DE102015012519A1 - Determination in blood of dissolved gases in the extracorporeal circulation - Google Patents

Abstract

The invention relates to a blood treatment device with an extracorporeal blood circulation, which measures the concentration of a gas by means of a gas sensor in the gas supernatant of the drip chamber of the extracorporeal blood circulation. In this case, the blood treatment apparatus has an evaluation unit which calculates the corresponding partial pressure of the gas in the blood from the values measured in the gas supernatant of the drip chamber.

Description

Technical area

The invention relates to a blood purification device with an extracorporeal blood circulation, a gas sensor and an evaluation unit, whereby the partial pressure of a gas in the extracorporeal blood circulation can be determined and monitored, and a method for determining the partial pressure of a gas in blood.

background

When performing blood purification treatments associated with extracorporeal blood circulation, monitoring of patient parameters, especially vital signs, is of great importance.

In dialysis clinics, this is typically done by regular observation of the patient by the nursing staff. In long-term dialysis overnight or in home dialysis nurse monitoring is limited or absent.

Further possibilities result from automated monitoring, which is carried out independently by the dialysis machine. Examples are blood pressure measurements, electrocardiograms and monitoring with pulse oximeters. For these measurements, however, the use of additional sensors is necessary, which is often difficult in home dialysis and often also disturbing the sleep of the patient.

If the determination of the partial pressure of a gas in blood is used for monitoring a vital parameter, this is usually done by measurements in the respiratory air of the patient, where these substances pass through the gas exchange into the alveoli ( "Potential Application of Exhaled Breath Monitoring in Renal Replacement Therapy," Kelly et al., Poster Presentation ASN 2113 ).

Examples of blood gases that can provide relevant information for monitoring patients are carbon dioxide, acetone, and ammonium.

The determination of acetone can, for. B. in the treatment of diabetic patients provide helpful data, as a ketoacidosis can be diagnosed. Recording the values across multiple treatments may be helpful in the dosage of insulin in diabetics in dialysis.

The determination of the ammonium concentration in the breath is related to the urea concentration in blood ( "Correlation of breath ammonia with blood urea nitrogen and creatinine during hemodialysis, Marashimhan et al. PNAS Vol. 98, p. 4617ff ). Therefore, by means of an ammonium sensor virtually all analyzes are possible, which are otherwise based on the determination of the urea concentration in blood.

Of particular interest and also the most widespread is the monitoring of the CO2 partial pressure of the blood, which is directly related to respiration or oxygen saturation and thus represents an important vital parameter. An increase in the CO2 partial pressure can be due to inadequate or even missing respiration, such as. B. in sleep apnea, indicate. Above all, people who are older and / or overweight (possibly also with other neurological disorders) are affected by sleep apnea. The prevalence is estimated in the US from 18 million patients.

Dialysis patients are disproportionately affected due to their demographics and their typical comorbidities. With an ESRD prevalence of about 600 ppm and an assumed increased sleep apnea prevalence by a factor of 2 compared to the normal population,> 2000 dialysis patients in the US alone would be affected by sleep apnea. Sleep apnea leads to a reduced nocturnal recovery and can lead to cardiovascular diseases such as hypertension, right heart failure and sudden cardiac death.

In the conventional apnea monitoring z. B. the measurement of the CO ₂ content of the breath used. For this purpose, the direct determination of the CO ₂ content of the respiratory air can be carried out by analyzing the air flowing through a breathing mask or the air flowing into a tube inserted into the nose (end tidal CO ₂ monitoring = EtCO ₂ monitoring). Alternatively, the determination in blood by transcutaneous CO ₂ measurements or the blood gas analysis based on blood samples applicable. All these procedures require additional equipment, sensors fixed to the patient and specially trained personnel. They are with burdens on the patient, z. As dialysis patients connected, go from limited comfort by fixing additional sensors and possible skin irritation by heating the sensor in transcutaneous CO ₂ monitoring to blood withdrawals for blood gas analysis. The noninvasive methods of CO ₂ monitoring are also prone to failure. While in EtCO ₂ monitoring in particular mouth breathing instead of breathing through the nose can falsify the measurement result, in the case of transcutaneous CO ₂ monitoring a lack of perfusion of the skin area under the sensor causes erroneous results.

Another application of CO ₂ concentration determination especially in dialysis patients is to control the pH status of the blood to detect acidosis.

