Plethysmograph

 

The invention relates to medical equipment, namely, devices for studies of peripheral blood flow. Plethysmograph contains a camera with an internal cavity for placement of the investigated limb with element for sealing the internal cavity when placed in her study limb, an inflatable cuff to create a venous stop the blood in the limb, equipped with a pressure gauge and a device for measuring the increase limb venous stop. According to the invention introduced an atmospheric pressure sensor, a bellows with inlet and a movable bottom, which is mechanically linked to drive the reciprocating motion, the microcompressor, pneumatomachi, two variables pneumatocele, equipped with inlet and outlet fittings, and electronic computing device. Device for measuring the increase limb venous stop is made in the form of gauge pressure, equipped with inlet, the sealing element is made in the form of an inflatable cuff with a pressure gauge, with the possibility of accommodation in the gap between the investigated limb and forming the inner surface of the chamber, and inlet fittings d is nutrena oral camera. The microcompressor is connected with the possibility of connection through the respective pneumatomachi to the inlet of the second pneumatocele, inflatable cuff to create a venous stop and element for sealing the internal cavity of the chamber and the outlet fitting of the first pneumatocele through pneumatometer connected with the atmosphere. The outputs of the redundant sensors and atmospheric pressure is connected to the electronic computing device. The technical result consists in providing a definition of the absolute value of the intensity of the blood flow without the use of additional hyperstory. 3 Il., table 1.

The invention relates to medical equipment, namely, devices for studies of peripheral blood flow.

Known plethysmograph (Naumenko, A. N., Skotnikov Century Century demand a technique which incorporates the Basics. HP : Medicine. 1975, S. 87-96) to study peripheral blood flow, containing two electrodes and apparatus for measuring electrical resistance. When defining peripheral blood flow electrodes are superimposed on the investigated part of a human body, such as leg or arm, and the determination of the blood flow is reduced to the measurement of electric soprotivlenie information related to the fact that the dependence of electrical resistance on the speed of blood flow is complex and, in General, different for each person.

The closest in technical essence is plethysmograph (Experimental physiology /Ed. by B. L. Andrew. M.: Mir, 1974, S. 226-233) containing chamber with an internal cavity for placement of the investigated limb with element for sealing the internal cavity when placed in her study limb, an inflatable cuff to create a venous stop the blood in the limb, equipped with a manometer, and a device for measuring the increase limb venous stop. When determining blood flow with this plethysmograph by inflate the cuff creates a venous stop the blood in the tested limb is placed in the chamber, and the volume of air displaced from the chamber in the device for measuring the volume of gas judged the intensity of blood flow in the limb. In addition to information about the intensity of blood flow per unit volume of the investigated limb additionally carried out with the help of special equipment volume measurement this part of the limb.

Fault is the need for additional measurements with the help of special equipment volume of the investigated limb.

The task of the invention is to increase the accuracy of determination of blood flow, simplifying the measurement process and its results.

The technical result - the creation of plethysmograph capable of determining the absolute value of the intensity of the blood flow without the use of additional equipment for measuring the volume of the investigated limb.

The technical result is achieved by the fact that the composition of plethysmograph containing chamber with an internal cavity for placement of the investigated limb with element for sealing the internal cavity when placed in her study limb, an inflatable cuff to create a venous stop the blood in the limb, equipped with a manometer, and a device for measuring the increase limb venous stop, according to the invention also includes an atmospheric pressure sensor, a bellows with inlet and a movable bottom, which is mechanically linked to drive the reciprocating motion, the microcompressor, pneumatomachi, two variables pneumatocele, equipped with inlet and outlet fittings, and electronic computing device, where the device for measuring the increase fitting, a sealing element made in the form of an inflatable cuff with a pressure gauge, with the possibility of accommodation in the gap between the investigated limb and forming the inner surface of the chamber and the inlet fittings of the gauge pressure and the first pneumatocele and the output fitting of the second pneumatocele connected with the inner cavity of the camera, the microcompressor is connected with the possibility of connection through the respective pneumatomachi to the inlet of the second pneumatocele, inflatable cuff to create a venous stop and element for sealing the internal cavity of the chamber and the outlet fitting of the first pneumatocele through pneumatometer connected with the atmosphere, and the outputs of the redundant sensors and atmospheric pressure is connected to the electronic computing device.

