Stethoscope and BP apparatus (Sphygmomanometer)

INTRODUCTION
TO
STETHOSCOPE &
SPHYGMOMANOMETER
Dr.Sudeesh Shetty,
Assistant Professor,
Department of Roganidan and Vikriti Vijnana,
Mobile:+91-9481818631
Email: drsudeeshshetty@gmail.com
drsudeeshshetty@gmail.com 1

•The stethoscope (stethophone) is an acoustic medical
device for auscultation, or listening to the internal sounds
of an animal or human body
•Listen to intestines and blood flow in arteries and veins.
STETHOSCOPE

A French doctor named Rene -Theophile- Hyacinthe-Laennec
invented the first stethoscope in 1816.
Laennec's Stethoscope

• In the early 1850's there was a
rush of designs for a new
stethoscope that used both ears.
• This new 'Bi-aural' or 'Binaural'
instrument was felt to be the
future of auscultation.
Binaural Stethoscope/ Predeccessor to Modern Stethoscope

 Acoustic stethoscopes are familiar to most people, and
operate on the transmission of sound from the chest piece,
via air-filled hollow tubes, to the listener's ears
Acoustic stethoscopes/Modern Stethoscope

Parts:
•Ear pieces, binaural pieces, flexible tubing, a stem, and a
chestpiece.

Principle-Stethoscope works on the principle of multiple
reflection of sound.
Working-
• When a doctor or nurse places a stethoscope diaphragm on a
patient's chest, sound waves traveling through the patient's
body cause the flat surface of the diaphragm to vibrate.
• Those vibrations would travel outward, but because the
vibrating object is attached to a tube, the sound waves are
channeled in a specific direction.
• Each wave bounces, or reflects, off the inside walls of the
rubber tube, a process called multiple reflection.
• In this way, each wave, in succession, reaches the eartips, or
rubber nubs on the ends of the device, and finally the listener's
eardrums.

Specifications
Stethoscope Head Specifications
• The size of an adult stethoscope head is 45mm, while a pediatric head is
35mm.
• Some stethoscopes have single chest pieces, which mean they are
specifically made for either an adult or pediatric patient. However, some
have dual heads.
• These stethoscopes are designed with both chest pieces and can be used
for either adults or children.
• The chest piece is made from surgical stainless steel.

Tube Specifications
• The tubing varies on each model. Stethoscopes with tapered inner
bores provide a better sound transmission when listening to the heart
or lungs.
• If the stethoscope has extra-thick tubing, outside noise is reduced.
• You can choose between stethoscopes with a 21-inch single bore
flexible tubing or 19-inch two-in-one bi-lumen tubing.
• The length of the stethoscope can vary from 27 inches to 29 inches.
• It can weigh between 6 ounces and 7.6 ounces.
• Tubing can come in black, blue, green, orange, pink and burgundy
colors.

Type of Stethoscope
1.ACOUSTIC STETHOSCOPE-
• This stethoscope-operate on the transmission of sound from the
chestpiece, via air-filled hollow tubes, to the listener's ears
• Demerit:-Demerit of acoustic stethoscopes was that the sound level is
extremely low.
• Price of stethoscope:- It is vary from Rs-300 to Rs-20,000.

2.Electronic stethoscope
• An electronic stethoscope (or) overcomes the low sound levels by
electronically amplifying body sounds and may be broadcast through
loudspeakers, but in both instances the results are mediocre
• The simplest and least effective method of sound detection is achieved
by placing a microphone in the chest piece.
• can be a wireless device, can be a recording device, and can provide
noise reduction, signal enhancement, and both visual and audio output.
•Price of stethoscope:- It is vary from Rs-10,000 to Rs-50,000.

SPHYGMOMANOMETER
• A sphygmomanometer, blood pressure meter, or blood pressure gage (also referred
to as a sphygmometer) is a device used to measure blood pressure.
• The sphygmomanometer was invented by Samuel Siegfried Karl Ritter von
Basch in the year 1881.
• Scipione Riva-Rocci introduced a more easily used version in 1896.

