Arterial Blood Pressure

Definition.Factor affecting blood pressure .Causes .Classification .Type of blood pressure apparatuses .How to measure .Treatment .

Arterial Blood Pressure (BP)Is a measure of the force that the circulating blood exerts against the arterial wall

OR

The pressure force generated by the pumping action of the heart on the wall of aorta & arterial blood vessels per unit area.

It tells us how hard the heart is working.

Too high means the heart is working extra hard and this could be very dangerous!

Blood pressure almost always is measured in millimeters of mercury (mmHg).

Occasionally pressure is measured in centimeters of water ( cm H2O)

1 mmHg = 1.36 cm H2O

Factors affecting BPSex M > F due to hormones/ equal at menopause. Age Elderly > children due to atherosclerosis. Emotions due to secretion of adrenaline & noradrenaline. Exercise due to venous return.Hormones (e.g. Adrenaline, noradrenaline, thyroid H). Gravity Lower limbs > upper limbs.Race Orientals > Westerns ? dietry factors, or weather. Sleep due to venous return.

Factors determining BPBlood Pressure = Cardiac Output X Peripheral Resistance BP depends on: 1. Cardiac output. 2. Peripheral resistance. 3. Blood volume.

Cardiac Output Is the volume of blood being pumped by the heart, in particular by a Left or Right ventricle in the Time interval of one minuteCardiac Output (Q) = SV HRPeripheral ResistanceThe sum of resistance to flow that must be overcome to push blood through the circulatory systemStroke VolumeIs the volume of blood pumped from one ventricle of the heart with each beat

Causes Of HypertensionEssential hypertension 95%Secondary hypertension 5%RenalEndocrinePregnancyDrugsCoartation of aortaOthers

Blood Pressure

Pulse pressure Systolic BP Diastolic BP

The most important determinant of pulse pressure is STROKE VOLUME.

Mean arterial pressure Diastolic BP + 1/3 Pulse pressure

Is a term used in medicine to describe an average blood pressure in an individual

NOTE !!!

HypertensionSustained raised in BP which require medical interventions.

Classification of blood pressure for adultsCategorySystolic mmHgDiastolic mmHgHypotension< 90< 60Normal90 12060 80Prehypertension121 13981 89Stage 1 Hypertension140 15990 99Stage 2 Hypertension 160 100

How is Blood Pressure Taken?

Types Of BP ApparatusesMercury TypeAneroid Type Digital Type

A- Palpatory MethodFeel the radial pulse.An occlusive cuff is placed on arm and inflated above the level at which the pulse become impalpable.Gradually deflate it.The level at which the pulse become palpable again is taken as systolic pressure.

B- Auscultatory MethodApply the cuff one inch above the elbowPalpate the brachial arteryPlace the stethoscope lightly over itInflate the cuff above the systolic level determined by the palpatory methodLower the pressure in the cuff The level at which Korotkoff sound are heard is the Systolic pressure.The level at which sound disappear is diastolic pressure.

ADVANTAGESDISADVANTAGES1- Auscultatory tecnique cannot be used in noisy environment2- The observations differ from observer to another3- A mechanical error might be introduced into the system e.g. mercury leakage, air leakage, obstruction in the cuff etc.4- The technique does not give accurate results for infants and hypotensive patients

The first Korotkoff sound is Clear tapping, repetitive sounds for at least two consecutive beats is considered the systolic pressure.The second sounds are the murmurs heard for most of the area between the systolic and diastolic pressures.The third = A loud, crisp tapping sound.The fourth sound, at pressures within 10 mmHg above the diastolic blood pressure, were described as muffling" and "muting".The fifth Korotkoff sound is silence as the cuff pressure drops below the diastolic blood pressure. The disappearance of sound is considered diastolic blood pressure .

Korotkoff sound

Common problem in BP measurementWrong cuff sizeExcess pressure of stethoscopePatient arm at the wrong levelWhite coat effectAuscultatory Gap (silent gap)

Auscultatory GapIn some hypertensive patients the Krotokoff sound disappear for some time between systolic and diastolic pressure.So there is a risk of either recording a low systolic or high diastolic .Avoid it by using palpatory method before the Auscultatory method.

Treatment Treatment goal

Postural HypotensionDrop in systolic BP>20 mmHg OR diastolic BP>10 mmHg after standing for 3 minutes.Causes:HypovolemiaAntipsychoticsAddisons diseasehypopituitarism

Apply Your KnowledgeNormal Blood Pressure in Adults (18 or older) is ??What can cause sounds to be heard down to zero mmHg??A cuff with a bladder too small for the patients arm will result in ??If the cuff is applied too loosely, the pressure reading will be ?? How you can avoid incorrectly assessing the systolic blood pressure due to the auscultatory gap??

Thank you

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