So will in the WO 2013/156435 describes a device for extracorporeal blood treatment, which directly determines the CO ₂ partial pressure by measuring the bicarbonate concentration and the pH in blood. Here, the data are used to adjust the pH of the blood by controlling the bicarbonate concentration in the dialysate depending on the measured data obtained. Here a direct contact of the sensor with the patient's blood is required, which brings with it the risk of cross-contamination.

The present invention is therefore based on the object to ensure a safe, automatic and continuous monitoring of a patient parameter, in particular the CO ₂ partial pressure of the blood, without additional use materials are required or additional burdens for the patient arise.

Summary of the invention

This object is achieved by a blood treatment device according to claim 1 and a method according to claim 15. Particular embodiments of the invention are the subject of the dependent claims.

In one embodiment, a blood treatment device having extracorporeal blood circulation comprises the standard components of a blood tubing system. This blood tube system comprises a first line, which is connectable to the patient for blood sampling with a first end and is connected to the compensation chamber at a second end. In this first line, a first blood pump is arranged, which promotes the blood taken from the patient in the extracorporeal circuit in the compensation chamber. In this compensation chamber then creates a blood level, which forms a contact of the blood to a located above the blood level gas space. From the compensation chamber, the blood is passed through a second line to the blood purification unit. Furthermore, the blood treatment device according to the invention has at least one gas sensor connectable to the compensation chamber for measuring the concentration of a gas in the gas space of the compensation chamber. It can be assumed that similar equilibrium concentrations occur in the gas space above the blood level in a compensation chamber of an extracorporeal circuit as in the alveoli of the lungs. Furthermore, the blood treatment apparatus also includes an evaluation unit for reading and evaluating the measurement data of the gas sensor.

Advantageously, a positioning of the gas sensor, which allows a contactless, largely maintenance-free and against cross contamination safe measurement. It is also advantageous that the consumables used by default in the blood treatment can be used for the extracorporeal tube system.

Depending on the parameter or parameters to be monitored, a sensor for carbon dioxide or ammonium or acetone can be used as the gas sensor. It is also conceivable to combine different gas sensors.

Gas sensors z. As for carbon dioxide for the relevant concentration range are commercially available and based z. B. on a determination of the specific adsorption of radiation in the infrared range. These sensors can be used up to 100% relative humidity under non-condensable conditions.

To avoid condensation on the gas sensors, these can be designed to be heatable.

Since, in the evaluation of the measurement data, the consideration of the blood temperature leads to a more accurate result, in the extracorporeal circuit z. B. in the supply line, the derivative or in the Compensating a temperature sensor may be provided which delivers the measurement results to the evaluation unit, which takes into account in the evaluation of the measured data of the gas sensor.

Another parameter that can lead to an improvement in the accuracy of the measurement result in the evaluation of the measured data is the pressure currently present at the gas sensor. An embodiment of the blood treatment device according to the invention can have a pressure sensor which can measure the pressure in the gas space in which the gas sensor is arranged, and which supplies the measurement results to the evaluation unit, which takes this into account in the evaluation of the measurement data of the gas sensor.

While the compensation chamber is advantageously part of the blood tube system, the gas sensor and the evaluation unit can be integrated in the blood treatment machine. In an alternative embodiment, the gas sensor and the evaluation unit may be designed as a separate module that can be connected to the blood treatment device.

The connection of the compensation chamber with the gas sensor can take place via a connecting line, in particular a connecting tube. A hydrophobic filter may be provided between the connection tube and the gas sensor to prevent contamination of the treatment machine by blood.

Depending on the length of the connecting line, the transport by pure diffusion may be too slow, so that the directly in the compensation chamber above the blood level adjusting gas concentration must be actively transported to the gas sensor.

For this purpose, the blood treatment device according to the invention may comprise means for generating a gas flow. By means of a flow restriction in the second line of the extracorporeal blood circulation, these means can bring about a stroke of the blood level in the compensation chamber and thus a displacement of the gas volume from the compensation chamber or, alternatively, be provided as a direct gas delivery means.

To shift the blood level in the compensation chamber, a valve may be provided in the extracorporeal circuit in the second conduit. This valve can be controlled by the control and evaluation so that it sets a lower blood flow at certain times in the second line of the extracorporeal circuit than in the first line, so that the blood level in the compensation chamber increases, d. H. an increase in the blood level is produced. As the blood level increases, a volume of gas is displaced from the balance chamber to the gas sensor. To ensure that the concentration set in the compensation chamber also reaches the gas sensor, the displaced volume should preferably be at least twice as large as the volume located in the connection between the compensation chamber and the gas sensor. In the tube systems commonly used in blood purification procedures, with an increase in blood level in the balance chamber with a stroke of about 1-2 cm, the gas volume from the balance chamber can be transported to the gas sensor.

