SU552960A1 - Reoplethysmograph - Google Patents

Description

one

This invention relates to medical technology, in particular to diagnostic devices.

A reoplethysmograph, comprising a high frequency generator, electrodes, an impedance-voltage converter, a calibrator, a high-frequency amplifier, and a power source, is known.

However, such a reoplethysmograph does not provide measurement of volumetric hemodynamic parameters with high accuracy and the possibility of calibrating the reoplethysmograph during the recording process.

In order to ensure the measurement of volumetric hemodynamic parameters with high accuracy, the calibrator is made in the form of a series-connected generator and controlled resistance, which is connected to the input of the impedance converter and to the output of the high-frequency generator. In addition, in order to calibrate the reoplethysmograph in the process of recording with a two- and four-electrode inclusion of a biological object, the control unit

resistance is connected to the summing input of the high frequency amplifier.

FIG. 1 shows a block diagram of a reoplethysmograph; in fig. 2 is an example of an approximation of a rheogram in determining the amount of cardiac output.

The rheoplethysmograph contains a high-frequency generator 1, electrodes 2, an impedance-voltage converter 3, a calibrator made in the form of series-connected generator 4 and a controlled resistance 5, which is connected to the input of the impedance-voltage converter 3 and to the high frequency generator 1, high frequency amplifier 6, detector 7 and power supply 8.

The device works as follows

The voltage from the high frequency generator 1 is fed to the impedance-voltage converter 3,

A biological object or controlled resistance 5, equivalent to a biological area, is connected to the converter 3 through current and potential electrodes 2.

Controlled resistance 5 receives voltage from generator 4 with a given amplitude and a form of a calibrating voltage, for example, a sinusoidal voltage. A high-frequency signal, the value of which is proportional to the interelectrode impedance of a biological object, modulated by pulse changes or equal to the value of the equivalent controlled resistance modulated by sinusoidal changes, is fed to the high-frequency amplifier 6. After amplification, the high-frequency signal is fed to the detector 7, where the constant component is measured, measured as the magnitude of the interelectrode impedance and the envelope of the pulse oscillations - AH - reopletismogram. The rheogram is then fed to a low frequency amplifier and a differentiating amplifier to record its first derivative, and a plethysmogram to a DC amplifier with compensation of the recording level (not shown in the drawing).

When the controlled resistance varies sinusoidally by an amount (tlMotkc OD cm with a generator frequency of 4f 1.59 Hz, a sinusoidal signal should be recorded on the recorder (rheogram channel) (for example, on a scale of 20 mm by 0.1 ohm).

The first derivative or rate of change of the signal is

A2 (t) anf A2 -COS2nf.t

Maximum value of the amplitude of the differentiated signal

(dt) a (; fl2, (t) a, .. will be equal to

 a 3.144.59 0.1-10m / s

At the output of the differentiated rheogram, a cone-shaped signal should be recorded (for example, in a scale of 20 mm at 1 Ω / s).

After calibration of the recording scale, the reo plethysmograph switches to its working position for registration from the biological

object. When a calibration signal is applied during recording from the patient, the calibration signal is fed to the summing input of the high-frequency amplifier 6, and the calibration signals are superimposed on the rheogram and its first derivative.

To determine the amount of cardiac output, it is necessary to apply electrodes and measure the distance between them Z (cm). On the measuring device it is necessary to count the value of the interelectrode impedance Z (Ohm). Next, it is required to make a recording and, based on the results of the registration, determine the amplitude value Ad Ω / s of the first derivative of the rheogram and the time of the expulsion T (s) of blood from the heart.

After determining the required values, a calculation is made of the amount of cardiac output in millimeters, the determination of the heart rate and the minute volume of blood circulation in liters per 1 minute.

Claims (2)

1. A rheoplethismograph containing a high-frequency generator, electrodes, an impedance-voltage converter, a calibrator, a high-frequency amplifier, a power source, characterized in that, in order to ensure the measurement of volumetric hemodynamic parameters with high accuracy, the calibrator is designed as a series-connected generator and a control impedance which is connected to the input of the impedance-voltage converter and to the output of the high-frequency generator. 2. A reoplethismograph according to claim 1, which is based on the fact that, in order to calibrate the reoplethyscograph during recording with a two- and four-electrode switching on of a biological object, a controllable resistance unit is connected to a summing input of a high-frequency amplifier.