon dioxide level.

Claims

1-15. (canceled)

16. A device for obtaining an indicator of a microcirculatory condition of a patient, comprising: at least one first sensor for measuring data indicative of first carbon dioxide levels, the first sensor comprising a measurement area to be contacted with the patient's tissue, and adapted for a transcutaneous carbon dioxide measurement at a first temperature, wherein the measurement area is kept below 38° C.; at least one second sensor for measuring data indicative of second carbon dioxide levels, the second sensor comprising a measurement area to be contacted with the patient's tissue and adapted for a transcutaneous carbon dioxide measurement at a second temperature being higher than the first temperature, wherein the measurement area is heated above 38° C.; and a control unit for detecting changes in skin perfusion, the control unit having at least one input for receiving a measured or estimated first carbon dioxide level value, at least one input for receiving a measured or estimated second carbon dioxide level value from the second sensor; and at least one output interface for outputting an indicator of a microcirculatory condition of a patient based on the received inputs.

17. The device according to claim 16, wherein the control unit has at least one input for receiving a tissue carbon dioxide level value from the first sensor, and/or at least one input for receiving an arterial blood carbon dioxide level value.

18. The device according to claim 16, wherein the first sensor is a first sensing unit and the second sensor is a second sensing unit different from the first sensing unit.

19. The device according to claim 16, wherein the device comprises at least one additional sensor adapted for measuring data indicative of a further parameter.

20. The device according to claim 19, wherein the additional sensor is adapted for measuring data indicative a temperature, the oxygen level or a pH-value of the blood and/or another blood parameter.

21. The device according to claim 16, wherein the sensors are adapted for continuous and/or intermittent and/or alternating measurement.

22. The device according to claim 16, wherein the first sensor and the second sensor are arranged in a common housing.

23. The device according to claim 16, wherein the first sensor and the second sensor are adapted to be placed on a part of the skin.

24. The device according to claim 16, wherein the control unit is adapted for inducing a measurement of the first carbon dioxide level at a first temperature and for inducing a measurement of the second carbon dioxide level, with the measurement area being heated to the second temperature, the second temperature being higher than the first temperature, wherein the control unit is adapted for controlling at least one heating element for keeping the measurement site of the skin at a certain temperature and wherein the control unit comprises an output for controlling the heating element, the first sensor and/or the second sensor.

25. The device according to claim 24, wherein the second temperature is above 38° C.

26. The device according to claim 16, wherein the control unit is adapted for estimation of an arterial partial carbon dioxide pressure PaCO.sub.2 based on a transcutaneous partial carbon dioxide pressure tcPCO.sub.2, obtained by a measurement by the second sensor, wherein the measurement area is heated to temperature above 38° C. and/or a temperature that achieves arterialization.

27. The device according to claim 16, wherein the control unit is adapted for estimation of tissue partial carbon dioxide pressure PcCO.sub.2 based on a transcutaneous partial carbon dioxide pressure PcCO.sub.2, obtained by a measurement by the first sensor, wherein the measurement area is kept below 38° C.

28. Device according to claim 16, wherein the control unit is adapted for determining the indicator of a microcirculatory condition of a patient based on the difference between the first and the second carbon dioxide level, the ratio of the first and the second carbon dioxide level and/or an index based on the first and the second carbon dioxide level.

29. The device according to claim 16, wherein the output interface of the control unit is connected or connectable to an output device.

30. A method for obtaining an indicator of tissue perfusion by a computer, comprising: providing a first carbon dioxide level from a first sensor; providing a second carbon dioxide level from a second sensor; and determining a measure for microcirculation, on the basis of the first and the second carbon dioxide level.

31. The method according to claim 30, wherein the first carbon dioxide level is a tissue carbon dioxide level.

32. The method according to claim 31, wherein the tissue carbon dioxide level is a transcutaneously measured tissue PcCO.sub.2 value.

