A device for obtaining indicators of microcirculatory status

Abstract

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

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for obtaining an indication of the microcirculatory status of a patient. [Background technology]

[0002] Several clinical conditions, such as sepsis, hemorrhage, and cardiac arrest, cause a decrease in tissue perfusion. The small blood vessels and capillaries that provide the microcirculation can be affected. This deterioration in microcirculation can lead to dysfunction or even organ failure, further worsening the patient's prognosis.

[0003] When bacteria enter the bloodstream and cause a systemic infection, the body's response to the infection is called sepsis. Sepsis is one of the most common causes of illness in neonatal, pediatric, and adult intensive care units (ICUs). The incidence of sepsis is approximately 25% in advanced neonatal ICUs. Multiple factors, including prematurity, immunologic defects, and multiple insertion points such as lines / intravascular catheters, often lead to infiltration of organisms into the bloodstream.

[0004] Sepsis lesions can be monitored by detecting EEG encephalopathy, fever, hypothermia, core / peripheral temperature differentials, decreased temperature fluctuations, tachypnea, apnea, increased respiratory rate variability, cardio-respiratory uncoupling, decreased heart rate variability, transient bradycardia, decreased blood pressure, decreased blood pressure variability and perfusion, and tissue oxygenation. The gold standard remains a positive blood culture in which pathological bacteria are cultured. By the time clinical symptoms of sepsis become evident and blood cultures are obtained, the patient's clinical condition may already be severely deteriorated. Despite immediate initiation of antibiotic treatment, mortality and morbidity rates are significant. Due to the time delay between blood collection for culture and the resulting bacterial growth, blood cultures actually serve to confirm the presence of bacteria and identify the bacterial species for treatment adjustment. Therefore, when sepsis is suspected based on clinical signs, treatment is initiated empirically. Detecting sepsis in its early stages, or even confirming sepsis when it becomes evident, remains problematic.

[0005] There is a need for a monitor capable of reflecting microcirculatory perfusion status in order to detect potential changes in microcirculatory status.

[0006] Current systems for measuring gases use different measurement principles. In medical technology, electrochemical sensors are mainly used to measure gases diffused transcutaneously, i.e., diffused through the skin of a human or animal. Current sensors for measuring transcutaneous O2 or CO2 are very sensitive and exhibit good response times.

[0007] Typically, the sensor contains a pH electrode, a reference electrode, an electrolyte solution, a membrane and a heating element.

[0008] The sensor may be secured to the skin, and a heating element may heat the skin to a temperature sufficient to improve perfusion, particularly above 40°C, more particularly between 42°C and 45°C. Blood gases diffuse through the stratum corneum as the skin warms, passing through the sensor's semipermeable membrane and into the electrolyte solution in the sensor chamber.

[0009] A glass electrode measures the change in pH value. The output of the electrode is converted into a signal indicative of the partial pressure of the blood gas. The signal can be read out or displayed.

[0010] Transcutaneous monitoring of oxygen tension is widely used in neonates because, due to the thin epidermal layer, the transcutaneous oxygen tension (PtcO2) reaches levels comparable to the arterial oxygen tension (PaO2). Similarly, for adult patients, Tremper and Showmaker (Critical Care Medicine, Vol. 8, No. 10, pp. 706-709, 1981) reported that PtcO2 is a reliable trend monitor of PaO2 in certain circumstances. When applied to the skin, the sensor must heat the skin to 42-45°C to obtain a measurable reading.

[0011] Heating the skin increases blood flow to such an extent that oxygen levels rise and carbon dioxide levels decrease in the heated skin, a process called arterialization. Once the skin is sufficiently heated and skin and microcirculatory conditions are enabled, oxygen and carbon dioxide levels can be measured at the skin surface, corresponding to arterial oxygen and carbon dioxide levels. This principle is applied to transcutaneous blood gas monitoring in patients.

[0012] Furthermore, heat causes skin hyperemia due to dilation of arterioles, which is referred to as "capillary arterialization" in terms of oxygen levels. However, PtcO2 is a surface measure of tissue-oxygen tension in heated skin and is therefore a reflection of peripheral oxygen supply. Despite skin heating, sepsis has been shown to significantly impair cutaneous microcirculation and thereby oxygen delivery to the skin surface. Summary of the Invention [Problem to be solved by the invention]

[0013] An object of the present invention is to avoid the drawbacks of the state of the art and to provide an apparatus and method for obtaining an indication of the microcirculatory state, in particular for indicating and / or predicting sepsis, which allows a non-invasive and reliable measurement that provides results within an acceptable reaction time. [Means for solving the problem]

[0014] According to the present invention, this object is achieved by an apparatus for obtaining an indication of the microcirculatory status of a patient, the apparatus comprising at least one sensor for measuring data indicative of arterial blood oxygen level, at least one sensor for measuring data indicative of tissue oxygen level, and a control unit for determining a measure of microcirculation based on the tissue oxygen level and the arterial blood oxygen level.

