Heart Rate Measurement
The walls of the arteries felt vibrations associated with the rhythmic contractions of the heart. These fluctuations are referred to as pulse.
Recording pulse curve fluctuations artery wall is made by a special device – called sphygmography sphygmograms.
On sphygmograms distinguish steep climb – anakroticheskoe knee descent – katakroticheskoe knee and downhill dicrotic rise.
The person recording the pulse of the radial artery, and in large animals – the abdominal aorta.
The pulse wave is undulation elastic walls of blood vessels. This oscillation occurs at the time of systole in the aorta when the systolic blood volume expands its walls and the consequent oscillation propagates along the walls of arteries and the pole being in their blood. Pulse fluctuations reflect hence the heart. Speed distribution closely matches the speed of propagation of oscillations in blood pressure.
In a healthy human pulse wave velocity varies from 7 to 10 m / s.
Consequently, the pulse wave is far ahead of the velocity of blood (0.5 m / s), as the pulse wave velocity in the 14-20 times higher than the maximum speed of the blood. Therefore, if the aortic wall oscillation pulse occur simultaneously with the arrival of its systolic blood volume in the peripheral arterial blood ejected by the heart at the time when the pulse wave is not far behind it causes fluctuations in the walls of arteries in the periphery. Consequently, the rhythmic contractions of the walls of blood vessels (the so-called “peripheral heart”) is not involved in the movement of blood.
Dicrotic rise occurs after the end of systole, when the blood in the aorta located closed semilunar valves, gets a boost from slamming semilunar valves and dropped them to the periphery. When this occurs the reflected shock transient increase aortic pressure fluctuations accompanied by its wall, which is expressed dicrotic rise. Thus, the dicrotic wave occurs in the aorta and extends with the same speed as the primary pulse wave.
Pulse wave velocity is directly proportional to the voltage of the arterial wall and its thickness and inversely proportional to the diameter of the artery. The stiffer the artery, the higher the speed. The arteries of muscular type it more than the elastic arteries. The speed of propagation of the pulse increases with age. Up to 26 years, it is on average 7.5 m / s and from 45 to 55 years – 8 m / s. This increased propagation velocity depends on reducing elasticity of the arteries and aorta due to changes in the age structure of the walls of blood vessels, especially arteriosclerosis. In hypertensive pulse wave velocity increased significantly.
The length of the pulse wave can be determined by multiplying the propagation velocity of the length of the wave when passing through a certain point. The duration of the wave at any point is equal to the duration of the cardiac cycle, ie. F. 0.8. If the pulse wave velocity is 7 m / s, the wavelength of 5.6 m.
Pulse has the following characteristics: 1) frequency – the number of pulse beats per minute, which is equal to heart rate; 2) speed – the duration of the pulse wave; 3) the value of the height-oscillation of the vessel wall; 4) stress – the force with which you want to squeeze the artery to the disappearance of the pulse; 5) rhythm – the duration of the time intervals between pulse waves. Pulse is also found in large veins, located near the heart.
Volume pulse
The volume of normally fluctuates slightly due to the influx of blood during systole, which is accompanied by an increase in the volume of bodies and outflow during diastole, causing a decrease in volume.
Record fluctuations in the body such as the hands, produced a special device – plethysmograph, referred to as the plethysmogram. On Plethysmogram visible pulse fluctuations in the body.
Fluctuations in the volume of associated not only with the work of Iran, but also with the respiratory movements of the chest. They dramatically increase with emotions, heating and cooling of the body, muscular work in which change the heart and breathing. Fluctuations in the volume of bodies also occur when changing vascular tone.
Since the work of the heart, breathing and vascular tone regulated by the nervous system, it is, therefore, due to fluctuations in the volume of activity of the nervous system.
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