Alternatively, a shift of the water level by a second blood pump in the second line can be carried out, which is controlled by the control unit such that it runs with a deviating from the first, before the compensation chamber in the first line of the extracorporeal blood pump. If the delivery rate of the second blood pump is lower than the delivery rate of the first blood pump, there is an increase in the blood level in the compensation chamber. Conversely, when the second blood pump is running at a higher delivery rate than the first blood pump, there is a decrease in blood level in the compensation chamber.

In order to avoid an increase in the pressure at the gas sensor or the compensation chamber when the level is raised, the blood treatment device according to the invention can have compensation means arranged behind the gas sensor, more precisely pressure equalization means. These compensating means can, for. B. valves that open to the environment or against a compliance vessel. Through the opening, a pressure equalization is achieved in the gas sensor.

The blood treatment device according to the invention may further comprise a compressor, which can cause a lowering and thus return of the blood level in the compensation chamber by introducing ambient air.

For a new measurement of the gas concentration in the compensation chamber, the blood level can then be raised again.

With this arrangement, intermittent measurements of the gas concentration are preferably possible. The time intervals can be chosen sufficiently small, so that a close screening of the concentration curve is possible.

Alternatively, the blood treatment device according to the invention, a gas conveying means, for. As a miniaturized bellows, which actively generates a continuous gas flow. For this purpose, the compensation chamber is designed such that it is connected in addition to the first connecting hose by a further connecting hose as a return hose to the gas sensor. The control unit of the blood treatment apparatus is designed to control the gas delivery means so that a circulating gas flow is generated and a continuous measurement of the gas concentration can take place.

In the evaluation unit, which calculates the partial pressure of the gas in the blood from the measured data of the gas sensor, a setpoint range for the measured gas concentration or the partial pressure of the gas in blood can be stored. If values outside this setpoint range occur during the measurement of the gas concentration, a signal can be output by the evaluation unit.

This signal can z. B. forwarded to an alarm device that outputs an alarm signal, causing further action to be triggered.

Furthermore, the measurement data can be used in the control of the Dialysatzusammensetzung, z. B. the setting of the bicarbonate concentration in the dialysis solution in the case of a dialysis treatment.

The blood treatment device according to the present teachings can operate on the principle of hemodialysis, hemofiltration or hemodiafiltration or plasma physis. The blood purification unit used can thus be designed as a dialysis filter or hemofilter or plasma filter.

A method according to the present invention determines the partial pressure of a gas in blood of extracorporeal blood circulation in a blood treatment apparatus according to claim 1 by measuring the gas concentration in the compensation chamber by means of a gas sensor and calculating the partial pressure in blood, e.g. B. the p _CO2 in blood, by evaluating the measured data of the gas sensor by means of the control and evaluation.

In order to bridge a spatial distance between the compensation chamber and the gas sensor, the production of a gas flow from the compensation chamber to the gas sensor may be provided.

This gas flow can be established by a stroke of the blood level in the compensation chamber. By raising the blood level in the compensation chamber, a displacement of the gas in the compensation chamber is achieved in the connecting line to the gas sensor. To ensure that the concentration set in the compensation chamber reaches the gas sensor, the displaced volume should preferably be at least twice as large as the volume in the connection tube. With the commercially available blood hose systems, a stroke of 1-2 cm in the compensation chamber is sufficient to transport the gas in the compensation chamber to the gas sensor. The stroke can be done by an intermittent flow restriction in the bloodstream downstream of the compensation chamber. For this purpose, the evaluation and control unit can control a arranged in the second line valve so that this partially or briefly completely closes. At the same time appropriate means for pressure equalization, such. B. a throttle valve or a valve to a compliance vessel, are opened so that the gas sensor no pressure is created. A subsequent lowering of the level can be reversed by a pressure surge by a compressor.

Alternatively, a level shift in the balance chamber may be achieved by means of a second blood pump in the second conduit, the drain. By controlling the evaluation and control unit, different delivery rates can be set for the first and for the second blood pump. If the first blood pump delivers at a greater delivery rate than the second blood pump, the blood level in the compensation chamber is raised. Conversely, a delivery rate of the first blood pump, which is smaller than that of the second blood pump, results in a lowering of the blood level in the compensation chamber.