[0015] In the present application, "microcirculatory status" refers in particular to the amount of blood perfusion in the skin, measured as the difference between the transcutaneously measured oxygen level and the arterial blood oxygen level.

[0016] The sensor measuring data indicative of the arterial oxygen level may be a sensor for an indication of the overall or systemic condition, particularly the microcirculatory condition, of the patient based on the measured data.

[0017] The sensors may detect one measured quantity or multiple measured quantities at once or sequentially. The measured data may correspond to one or more parameters and / or a time series of the measured quantities.

[0018] The sensor measuring data indicative of arterial blood oxygen level and the sensor measuring data indicative of tissue oxygen level may be formed by the same sensor element but operate under different conditions. The sensor may, for example, be used to measure data indicative of arterial blood oxygen level at a first temperature and to measure data indicative of tissue oxygen level at a second temperature. The sensor may be a heatable sensor, particularly for transcutaneous gas measurement, that may be adapted for use in temperature cycling, so that data indicative of arterial blood oxygen level is acquired during a first time period and data indicative of tissue oxygen level is acquired during a second time period. These time periods may alternate.

[0019] Measures of microcirculation provide an indication of the degree of vascularization, blood flow and tissue perfusion and thus the state of the microcirculation.

[0020] In particular, the control unit is adapted to determine changes in tissue perfusion. In particular, the control unit has at least one input for receiving a measured or estimated first oxygen level value, e.g., a tissue oxygen level value, and at least one input for receiving a measured or estimated second oxygen level value, e.g., an arterial oxygen level value. Further, the control unit may include at least one output interface for outputting an indication of the patient's microcirculation based on the received input, e.g., outputting a change in tissue perfusion status based on a relative change in the received input.

[0021] The control unit is particularly adapted to determine a measure of microcirculation in septic patients, which is expected to be impaired by reduced vascularization and blood flow in the epidermis and other peripheral tissues.

[0022] The device exploits the fact that changes in the relationship between arterial blood oxygen level and tissue oxygen level result in changes in microcirculation. As long as tissue perfusion is unaffected, tissue oxygen level can be considered a measure of arterial blood oxygen level. However, when tissue perfusion decreases, arterial blood oxygen level and tissue oxygen level are no longer corresponding parameters. Furthermore, the lack of correspondence can be used as a measure of the degree of microcirculatory deterioration.

[0023] Changes in tissue oxygen levels can be caused by changes in arterial blood oxygen levels without any effect on tissue perfusion. Therefore, if arterial blood oxygen levels and tissue oxygen levels are measured independently, reliable detection of a patient's microcirculatory status can be achieved.

[0024] However, changes in the microcirculatory state are not necessarily indicative of significant disturbances in blood flow, angiogenesis or tissue perfusion. Changes in the microcirculatory state may in any case indicate possible subsequent problems, depending on the time course of the changes. Therefore, preferably, the control unit is adapted for predicting measures of microcirculation, preferably for predicting sepsis.

[0025] The sensor that measures data indicative of arterial blood oxygen level and / or the sensor that measures data indicative of tissue oxygen level may include a chemical sensor, an optochemical sensor, an optical sensor, an electrical sensor, an electrochemical sensor, an optoelectric sensor, a pressure sensor, and / or a temperature sensor.

[0026] In one embodiment of the device, the sensor that measures data indicative of tissue oxygen level is a first sensor element, and the sensor that measures data indicative of arterial blood oxygen level is a second sensor element different from the first sensor element.

[0027] Two or more separate sensors allow different data to be measured at the same time. Simultaneous or at least timely measurement of data allows for reasonable comparison of the data.

[0028] There are several ways to determine arterial oxygen levels. The second sensor element may be adapted to analyze a blood sample. The blood sample may be taken from a patient. The sample may be taken from an artery or a capillary. Blood may also be Arterial catheter Alternatively, continuous intra-arterial or intravascular measurements may be taken.

[0029] Blood samples may also be taken to calibrate the transcutaneous measurements, as described below. The sensing unit may include a microneedle together with a second sensor element. The microneedle may be applied to tissue, preferably at a distance of 0.2 to 1 mm from the skin surface. The microneedle may reach a capillary loop so that oxygen reaches the needle tip.

[0030] The microneedles can be heated or non-heated. Preferably, the body area surrounding the measurement site is heated.