Construction/Specifications
• A sphygmomanometer consists of an inflatable cuff, a measuring unit
(the mercury manometer, or aneroid gauge), and a mechanism for
inflation which may be a manually operated bulb and valve or a pump
operated electrically.

Working :
• There are two numbers in a blood pressure reading: systolic and
diastolic.
• When the doctor puts the cuff around your arm and pumps it up, what
he/she is doing is cutting off the blood flow with the pressure exerted by
the cuff.
• As the pressure in the cuff is released, blood starts flowing again and
the doctor can hear the flow in the stethoscope.
• The number at which blood starts flowing (120) is the measure of the
maximum output pressure of the heart (systolic reading).
• The doctor continues releasing the pressure on the cuff and listens until
there is no sound.
• That number (80) indicates the pressure in the system when the heart is
relaxed (diastolic reading).

• If the numbers are too high, it means that the heart is
having to work too hard because of restrictions in the
pipes.
• Other things that can increase the blood pressure include
deposits in the pipes and a loss of elasticity as the blood
vessels age.
• High blood pressure can cause the heart to fail (from
working too hard), or it can cause kidney failure (from
too much pressure).
For example, a typical reading might be 120/80 or 110/80
mm Hg.

1. Should be Portable mercurial type.
2. Should have ISI mark.
3. Should have ON and OFF provision for mercury reservoir.
4. Should have a measuring range from 0 to 300 mmHg.
5. Should be provided with adult arm cuffs of size medium & large and paediatric
cuff.
6. The control valve should have a knurled thumb control device.
7. The leak rate should not exceed 10 mm of mercury per minute.
8. The manometer scale markings and graduations should be permanent and clearly
visible and filled with pigments.
9. The internal diameter of the manometer glass tube should be 4.1 ± 0.1 mm and
the thickness not less than 2 mm.
10. All plastic parts, if any used should not crack, flake, peel or disintegrate in
normal use.
11. The inflating rubber bag should be capable of withstanding an internal pressure
of 450 mmHg without leaking.
12. The inflating bulb should be soft and should not have any joints or ridges.
Technical Specification

Aneroid sphygmomanometers :
• Mmechanical types with a dial are in common use; they require
regular calibration checks, unlike mercury manometers.
• Aneroid sphygmomanometers are considered safer than mercury
based, although less accurate.
• A major cause of departure from calibration is mechanical jarring.
• Aneroids mounted on walls or stands are less susceptible to this
particular problem.
Mercury sphygmomanometers :
• They are considered to be the gold standard.
• They measure blood pressure directly by observing the height of a
column of mercury; errors of calibration cannot occur
TYPES

Digital:
• Digital sphygmomanometers are automated, providing blood pressure
reading without needing someone to operate the cuff or listen to the
blood flow sounds.
• However digital types are less accurate.
• Some healthcare providers use digital for screening but use manual
sphygmomanometers to validate readings in some situations.
Price:-The price of sphygmomanometer vary from Rs-600 to
Rs-6000.

Blood pressure measurement
• Arterial blood pressure is most commonly measured via
a sphygmomanometer, which historically used the height of a column
of mercury to reflect the circulating pressure.
• Blood pressure values are generally reported in millimeters of
mercury (mmHg), though aneroid and electronic devices do not
contain mercury. For each heartbeat, blood pressure varies between
systolic and diastolic pressures.
• Systolic pressure is peak pressure in the arteries, which occurs near
the end of the cardiac cycle when the ventricles are contracting.
Diastolic pressure is minimum pressure in the arteries, which occurs
near the beginning of the cardiac cycle when the ventricles are filled
with blood.