This design provides the possibility of measuring a volume of the investigated limb and increase its volume during venous stop that is determined by the use of accurate and reliable sensors, absolute and gauge pressure with standardized electrical output signals and electronic computing device that provides signal processing sensor which adjust the camera to work with two pneumatocele.

Compared with the prototype of the proposed design has distinctive features in the set of elements, their design and arrangement.

Scheme plethysmograph shown in Fig.1.

In Fig.2 shows the change of the excess pressure in the chamber plethysmograph in the measurement volume of the investigated limb.

In Fig.3 shows the change of the excess pressure in the chamber plethysmograph in the measurement volume of the investigated part of the limb venous stop.

Plethysmograph contains the camera 1 with an internal cavity 2 for placement of the investigated limb 3 with item 4 for sealing the internal cavity when placed in her study limb, an inflatable cuff 5 to create venous stop the blood in the limb, equipped with a pressure gauge 6, and a device 7 for measuring the increase in volume of the limb venous stop the blood, which serves as the gauge pressure with standardized electrical output signal, provided with inlet 8. Additionally, the composition of plethysmograph included an atmospheric pressure sensor 9 with standardized electrical output signal, the bellows 10 to the inlet 11 and the movable domtemplate T1, T2T3two variables pneumatocele DR1 and DP2 equipped with input 15, 16 and output 17, 18 fittings, and electronic computing device 19.

The sealing element 4 is made in the form of an inflatable cuff with a pressure gauge 20, with the possibility of accommodation in the gap between the investigated limb 3 21 and forming the inner surface of the chamber 1. Input fittings 8, 11, 15 and outlet fitting 18 is connected with the internal cavity 2 of the camera 1, and microcompressor connected with the possibility of connection through pneumatometer T1the inlet of pneumatocele DP2, through pneumatometer2with the sealing element and through pneumatometer T3with an inflatable cuff to create a venous stop, and the output fitting pneumatocele DR1 through pneumatometer T4connected with the atmosphere. The outputs of the sensors 7 and 9 are connected to the electronic computing device 19, which is, for example, a personal computer. In the camera 1 plethysmograph are auxiliary elements: supports 22, 23 and the annular plate 24 attached to the walls of the chamber 1.

Work plethysmograph as follows.

The investigated limb, for example R is in the cuff 4 to seal the hand starts flowing air from the microcompressor 14. The cuff 4 is inflated and rests on the annular plate 24, thus preventing the displacement of the cuff into the cavity 2. This determines the constancy of the camera 2. When the pressure in this cuff reaches 50006000 PA, which is determined using the pressure gauge 20, and is sealed camera placed in her hand, pneumotussin T2unlock the. Then close sequentially in time pneumatomachi T4and T1. In this connection creates a pneumatic flow Luggage, which includes inductors DR1, DP2 and the internal cavity 2 of the camera 1, the portion of the volume which is occupied by the investigational arm. At constant pressure P0at the entrance to pneumatocele DP2 generated by the microcompressor, the pressure in the internal cavity of the chamber will increase exponentially (see Fig.2). The pressure P of the chamber 2 is continuously measure the gauge pressure and remember in electronic computing device. For the dimensions of the curve are the so-called time constant T [Ibragimov, I. A. and other Elements pneumatomachi. M.: Higher school, 1984, S. 63-69] running pneumatic chamber, which with a constant value of conductivity of pneumat ukai: T=V/RQ(k1+k2), (1) where R is the gas constant; Q is the absolute temperature of the gas (to be taken within the experience constant); kl and k2 - conductivity pneumatocele DR1 and DP2.

The volume of the investigated part of the hands Vp at a known value of the volume V to the internal cavity 2 camera plethysmograph calculated by the formula: Vp=V-T/a, (2) where a=RQ(k1+k2) - constant value.

The value of T when it is determined from the graph of the function as shown in Fig. 2 (RK on the graph - steady-state chamber pressure). The time required for one measurement is 25-35 C.