[0031] The microneedles may include optical fibers and / or may use fluoroscopy. The microneedle may include an optical fiber, a chemical sensor, or an electrochemical probe such as a Clarke probe to measure the oxygen concentration in the liquid.

[0032] The second sensor element may be adapted for transcutaneous measurement, preferably using a heating element capable of heating the skin to a temperature above 40°C, preferably above 42°C, more preferably above 44°C, so that the transcutaneous measurement provides representative data for arterial blood oxygen levels in situations where microcirculation is not compromised. This works best for newborns, where absolute transcutaneous oxygen levels roughly correspond to arterial blood levels. For older children and adults, who have thicker skin, diffusion is less.

[0033] However, for analysis, absolute values ​​are not necessary and a qualitative measurement would suffice.

[0034] The second sensor element may be adapted to use NIRS (near infrared spectroscopy) for assessment of tissue oxygenation. Spectroscopy may be performed in tissue and therefore as an invasive procedure.

[0035] In a preferred embodiment, the second sensor element includes a sensor adapted to measure data indicative of arterial blood oxygen level by optical detection of oxygen saturation, preferably by pulse oximetry detection.

[0036] The second sensor element preferably comprises a photodetector, preferably using two wavelengths, in particular a sensor for pulse oximetry detection.

[0037] Pulse oximetry detection provides a measure of hemoglobin saturated with oxygen as a percentage of total hemoglobin. When measured peripherally in the body, oxygen saturation measured by pulse oximetry is called SpO2.

[0038] Sensors for pulse oximetry detection typically pass light of at least two wavelengths through a body part or tissue to a photodetector. wavelength measuring the changing absorbance at each of venous blood , excluding skin, bones, muscles and fat, pulsating arterial blood Only by absorbance Therefore, the sensor Arterial blood gases The analysis yields a reading of peripheral oxygen saturation (SpO2), which is roughly related to arterial oxygen saturation (SaO2).

[0039] However, SpO2 readings are not identical to the more desirable SaO2 readings. Both values ​​represent arterial oxygen saturation of hemoglobin, but they are measured differently. The relationship with arterial oxygen partial pressure (PaO2) is described by the oxygen-hemoglobin dissociation curve, which can shift right or left depending on the patient's condition. Using the relationship between SaO2 or SpO2 and PaO2 as described by the oxygen-hemoglobin dissociation curve, a PaO2 estimate can be calculated from SpO2. This estimate can be improved by inputting other factors that affect the oxygen-hemoglobin dissociation curve, such as CO2, temperature, 2-3DPG, (fetal) hemoglobin, and pH.

[0040] Therefore, after pulse oximetry detection, the arterial blood oxygen partial pressure is determined from the measured SpO2 value, preferably by using the oxygen-hemoglobin dissociation relationship.

[0041] Preferably, in addition to the first and second sensors, the device comprises at least one further sensor for measuring data indicative of further parameters for determining the patient's condition, such as blood temperature, pH value, carbon dioxide value and / or another blood parameter, in particular for correction and / or calibration of arterial blood oxygen level and / or tissue oxygen level.

[0042] The data may also be used to calibrate sensors for pulse oximetry detection or to compensate for deviations from the standard oxygen dissociation curve.

[0043] An additional sensor adapted to measure data indicative of carbon dioxide levels may utilize transcutaneous measurements, preferably using a heated sensor, which may help to more accurately estimate PaO2 using a correlation between carbon dioxide levels and oxygen dissociation curves.

[0044] A further sensor may be adapted to measure temperature, preferably skin temperature, which may be used to correct the oxygen dissociation curve.

[0045] Further sensors can be adapted to measure the pH value or 2,3-diphosphoglycerate, another regulator of the binding affinity of hemoglobin, which can be applied to the blood sample being analyzed.

[0046] The additional sensor may also be adapted to measure fetal hemoglobin if the device is to be used on a neonate.

[0047] The first sensor, the second sensor and the further sensor may be disposed within a common housing.

[0048] The second sensor element may include a heating element. Stabilizing the temperature of the skin generally allows for reproducible data.

[0049] There are also several alternative ways of determining tissue blood oxygen levels, and therefore several possible embodiments for the first sensor element.

[0050] The first sensor element may include a microneedle that may be applied to tissue. The needle may include fiber optics for spectroscopic measurements and / or chemical sensors that may be read out optically or electrically.

[0051] The first sensor element may be adapted to use NIRS (near-infrared spectroscopy) for assessing tissue oxygenation. Spectroscopy may be performed in tissue and thus as an invasive procedure. Alternatively, spectroscopy may be performed non-invasively, for example, on a sample of gas diffused transdermally near the skin.