• Systolic and diastolic arterial blood pressures are not static but undergo
natural variations from one heartbeat to another and throughout the day
(in a circadian rhythm).
• They also change in response to stress, nutritional factors, drugs,
disease, exercise, and momentarily from standing up.
• Sometimes the variations are large.
• Along with body temperature, respiratory rate, and pulse rate, blood
pressure is one of the four main vital signs routinely monitored by
medical professionals and healthcare providers.

Location of measurement
• The standard location for blood pressure measurement is the
brachial artery.
• Monitors that measure pressure at the wrist and fingers have
become popular, but it is important to realize that systolic and
diastolic pressures vary substantially in different parts of the
arterial tree with systolic pressure increasing in more distal
arteries, and diastolic pressure decreasing.

1.INVASIVE 2.NONINVASIVE
Basic techniques of blood pressure measurement:

Non-invasive
• The non-invasive auscultatory and oscillometric measurements
are simpler and quicker than invasive measurements, require less
expertise, have virtually no complications, are less unpleasant
and less painful for the patient.
• However, non-invasive methods may yield somewhat lower
accuracy and small systematic differences in numerical results.
• Non-invasive measurement methods are more commonly used
for routine examinations and monitoring.
1.Palpation/Manual /Placatory method
• A minimum systolic value can be roughly estimated
by palpation, most often used in emergency situations, but
should be used with caution
• A more accurate value of systolic blood pressure can be
obtained with a sphygmomanometer and palpating the radial
pulse

2.Auscultatory
• The auscultatory method (from the Latin word for "listening")
uses a stethoscope and a sphygmomanometer
• Listening with the stethoscope to the brachial artery at
the antecubital area of the elbow, the examiner slowly releases
the pressure in the cuff.
• When blood just starts to flow in the artery, the turbulent
flow creates a "whooshing" or pounding (first Korotkoff sound).
• The pressure at which this sound is first heard is the systolic
blood pressure.
• The cuff pressure is further released until no sound can be heard
(fifth Korotkoff sound), at the diastolic arterial pressure.
• The auscultatory method is the predominant method of clinical
measurement

• Although the auscultatory method using mercury sphygmomanometer is
regarded as the ‘gold standard’ for office blood pressure measurement,
widespread implementation of the ban in use of mercury
sphygmomanometers continues to diminish the role of this technique.
• The situation is made worse by the fact that existing aneroid manometers,
which use this technique, are less accurate and often need frequent
calibration.
• New devices known, as “hybrid” sphygmomanometers, have been
developed as replacement for mercury devices.
• Basically, these devices combine the features of both electronic and
auscultatory devices such that the mercury column is replaced by an
electronic pressure gauge, similar to oscillometric devices, but the blood
pressure is taken in the same manner as a mercury or aneroid device, by an
observer using a stethoscope and listening for the Korotkoff sounds

3. The oscillometric technique
• The oscillometric method was first demonstrated in 1876 and
involves the observation of oscillations in the sphygmomanometer
cuff pressure which are caused by the oscillations of blood flow, i.e.,
the pulse.
• The electronic version of this method is sometimes used in long-term
measurements and general practice.
• It uses a sphygmomanometer cuff, like the auscultatory method, but
with an electronic pressure sensor (transducer) to observe cuff
pressure oscillations, electronics to automatically interpret them, and
automatic inflation and deflation of the cuff.
• The pressure sensor should be calibrated periodically to maintain
accuracy.

This was first demonstrated by Marey in 1876,and it was subsequently shown that
when the oscillations of pressure in a sphygmomanometer cuff are recorded during
gradual deflation, the point of maximal oscillation corresponds to the mean intra-
arterial pressure.The oscillations begin at approximately systolic pressure and
continue below diastolic, so that systolic and diastolic pressure can only be estimated
indirectly according to some empirically derived algorithm. This method is
advantageous in that no transducer need be placed over the brachial artery, and it is
less susceptible to external noise (but not to low frequency mechanical vibration),
and that the cuff can be removed and replaced by the patient during ambulatory
monitoring, for example, to take a shower. The main disadvantage is that such
recorders do not work well during physical activity when there may be considerable
movement artifact. The oscillometric technique has been used successfully in
ambulatory blood pressure monitors and home monitors. It should be pointed out that
different brands of oscillometric recorders use different algorithms, and there is no
generic oscillometric technique. Comparisons of several different commercial models
with intra-arterial and Korotkoff sound measurements, however, have shown
generally good agreement.