To increase the accuracy of measurement of the volume of the investigated part of the hand is re-measurement of this quantity as follows. Unlock pneumatometer T1and after the pressure in the chamber becomes equal to zero, which is determined by the signal of the pressure sensor 7, unlock pneumatometer T4. Include the drive 13 of the reciprocating motion, which moves the bottom 12 of the bellows 10 until it stops (Fig.1 to the left). In the cavity 2 introduced some constant additional volume of air V (V=10 cm3). Therefore, the pressure in the cavity 2 is increased byR.

With the help of sensors 7 and 9 measure the value ofP)Pa. (3) the Results of two measurements of the volume of the investigated part of the average hands and find the average value of Vpcf.

After determining Vpcfclose pneumatomachi T1and T4and some time purge chamber 1 air to avoid heating the air in it due to the heat released by the hand. Then unlock pneumatomachi T1and T4and bring the chamber pressure to atmospheric. Close pneumatometer T3. In the cuff 5 starts flowing air. When the pressure reaches values 9500 PA (the pressure venous stop) that is determined by a pressure gauge 6, pneumotussin T3unlock the. When this begins to increase the volume of the investigated part of the hands due to the inflow of blood, causing an increase in pressure in the inner cavity 2 (see Fig.3), which is continuously measured by the sensor 7, the signals of which are remembered electronic computing device.

The process of increasing the pressure in the chamber lasts 10 - 20 and has an exponential form, and the maximum increment of pressure is 400 to 700 PA. When processing this signal selects the portion of the curve from the beginning of the process until Urania pressureRL is used in the calculation of the blood flow.

If we assume that in the process of increasing the pressure, the temperature in the chamber of plethysmograph does not change, then at time t1true expression: V =RL(V-Vp)/Pa, (4)
where V - volume of blood received in the investigated part of the hands to the time t1.

The volume flow of blood Q received in the analyzed part of the hand from the beginning of venous stop until time t1can be identified by the formula:
Q=V/t1. (5)
Usually, the characteristics of blood flow using the specific volume flow rate q u [Experimental physiology /Ed. by B. L. Andrew. M.: Mir, 1974, S. 233] , i.e. the volume flow of blood that enters the volume of the investigated limb of 100 cm3. According to the results of the measurement values Vpcfand Q specified characteristic calculated by the formula:
Q u=(Q/Vpcf)100. (6)
All of the above calculations are carried out using an electronic computing device.

Described plethysmograph was created and tested in laboratory conditions.

The table shows the results of measurement of the intensity of blood flow in five patients.

Advantages of the proposed technical solutions aleutia volume of the investigated limb;
- possibility of automation of the measurements;
the absolute nature of the measurements, eliminating the need for prior calibration of the device.

The proposed plethysmograph can be implemented on the basis of standard measuring, computing and assistive devices. It may find application in medical institutions for the study of blood flow in the extremities, it can also be used for the calibration of plethysmographs implementing other relative principles of measurement of blood flow.


Claims

Plethysmograph containing chamber with an internal cavity for placement of the investigated limb with element for sealing the internal cavity when placed in her study limb, an inflatable cuff to create a venous stop the blood in the limb, equipped with a pressure gauge and a device for measuring the increase limb venous stop, characterized in that it further comprises an atmospheric pressure sensor, a bellows with inlet and a movable bottom, which is mechanically linked to drive the reciprocating motion, the microcompressor, pneumatomachi, two variables pneum eusto to measure the increase limb venous stop is made in the form of gauge pressure, equipped with inlet, the sealing element is made in the form of an inflatable cuff with a pressure gauge, with the possibility of accommodation in the gap between the investigated limb and forming the inner surface of the chamber and the inlet fittings of the gauge pressure and the first pneumatocele and the output fitting of the second pneumatocele connected with the inner cavity of the camera, the microcompressor is connected with the possibility of connection through the respective pneumatomachi to the inlet of the second pneumatocele, inflatable cuff to create a venous stop and element for sealing the internal cavity of the chamber and the outlet fitting of the first pneumatocele through pneumatometer connected with the atmosphere, moreover, the outputs of the redundant sensors and atmospheric pressure is connected to the electronic computing device.

 

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FIELD: medicine.

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1 ex, 1 tbl

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EFFECT: enhanced effectiveness of treatment.

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FIELD: medicine.

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EFFECT: wide range of functional applications.

2 tbl

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