Exercise 13. Biophysical basis of the rheography. Determination of temporal and amplitude rheographic parameters, characterising the functioning of the heart and of the pulsatile blood influx.

396. Which parameters of the hemodynamics can be studied with rheographic equipment?

a) the sounds generated by the motion of blood in the studied tissue;

b) the pressure pulses caused by blood the examined blood vessels;

c) the blood filling of tissues in the examined areas.

c) the blood filling of tissues in the examined areas.

397. What quantity is directly measured by the rheographic equipment?

a) the cyclic variation of electric resistance, which is inversely proportional to the blood volume in a given area of the body;

b) the variation of electric resistance for given organ for one cardiac cycle, which is proportional to the frequency of the applied electric field;

c) the variation of the electric resistance of given organ, which depends on the area covered by the applied electrodes.

a) the cyclic variation of electric resistance, which is inversely proportional to the blood volume in a given area of the body;

398. What type of electrical impedance (resistance or reactance) is measured with the rheographic equipment?

a) capacitive reactance, because it changes with the change of blood volume;

b) (active) resistance, because it is inversely proportional to the blood filling of a given organ;

c) reactive impedance, because it changes with the electrolyte content of the blood.

b) (active) resistance, because it is inversely proportional to the blood filling of a given organ;

399. What is the frequency of the electric current used in rheography?

a) high-frequency current, because it flows in equal amounts through cells and extracellular fluids;

b) mid-frequency current, because it flows preferentially through the large blood vessels;

c) low-frequency current, because it flows mostly through the extracellular fluids.

b) mid-frequency current, because it flows preferentially through the large blood vessels;

400. What causes the cyclic (pulsed) character of the rheographic recordings?

a) it follows from the periodic variation of the measured resistance (the periodic change of the amount of blood) during cardiac cycles;

b) it follows the periodic variation of the measured resistance caused by the propagation of pulse waves;

c) it is caused by the blood retention during the systolic cardiac cycle, which increases the capacitive properties of the organ, and the respective decrease during the diastole.

a) it follows from the periodic variation of the measured resistance (the periodic change of the amount of blood) during cardiac cycles;

401. Which type of tissue is characterised by the least value of specific impedance?

a) blood;

b) bones;

c) adipose tissue.

a) blood;

402. Anacrotic part of the rheographic curve, caused by:

a) the inflow of blood into the examined area, during the systole;

b) the speed matching of blood and the pulse wave in the examined area;

c) the closing of the aortic valve.

a) the inflow of blood into the examined area, during the systole;

• anacrotic part

  • initial rise in the graph during systole

  • due to inflow of blood into the examined area as heart contracts

403. What is rheoencephalography?

a) rheography of the brain;

b) rheography of the heart;

c) geography of the extremities.

a) rheography of the brain;

404. How is skull bone resistance bypassed during rheographic examination of the brain?

a) brain rheography is impossible;

b) through skull trepanation and application of electric current through the hole;

c) skull bones have low resistance for the midrange frequencies used in rheography.

c) skull bones have low resistance for the midrange frequencies used in rheography.

405. What type of current is used in rheography?

a) alternating current with frequency range: 30,000 Hz -100,000 Hz;

b) direct current with magnitude: 3 μA- 5 μA;

c) low frequency current with low power.

a) alternating current with frequency range: 30,000 Hz -100,000 Hz;

406. Rheography is non-invasive method for investigation of the dynamics of pulsed blood-filling of tissues through the graphical recording of:

a) electrical resistance;

b) electrical bio-potentials;

c) cardiac sounds.

a) electrical resistance;

407. Choose the correct statement:

a) when blood volume, in the investigated area, increases the specific resistance decreases;

b) when blood volume, in the investigated area, increases the specific resistance also increases;

c) when blood volume, in the investigated area, increases the specific resistance remains the same.

a) when blood volume, in the investigated area, increases the specific resistance decreases;

• blood is conductive medium

• more blood, more electrical conductivity

408. Which of the following curves is a “volume rheogram”?

a) first curve;

b) second curve;

c) third curve.

b) second curve;

409. Decreased blood volume in vessels during the diastole leads to:

a) increase of the electrical resistance in that area;

b) decrease of the electrical resistance in the area;

c) exponential change of the resistance in that area.

a) increase of the electrical resistance in that area;

410. Rheography uses the following electric current:

a) sawtooth alternating current with frequency: 300 kHz to 10 MHz;

b) sinusoidal alternating current with frequency: 30 kHz to 100 kHz;

c) pulsed electric current with varying frequency according to the organ or tissue under investigation.

b) sinusoidal alternating current with frequency: 30 kHz to 100 kHz;

411. As the blood volume in certain tissue decreases, the resistance:

a) decreases;

b) increases;

c) remains the same.

b) increases;

412. The rising part of the rheographic curve is called:

a) anacrota;

b) catacrota;

c) incisura

a) anacrota;

413. The declining part of the rheographic curve is called:

a) anacrota

b) catacrota

c) incisura

b) catacrota

414. Which of the following factors has an effect on the steepness of the anacrotic part of the rheogram?

a) cardiac stroke volume;

b) total blood volume;

c) the heart rate.

a) cardiac stroke volume;

415. What is the physiological meaning of the part of the rheogram called incisura (dicrotic notch)?

a) the beginning of the cardiac contraction cycle;

b) the end of the systolic period;

c) the moment where the outflow overcomes the inflow of blood, in a given tissue.

b) the end of the systolic period;

416. the part of the rheogram showing an increase of the blood volume in the beginning of the diastole is called:

a) anacrota;

b) catacrota;

c) dicrotic wave.

c) dicrotic wave.

417. What causes the appearance of the dicrotic wave?

a) non-linear elastic changes of the aortic arc;

b) the appearance of extra-systolic activity and parallel increase of the heart rate;

c) secondary increases of blood inflow in the aortic region, as a result of its reflection off the closed aortic valve at the end of the systole.

c) secondary increases of blood inflow in the aortic region, as a result of its reflection off the closed aortic valve at the end of the systole.

• systole- contraction, heart pumps blood into circulation

• diastole- relaxation, heart chambers fill with blood

418. Which of the following factors determines the different number of waves, appearing after the incisura (dicrotic notch) of the rheographic curve?

a) the cardiac contraction during the systole;

b) the wobbling of the heart wall during the closure of the aortic valve;

c) the condition of the vascular system.

c) the condition of the vascular system.

• incisura (dicrotic notch)

  • notch seen on descending limb of arterial pulse wave on rheographic curve

    • caused by closure of aortic valve

• additional waves after incisura influenced by compliance and elasticity of arterial system

1. Define and describe the rheographic method.

 Definition:  A method used to study the filling of a part of the body with blood by graphically recording the fluctuations in the resistance of that part of the body. It is used in physiology and medicine.

Describe the Rheographic method

The method of sending alternating current through living tissue permits the recording of changes in electrical impedance during pulsations. Arterial pulsations induce fluctuations in the total amount of blood, which is an electrolytic solution in a given tissue volume.

1. A fully automatic apparatus for measuring systolic and diastolic BP has been developed using the ordinary cuff and the principle of rheographic detection of an arterial pulse

2. Change in impedance at 2 points under occluding cuff form basis of detection of the diastolic pressure

3. In this method, a set of 3 electrodes are placed in contact w the skin

4. A good contact is essential to reduce skin electrode contact impedance

5. Electrode B which acts as a common electrode is positioned slightly distanced the midline of the cuff

2. Sketch the characteristic form of volume rheogram. Explain the meaning of the wave features: anacrota, catacrota, incisura (dicrotic notch) and their relation to the blood flow in the cardiovascular system.