[0052] Preferably, the first sensor element comprises a sensor adapted for transcutaneous measurement, in particular for heated transcutaneous measurement.

[0053] The first sensor element may include a sensor for transcutaneous oxygen measurement, and the second sensor element may also include a sensor for transcutaneous carbon dioxide measurement.

[0054] The first sensor element may include a pH electrode, a reference electrode, an electrolyte solution, and a membrane. Optionally, the second sensor element may include a heating element.

[0055] Preferably, the device comprises, in addition to the first and second sensors, at least one additional sensor adapted to measure data indicative of further parameters for determining the patient's condition, such as blood temperature, carbon dioxide level, pH value and / or another blood parameter, in particular for correcting the arterial blood oxygen level and / or tissue oxygen level.

[0056] The additional sensor may be adapted to measure data indicative of carbon dioxide levels. The additional sensor may be adapted to measure temperature, preferably the temperature of the skin.

[0057] The additional sensor may be adapted to measure pH or 2,3-diphosphoglycerate values, which may be performed using a blood sample that is analyzed.

[0058] The additional sensor may also be adapted to measure fetal hemoglobin if the device is to be used on a neonate.

[0059] The additional sensor may be adapted to measure heart rate and / or heart rate variability. The additional sensor may be adapted to measure pulse and / or pulse variability.

[0060] The additional sensors may be adapted to measure electrical activity, such as ECG values, and / or muscle movement and / or blood flow and / or respiratory gas flow.

[0061] The device may include a heating element. The sensor measuring data indicative of arterial blood oxygen level and / or the sensor measuring data indicative of tissue oxygen level, and / or, if applicable, further and / or additional sensors, may be adapted for continuous measurement and / or intermittent measurement and / or alternating measurement.

[0062] Continuous measurement allows for analysis of a parameter over time. For parameters known to change slowly or not involving rapid changes, continuous measurement may mean that data is collected at predetermined time intervals, such as every few seconds or minutes.

[0063] In an advantageous embodiment of the device, the sensor for measuring data indicative of the arterial blood oxygen level and the sensor for measuring data indicative of the tissue oxygen level, and preferably, if applicable, additional sensors, are arranged in a common housing. The device may comprise a sensor head that can be placed on the patient. The sensor head may house the sensor for measuring data indicative of the arterial blood oxygen level, the sensor for measuring data indicative of the tissue oxygen level, and, if applicable, further and / or additional sensors. By placing the sensor head, all sensors are positioned relative to the patient.

[0064] The sensors may be designed as composite sensors that use and / or share the same sensor elements, such as a temperature sensor.

[0065] Advantageously, the sensor for measuring data indicative of arterial blood oxygen level and / or the sensor for measuring data indicative of tissue oxygen level is adapted to be placed anywhere on the skin or other peripheral tissue, for example on an earlobe or fingertip, and the device may preferably comprise a sensor head designed to form a clasp for gripping the finger or earlobe, as described above.

[0066] In a preferred embodiment of the device, the control unit is adapted to measure a difference between the tissue oxygen level and the arterial blood oxygen level, a ratio between the tissue oxygen level and the arterial blood oxygen level, and / or an index based on the tissue oxygen level and the arterial blood oxygen level.

[0067] The index may be calculated based on tissue oxygen level, arterial oxygen level, and optionally further measured or predetermined parameters.

[0068] The control unit may also be adapted to monitor tissue oxygen levels, arterial oxygen levels, differences, ratios and / or indices over time and to determine changes over time.

[0069] In particular, the control unit is adapted to receive, collect, store and process in particular time-dependent data.

[0070] In particular, the control unit is adapted to determine changes in tissue perfusion on a predetermined and / or selectable timescale.

[0071] The control unit may be adapted to correct the oxygen dissociation curve based on measurements of further or additional sensors.

[0072] Furthermore, the control unit may be adapted for extrapolating time-dependent data and / or for predicting, for example, tissue perfusion status.

[0073] The control unit may be adapted to average and / or filter the measured and / or determined values ​​and / or to determine a rolling average over a predetermined time interval.

[0074] The control unit may be adapted to compare the tissue oxygen level, arterial oxygen level, difference, ratio, index and / or estimated value with respective nominal values.

[0075] In particular, the control unit is adapted to determine a difference between the first oxygen level and the second oxygen level, in particular a difference between the tissue oxygen level and the arterial blood oxygen level, a ratio between the first oxygen level and the second oxygen level, in particular a ratio between the tissue oxygen level and the arterial blood oxygen level, and / or an index based on the first oxygen level and the second oxygen level, e.g. based on the tissue oxygen level and the arterial blood oxygen level.

