Clinical measurement of systolic and diastolic blood pressure

2021-05-29 01:10 PM

There is a slight increase in systolic blood pressure that usually occurs after the age of 60. This increase is caused by decreased elasticity or stiffness, mainly due to atherosclerosis.

It is impractical to use secondary blood pressure recordings that require an indwelling needle for daily human arterial blood pressure measurements, although this approach can be used as needed in specific studies. separate. Instead, there is clinical evidence to measure systolic and diastolic blood pressure indirectly, often using auscultation.

Method of listening to the circuit

The figure shows the method of auscultation to obtain arterial blood pressure during systolic and diastolic periods. A stethoscope is placed in the path of the artery and a blood pressure cuff is wrapped around the lower part of the arm. If the bandage continues to press firmly against the arm with a small amount of force, it is possible to squeeze the brachial artery until no pulse is heard. However, when the ice pressure is sufficiently close to the pulse pressure in the brachial artery, a pulsation is heard. This beating is called the Korotkoff thump, named after Nikolai Korotkoff, a Russian physicist described in 1905.

The Korotkoff pulsation is thought to be caused by the spurt of blood as it passes through the narrowing of the blood vessel and by the vibrating of the vessel wall. This election is caused by the turbulent flow of blood far away from the measuring tape, and this turbulent movement causes vibrations that are heard through the stethoscope.

Figure. A clinical method of measuring systolic and diastolic blood pressure

Measuring blood pressure with this method of listening, the first blood pressure obtained at the blood pressure band will be the systolic blood pressure. If the gauge pressure is higher than the systolic pressure, the brachial artery remains depressed so there is no ejection of blood into the lower arteries during the cuff. Therefore, no Korotkoff sounds are heard in the inferior arteries. But after that, the gauge pressure gradually decreased. Just as soon as the gauge pressure drops to systolic pressure (point B).

Figure. Changes in mean systolic, diastolic, and age-related blood pressure. The surrounding border is limited to the normal value only.

Diastolic blood pressure is measured by placing an intravascular catheter. When the gauge pressure drops to less than a few mm Hg, the artery is no longer constricted during diastole, which means that the underlying factors for the pulsation (the sound of blood flowing through the constricted vessel) ligation) no longer appears. So, the banging sound is completely gone. Clinicians believe that the blood pressure at which the Korotkoff beats completely disappear can be regarded as diastolic blood pressure, except in cases where the disappearance of the beats is confirmed in an unreliable way. because the thumping sound can still be heard even after the blood pressure is completely discharged.

This method of auscultation to determine systolic and diastolic blood pressure is not absolutely accurate, however, it gives a value within 10% of the measurement by direct catheter insertion.

Normal arterial blood pressure is measured by auscultation. The figure depicts the mean values ​​of systolic and diastolic blood pressure by age. Blood pressure increases with age because of age on blood pressure control mechanisms. The kidneys are the primary baseline in long-term blood pressure control, and the kidneys are well known for marked changes in function, especially after the age of 50.

There is a slight increase in systolic blood pressure that usually occurs after the age of 60. This increase is caused by decreased elasticity or stiffness, mainly due to atherosclerosis. The result is an increase in systolic blood pressure with an increase in the BP difference, as explained above.

Meaning of arterial blood pressure

Arterial blood pressure is the average of the pressure on the arteries measured per millisecond over milliseconds over a period. It is used during systole rather than diastole, so arterial blood pressure remains closer to diastolic pressure than diastolic throughout the cardiac cycle. The value of arterial blood pressure is determined by about 60% of the diastolic blood pressure and 40% of the systolic blood pressure. The figure shows that blood pressure values ​​(blue figure) at all ages are closer to diastolic blood pressure than systolic blood pressure. However, when the heart rate is too fast, the diastolic period is shortened, and the blood pressure reading is closer to the mean blood pressure value.