The rhythmic contractions of the heart muscle consist of two phases of systole and diastole.
Systole is a moment of sharp expulsion of blood into the aorta and pulmonary artery, and diastole is a period of myocardial relaxation, during which the heart cavity is filled and expanded.
At the time of the ejection of blood from the cardiac cavities, the pressure approaches values of 140-150 mm Hg. In the aortic cavity, this indicator decreases to the level of 130 mm Hg. Art. The farther the distance from the heart, the lower the blood pressure.
In the venules it is 10-20 mm, and in the veins of the lower extremities its value is lower than atmospheric.
When blood is pushed out of the heart, a pulse wave forms, which, propagating through the vascular system, gradually fades. The propagation speed of pulse fluctuations depends on the level of blood pressure and the degree of elasticity and elasticity of the walls of the vascular system.
With age, the blood pressure indicator increases, so in the period from 16 to 50 years, 110 to 130 mm Hg is considered normal. Art., and when an adult reaches 60 years, the indicator is able to rise to 140 mm Hg. Art. The cause of the deviation may be the development in the patient’s body of cardioarrhythmia. In the case of a sharp jump in the indicator, the patient may develop a hypertensive crisis.
Increased blood pressure leads to an increase in intraocular and intracranial pressure. Determining the increase in intraocular value is carried out by examining the vessels of the fundus.
Methods for measuring blood pressure
Methods have been developed for direct and indirect measurement of the CD index. A direct method is the introduction of a special catheter into the blood vessel that has a transducer and a direct determination of blood pressure.
For the first time, the direct method was used by Hales in determining CD in the horse’s arterial vessel. During further research, a pressure gauge and a float were added to the device, which made it possible to carry out continuous monitoring of blood pressure with the recording of readings.
Modern devices are equipped with sensors of mechanical stress and special electronic systems that allow recording indicators using special software on a computer.
This control method is used for scientific purposes and for conducting serious diagnostic studies in large specialized laboratories.
You can not squeeze the artery with excessive membrane, otherwise the indicators will be incorrect, and the manipulation will need to be repeated. therefore, it is important to know how to measure pressure correctly.
Indirect methodology for determining the indicator can be carried out in several ways:
The first method is based on the gradual squeezing and relaxation of the limb in the area of the artery with the simultaneous digital determination of the pulse in the wrist. Rivva-Rocci suggested using a narrow cuff having a width of 4-5 cm and a mercury manometer to determine the pressure with this method. But the use of such a narrow design leads to some overestimation of the true indicators. Later, the cuff width was increased to 12 centimeters. Determination of blood pressure is carried out by palpating the pulse. The systolic indicator is fixed at the moment of pulsation, and the diastolic indicator – at the moment of decay or acceleration of the passage of the pulsation wave.
N. S. Korotkov in 1905 proposed the use of the auscultation method to determine the upper and lower values of CD. For measurements, a special device is used – a tonometer.
The device consists of a special cuff for pumping air and a manometer having a scale marked in mmHg. A mechanical rubber bulb is used to pump air into the device.
In order to correctly determine the level of Blood pressure, you should adhere to a clearly step-by-step instruction on the rules for measuring parameters.
Measurement Blood pressure by an auscultatory method is a way to independently detect the presence of hypertension or hypotension in the body. To correctly determine the indicator, the measuring device must be placed at eye level.
Application of the oscillometric method
Oscillometric measurement technology Blood pressure has found application in automatic and semi-automatic new digital devices. Such devices are installed in intensive care boards. The use of this technique for determining blood pressure does not require constant air injection.
Fixing Blood pressure can occur at different stages of air volume reduction. Using this technique allows you to establish the exact values of arterial and venous pressure in the event of auscultatory failures and the presence of weak tones Korotkova.
The oscillometric technique of determining values is the least dependent on the elasticity and elasticity of the walls of blood vessels of the circulatory system. This advantage is especially important when determining parameters in the case of a person having atherosclerotic lesions of the vascular system.
The use of the oscillometric method allows you to determine indicators on various arteries located on the upper and lower extremities.
Oscillometry makes it possible to conduct more accurate measurements, in which the influence of the human factor is excluded.
The main advantage of the technique is resistance to external noise and the ability to work through thin tissue.
In addition, the use of this method does not require special training and special skills.
The disadvantage of oscillometry is the distortion of the measurement results when moving the hand during the procedure and the likelihood of distortion in the presence of arrhythmias in the heart.
Rules for measuring blood pressure
When measuring CDs, it is necessary to strictly observe the rules and follow the recommendations given by the manufacturer of the tonometer in the operating instructions.
The most important rules are to keep the patient in a calm state, during the procedure it is forbidden to make any movements and talk, the cuff used should be located on the arm at heart level.
To correctly measure pressure and obtain accurate data, several requirements must be met:
- Select the appropriate equipment. To carry out the procedure, you will need a high-quality stethoscope, a cuff of the right size, an aneroid barometer or an automated sphygmomanometer — an instrument that provides manual inflation.
- It is necessary to properly prepare the patient for manipulation. For this, the patient needs to relax. It is forbidden to smoke and drink alcohol half an hour before the measurement, in addition, it is forbidden to drink drinks containing caffeine in its composition. The patient needs to be planted in an upright position, to free the upper part of the hand from clothing. The arm should have solid support underneath, and the feet should be placed with the entire surface on the floor. When taking measurements it is forbidden to talk. If the patient is positioned horizontally, the arm on which the measurement is performed should be placed at the level of the heart.
- When carrying out the manipulation, you need to choose the cuff of the optimal size depending on the volume of the arm, an improper device can distort the results.
- The phonendoscope used to listen to tones should be placed on the same arm on which the procedure is performed, on the elbow bend.
- Air is pumped into the cuff simultaneously with listening to the pulse, the air pressure rises until the heard pulsations disappear.
- Air bleeding is carried out gradually through a special valve.
The value of systolic Blood pressure – the readings of the device at the first sounds of the pulse, diastolic – the values on the scale at which pulsating sounds disappear.
Verification of accuracy of indicators and method deficiencies
To clarify the data obtained, a procedure for measuring pressure on both hands should be performed. The value should not have significant differences.
Blood pressure in the morning is slightly higher than in the evening.
In some cases, the data may not be reliable due to noticeable excitement of the patient.
To obtain more accurate results, daily measurement of parameters is used.
The method used to obtain data has certain disadvantages:
- The obtained values of the arterial pressure are somewhat lower, and the values of the arterial pressure are higher compared with the indices of the invasive technique.
- In addition, when using this method, the result can be significantly affected by extraneous noise and movements of the patient’s arm.
- The application of the technique requires the correct location of the stethoscope.
- The error of determination when fulfilling all the requirements is from 7 to 10 units.
This technique for determining blood pressure parameters is not suitable for monitoring throughout the day, therefore it is not used in intensive care units.Ask a Question