[0076] The control unit may be adapted to receive data from an input device such as a control panel, console or data carrier reader.

[0077] In particular, the control unit is adapted to receive, store and process algorithms, correction parameters, nominal values ​​and trigger values.

[0078] The correction parameters may be used to process the measured and / or determined data in accordance with a rule. For example, medications, vascular tone factors, and chemical drift of the sensor may be taken into account when analyzing the measured data.

[0079] The control unit may be adapted to indicate a sensor disturbance, a need for maintenance, or a need for a new sensor calibration.

[0080] If the difference between the measured and / or determined value and the respective nominal value exceeds a predetermined trigger value, the control unit may generate respective output information on at least one output interface to present an indication of the patient's microcirculatory status based on the received input. The output interface may, for example, indicate the presence of a health problem, provide a warning if a health problem is about to occur, or indicate the likelihood of a health problem occurring.

[0081] The device may provide a definite result based on current measured and / or determined values. The device may provide a definite result based on the time evolution of measured and / or determined values.

[0082] The control unit may be adapted to determine the difference, ratio and / or index based on data measured during a time interval. Preferably, the control unit may be adapted for continuous measurements based on a rolling time interval.

[0083] Thus, the device allows for retrospective analysis of the data. The changes caused by sepsis are caused by a slow process. Therefore, the desired results take some time, typically minutes to hours. However, the device can provide an indication of the microcirculatory status, and therefore of sepsis, faster than conventional blood sample analysis, which can take one or more days.

[0084] In a preferred embodiment of the apparatus, the control unit is preferably connected or connectable to an output device such as a monitor or display for displaying measures of microcirculation and / or for displaying signals generated by the control unit.

[0085] The output device may be part of the apparatus. The output device may be adapted to emit an acoustic signal and / or an optical signal.

[0086] The output device may be adapted to display the measured and / or determined values ​​and / or time-dependent representations of the measured and / or determined values.

[0087] The output device may be adapted to indicate a measure of microcirculation. For example, the output device may include a display designed to include a three-level scale, with the first level indicating "no problem," the second level indicating "potential problem," and the third level indicating "caution: problem."

[0088] The output device may be adapted to display a measure of the quality of the measured and / or determined values, such as an estimated measurement error or standard deviation of the mean.

[0089] The output device may be adapted to display a measure of the quantity of the microcirculation measure, such as a reliability index, which may be based on the amount of data used. The more data used, the more reliable the results. Such a reliability index may be derived from the deviation of the measurement data over a period of time, i.e., if the deviation is relatively low over a sustained period of time, the reliability index will be high.

[0090] In an advantageous embodiment of the device, the control unit is adapted to indicate the arterial oxygen partial pressure PaO2, preferably estimated from SpO2, and / or the control unit is adapted to indicate the transcutaneous oxygen partial pressure PtcO2.

[0091] The values ​​measured by the described sensors can be displayed by an output device, thus providing the user with additional information and the ability to control the amount of microcirculation measurement.

[0092] The device can be a stand-alone device placed at the patient's bedside, or the device can be a hook-up element for an existing system.

[0093] The device may be part of an existing system, for example, it may share a sensor or output device with the existing system.

[0094] The object of the present invention is also achieved by a method for obtaining an index of tissue perfusion, comprising the following steps: The index is preferably obtained using the device described above.

[0095] The patient's arterial blood oxygen level is provided, and the patient's tissue oxygen level, particularly the skin oxygen level, is provided.

[0096] Based on tissue oxygen levels and arterial oxygen levels, a measure of microcirculation is determined.

[0097] Preferably, the measures of microcirculation are displayed in real time. The arterial blood oxygen level can be provided by data collection or, preferably, can be measured by pulse oximetry measurement of SpO2, and the arterial blood oxygen partial pressure is calculated from the measured SpO2 by use of the oxygen-hemoglobin dissociation relationship. Other measurement principles may also be used, as explained above.

[0098] Tissue oxygen levels can be provided as data collection or can be measured, preferably by transcutaneous measurement. Other measurement principles may also be used as explained above.

[0099] The measurements can be made simultaneously or alternately. Measures of microcirculation can be determined based on tissue oxygen levels and arterial oxygen levels.

[0100] Preferably, measures of microcirculation are displayed in real time, preferably based on continuous and / or intermittent measurements.

[0101] A measure of microcirculation is preferably determined for the prediction of sepsis, for example, by determining the difference between tissue oxygen level and arterial blood oxygen level, the ratio of tissue oxygen level to arterial blood oxygen level, and / or an index based on tissue oxygen level and arterial blood oxygen level.

[0102] The objects of the present invention are also achieved by a computer program, when loaded into and / or executed on a computer, adapted to perform the method for obtaining an index of tissue perfusion as described above.

