Measurement and assessment of blood pressure in children

Blood pressure is usually measured using a sphygmomanometer (mercury or aneroid) and a phonendoscope (stethoscope). The division value of the sphygmomanometer scale (mercury or aneroid) should be 2 mm Hg. The readings of the mercury manometer are assessed by the upper edge (meniscus) of the mercury column. Determining blood pressure using a mercury manometer is considered the "gold standard" among all methods of measuring blood pressure using other devices, since it is the most accurate and reliable.

Blood pressure should be measured no earlier than 1 hour after eating, drinking coffee, stopping physical activity, smoking, or being in the cold. The measurement procedure should be explained to the patient to avoid a defensive reaction on his part, which may cause an increase in blood pressure. During the measurement, the patient should sit, leaning against the back of a chair, with relaxed, uncrossed legs, not change position, and not talk throughout the entire blood pressure measurement procedure. It is necessary to select the cuff correctly, corresponding to the arm circumference of the patient - a child, teenager, or adult. The width of the inner (rubber) chamber of the cuff should be at least 40% of the arm circumference, the length of the rubber chamber of the cuff should cover from 80 to 100% of the arm circumference. The arm circumference is measured with a centimeter tape with an accuracy of 0.5 cm at the middle of the distance between the olecranon process and the acromial process of the scapula. The cuff is applied so that the center of the rubber chamber is located above the brachial artery on the inner surface of the arm, and the lower edge of the cuff is 2.0-2.5 cm above the elbow bend. The density of the cuff application should be such that one finger can be inserted between the cuff and the surface of the patient's arm.

Recommended cuff width for children, according to WHO

	Age	Cuff dimensions, cm
Less than 1 year		2.5
1-3 years		5-6
4-7 years		8-8.5
8-9 years old		9
10-13 years		10
14-17 years old		13

The cuff must be inflated quickly to the maximum level (30 mm Hg above the palpable SBP level). Slow inflation of the cuff disrupts venous outflow, increases pain, and blurs the sound. The cuff is released at a rate of mercury column decrease of 2 mm Hg per second, and with the appearance of Korotkov tones - 2 mm Hg for each pulse beat. If the mercury column meniscus is between two divisions of the manometer scale at the moment of appearance or disappearance of Korotkov tones, the SBP or DBP readings are estimated by the nearest upper value. If audibility is poor, the cuff must be quickly released, the stethoscope position must be checked, and the procedure must be repeated after 2-3 minutes. Knowledge of the distinctive features of the various phases of Korotkov tones allows the SBP and DBP levels to be determined most accurately. The accuracy of blood pressure determination also depends on the rate of decompression: the higher the rate, the lower the accuracy of measurement.

Characteristics of Korotkov tones by phases

Phase	Characteristics of Korotkov tones
I(K1)	The sounds are weak, tapping with gradually increasing intensity
II (KII)	The sounds are softer and longer, muffled, buzzing
III (KIII)	The sounds become clear and loud again
IV (KIV)	The sounds are soft, muffled, less distinct
V(KV)	Complete disappearance of sounds

The level of the SBP is determined by the beginning of the first phase of Korotkov sounds - by the first of a series of tones following one another, i.e. the first tone must be followed by the second. A single tone at the beginning of the phase (when the first tone is followed by silence - an auscultatory gap) is ignored.

The DBP value is determined by the beginning of the V phase of Korotkov sounds - by the silence following the last tone of the IV phase. The last tone at the end of the phase, even if it is single (when the last tone is preceded by an auscultatory gap), is always taken into account. Auscultation should be continued for 20 mm after the disappearance of the last tone, and for DBP above 90 mm Hg - for 40 mm. This is due to the fact that after an auscultatory gap, the tones may resume. Compliance with this rule will help to avoid determining a falsely elevated DBP.

The absence of phase V, i.e. when Korotkov sounds are heard until the end of the mercury column decrease ("infinite tone phenomenon"), can be observed with high cardiac output (in children; patients with thyrotoxicosis, fever, aortic insufficiency; pregnant women). In these cases, the DBP level is assessed by the beginning of phase IV - by the first of a series of successive fading Korotkov sounds.

Diagnosis of arterial hypertension in children and adolescents is carried out using special tables based on the results of population studies. Diagnosis consists of the following stages:

• determination of the growth percentile according to special tables, corresponding to the patient’s gender and age;
• calculation of average values of SBP and DBP based on three blood pressure measurements taken at intervals of 2-3 minutes;
• comparison of the patient's mean SBP and DBP values, obtained from three blood pressure measurements taken during a single visit, with the 90th and 95th percentiles of blood pressure corresponding to the patient's gender, age, and height percentile;
• comparison of the mean values of SBP and DBP recorded in a patient at three visits with an interval between visits of 10-14 days, with the 90th and 95th percentiles of blood pressure corresponding to the patient's sex, age and height percentile.

Blood pressure is considered normal when the average levels of SBP and DBP over three visits do not exceed the 90th percentile for a given age, gender, and height.

High normal blood pressure is when the mean SBP and/or DBP levels at three visits are equal to or greater than the 90th percentile but less than the 95th percentile for age, sex, and height.

Arterial hypertension - when the average levels of SBP and/or DBP at three visits are equal to or exceed the 95th percentile values for a given age, sex and height.

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