4.Ultrasound techniques
Devices incorporating this technique use an ultrasound transmitter and receiver
placed over the brachial artery under a sphygmomanometer cuff. As the cuff is
deflated, the movement of the arterial wall at systolic pressure causes a Doppler
phase shift in the reflected ultrasound, and diastolic pressure is recorded as the
point at which diminution of arterial motion occurs. Another variation of this
method detects the onset of blood flow at systolic pressure, which has been found
to be of particular value for measuring pressure in infants and children. In patients
with very faint Korotkoff sounds (for example those with muscular atrophy)
placing a Doppler probe over the brachial artery may help to detect the systolic
pressure, and the same technique can be used for measuring the ankle-brachial
index, in which the systolic pressures in the brachial artery and the posterior tibial
artery are compared, to obtain an index of peripheral arterial disease.

5.The finger cuff method of Penaz
This interesting method was first developed by Penaz and works on the principle of
the “unloaded arterial wall.” Arterial pulsation in a finger is detected by a photo-
plethysmograph under a pressure cuff. The output of the plethysmograph is used to
drive a servo-loop, which rapidly changes the cuff pressure to keep the output
constant, so that the artery is held in a partially opened state. The oscillations of
pressure in the cuff are measured and have been found to resemble the intra-arterial
pressure wave in most subjects This method gives an accurate estimate of the
changes of systolic and diastolic pressure when compared to brachial artery
pressures; the cuff can be kept inflated for up to 2 hours. It is now commercially
available as the Finometer and Portapres recorders and has been validated in several
studies against intra-arterial pressures.The Portapres enables readings to be taken
over 24 hours while the subjects are ambulatory, although it is somewhat
cumbersome.

Invasive Method
• There are a variety of invasive vascular pressure monitors for
trauma, critical care, and operating room applications.
• These include single pressure, dual pressure, and multi-parameter
(i.e. pressure / temperature).
• The monitors can be used for measurement and follow-up of
arterial, central venous, pulmonary arterial, left atrial, right atrial,
femoral arterial, umbilical venous, umbilical arterial, and
intracranial pressures.

Arterial blood pressure is most accurately measured invasively through an arterial
line. Invasive arterial pressure measurement with intravascular cannulae involves
direct measurement of arterial pressure by placing a cannula needle in an artery
(usually radial, femoral, dorsalis pedis or brachial). The cannula is inserted either
via palpation or with the use of ultrasound guidance.The cannula must be
connected to a sterile, fluid-filled system, which is connected to an electronic
pressure transducer. The advantage of this system is that pressure is constantly
monitored beat-by-beat, and a waveform (a graph of pressure against time) can be
displayed. This invasive technique is regularly employed in human and
veterinary intensive care medicine, anesthesiology, and for research purposes.
Cannulation for invasive vascular pressure monitoring is infrequently associated
with complications such as thrombosis, infection, and bleeding. Patients with
invasive arterial monitoring require very close supervision, as there is a danger of
severe bleeding if the line becomes disconnected. It is generally reserved for
patients where rapid variations in arterial pressure are anticipate

Technical issues with measurement from the arm
• There are important potential sources of error with measurements from the
upper arm, which are discussed in the following sections.
Effects of posture
• There is no consensus as to whether blood pressure should be routinely
measured while seated or supine, although most guidelines recommend sitting.
• In a survey of 245 subjects of different ages, Netea et al found that systolic
pressures were the same in both positions, but there was a systematic age-
related discrepancy for diastolic pressure such that at the age of 30 the sitting
diastolic was about 10 mm Hg higher than the supine reading, whereas at the
age of 70 the difference was only 2 mm Hg.