[0103] The computer program may be loaded into and / or executed on a control unit of an apparatus such as those described above.

[0104] The computer program may be loaded into and / or executed on a central computer device at a clinic or medical practice, or may be loaded into and / or executed on a measuring device that measures a patient's arterial oxygen level and / or tissue oxygen level.

[0105] The present invention will now be further described with reference to preferred embodiments and the accompanying drawings. [Brief explanation of the drawings]

[0106] [Figure 1] 1 is a schematic diagram of a first example of an apparatus. [Figure 2] FIG. 10 is a schematic diagram of a sensor head of a second example of the device. [Figure 3] FIG. 3 is a schematic cross-sectional view of the sensor head of FIG. 2. [Figure 4] FIG. 10 is a schematic diagram of a third example of the device. [Figure 5] FIG. 10 is a schematic cross-sectional view of a sensor head of a third example of the device. [Figure 6a] FIG. 1 is a first schematic diagram of O2 levels. [Figure 6b]FIG. 2 is a second schematic diagram of O2 levels. DETAILED DESCRIPTION OF THE INVENTION

[0107] 1 shows a schematic diagram of a first example of an apparatus 1 for obtaining an indication of a patient's microcirculatory status. The apparatus 1 comprises a first sensor 3 for measuring data indicative of tissue oxygen level and a second sensor 2 for measuring data indicative of arterial blood oxygen level.

[0108] The second sensor 2 that measures data indicative of the arterial blood oxygen level is a second sensor element 12, and the first sensor 3 that measures data indicative of the tissue oxygen level is a first sensor element 13 that is different from the first sensor element 12 in this example.

[0109] The device 1 comprises a further additional sensor 5 adapted to measure data indicative of carbon dioxide level, pH level and / or temperature, in particular to correct the pulse oximetry detection of arterial blood oxygen level.

[0110] The first sensor element 13 and the second sensor element 12 are arranged in a common housing 6 forming a sensor head 8 .

[0111] The device 1 comprises a control unit 4 which determines measures of microcirculation, in particular changes in tissue perfusion, based on tissue oxygen levels and arterial blood oxygen levels.

[0112] The device 1 comprises an additional sensor 5 for measuring data indicative of further parameters such as blood temperature, carbon dioxide level, pH value and / or another blood parameter, in particular for correcting the arterial blood oxygen level and / or tissue oxygen level.

[0113] The sensor head 8 may be connected to an instrument base 9 by a cable 10. The control unit 4 may be located within the instrument base 9.

[0114] The control unit 4 is connected to an output device 7, such as a monitor or display that displays measures of microcirculation. The output device 7 may also be located within the device base 9.

[0115] The sensor head 8 comprises a contact surface 11 which is orientable towards a measuring side, which in this case is an area on the patient's skin.

[0116] The device 1 shown in Figures 2 and 3 allows combined measurement of arterial oxygen saturation (SpO2) and transcutaneous O2 partial pressure (PtcO2).

[0117] 2 comprises a second sensor 17 adapted to measure arterial blood oxygen saturation by pulse oximetry detection, and thus a pulse oximetry measurement system, which includes, among other things, a bicolor light-emitting diode 22 (LED) and a photodetector 23. The bicolor light-emitting diode 22 comprises two light-emitting diodes 22a, 22b arranged close to each other and in a common housing, one of which is light-emitting diode 22a having a wavelength of, for example, about 660 μm (red), and the other is light-emitting diode 22b having a wavelength of, for example, about 890 μm (infrared).

[0118] The device 1 has a surface 15, on which, in the illustrated embodiment, a membrane 50 is disposed with a thin layer of electrolyte 51 between the membrane and the surface. The membrane 50 is placed on the skin at a location of the human body with good blood flow, for example, the skin of a finger, forehead, or earlobe. Light transmitted by the two light-emitting diodes 22a, 22b radiates through the electrolyte 51 above the light-emitting diodes 22a, 22b and through the membrane 50, and is guided by the good blood flow to a body part (not shown), where it is diffused and partially absorbed. The light reflected by the body part is measured using a photodetector 23. The signal measured by the photodetector 3 is provided to a control unit 4.

[0119] The illustrated device 1 further includes a first sensor 19 adapted for transcutaneous measurement, i.e., an electrochemical measuring device 19, for measuring transcutaneous oxygen partial pressure (PtcO2 measurement). This measuring device 19 preferably includes a micro-pH electrode 24 and an Ag / AgCl reference electrode 25. In this example, the transcutaneous oxygen partial pressure is measured potentiometrically, in that the pH of a thin layer of electrolyte solution 51 is measured, which is in communication with the skin via a hydrophobic membrane 50 with good gas permeability. Changes in the pO2 value at the skin surface cause a change in the pH of the electrolyte solution. The pH is measured by measuring the potential between the miniature pH electrode 24 and the reference electrode 25. The micro-pH electrode 24 is conductively connected to the control unit 4 via an electrical internal deflector 16.

