DE4212507A1 - Non-invasive detector of variations in blood vol. or pressure - uses microprocessor and electronic pump controller for computation and display of incremental volume of exercised limb - Google Patents

Abstract

Air is pumped (8) through a valve (7) and pneumatic coupler (4) into a cuff at a basic pressure of 10 to 20 torr. An electronic controller (10) instigates additional pumping during one or more short intervals while the consequent increase in pressure is measured by a sensor (S) calibrated in millilitres from knowledge of the pump vol. and air compressibility and temp. The controller calculates the enclosed tissue vol. at rest so that the measured changes in vol. can be expressed also in percentage terms when the limb (E) is exercised. USE/ADVANTAGE - Variations in vol. of extremities or of pressure in a subcutaneous vessel during exercise can be evaluated in both relative and absolute units.

Description

The invention relates to a device for noninvasive detection of blood volume change in Extremities or to change blood pressure in one gene, near the skin surface due to certain Exercise programs.

For example, in a vein occlusion test Using a tourniquet on the thigh of the venous Blood flow stopped for a short time. The patient is usually lies supine, the examined  Extremity is raised slightly and stored softly. It comes to a defined vein congestion in the lower leg, associated with an increase in blood volume and Venous pressure. The outflow kinetics after the end of the congestion is then evaluated for thrombosis diagnosis. At physiolo Venodynamics is hydraulic conductivity the leg veins are very large and thus the emptying phase accordingly short. With thrombosis or outflow other genesis (tumors, pregnancy, etc.) the emptying phase is extended accordingly. To several plethysmographs are state of the art known that can be used for these tests. The following types of sensors are used:

• - optical sensors,
• - strain gauge sensors,
• - gravimetric sensors,
• - Volumetric sensors.

Especially the photoplethysmographs (plethysmographs with optical sensors) have been around since the launch the quantitative measurement principle (DE 36 09 073 A1, DE 36 09 075 A1 and DE 38 27 501 A1) have proven themselves. You captured However, the blood flow changes only in one small area of the skin. Under certain measuring conditions the Venody namik not properly detected in deep vascular networks will. You can also change the blood flow only in relative units, i.e. H. based on the Specify calm reflection before the test.

For plethysmographs with strain gauges (with a Hose, so-called strain gauge, cf. B. WHITNEY: J. Physiol 109 (1949), 5, DPA 4032 152) is the electri  cal resistance of the sensor as a function of blood volume-dependent extent of the limb registered. However, this method also only allows relative information the blood flow parameters.

In gravimetric plethysmography, the Ex tremor weighed during the test (DE 37 44 538 A1). The blood volume kinetics can thus both in rela tive, as well as absolute units. Disadvantageous is the great dependence of the measuring systems on Motion artifacts.

In volumetric plethysmography according to the state der Technik (DAHN et al., J. Appl. Physiol. 28 (1970, 333; CHRISTOPOULOS et al., J. Vasc. Surg. 5 (1987), 148; BLAZEK and SCHULTZ-EHRENBURG, Vasomed currently 7 (1991), 12), the blood volume-related expansion of the limb based on air tests filled cuff. The kinetic evaluation parameters are expressed in absolute units (ml, grams, ml / min). So tempting it at first may seem, but in practice it turns out that these parameters in absolute units sometimes from Scatter patient to patient so that an assignment normal / pathological venodynamics often not possible is. This disadvantage results from dependency of the measurement results from the ratio of the cuff volume mens to the Ge enclosed by the cuff web volume.

The invention is therefore based on the object Device for non-invasive detection of blood change in volume in extremities or to change blood pressure in a single container close to the skin surface  as a result of certain exercise programs that indicate a Evaluation of the kinetics in absolute as well as in relative units.

The achievement of these tasks is with know their further training in the claims draws.

According to the invention, a device for not vasive recording of changes in blood volume in extremities or to change blood pressure in a single skin near-surface vessel due to certain exercise pro created grams that have at least one pneumatic Sensor, the sensor bubble with a compressible Fluid and in particular air can be acted upon Pressure transducer, which detects the pressure in the sensor bubble, a device for detecting the circumference of the sensor, and has control and evaluation electronics the the output signals of the pressure transducer and the on direction to capture the scope, and the controls the application of the sensor bubble in such a way that by applying the sensor bubble accordingly Measurement signal calibration takes place before each measurement and thus the blood volume or blood pressure fluctuations in the measurement area under the sensor simultaneously in relative and absolute units can be measured.

Pneumatic sensors are used for blood volume measurement sensors preferably designed as air-filled rubber mature (cuffs) that the examined extremities wrap around the area. Depending on the circumference The extremity segment will change the Air volume in the sensor registered at constant gere valid pressure. Alternatively, the change can also be made  the air pressure in the sensor at constant air volume be measured.

The sensors are preferred for blood pressure measurement trained as small rubber balls and are over skin nearby vessels (e.g. dorsal vein) so that they act as a force sensor. In this case, the Pumped up sensors so that the examined vessel is slightly pushed in, but without completely collapse. The change in blood pressure in the vessel will act on the sensor as a change in force ken and from this ultimately about the change of the Air volume or air pressure registered. This kind of sensors are very useful for the non-invasive peripheral circulatory diagnostics.

