BLOOD BLOOD PRESSUREPRESSURE

Arterial Blood Pressure Arterial Blood Pressure (BP)(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

In normal adult 120/80 mmHg.

(BP)

Factors determining BPFactors determining BP

(CO)Flow

Blood Pressure = Cardiac Output X Peripheral Resistance

(PR)Diameter

of arterioles

BP depends on:

1. Cardiac output. 2. Peripheral resistance. 3. Blood volume.

Cardiac OutputCardiac 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 ResistancePeripheral 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 VolumeStroke VolumeIs the volume of blood pumped from one ventricle of the heart with each beat

Blood PressureBlood 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 press

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

NOTENOTE !!! !!!

How is Blood Pressure How is Blood Pressure Taken?Taken?

Invasi

ve

Non-I

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Blood Pressure

Palpatory Method

Auscultatory Method

Ultrasonic MethodOscillometric Method

Tonometry

Extravascular Sensor

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 heartConvenient 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 patientPatient should be seated with

back and arms supported, feet on floor, and legs uncrossed with upper arm at heart level

3.Measure baseline BP bilaterally

Cuff applied 1 inch above crease at elbow

Locate brachial arteryPalpate radial pulseInflate cuff until pulse disappears

Types Of BP ApparatusesTypes Of BP ApparatusesMercury Type Aneroid Type

Digital Type

A- Palpatory MethodA- 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.

The blood pressure can be measured in noisy environment too

ADVANTAGES

Technique does not require much equipment

Only the systolic pressure can be measured (not DP)

DISADVANTAGES

The technique does not give accurate results for infants and hypotensive patients

B- B- Auscultatory MethodAuscultatory 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.

Auscultatory technique is simple and does not require much equipment

ADVANTAGES

DISADVANTAGESAuscultatory tecnique cannot be used in noisy

environmentThe observations differ from observer to anotherA 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

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.

Korotkoff soundKorotkoff sound

3

RECOMMENDED BLOOD PRESSURERECOMMENDED BLOOD PRESSUREMEASUREMENT TECHNIQUEMEASUREMENT TECHNIQUE

2.• The cuff must be level with heart.

• If arm circumference exceeds 33 cm,a large cuff must be used.

• Place stethoscope diaphragm overbrachia l artery.

2.2.•• The cuff must be level with heart.The cuff must be level with heart.

•• If arm circumference exceeds 33 cm,If arm circumference exceeds 33 cm,a large cuff must be used.a large cuff must be used.

•• Place stethoscope diaphragm overPlace stethoscope diaphragm overbrachia l artery.brachia l artery.

1.• The patient should

be relaxed and thearm must besupported.

• Ensure no tightclothing constrictsthe arm.

1.1.•• The patient shouldThe patient should

be relaxed and thebe relaxed and thearm must bearm must besupported.supported.

•• Ensure no tightEnsure no tightclothing constrictsclothing constrictsthe arm.the arm.

3.• The column of

mercury must bevertical .

• Infla te to occlude thepulse. Deflate at 2 to3 mm/s. Measuresystolic (first sound)and diastolic(disappearance) tonearest 2 mm Hg.

3.3.•• The column ofThe column of

mercury must bemercury must bevertical .vertical .

•• Infla te to occlude theInfla te to occlude thepulse. Deflate at 2 topulse. Deflate at 2 to3 mm/s. Measure3 mm/s. Measuresystolic (first sound)systolic (first sound)and diastolicand diastolic(disappearance) to(disappearance) tonearest 2 mm Hg.nearest 2 mm Hg.

StethoscopeStethoscope

MercuryMercurymachinemachine

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

Auscultatory GapAuscultatory 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.

Factors affecting BPFactors 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.

HypertensionHypertension

Sustained raised in BP which require medical interventions.

JNC 7 Guidelines (2003) Category SBP DBPNormal < 120 or < 80Prehypertension 120-139 or 80-89Stage 1 140-159 or 90-99Stage 2 ≥ 160 or ≥ 100

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

Treatment Treatment Treatment goal <140/85 mmHg

(130/80 mmHg in diabetic)

Lifestyle changes include :

Stop smokingLow fat dietLow salt intakeExerciseReduce wt

Drugs:

ACE inhibitorB-blockerCa channel blockerDiurtics

Postural HypotensionPostural HypotensionDrop in systolic BP>20 mmHg OR

diastolic BP>10 mmHg after standing for 3 minutes.

Causes:HypovolemiaAntipsychoticsAddison‘s diseasehypopituitarism