blood perssure

8/7/2019 blood perssure

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Blood pressure is the lateral pressure exerted

by the blood against the walls of the blood

vessels, especially the arteries while flowingthrough it.

It varies with the-

Strength of the heartbeat,

The elasticity of the arterial walls,

The volume and viscosity of the blood, anda person's health, age, and physical

condition.

BP = CO X PR

= SV X HR X PR

Blood pressure is always given as these two numbers, the systolic and

diastolic pressures.

What Is Normal Blood Pressure?

A blood pressure reading below 120/80 (120 over 80) mmHg is

considered normal. In general, lower is better. (Not too low)


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Systolic pressure (SP) (120 mm Hg) is the highest pressure measured

when the ventricles are contracting and exerting maximal force on the

bloodDiastolic pressure (DP) (80 mmHg) is the lowest pressure measured

when the ventricles are completely relaxed.

The pressure is due the walls of the artery constricting blood.

Pulse pressure (PP): The difference between the systolic and diastolicblood pressure.

PP= (SP-DP) mm Hg = 40 mm Hg

Mean pressure (MP): It is roughly the arithmetic mean of the diastolic

and systolic blood pressure.MP = (SP+ DP)/2= 100 mm Hg

A close approximation to the mean pressure may be obtained by adding

the diastolic pressure with one third of the pulse pressure.


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Basal blood pressure:

BP normally differs from person to person

It also varies in the same individual under different condition.

So the term used Normal range of blood pressure

When an individual is with the least possible stress Basal blood

pressure is generally considered.

it may also be regarded as the lowest pressure necessary in maintaining

blood flow sufficient for need of the body .

When a subject is in reclining state, 5-6 hours after last meal, in a

comfortably warm room, after resting for at least 30-40 minutes and with

a mind at possible ease, the basal pressure is obtained.

In adult males, the average systolic pressure is 125-130 mm of hg 15

(viz., from 110-145 mm of Hg) and

Average diastolic pressure, 70-90 mm of Hg.


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There is an exception to the above definition of high blood pressure. Ablood pressure of 130/80 mmHg or higher is considered high blood

pressure in people with diabetes and chronic kidney disease.


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Factors affecting normal BP

Emotion: increases cardiac output and peripheral resistance.

Stress:

T

he effects of stress can vary, but long-term, chronicstress appears to raise blood pressure.

Sleep: reduces BP up to 20 mm Hg.

Age: BP increases with advancing age.

Fat in the diet: saturated fats and cholesterol in foods raise blood

cholesterol, which increases the risk for heart disease.Obesity: is a contributing factor because excess body fat,especially central fat, can precipitate hypertension.

Smoking: causes peripheral vascular disease (narrowing of thevessels), as well as hardening of the arteries. These conditions can

lead to heart disease and stroke, and are contributing factors in highblood pressure.

Some drugs: may cause hypertension or make controllinghypertension more difficult.


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Measurement and recording of Blood Pressure

Arterial BP can be measured by two methods-

1.Direct method-Requires surgical procedure2.Indirect method-

-This is the standard method for measuring BP.

-It requires no surgical procedure

-Pressure can be measured only through listening sound.

-The instrument used is known as sphygmomanometer

- There are three indirect methods

a)Oscillatory method

b)Palpatory method

c)Auscultatory method

All these method commonly measure the pressure of thebrachial artery.


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Invasive Measurement

This is the only direct measurement of

blood pressure.

In order to perform this measurement,

a tube (catheter) is inserted into an

artery of interest.

A pressure transducer is connected to

the tube and the pressure is measured.Because there is risk associated with

puncturing an artery, this invasive means

of measurement is not commonly used

except in cases when it is vitally

important to quickly determine changesin blood pressure.

Most commonly, the catheter is

inserted into the radial artery (located at

the wrist).


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When blood pressure is measured, it is considered that the blood flowing

through the arteries because it has a higher pressure than the blood in the

veins.

Blood pressure is measured using two numbers. The first number, which

is higher, is taken when the heart beats during the systole phase.

The second number is taken when the heart relaxes during the diastole

phase.

Acolumn of mercury rises and falls with the beat of the heart. The heightof the column is measured in millimeters.

Auscultatory Method:

A cuff attached to a mercury manometer (sphygmomanometer) is wrapped

around the arm at the label of the heart.

A

stethoscope is placed over the brachial artery at the elbow.The cuff is rapidly inflated until the pressure in it is raised (200 mm Hg)

well above the expected systolic pressure in the brachial artery.

The artery is occluded by the cuff, and no sound is heard with the

stethoscope.

The pressure in the cuff is then lowered slowly.


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At the point at which systolic pressure in the artery just exceeds the

cuff pressure a tapping sound is heard. (The sound is due to the

occurrence of turbulence in the flow of blood through the narrowedblood vessels when the manometric pressure just coincides with the

systolic BP)

The cuff pressure at which the tapping sounds are first heard systolic

pressure.

As the cuff pressure is lowered further - the sounds become louder,

then dull and muffled.

Finally disappear (Sounds of Korotkoff.)

The lowest pressure at which the sound can still be heard is thediastolic pressure.

The blood pressure in the brachial artery in young adults in the sitting

or lying position at rest in approximately 120/80 mm Hg.


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Four most common errors in measuring BP are:

1. Using the wrong size cuff.

2. Applying the cuff incorrectly

3. Not positioning the stethoscope directly above the artery. Incorrect

placement will result in too low of a systolic and too high of a diastolic

pressure measurement.

4. Incorrect interpretation of the sounds heard.

As the pressure is released the following variation of sounds are heard:

First Phage- Sudden appearance of a clear tapping sound. This indicates

systolic pressure. It persists while the pressure falls through 15mm of Hg

Second Phage- the tap sound is replaced by murmur persisting for

another 15mm of Hg.

Third phage- the murmur is replaced by a clean loud gong sound lasting

for the next 20 mm of hg.

Fourth Phage- the loud sound suddenly becomes muffled and rapidlybegins to fade. This point indicates diastolic pressure.

Fifth Phage- absence of all sounds.


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Secondary hypertension accounts for 5% of hypertension, the high

blood pressure is secondary to (caused by) a specific abnormality in

one of the organs or systems of the body.

Causes: Secondary hypertension may be linked to-

Kidney disease,

Endocrine disorders,

The use of oral contraceptives, and

Excessive use of alcohol.

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