The gas flow can also be effected by an active transport of the gas through a gas conveyor.

Brief description of the drawings

1 : Schematic representation of a first embodiment of the blood treatment device according to the invention.

2 : Schematic representation of a second embodiment of the blood treatment device according to the invention.

3 : Correlation between predialytic p _CO2 and bicarbonate

4 Simulated p _CO2 curve during a long-term dialysis with apnea.

Detailed description of an embodiment

In 1 is a first embodiment of a blood treatment device ( 25 ) according to the present teaching. From the patient ( 20 ) gets blood from the blood pump ( 4 ) through the first line ( 16 ), the arterial line, promoted and passes through the port ( 2a ) into the compensation chamber ( 1 ). In the compensation chamber ( 1 ), a blood level is formed ( 1a ). Connection ( 2a ) may be above or below the blood level ( 1a ), ie eg also adjacent to connection ( 2 B ), which forms an outlet from the compensation chamber. From the outlet ( 2 B ) of the compensation chamber ( 1 ) the blood then flows on via the second line ( 17 ) to the blood purification unit ( 22 ), z. As a dialyzer and further back to the patient. The blood purification unit ( 22 ) is still with a Dialysatzubereitungseinheit ( 23 ), in which the dialysis solution can be prepared with the desired bicarbonate concentration.

In the compensation chamber ( 1 ) above the blood level, gases dissolved in blood are in equilibrium with a corresponding gas concentration in the gas space of the compensation chamber ( 1 ). The gas space of the compensation chamber ( 1 ) is via the connecting tube ( 18 ) with the gas sensor ( 6 ) connected. The gas sensor is in the fixed part of the blood purification device, for. As the dialysis machine arranged. To protect the gas sensor from contamination by blood, which may possibly rise into the connection hose in the event of malfunction, it is necessary at the end of the connection hose ( 18 ) a hydrophobic filter ( 5 ) intended. Behind the hydrophobic filter, the gas mixture becomes a CO ₂ sensor ( 6 ). This is optimized for a concentration measurement range of about 2-10% by volume of CO ₂ , corresponding to the physiologically relevant CO ₂ partial pressures of 15-80 mm Hg.

The measured data recorded by the CO ₂ sensor are transmitted by the control and evaluation unit ( 21 ) and the CO ₂ partial pressure is calculated by the control and evaluation unit on the basis of the formulas described below.

The relationship between the CO ₂ concentration c _CO2 in blood and the CO ₂ partial pressure of pCO2 in the gas space is described by Henry's Law.

The Henry's constant for CO ₂ is temperature-dependent:

Furthermore, the CO ₂ concentration c _CO2 in blood is related to the hydrogen carbonate concentration c _HCO3 according to the Henderson-Hasselbalch equation: CO _{2, aq} + H ₂ O ↔ H ⁺ + HCO

Which adjusting in the gas space above the level of blood CO ₂ partial pressure p _CO2 corresponds to the measured blood gas analyzer at the same temperature by means of a CO ₂ partial pressure.

The current temperature is determined by the temperature in the line ( 17 ) arranged temperature sensor ( 8th ) certainly.

As well as the temperature, the standard pressure must also be taken into account for an exact determination of the partial pressure. When the gas mixture is compressed to a pressure p other than the normal pressure p _norm , the CO ₂ partial pressure under standard conditions is obtained

The temperature- and pressure-compensated CO ₂ partial pressure (p _CO2 (T, pnorm) in the blood is then calculated using formulas 1 and 4 from the CO ₂ concentration in the headspace above the blood level.

Particularly advantageous is the use of customary in a hemodialysis consumables for the extracorporeal tube system. In order to enable a contactless, largely maintenance-free and cross-contamination-safe measurement, the gas sensor is preferably arranged in the blood treatment machine.

The arrangement of the gas sensor in the blood treatment machine and not directly in the compensation chamber also brings with it the advantage that no changes are required to the standard hose systems used. The gas sensor is part of the hardware of the blood treatment machine. Depending on the distance of the compensation chamber to the gas sensor, which results essentially from the length of the hose connection (eg 10-30 cm), it is necessary to actively transport the gas concentration above the blood level to the gas sensor.