33. The method according to claim 30, wherein the second carbon dioxide level is an arterial blood carbon dioxide level.

34. The method according to claim 33, wherein the arterial blood carbon dioxide level is a transcutaneously measured arterial PaCO.sub.2 value.

35. The method according to claim 30, wherein the measure for microcirculation is determined in septic patients.

36. The method according to claim 30, comprising: measuring the first carbon dioxide level at a first temperature; and measuring the second carbon dioxide level with the measurement area been heated to a second temperature higher than the first temperature.

37. The method according to claim 30, wherein the second carbon dioxide level is measured with the measurement area been heated above 38° C.

38. The method according to claim 30, wherein further data are provided indicative of an oxygen level, a pH-level and/or a temperature.

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

40. An executable computer program product directly loadable into the internal memory of a digital device, the computer program comprising software code for performing the steps of a method according to claim 30, when said product is run on a computer.

Description

[0137] The invention is further explained with reference to preferred embodiments and the following drawings which show:

[0138] FIG. 1: a schematic representation of a first example of a device;

[0139] FIG. 2: a schematic representation of a second example of a device;

[0140] FIG. 3: a schematic view on a sensor head of a third example for a device;

[0141] FIG. 4: a schematic cross-sectional view of the sensor head of FIG. 3;

[0142] FIG. 5: a schematic representation of a fourth example of a device;

[0143] FIG. 6: a schematic cross-sectional view of the sensor head of the fourth example of a device;

[0144] FIG. 7: a schematic representation of an example of microcirculatory conditions as measured by a device.

[0145] FIG. 1 shows a schematic representation of a first example of a device 1 for obtaining an indicator of microcirculatory condition of a patient. The device 1 comprises a first sensor 13 measuring data indicative of tissue carbon dioxide levels and a second sensor 12, for transcutaneously measuring data indicative of arterial blood carbon dioxide levels.

[0146] The second sensor 12 is formed by a second sensing unit and the first sensor 13 is formed by a first sensing unit different from the second sensing unit.

[0147] The second sensor 12 and the first sensor 13 are arranged in a common housing 6 forming a sensor head 8.

[0148] The device 1 comprises a control unit 4 for determining a measure of microcirculation, in particular changes in tissue perfusion or microcirculatory condition, on the basis of values, measured by the first sensor 13 and the second sensor 12, in particular on the basis of the tissue carbon dioxide level and the heated transcutaneously measured carbon dioxide level.

[0149] The device 1 comprises an additional sensor 5 for measuring data indicative of a further parameter, such as the temperature, the oxygen level, the pH-value of the blood and/or another blood parameter, in particular for correcting the arterial blood carbon dioxide level and/or the tissue carbon dioxide level.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] FIG. 2 shows a schematic representation of a second example of a device 1′ for obtaining an indicator of microcirculatory condition of a patient.

[0154] The device 1′ comprises a sensor head 8 with a single sensing unit 14, comprising first and second sensors 13 and 12 respectively. Depending on the temperature, the sensing unit 14 is controlled for transcutaneously measuring data indicative of arterial blood carbon dioxide levels or indicative of tissue carbon dioxide levels. Skin temperature is controlled by a heating element 15 controlled by the control unit 4. Hence, the sensing unit 14 acts as a sensor for measuring data indicative of arterial blood carbon dioxide levels at a first temperature and as a sensor for measuring data indicative of tissue carbon dioxide levels at a second temperature.

[0155] The device 1 shown in FIGS. 3 and 4 comprises a surface 30 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 (see FIG. 4).

[0156] The device 1 shown includes a sensor unit 19 adapted for transcutaneous measurement of the first and second tissue carbon dioxide level by electrochemical detection. The device 1 to this end preferably includes a micro-pH electrode 24 as well as an Ag/AgCl reference electrode 25 (see FIG. 3). The carbon dioxide level can be 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 carbon dioxide 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.

