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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 (mm. Hg). Occasionally pressure is measured in centimeters of water ( cm H O) 2 1 mm. Hg = 1. 36 cm H 2 O
Factors affecting BP Sex M > F …due to hormones/ equal at menopause. Ø Age Elderly > children …due to atherosclerosis. Ø Emotions due to secretion of adrenaline & Ø noradrenaline. Exercise due to venous return. Ø Hormones … (e. g. Adrenaline, noradrenaline, Ø thyroid H). Ø Gravity Lower limbs > upper limbs. Ø Race Orientals > Westerns … ? dietry factors, or weather. Ø Sleep due to venous return.
Factors determining BP Blood Pressure = Cardiac Output X Peripheral Resistance (BP) (CO) Flow BP depends on: 1. Cardiac output. 2. Peripheral resistance. 3. Blood volume. (PR) Diameter of arterioles
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 minute Cardiac Output (Q) = SV × HR Peripheral Resistance The sum of resistance to flow that must be overcome to push blood through the circulatory system Stroke Volume Is the volume of blood pumped from one ventricle of the heart with each beat
Causes Of Hypertension Essential hypertension 95% Secondary hypertension 5% ØRenal ØEndocrine ØPregnancy ØDrugs ØCoartation of aorta ØOthers
Blood Pressure Systolic Blood Pressure Is the measured pressure placed on the blood vessels while the heart is contracting. Diastolic Blood Pressure Is the measured pressure placed on the blood vessels while the heart is at rest. (not contracting)
NOTE !!! Pulse pressure Systolic BP – Diastolic BP The most important determinant of pulse pressure is STROKE VOLUME. Mean arterial pressure Diastolic BP + 1/3 Pulse Is a term used in medicine to describe an average blood pressure in an individual
Hypertension Sustained raised in BP which require medical interventions. Classification of blood pressure for adults Category Systolic mm. Hg Diastolic mm. Hg Hypotension < 90 < 60 Normal 90 – 120 60 – 80 Prehypertension 121 – 139 81 – 89 Stage 1 Hypertension 140 – 159 90 – 99 Stage 2 Hypertension ≥ 160 ≥ 100
How is Blood Pressure Taken? Non-Invasive Blood Pressure Palpatory Method Auscultatory Method Ultrasonic Method Oscillometric Method Invasive Tonometry Extravascular Sensor Intravascular Sensor
Types Of BP Apparatuses Mercury Type Aneroid Type Digital Type
A- Palpatory Method Feel 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.
ADVANTAGES 1 - The blood pressure can be measured in noisy environment too 2 - Technique does not require much equipment DISADVANTAGES 1 - Only the systolic pressure can be measured (not DP) 2 - The technique does not give accurate results for infants and hypotensive patients
B- Auscultatory Method Apply the cuff one inch above the elbow Palpate the brachial artery Place the stethoscope lightly over it Inflate the cuff above the systolic level determined by the palpatory method Lower 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.
ADVANTAGES 1 - Auscultatory technique is simple and does not require much equipment DISADVANTAGES 1 - Auscultatory tecnique cannot be used in noisy environment 2 - The observations differ from observer to another 3 - 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
Korotkoff sound 1. 2. 3. 4. 5. 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 mm. Hg 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.
Common problem in BP measurement Wrong cuff size Excess pressure of stethoscope Patient arm at the wrong level White coat effect Auscultatory Gap (silent gap)
Auscultatory Gap In 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 goal <140/85 mm. Hg (130/80 mm. Hg in diabetic) Lifestyle changes include : Stop smoking Low fat diet Low salt intake Exercise Reduce wt Drugs: ACE inhibitor B-blocker Ca channel blocker Diurtics
Postural Hypotension Drop in systolic BP>20 mm. Hg OR diastolic BP>10 mm. Hg after standing for 3 minutes. Causes: Hypovolemia Antipsychotics Addison‘s disease hypopituitarism
Apply Your Knowledge Normal Blood Pressure in Adults (18 or older) is ? ? What can cause sounds to be heard down to zero mm. Hg? ? 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? ?