Without aids that generate a flow from the gas space directly above the blood level to the measuring sensor, the transport of the gas concentration at the blood / air contact point, in particular the carbon dioxide concentration, to the gas sensor is determined solely by the diffusion. For the one-dimensional diffusion of a gas into a space, which previously did not contain the gas to be considered, the concentration maximum of the diffusion front applies: x 2 / max = 2Dt _max

With a typical diffusion constant D ~ 1.6 · 10 ^-5 m ² / s, the gas already requires several minutes for a diffusion of several centimeters (eg x _max = 20 cm more than 20 min).

In the in 1 shown embodiment are for the purpose of gas transport to the gas sensor ( 6 ) in the second line ( 17 ) various alternative means, a valve ( 14 ) or a second blood pump ( 15 ) (shown in phantom).

Both alternatives ( 14 . 15 ) can be read by the evaluation and control unit ( 21 ) are controlled so that they downstream of the compensation chamber ( 1 ) create a flow restriction. In the case of the valve ( 14 ), this flow restriction is created by closing the valve. In the case of the second blood pump ( 15 ) is the flow restriction by the setting of a delivery rate of the second blood pump ( 15 ), which is lower than the delivery rate of the first blood pump ( 4 ). By creating a flow restriction in the second line ( 17 ) is a lifting of the liquid level in the compensation chamber ( 1 ) from the position ( 1a ) on ( 1b ) reached. This gas is from the gas space of the compensation chamber ( 1 ) and thus a flow through the gas sensor ( 6 ) reached. To make sure that in the compensation chamber ( 1 ) adjusting gas concentration the gas sensor ( 6 ), the displaced volume should preferably be at least twice as large as that in the connection between the connection ( 3a ) of the connecting line ( 18 ) at the compensation chamber ( 1 ) and the gas sensor ( 6 ) located volumes. In hemodialysis usual blood tubing systems a stroke of about 1-2 cm is sufficient.

The build-up of air pressure when lifting the blood level can be reduced by either the outlet valve ( 12 ) and open the air via throttle valve ( 10 ) to the environment, or alternatively, by opening the compliance valve ( 13 ) a pressure equalization in a compliance vessel ( 9 ) (shown in dashed lines) is made possible. In both alternative ways, an air flow through the gas sensor ( 6 ) causes, so that at this now in the gas space of the compensation chamber ( 1 ) prevailing gas concentration can be measured.

To reset the blood level ( 1b ) on ( 1a ) valve ( 14 ), or the second blood pump ( 15 ) with a higher delivery rate. Pressure equalization can then be achieved by introducing ambient air by means of a compressor ( 11 ) or via the compliance vessel ( 9 ) respectively.

Alternatively, when using a like in illustrated compensation chamber ( 1 ) a continuous flow through the gas sensor can be achieved. Here, over the gas space of the compensation chamber ( 1 ) by means of a gas conveyor ( 19 ) a circulation of connection ( 3a ) via the gas sensor ( 6 ) via a return line ( 26 ) back to port ( 3b ) reached. As contamination protection are here in the connecting line ( 18 ) and the return line hydrophilic filter ( 5 ) intended. In the gas conveyor ( 19 ) may be any type of means that produce a low continuous flow of air. For example, a miniaturized bellows can be used, in which the movement of the legs is effected by piezo elements.

That of the gas sensor ( 6 ) are measured by the evaluation unit ( 21 ) and formula (5) determines the partial pressure of carbon dioxide in blood.

This partial pressure can give indications for different pathological conditions.

Determination of predialytic p _CO2

Values for the partial pressure of carbon dioxide measured at the beginning of the blood treatment differ only slightly from the predialytic partial pressure. A low value, in particular below the normal range of 35-45 mmHg, usually has a respiratory compensated metabolic acidosis as the cause. Thus, when measuring a P _CO2 , which is below a defined threshold value, a warning to the user can be issued by the dialysis machine (user interface / alarm unit ( 24 )). This threshold value can be an absolute value (eg clinical standard range) or a value that is individually determined for this patient and stored in a storage unit. B. is determined from the mean of past measurements for this patient.

