To Study the Indirect BP Measuring Method and to Measure BP Using Sphygmomanometer and Electronic BP

8/12/2019 To Study the Indirect BP Measuring Method and to Measure BP Using Sphygmomanometer and Electronic BP

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Applied Instrumentation Lab 8EI7

Global Technical Campus, Jaipur

Experiment No. – 6

Object: - To study the indirect BP measuring method and to measureBP using sphygmomanometer and electronic BP instrument

Apparatus: - Sphygmomanometer, Electronic BP meter

Theory: - Blood pressure assessment is an integral part of clinical practice. Routinely,

a patient’s blood pressure is obtained at every physical examination, including outpatient

visits, at least daily when patients are hospitalized, and before most medical procedures.

Blood pressure measurements are obtained for a wide variety of reasons, includingscreening for hypertension, assessing a person’s suitability for a sport and determining

risk for various medical procedures. Blood pressure measurements are also obtained

routinely when following a hypertensive patient to assist with tailoring of medicationsand treatment of hypertension. Finally, blood pressure measurements are an integral part

of identifying if a patient is in potential or actual clinical deterioration.

Two methods for measuring a blood pressure exist, the direct and indirect method. Thedirect method is the criterion standard and consists of using an intra-arterial catheter to

obtain a measurement. This method, however, is not practical due to its invasiveness and

its inability to be applied to large groups of asymptomatic individuals for hypertensionscreening. Therefore, the indirect (noninvasive) method is typically used. The indirect

method involves collapsing the artery with an external cuff, providing an inexpensive and

easily reproducible way to measure blood pressure. The indirect method can be

performed using a manual cuff and sphygmomanometer or with an automatedoscillometric device. The manual method requires auscultation of the blood pressure,

whereas the automated system depends on oscillometric devices.

Blood Pressure measurement using Sphygmomanometer:-

With manual blood pressure measurements, both observer and methodological errors can

occur. Observer errors include digit preferences, inattention, overly rapid cuff deflation,and hearing deficits, while methodological errors include not accounting for beat-to-beat

variations in the pulses and sequential rather than simultaneous comparisons. Automated

oscillometric devices remove the observer errors that can occur with manual

measurements but are not without faults. The inaccuracy of the oscillometric devices has been criticized, and some concern exists that using these devices in certain populations,

such as hypotensive, hypertensive, trauma, or cardiac arrhythmia patients, can lead to

inappropriate management. For example, in one study, mean systolic and diastolic blood pressures were significantly greater using a mercury manometer than automated

oscillometric techniques. These findings have important clinical implications, as the

oscillometric techniques may falsely indicate that a patient treated for hypertension is

now normotensive and requires no further medication adjustment.

http://emedicine.medscape.com/article/241381-overview







Regardless of these inaccuracies, automated oscillometric devices are used more

frequently and appear to be sufficiently accurate for most clinical uses. Furthermore,automated devices may give more accurate readings in the setting of patients with the

syndrome of white-coat hypertension. Another key component of measuring a manual blood pressure is an understanding of the Korotkoff phases. The Korotkoff phases have been classified as 5 phases with phases I, IV, and V integral to obtaining an accurate

blood pressure measurement. Descriptions of the 5 Korotkoff phases are outlined in the

table below.

Phases Description of sound Clinical implication

Phase I Appearance of clear tapping

sounds

Correlates with systolic blood pressure

Phase II Sounds become softer andlonger

No clinical significance

Phase

III

Sounds become crisper and

louder

No clinical significance

Phase

IV

Sounds become muffled and

softer

Correlates as alternate measure of diastolic

blood pressure

Phase V Sounds disappear completely Correlates with diastolic blood pressure

The Korotkoff sounds are believed to originate from a combination of turbulent blood

flow and oscillations of the arterial wall. Of note, some believe that using the Korotkoffsounds instead of direct intra-arterial pressure typically gives lower systolic pressures,

with one study finding a 25 mmHg difference between the 2 methods in someindividuals. Furthermore, some disagreement exists as to whether Korotkoff phase IV or

V correlates more accurately with the diastolic blood pressure. Typically, phase V is

accepted as the diastolic pressure due to both the ease of identifying phase V and the

lower discrepancy between intra-arterial pressure measurements and pressures obtainedusing phase V. Phase IV, alternatively, is used to measure the diastolic pressure if a 10

mmHg or greater difference exists between the initiation of phase IV and phase V. This

may occur in cases of high cardiac output or peripheral vasodilatation, children under 13

years old, or pregnant women. Regardless of whether a manual or automated method is

used, the blood pressure measurement is a key part of clinical medicine. The following isa description of the indications, contraindications, and techniques for obtaining a blood

pressure using both manual and automated devices. To obtain a blood pressure, one canuse either a manual blood pressure cuff or an automated oscillometric cuff. When

obtaining a manual blood pressure, a stethoscope and blood pressure cuff with a

sphygmomanometer is required (see image below).

http://reference.medscape.com/calculator/cardiac-output

http://reference.medscape.com/calculator/cardiac-output





Fig. 1.1 Standard blood pressure cuff and stethoscope (Sphygmomanometer)

Any standard stethoscope can be used to hear the Korotkoff sounds while measuring the blood pressure. Although the bell of the stethoscope allows for more accurate

auscultation, the diaphragm is more routinely used because of ease of using an automated

oscillometric cuff, a stethoscope is not needed. Manual blood pressure cuffs have eithermercury or aneroid sphygmomanometers. Although mercury sphygmomanometers are

more accurate, they have become less common due to the toxic effects of mercury spills.

Therefore, most blood pressure devices now contain aneroid sphygmomanometers, andcalibrating the aneroid sphygmomanometers against a mercury sphygmomanometer

every 6 months is important. The aneroid sphygmomanometer consists of a bellow

system connected to a needle to indicate the pressure on a dial. If the readings between

the mercury and aneroid sphygmomanometers differ by more than 4 mmHg then

recalibration is required.