[0157] The device 1 comprises a heating element 26 and a temperature sensor 27.

[0158] The sensor unit 19 is adapted for a transcutaneous measurement at a first temperature, wherein the measurement area is kept below 38° C.

[0159] The sensor unit 19 is also adapted for a transcutaneous measurement at a second temperature being higher than the first temperature, wherein the measurement area is heated above 38° C. by the heating element 26.

[0160] Thus the sensor unit 19 is a first sensor for measuring data indicative of first carbon dioxide levels, in particular tissue carbon dioxide levels, and a second sensor for measuring data indicative of second carbon dioxide levels, in particular arterial blood carbon dioxide levels.

[0161] FIG. 5 shows a schematic representation of a fourth example of a device 1 for obtaining an indicator of microcirculatory condition of a patient.

[0162] A first sensing unit 13, a second sensing unit 12, an additional sensor 5, a housing of a processor or control unit 4 and an output device 7 may be arranged in a common housing 6.

[0163] Preferably the housing allows a combination, integration and suitable separation of components.

[0164] The first sensing unit 13 may be a first transcutaneous measurement device. The second sensing unit 12 may be a second transcutaneous measurement device and may comprise a heating element

[0165] The additional sensor 5 may detect temperature, transcutaneous O.sub.2 and/or may comprise an input for external values.

[0166] The output device 7 may comprise a display for showing a digital or analogue output.

[0167] FIG. 6 shows a schematic cross-sectional view of a sensor head 8 for obtaining an indicator of a microcirculatory condition of a patient in a fourth example of a device 1.

[0168] The sensor head 8 is placed in contact to the skin 103 of a patient.

[0169] A first sensing unit 13 for measuring data indicative of a tissue carbon dioxide level, an additional sensor 5, a second sensing unit 12 for measuring data indicative of an arterial carbon dioxide level and a heating element 15 are arranged in a common housing 6. The sensing unit 13 is adapted for a transcutaneous carbon dioxide measurement at a first temperature, wherein the measurement area is kept below 38° C. The sensing unit 12 is adapted for a transcutaneous carbon dioxide measurement at a second temperature being higher than the first temperature, wherein the measurement area is heated above 38° C. 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. The processor 4 is programmed to detect changes in skin perfusion and has an input for receiving a measured or estimated first carbon dioxide level value, in particular a tissue carbon dioxide level value from the first sensor 13, an input for receiving a measured or estimated second carbon dioxide level value from the second sensor 12, in particular an arterial blood carbon dioxide level value; and at least one output interface for submitting an indicator of a microcirculatory condition of a patient based on the received inputs.

[0170] 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.

[0171] The skin 103 is permeated with arteries 101 and capillaries 102.

[0172] FIG. 7 shows a schematic representation of an example of microcirculatory conditions as measured by a first sensor 13 and a second sensor 12 under condition of sepsis and under normal condition.

[0173] Blood supply in the skin arteries 101 remains unimpaired during sepsis.

[0174] However, blood supply in the capillaries 102 may be impaired in a septic condition. Consequently a significantly different amount of carbon dioxide diffuses from the skin surface, which may be detected by a transcutaneous measurement without heating the skin.

[0175] Surprisingly, heating of the skin leads to sufficient arterialization to mitigate influences that would affect skin diffusion, even in the presence of sepsis. Thus, carbon dioxide levels measured transcutaneously while heating the skin correlate with arterial carbon dioxide levels.

[0176] A septic condition indicator can be outputted by the processor e.g. by outputting the difference between the first and the second carbon dioxide level, for example the difference between tissue carbon dioxide level and the arterial carbon dioxide oxygen level, the ratio of the first and the second carbon dioxide level, for example the ratio of the tissue carbon dioxide level and the arterial blood carbon dioxide level and/or an index based on the first and the second carbon dioxide level, for example the tissue carbon dioxide level and the arterial blood carbon dioxide level, preferably for a prediction of sepsis.