Correction of metabolic acidosis

Metabolic acidosis can be corrected in dialysis treatments by adding bicarbonate through the dialysis solution. In 3 is the correlation of the predialytic p _CO2 and the bicarbonate concentration HCO ₃ ^- shown in blood. After a measurement of the pCO ₂ value, the dialysis preparation unit ( 23 ) of the dialysis machine automated setting of the bicarbonate concentration in the dialysate c _D done. For this purpose, a 1-pool model can be used, in which the distribution volume V of the patient, the by means of online clearance measurements determined dialysis dose Kt / V, as well as the estimated from the pCO ₂ measurement blood bicarbonate concentration c _{B, O} enter.

Factor a takes into account the lower clearance of bicarbonate compared to urea and is ~ 0.7.

The coefficients a ₀ and a ₁ can be derived from a linear fit of the in 3 shown value pairs. Since the metabolic processes are patient-dependent, a better agreement between the estimated and real value can be achieved if p _CO2 and bicarbonate are determined over a certain period of time by means of a reference instrument (blood gas analyzer) and the coefficients a ₀ and a _{1 are} determined on a patient-specific basis.

If the Kt / V reached at time t ₁ can be estimated on the basis of the dialysis settings (blood, dialysate, substituate flow, dialyzer characteristic), then the dialysate bicarbonate to be adjusted to obtain a blood bicarbonate concentration at time t ₁ can be calculated from formula 8:

By repeated measurements of the p _CO2 and the dialysis dose achieved so far, it is also possible to correct the dialysate bicarbonate during dialysis.

Apnea Monitoring

As already described, poor respiration can occur, especially in the case of long-term night-time dialysis due to errors in the physiological control mechanisms or due to partial obstruction of the respiratory tract. This leads to an increase in p _CO2 . Studies in patients with obstructive sleep apnea have shown that p _CO2 on waking up in the morning is> 11 mmH higher than before sleep ( "Changes in the arterial CO2 during a single nights sleep in patients with obstructive sleep apnea" Chin et al., Internal Medicine, Vol. 36, p. 454ff ). In the case of transient respiratory arrest, which can last over one minute, it is to be expected that the increase in p _CO2 will be significantly higher than that in 4 shown simulated p _CO2- run during a long-term dialysis with apnea. It is precisely this critical breathing interruptions are thus recognized by the described continuous p _CO2 -Monitoring.

When recording the course of the p _CO2 , respiratory misfires can be diagnosed and taken into account in therapy planning.

However, it is also conceivable online monitoring to avoid prolonged respiratory misfire. Thus, in the blood treatment device ( 25 ), or evaluation unit ( 21 ) different warning criteria be deposited, z. For example, exceeding an absolute concentration threshold, increasing the p _CO2 above a concentration threshold calculated from past history or typical history of previous treatments. In this case, other criteria, such. B. a certain duration of the threshold exceeded or the change in the time course of the p _CO2 , z. B. greatly accelerated increase over the previous course, are taken into account.

Upon the occurrence of these critically evaluated states, an audible signal may be generated, e.g. B. alarmed the patient or the nursing staff.

It would also be conceivable to wake up or to stimulate the respiration by triggering a weak electric pulse on the patient.

When using a breathing mask, the ventilation pressure or the airflow can increase.

diabetes monitoring

By means of an acetone sensor ( Massick et al., Proc. SPIE 6386, Optical Methods in Life Sciences, 63860O (October 17, 2006) ) can the course of metabolic diseases, eg. As ketoacidosis in diabetes, diagnosed and observed when recording the values over several treatments their course. This can be helpful in the dosage of insulin in diabetics on dialysis.

Determination of dialysis efficiency

There is a correlation between the urea concentration and the ammonium concentration in the breath ( "Correlation of ammonia with blood urea nitrogen and creatinine during hemodialysis", Narasimhan et al., PNAS Vol. 98, p. 4617ff ). Therefore, by means of an ammonium sensor (eg. "High sensitivity ammonia sensor using a hierarchical polyaniline / poly (ethylene-co-glycidyl methacrylate) nanofibrous composite membrane", Chen et al., ACS Appl Mater Interfaces, Vol. 24, pp. 6473ff ) virtually all analyzes that are otherwise based on the determination of urea concentration in the blood. From the course of the ammonium concentration at the beginning of successive dialysis can therefore be concluded on the protein turnover (PCR = protein catabolic rate). From the intradilaytic change in the ammonium concentration, the dialysis efficiency Kt / V can be calculated:

In contrast to measurements on the dialysate side, no correction of the measured values with regard to the flow rates is necessary here (see BBraun: Adimea).