Procedure: - The following steps for measuring a manual arterial blood pressure

follow the recommendations of the American Heart Association:

1. Initially, before taking the blood pressure, the patient should remain seated and atrest for 5 minutes.





2. Consumption of caffeinated products such as coffee, cola, or tea should be

avoided for at least 30 minutes prior to measuring the blood pressure.Additionally, activities such as smoking and exercising 30 minutes prior to

measuring the blood pressure should also be avoided.3. Choose a standardized mercury or aneroid sphygmomanometer with an adequate

cuff size based on the patient's arm size.

4. Place the chosen cuff on either the right or left arm of the participant.

5. While obtaining the blood pressure, neither the patient nor the person obtainingthe blood pressure should talk.

6. The stethoscope should be placed lightly over the brachial artery. If the

stethoscope is pressed too firmly against the artery, it may cause turbulence and

the disappearance of sound, thus artificially reducing the diastolic pressure.

7. Inflate the cuff to a pressure of 30 mmHg above the level at which the radial pulse

is no longer palpable.

8. Aneroid sphygmomanometer at level 30 mmHg above the level at which theradial pulse is no longer palpable.

9. While slowly deflating the cuff (approximately 2-3 mmHg per heartbeat), listen

for Korotkoff phase I while watching the blood pressure gauge. Korotkoff phase I

can be identified by when the first pulse is auscultated. This sound is clear,repetitive, and tapping in nature and often coincides with the reappearance of a

palpable pulse. Record the measurement from the sphygmomanometer at which

the sounds first appear; this represents the patient’s systolic blood pressure.10. While watching the sphygmomanometer, continue to slowly deflate the cuff.

Initially, an abrupt soft, indistinct, muffling sound may be heard (Korotkoff phase

IV). After this sound, continue listening until the sounds disappear completely

(Korotkoff phase V). Record the measurement from the sphygmomanometerwhen Korotkoff phase V starts; this represents the patient’s diastolic blood

pressure. If there is a 10 mmHg or greater difference between Korotkoff phase IV

and phase V then the pressure reading at phase IV should be recorded as thediastolic blood pressure. This may occur in cases of high cardiac output or

peripheral vasodilatation, children under 13 years old, or pregnant women. After

the last Korotkoff sound is heard, continue deflating the cuff for another 10

mmHg to ensure that no further sounds are heard. Then deflate the cuff and allowthe patient to rest.

11. Wait at least 30 seconds and repeat the previous 3 steps to obtain a second blood

pressure measurement. If the measurements have greater than a 5 mmHg

difference, then readings should continue until 2 consecutive stable measurementsare obtained. An average of the 2 stable measurements should be recorded as the

patient’s blood pressure.

12. Wait another 1-2 minutes and repeat steps 4-10 to measure the blood pressure inthe patient’s opposite arm. If a measurement discrepancy exists between the 2

arms, then the arm with the highest measurement should be used.

13. When recording the blood pressure measurement, note not only the pressure but

also which arm was used, the arm position, and the cuff size used.





Blood Pressure Electronic Measurement:-

Traditionally blood pressure is measured using mercury manometer. Physicians get

adequate training in measurement of BP using the mercury manometer and stethoscope.

In the hands of trained physicians mercury manometer remains an excellent instrumentfor obtaining accurate and replicable measurement of blood pressure. However in recent

years there have been concerns about environmental hazards posed by use of mercury

and a tendency to look for alternative instruments for measuring blood pressure. The

aneroid blood pressure monitors have been used in many health care setting for the lastfew decades but remains the second choice of trained physicians. Automatic digital blood

pressure monitors are the preferred instrument for use when persons with hypertension

monitor their BP and seek medical care when it is not under control or paramedical

persons with limited training are given the responsibility of measuring blood pressure forhealth and nutrition surveys.The instrument is fully automated and monitor provides the

systolic, diastolic blood pressure and pulse rate reading. In most surveys British

Hypertension Society or European hypertension society validated brand of digital blood pressure monitors are being used. Unlike other instruments used in surveys, individual

BP monitors cannot be not tested for accuracy against the standard BP apparatus, because

the procedure is cumbersome and is considered redundant as these machines have beenvalidated by the manufacturer and certified by BHS/EHS for clinical use .

Fig 1.2 Digital Blood Pressure Monitor

Procedure:-

1. Insert the air plug into the air jack. The instrument should be on a level with the

heart of the person whose BP is to be measured.





2. Put the person’s arm through the cuff loops. Position the arm correctly – The

bottom edge of the cuff should be 1 or 2 cm above the elbow. Marker (arrow

under tube) is centered on the middle of inner arm.

3. Close the Velcro fastener when the cuff snugly encircles upper arm. Press the

START / STOP button. Note down the reading of systolic, diastolic pressure,

pulse rate.

4. Take the reading again five minutes later and note the readings and remove cuff.

5. Take the average of two BP readings is the BP of the individual person sits on a

chair. Left arm is comfortably resting on the table. The heart, the left arm and the

digital BP apparatus are in the same horizontal plane.

6. Put the person’s arm through the cuff loops. Position the arm correctly – The

bottom edge of the cuff should be 1or 2 cm above the elbow. Cuff of the BP

apparatus has been snugly wound round the upper arm.

7. Start button has been pressed and the cuff is inflating automatically.

Fig 1.3 BP Measurement using Electronic method

Result: - Thus we have studied about the Blood Pressure measuring method using

Sphygmomanometer and electronic BP instrument.

To Study the Indirect BP Measuring Method and to Measure BP Using Sphygmomanometer and Electronic BP

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