[0120] The device 1 comprises a heating element 26 and a temperature sensor 27 . FIG. 4 shows a schematic diagram of a third example of a device 1 for obtaining an indication of the microcirculatory status of a patient.

[0121] A second sensor 2, a so-called blood oxygen sensor, measuring data indicative of arterial blood oxygen level, a first sensor 3, a so-called tissue oxygen sensor, measuring data indicative of tissue oxygen level, a further sensor 5, a housing for a processor or control unit 4 and an output device 7 are arranged in a common housing 6.

[0122] Preferably, the housing allows for all combinations, integrations and separations of the components.

[0123] The second blood oxygen sensor 2 may be formed by a pulse oximeter and may include two parts 2a, 2b (see FIG. 5).

[0124] The first tissue oxygen sensor 3 may be a transcutaneous measurement device. The additional sensors 5 may detect temperature, transcutaneous CO2, and / or may include inputs for external values.

[0125] The control unit 4 may perform a calculation of PaO2 from the measured SpO2 values. The output device 7 may include a display that shows digital or analog output.

[0126] FIG. 5 shows a schematic cross-sectional view of the sensor head 8 of a third example of the device 1. The sensor head 8 is placed in contact with the patient's skin 103 .

[0127] A first sensor 3, a so-called tissue oxygen sensor, measuring data indicative of tissue oxygen level, an additional sensor 5, and a first part 2a and a second part 2b of a second blood oxygen sensor 2 are arranged in a common housing 6. The housing of a processor or control unit 4 and an output device 7 (see FIG. 4), not shown in this figure, may be arranged in the housing 6 as well.

[0128] The sensor head 8 is connected to an output connection 20 which may establish a connection with an external processor or control device and may act as a power source.

[0129] Thus, the device 1 for obtaining an indication of the microcirculatory status of a patient comprises at least one first sensor 3 for measuring data indicative of tissue oxygen levels, in particular skin oxygen levels, at least one second sensor 2 for measuring data indicative of arterial blood oxygen levels, and a control unit 4 (see Figures 1 and 4) for determining changes in tissue perfusion.

[0130] The control unit 4 in particular has at least one input, not explicitly shown in the figures, for receiving measured or estimated arterial oxygen level values, at least one input for receiving measured or estimated tissue oxygen level values, and at least one output interface for outputting an indicator of the patient's microcirculatory status based on the received inputs.

[0131] The skin 103 is permeated with arteries 101 and capillaries 102 . The blood supply in the arterioles and / or capillaries 102 may be impaired in septic conditions, resulting in significantly less oxygen being diffused to the skin surface, which can be detected by transcutaneous measurements.

[0132] The blood supply in the cutaneous arteries 101 remains intact during sepsis. By using pulse oximetry, arterial oxygen saturation (SpO2) can be measured, and the corresponding partial pressure PaO2 can then be calculated. The partial pressure PaO2 can be compared to the transcutaneously measured partial pressure of oxygen PtcoO2.

[0133] 6a and 6b show a representation of O2 levels in the skin S and blood B. Figure 6a shows that under normal conditions, the oxygen level in the skin corresponds to the oxygen level in the blood.

[0134] In contrast, in the septic state, the oxygen level in the skin (S) is much lower than that in the blood (B), as shown in Figure 6b.

Claims

1. A device (1) for obtaining an indication of the microcirculatory status of a patient, comprising: at least one sensor (3) for measuring data indicative of tissue oxygen level, in particular skin oxygen level; at least one sensor (2, 2a, 2b) for measuring data indicative of arterial blood oxygen level; a control unit (4) for determining changes in tissue perfusion, a control unit (4) having, in particular, 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 oxygen level value, and at least one output interface for outputting an indicator of a microcirculatory condition of a patient based on the received input; Equipped with the control unit (4) is adapted to determine the indicator of the patient's microcirculatory status based on an index based on the tissue oxygen level and the arterial blood oxygen level; the control unit is adapted to monitor the tissue oxygen level, the arterial blood oxygen level, and the index over time and to determine changes over time; the control unit is adapted to compare the tissue oxygen level, the arterial blood oxygen level, the difference between the tissue oxygen level and the arterial blood oxygen level, the ratio between the tissue oxygen level and the arterial blood oxygen level, the index and / or the estimated value with respective nominal values; the sensor (3) measuring data indicative of tissue oxygen level is a first sensor element (13), and the sensor (2, 2a, 2b) measuring data indicative of arterial blood oxygen level is a second sensor element (12) different from the first sensor element (13), and the first sensor element (13) includes a transcutaneous measurement sensor (19); the second sensor element (12) includes a pulse oximetry sensor (17) adapted to indicate the arterial blood oxygen level by optical detection of oxygen saturation; the control unit is adapted to subsequently determine the arterial blood oxygen partial pressure from the measured SpO2 value following pulse oximetry detection, to calculate the corresponding partial pressure PaO2, and to compare the partial pressure PaO2 with the transcutaneously measured oxygen partial pressure PtcoO2; Device.