Function test of the hydrophobic filter

In one embodiment of the invention, in the blood treatment device ( 25 ) next to the gas sensor ( 6 ) also the pressure sensor ( 7 ) for monitoring the pressure in the blood tubing system so that the connection tube ( 18 ) to both the gas sensor ( 6 ) as well as to the pressure sensor ( 7 ) leads. The measured data of the gas sensor ( 6 ) can then also be used to carry out a functional test of the hydrophobic filter ( 5 ) be used. When using a device such as in 1 shown, in which a pressure equalization takes place to the environment, the permeability of the hydrophobic filter ( 5 ) by means of the gas sensor ( 6 ) and the evaluation unit ( 21 ) be tested. By wetting the hydrophobic filter ( 5 ) with blood or dialysis fluid this is impermeable to gas, so that no reliable pressure measurement is possible. Since the adjusting itself due to the blood-p _CO2 CO ₂ concentration in the gas space (1) is approximately 5% of normal CO ₂ content of the ambient air but only about 400 ppm = 0.004%, can during lifting and lowering de Level in the compensation chamber ( 1 ), whether a gas connection between the compensation chamber ( 1 ) and the gas sensor ( 6 ) consists. With a blood-filled tube system, increasing the CO ₂ concentration to> 1% is to be expected when raising the level, and lowering to less than 0.1% when lowering. If this is not the case, then a blocked hydrophobic filter ( 5 ) getting closed.

The embodiments described herein provide the ability to determine and monitor the concentration of dissolved gases in blood during extracorporeal blood treatment without the use of additional sensors or blood sampling and analysis. The measurement of the gas concentration can be carried out using the usual blood tube systems, contact-free and without contamination, so that no additional burdens or risks arise for the patient. The measurements can be used to monitor patient vital signs, to determine treatment efficacy, or to test the function of extracorporeal circuit components.

LIST OF REFERENCE NUMBERS

1

compensation chamber

1a

liquid level

1b

liquid level

2a, 2b

Connection chamber

3a

Connection chamber

4

blood pump

5

hydrophobic filter

6

gas sensor

7

pressure sensor

8th

temperature sensor

9

compliance vessel

10

throttle valve

11

compressor

12

outlet valve

13

compliance valve

14

Valve

15

blood pump

16

Arterial part of the blood tube system

17

Venous part of the blood tube system

18

Connecting hose.

19

gas subsidies

20

patient

21

evaluation

22

Blood purification unit

23

Dialysatzubereitungseinheit

24

User interface / alarm unit

25

Blutbehandiungsvorrichtung

26

Return line

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2013/156435 [0013]

Cited non-patent literature

• "Potential Application of Exhaled Breath Monitoring in Renal Replacement Therapy", Kelly et al., Poster Presentation ASN 2113 [0005]
• "Correlation of breath ammonia with blood urea nitrogen and creatinine during hemodialysis, Marashimhan et al. PNAS Vol. 98, p. 4617ff [0008]
• "Changes in the arterial CO2 during a single nights sleep in patients with obstructive sleep apnea" Chin et al., Internal Medicine, Vol. 36, p. 454ff [0074]
• Massick et al., Proc. SPIE 6386, Optical Methods in Life Sciences, 63860O (October 17, 2006) [0080]
• "Correlation of ammonia with blood urea nitrogen and creatinine during hemodialysis", Narasimhan et al., PNAS Vol. 98, p. 4617ff [0081]
• "High sensitivity ammonia sensor using a hierarchical polyaniline / poly (ethylene-co-glycidyl methacrylate) nanofibrous composite membrane", Chen et al., ACS Appl Mater Interfaces, Vol. 24, p. 6473ff [0081]

Claims (16)

