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BLOOD PRESSURE. 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.
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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 H2OIn normal adult 120/80 mmHg.
Factors determining BP Blood Pressure = Cardiac Output X Peripheral Resistance • BP depends on: • 1. Cardiac output. • 2. Peripheral resistance. • 3. Blood volume.
Cardiac OutputIs 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 system-- combined resistance of all vessels -- vasodilation resistance decreases -- vasoconstriction resistance increasesStroke VolumeIs the volume of blood pumped from one ventricle of the heart with each beat
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 pressureDiastolic BP + 1/3 Pulse press Is a term used in medicine to describe an average blood pressure in an individual
How is Blood Pressure Taken? Blood Pressure 1 Palpatory Method Auscultatory Method Non-Invasive Ultrasonic Method Oscillometric Method Tonometry 2 Extravascular Sensor Invasive Intravascular Sensor
Is your patient ready? • If your patient has finished a cigarette or an alcoholic beverage within the last 15 minutes the readings will be altered. • If they haven’t sat quietly for at least 5 minutes or are talking during the procedure, the readings will be altered. • Systolic and diastolic BP's in hypertensive and normotensive patients increase with talking • And if you have placed the cuff over a shirt sleeve the readings will not be reliable
Brachial artery is the most common measurement site Close to heart Convenient measurement
1. Use appropriate size BP cuff Is the cuff you are using sized for the patient? A cuff too large can cause reading to be lower than actual and a cuff too small can cause reading to be higher than actual.
2. Position patient Patient should be seated with back and arms supported, feet on floor, and legs uncrossed with upper arm at heart level
Cuff applied 1 inch above crease at elbow Locate brachial artery Palpate radial pulse Inflate cuff until pulse disappears
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 The blood pressure can be measured in noisy environment too Technique does not require much equipment DISADVANTAGES Only the systolic pressure can be measured (not DP) 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 Auscultatory technique is simple and does not require much equipment DISADVANTAGES Auscultatory tecnique cannot be used in noisy environment The observations differ from observer to another A mechanical error might be introduced into the system e.g. mercury leakage, air leakage, obstruction in the cuff etc. The technique does not give accurate results for infants and hypotensive patients
Pulse waves that propagate through the brachial artery, generate Korotkoff sounds. There are 5 distinct phases in the Korotkoff sounds, which define SP and DP The Korotkoff sounds are ausculted with a stethoscope
Korotkoff sound • The first Korotkoff sound is the snapping sound first heard at the systolic pressure. 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 "thumping" 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 -- two mm Hg above the last sound heard.
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.
Factors affecting BP • Sex 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. • Pregnancy due to metabolism.
Hypertension Sustained raised in BP which require medical interventions. • JNC 7 Guidelines (2003) Category SBP DBP • Normal < 120 or < 80 • Prehypertension 120-139 or 80-89 • Stage 1 140-159 or 90-99 • Stage 2 ≥ 160 or ≥ 100
Causes Of Hypertension • Essential hypertension 95% • Secondary hypertension 5% • Renal • Endocrine • Pregnancy • Drugs • Coartation of aorta • Others
Treatment • Treatment goal <140/85 mmHg (130/80 mmHg 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 mmHg OR diastolic BP>10 mmHg after standing for 3 minutes. • Causes: Hypovolemia Antipsychotics Addison‘s disease hypopituitarism