2. 2. The device according to claim 1, wherein the device (1) comprises at least one further sensor (5, 14) adapted to measure data indicative of a carbon dioxide level, a pH level and / or a temperature, in particular for correcting the pulse oximetry detection of the arterial blood oxygen level.

3. 3. The device according to claim 1 or 2, wherein the first sensor element (13) is adapted for heated transcutaneous measurements.

4. 4. The device according to claim 1, wherein the sensors (2, 2a, 2b) for measuring data indicative of arterial blood oxygen levels and / or the sensors (3) for measuring data indicative of tissue oxygen levels are adapted for continuous and / or intermittent and / or alternating measurements.

5. 5. The device according to claim 1, wherein the sensors (2, 2a, 2b) for measuring data indicative of arterial blood oxygen level and the sensor (3) for measuring data indicative of tissue oxygen level are arranged in a common housing (6).

6. 6. The device according to claim 1, wherein the sensor (2, 2a, 2b) for measuring data indicative of the arterial blood oxygen level and / or the sensor (3) for measuring data indicative of the tissue oxygen level is adapted to be placed on a part of the skin, in particular on an earlobe, a fingertip, a palm, a foot and / or on the chest.

7. The control unit (4) a difference between the first oxygen level and the second oxygen level, the difference being the difference between the tissue oxygen level and the arterial oxygen level; and a ratio between the first oxygen level and the second oxygen level, the ratio being between the tissue oxygen level and the arterial oxygen level; 7. The device according to claim 1, adapted to determine an indicator of the microcirculatory status of the patient based on at least one of:

8. The device according to any one of claims 1 to 7, wherein the control unit (4) is adapted to collect, store and process time-dependent data.

9. Apparatus according to any one of the preceding claims, wherein the control unit (4) is connected or connectable to an output device (7) for displaying a measure of microcirculation.

10. The control unit (4) ２ Based on this, the arterial blood oxygen partial pressure PaO ２ and / or the control unit is adapted to indicate the transcutaneous oxygen partial pressure PtcO ２ 10. The device according to any one of claims 1 to 9, adapted to indicate:

11. A method for obtaining an index of tissue perfusion using the device according to any one of claims 1 to 10, comprising: providing an arterial blood oxygen level of the patient; providing a tissue oxygen level, in particular a skin oxygen level, of said patient; determining a measure of microcirculation in a septic patient based on the tissue oxygen level and the arterial blood oxygen level by determining an index of the patient's microcirculatory status based on the tissue oxygen level and the arterial blood oxygen level; displaying a measure of microcirculation in real time; monitoring the tissue oxygen level, the arterial blood oxygen level, and the index over time and determining changes over time, and comparing the tissue oxygen level, the arterial blood oxygen level, the difference between the tissue oxygen level and the arterial blood oxygen level, the ratio between the tissue oxygen level and the arterial blood oxygen level, the index, and / or the estimated values ​​with their respective nominal values; measuring arterial blood oxygen level by optical detection for pulse oximetry measurement of oxygen saturation; measuring tissue oxygen levels by transcutaneous measurement; determining arterial blood oxygen partial pressure from the measured SpO2 value following pulse oximetry detection; Calculating the corresponding partial pressure PaO 2 ; comparing the partial pressure PaO 2 with the transcutaneously measured oxygen partial pressure PtcoO 2 ; A method comprising:

12. 12. The method of claim 11, wherein the arterial blood oxygen level is provided by pulse oximetry detection using two or more wavelengths.

13. 13. The method of claim 11 or 12, wherein further data indicative of carbon dioxide level, pH level and / or temperature is provided by measuring data indicative of carbon dioxide level, pH level and / or temperature, in particular for correcting the pulse oximetry detection of the arterial blood oxygen level.

14. A computer program to be loaded into and / or run on a computer of a measuring device that measures a patient's arterial blood oxygen level and / or tissue oxygen level, the computer program being adapted to perform a method according to any one of claims 11 to 13.

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