The front according to the invention is particularly suitable direction for plethysmographic quantification veno dynamic processes due to the so-called muscle pump Tests, elevation tests and venous occlusion tests.

These tests have been used in physiological measurement technology and circulatory diagnostics have long been their usefulness proven. The patient performs the muscle pump test usually 8 to 10 active exercises within about 15 seconds through. Have proven themselves. B. Dorsalex tensions sitting and squats standing. Through the The muscles get the venous blood out of the pumped lower extremity to the heart and it comes to a short-term decrease in venous pressure or Volume of blood in the foot. From the kinetics of this drop then functional diagnostic parameters of the determine arterial and venous blood flow. In which Elevation test makes the patient passive, i.e. H. without  own muscle work, subjected to a change of position. This can be done, for. B. the influence of the hydrostatic Determine pressure on the blood flow parameters.

The invention is hereinafter without limitation general inventive concept based on execution examples with reference to the drawing exempla risch described on the rest of the Revelation of all not explained in the text explicitly referenced details becomes. Show it:

Fig. 1 shows the basic structure of an inventive device SEN,

Fig. 2 shows two embodiments of the sensor,

Fig. 3, 4 and 6 different measurement reports, and

Fig. 5 shows a device for measuring the back of the foot.

The device shown in Fig. 1 for non-vasive detection of the change in blood volume in extremities (E) or for blood pressure change in a single, near-skin vessel as a result of certain exercise programs has a pneumatic sensor (S) with a sensor bladder (B), which is connected to a pump ( 8 ) via a hose ( 1 ), a pneumatic plug connection ( 4 ) and a valve ( 7 ). A pressure / voltage converter ( 9 ) is provided on a spur line in front of the valve ( 7 ), the output signal of which is applied to control and evaluation electronics ( 10 ). Furthermore, a calibration unit ( 6 ) for the transducer ( 9 ) can be connected via a further pneumatic plug connection ( 5 ).

A device is provided for detecting the circumference of the sensor (S), which is shown in more detail in FIG. 2 and which in particular has a coding resistor (W). This device for detecting the circumference of the sensor (S) is connected to the control and evaluation electronics ( 10 ) via a line ( 2 ) and an electrical plug connection ( 3 ).

The control and evaluation electronics ( 10 ) act on a display ( 11 ) and an analog data output ( 12 ), control the pump ( 8 ) and the valve ( 7 ) and are connected to a microprocessor ( 13 ) which has a digital data output ( 14 ) acted upon.

LPG denotes a suitable housing.

The device shown in Figure 1 operates as follows:

The pump ( 8 ) builds up a base pressure of 10 to 20 mm Hg in the sensor bladder (B) of the sensor (S). The pump is then switched on by the control electronics ( 10 ) for one or more short intervals; the sensor (S) detects the resulting pressure increase in the pneumatic system. With a known delivery rate of the pump and taking into account the air compressibility and temperature, the sensor can then be calibrated in milliliters.

The evaluation and control electronics ( 10 ) can determine the resting tissue volume enclosed by the sensor (S) via the signal supplied by the device for detecting the extent of the sensor (S).

In this simple way, according to the invention  all subsequent changes in blood volume both in absolute as well as at the same time in relative volumes units (ml, ml / 100 ml tissue =%) or flow rates (ml / min,% / min) can be specified.

For external control of the quality of the self-calibration of the sensor, the measuring device is preferably equipped with the further pneumatic plug connection ( 5 ). With the calibration unit ( 6 ), a defined amount of air or gas can be injected into the sensor and compared with the volume changes highlighted and registered as a result.

Fig. 2 shows two possible embodiments of the pneumatic sensor for blood volume measurements on lower extremities.

In Fig. 2a the sensor jacket is fixed and designed in the form of a ring. It is pulled over the foot to the lower leg. Several sensors with different diameters are available to the user. The sensor bladder (B) fills the space between the sensor jacket (M) and the "leg disk under the sensor" (in Fig. 2b labeled SUM). Sensor coats of different sizes are coded with different resistances so that the evaluation and control electronics ( 10 ) can determine the circumference of the leg plate from them. TK and FK denote the tibia and fibula bones, respectively.

Another preferred embodiment is shown schematically in FIG. 2c. Here, the sensor jacket (M) is designed as a sleeve, on which the sensor bladder (B) is arranged below, and which is tightly applied over the extremity (E). With a closure device (K), the resistance chain (W) in the cuff is encoded according to the circumference and communicated to the measuring device via an electrical line ( 2 ).

The entire measurement process can be carried out either in the so-called constant volume mode or in the so-called constant pressure mode. In one mode, the air volume in the pneumatic system is constant, the pressure change in the system being evaluated as a result of the change in blood volume in the extreme. In the other mode, the air pressure in the sensor system is constantly controlled by the pump ( 8 ) or the valve ( 7 ); The blood volume fluctuation in the measuring area is determined electronically from the running time of the pump or the opening time of the valve.