Blood treatment device ( 25 ) with an extracorporeal blood circulation comprising a first line ( 16 ), at one end for blood sampling connectable to a patient ( 20 ) and at the other end connected to a compensation chamber ( 1 ), a first blood pump ( 14 ) for pumping blood in the extracorporeal circuit into the compensation chamber ( 1 ), whereby in this a blood level ( 1a . 1b ) is formed, and a contact of the blood is formed to a located above the blood level gas space, and a second line ( 17 ) for forwarding the blood from the compensation chamber ( 1 ) to a blood purification unit ( 22 ), characterized in that the blood treatment device ( 25 ) one with the compensation chamber ( 1 ) connectable gas sensor ( 6 ) for measuring the concentration of a gas in the gas space and an evaluation unit ( 21 ) for reading and evaluating the measured data of the gas sensor ( 6 ). Blood treatment device ( 25 ) according to claim 1, characterized in that the gas sensor ( 6 ) is a sensor for carbon dioxide or ammonium or acetone. Blood treatment device ( 25 ) according to claim 1 and / or 2, characterized in that the gas sensor ( 6 ) is heated. Blood treatment device ( 25 ) according to one of the preceding claims, characterized in that in the first line ( 16 ), the second line ( 17 ) or the compensation chamber ( 1 ) of the extracorporeal blood circulation a temperature sensor ( 8th ) is arranged for determining a measured value of the blood temperature, wherein the evaluation unit ( 21 ) is designed to take into account the measured value for temperature compensation. Blood treatment device ( 25 ) according to one of the preceding claims, characterized in that it comprises a pressure sensor ( 7 ) for determining a measured value for the pressure in the compensation chamber ( 1 ), whereby the evaluation unit ( 21 ) is designed to take into account the measured value for pressure compensation. Blood treatment device ( 25 ) according to one of the preceding claims, characterized in that the compensation chamber ( 1 ) by means of at least one connecting line ( 18 ), preferably a connecting hose ( 18 ), with the gas sensor ( 6 ) connected is. Blood treatment device ( 25 ) characterized in that in the connecting line ( 18 ) between the gas sensor ( 6 ) and the compensation chamber ( 1 ) a hydrophobic filter ( 5 ) is arranged. Blood treatment device ( 25 ) according to one of the preceding claims, characterized in that it comprises means for generating a gas flow from the compensation chamber ( 1 ) through the connecting line ( 18 ) to the gas sensor ( 6 ) and that the evaluation unit as a control and evaluation unit ( 21 ) is trained. Blood treatment device ( 25 ) according to claim 8, characterized in that the means for generating the gas flow as a valve ( 14 ) or as a second blood pump ( 15 ) in the second line ( 17 ) of the extracorporeal blood circulation, wherein the valve ( 14 ) or the second blood pump ( 15 ) from the control and evaluation unit ( 21 ) are controlled so that in the second line ( 17 ) at times a lower blood flow rate than before the compensation chamber ( 1 ) in the first line ( 16 ), causing a shift in the blood level ( 1a ) in the compensation chamber ( 1 ) can be generated. Blood treatment device ( 25 ) according to claim 9, characterized in that it comprises compensating means ( 9 . 10 . 11 12 . 13 ) for a pressure increase occurring at a blood level shift. Blood treatment device ( 25 ) according to claim 8, characterized in that the gas sensor ( 6 ) and the compensation chamber ( 1 ) with a return line ( 26 ), wherein in this return line ( 26 ) a gas conveyor ( 19 ) is arranged that between gas sensor ( 6 ) and compensation chamber ( 1 ) a circulating gas stream is formed. Blood treatment device ( 25 ) according to claim 1, characterized in that the blood purification unit ( 22 ) is a dialysis filter or a hemofilter or a plasma filter. Blood treatment device ( 25 ) according to claim 1, characterized in that the evaluation unit ( 21 ) is designed to determine the partial pressure of a gas in blood and in the evaluation unit ( 21 ) a desired range for the partial pressure of the gas is stored and in the case of a measured partial pressure outside the nominal range a signal to an alarm device ( 24 ), which then issues an alarm signal. Blood treatment device ( 25 ) according to claim 1, characterized in that it comprises a dialysate preparation unit ( 23 ) for the supply of the blood purification unit ( 22 ) with dialysate, and the evaluation unit ( 21 ) is designed as an evaluation and control unit to from the measured values of the gas sensor ( 6 ) to determine a partial pressure of a gas and to associate the partial pressure of the gas with a composition of the dialysate, which is then removed from the dialysis preparation unit ( 23 ) provided Method for determining the partial pressure of a gas in blood of the extracorporeal blood circulation of a blood treatment device ( 25 ) according to claim 1, characterized in that the concentration of the gas by means of a gas sensor ( 6 ) in the gas space of the compensation chamber ( 1 ) and from these measured data by the evaluation unit ( 21 ) the partial pressure of the gas in the blood is calculated. A method for determining the partial pressure of a gas in blood as claimed in claim 14 characterized in that (in the blood treatment apparatus 25 ) a gas flow from the compensation chamber ( 1 ) to the gas sensor ( 6 ) is produced.

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