Above all, the second measurement alternative is particularly important partial, since the contact pressure of the sensor (S) on the Tissue is always constant and thus the expansion of the Limb not ver by varying contact pressure is faked; however, it is also more complex.

Fig. 3 shows typical registrations taken with the constant pressure mode in a patient suffering from varicose veins; the sensor shown in Fig. 2c is arranged over the largest calf circumference.

In the muscle pump test ( Fig. 3a), the patient performed eight dorsal extensions (DEX) in the ankle within 15 seconds. A volume decrease Vo of 8.4 ml or 1.3% was registered. After a refill time of To = 18 seconds, the initial status was reached again.

In the elevation test ( FIG. 3b), the patient's lower extremity was passively raised above the heart level. This resulted in a maximum possible emptying of the venous blood of 12 ml ≈ 1.9% of the enclosed tissue volume. The effectiveness of the patient's muscle pump when the exercise was sitting was Mo = Vo / Vomax 100% = 70%.

Finally, Fig. 3c shows the registration during the classic venous occlusion test. The vein blockage was performed on the thigh for 90 seconds. Since the arterial inflow of blood into the lower leg is not initially affected, there is an increase in blood volume in the measurement area. After the end of the jam, the emptying speed is measured. The following evaluation parameters were determined from this test:

• - Arterial inflow AF = 32 ml / min ≈ 4.8% / min,
• - venous capacity VC = 19.7 ml ≈ 2.9%,
• - venous outflow VO = 540 ml / min ≈ 81% / min.

In the computer-aided version of the measuring device, the entire measuring sequences can also be controlled and the measuring results can be subjected to an automatic parameter evaluation. An example of this is shown in FIG. 4.

, FIG. 5 shows an example of the preferred sensor design for the measurement of venous pressure in a selected leg vein. The sensor bladder (B) is designed in the form of a small rubber ball and placed over the ankle vein (FRV). The sensor jacket (M) is now designed as a rigid clamp so that the blood pressure change in the vessel can be fully transferred to the sensor sorblase (B). In this measuring mode, the contact of the sensor with the vessel wall is monitored via the electrical line ( 2 ).

FIG. 6 shows a typical course of venous pressure P-vec (t) during a muscle pump test in a standing subject. The resting pressure in this case was approx. 90 mmHg. As a result of the leg exercise, the vein pressure dropped to approximately 40 mmHg. The rest pressure was reached again about 14 seconds after the end of the movement.

The measuring device described thus offers a non-invasive variant to the previously common bloody one Venous pressure measurement by the state of the art the dorsal vein is punctured.

The invention thus creates a non-invasive, time- and cost-saving screening measurement system, the physiolo capture genetic and pathophysiological venodynamics and can prove and complex, risky invasive Saving examination methods helps.

Claims (10)

1. Device for non-invasive detection of the change in blood volume in extremities or for blood pressure change in a single, near-skin surface vessel as a result of certain exercise programs

• at least one pneumatic sensor (S), the sensor bladder (B) of which can be acted upon by a compressible fluid and in particular air,
• - A pressure transducer ( 9 ) which detects the pressure in the sensor bubble (B),
• - A device for detecting the scope of the sensor, and
• - Control and evaluation electronics, to which the output signals of the pressure transducer and the device for detecting the extent are present, and which controls the exposure of the sensor bubble in such a way that a measurement signal is calibrated before each measurement and thus the blood volume by appropriate exposure of the sensor bubble. or blood pressure fluctuations in the measurement area under the sensor can be measured simultaneously in relative and absolute units.

2. Device according to claim 1, characterized in that an electronically controllable pump ( 8 ), which is controlled by the control and evaluation electronics ( 10 ), is provided to act on the sensor bladder (B). 3. Apparatus according to claim 1 or 2, characterized in that a valve ( 7 ) which is controlled by the control and evaluation electronics ( 10 ) is provided. 4. Apparatus according to claim 2 or 3, characterized in that the control and evaluation electronics controls the running time of the pump ( 8 ) and / or the opening time of the valve ( 7 ). 5. Device according to one of claims 1 to 4, characterized in that the control and evaluation electronics ( 10 ) includes compensation circuits which take into account the non-linear relationships between air pressure, air volume and temperature in the measured value evaluation. 6. Device according to one of claims 1 to 5, characterized in that the control and evaluations electronics the pressure in the sensor bladder (B) on one regulates constant value. 7. Device according to one of claims 1 to 6, characterized in that the sensor jacket (M) a has a rigid shape and the sensor bubble (B) has the shape differences difference between the sensor jacket (M) and the examined Filled in limb section. 8. Device according to one of claims 1 to 6, characterized in that the sensor bubble (B) and the soft sensor jacket (M) in cuff shape are and have a locking device (K), to automatically detect the scope of the order closed tissue volume serves. 9. Device according to one of claims 1 to 8, characterized in that a microprocessor  Device controls. 10. The device according to one of claims 1 to 9, characterized in that the contact pressure of the sensor bladder to the extremity is small and therefore both arterial blood inflow as well as that through venous blood conditional tissue expansion is not hindered.