Body position
• Blood pressure measurements are also
influenced by the position of the arm.
• As shown in, there is a progressive
increase in the pressure of about 5 to 6
mm Hg as the arm is moved down from
the horizontal to vertical position.
• These changes are exactly what would be
expected from the changes of hydrostatic
pressure.
• It is also important that the patient’s back
be supported during the measurement; if
the patient is sitting bolt upright the
diastolic pressure may be up to 6.5 mm
Hg higher than if sitting back.

Ambulatory monitors
First developed almost 40 years ago, ambulatory blood pressure monitoring is only
now beginning to find acceptance as a clinically useful technique. Recent technologic
advances have led to the introduction of monitors that are small and relatively quiet
and that can take up to 100 readings of blood pressure over 24 hours while patients go
about their normal activities. They are reasonably accurate while the patient is at rest
but less so during physical activity.

Thresholds for intervention
BP ≥ 220/120 mmHg: treat immediately
BP >180-189/110/119 mmHg: confirm over 1-2 weeks, then treat
BP 160-179/100-109 mmHg: with CVD complications: confirm
over 3-4 weeks, then treat
BP 140-159/90-99 mmHg: with CVD risk confirm over 12 weeks,
then treat.

Blood pressure measurement sources of error
Errors due to manometer
Errors due to cuff
Errors due to the observer
Errors due to the patient.

Manometers – automatic disadvantages
Inadequate choice of cuff sizes
Large cuffs are long enough but too deep
Need for the equivalent of the ‘alternative adult cuff’ only
available with the mercury manometer.

BP measurement
Three or more readings, separated by 1 minute
Discard first reading and average last two
If large difference take further readings.

BP measurement -cuffs
Cuff too small or too big
Normal cuff too small for 15% of patients
Cuff not level with the heart
Leaky rubber tubing or bladder
Faulty inflation/deflation device
Applies to mercury manometers only.

Cuff sizes
Type Size Suitability
Adult 12cm by 23cm
for smaller
arms
Alternative
cuff
12cm by 36cm
will cover 95%
arms
Large adult 15cm by 36cm
Often too wide
for ‘fat’ arms

Cuff Arm
circumference
(cm)
Bladder width
(cm)
Bladder length
(cm)
Newborn <6 3 6
Infant 6–15 5 15
Child 16–21 8 21
Small adult 22–26 10 24
Adult 27–34 13 30
Large adult 35–44 16 38
Adult thigh 45–52 20 42

6% of hypertensives can have as much as a 10 mmHg
difference between arms
If BP higher in one arm than the other, this arm must be
used from then on
Document this in records so that everyone uses the same
arm.
Which arm?

Technique
Patient seated and relaxed, not talking, legs uncrossed
Tight arm clothing removed
Correct cuff size
Arm supported with cuff horizontal with heart
Inform patient of discomfort and that several measurements will be
taken
Mercury manometer on firm and level surface at eye level
Locate brachial or radial pulse.

Technique – cont’d
Place stethoscope gently over brachial artery
Inflate mercury rapidly, 30 mmHg above occlusion of pulse
Deflate very slowly, 2 mmHg per second
Record first of regular sounds (systolic BP)
Record diastolic as disappearance of sound
Record measurements to the nearest 2 mmHg
Repeat twice more and average last two.

BP measurement – observer
Mercury column not level with the eyes
Failure to hear the Korotkoff sounds
Wrong diastolic endpoint (K4 or K5)
Subjective detection of Korotkoff sounds
Rapid cuff deflation
Single one off reading.

Stethoscope
Good quality
Short tubing
Well fitting ear pieces (cleaned regularly)
Place gently over the brachial artery
Avoid touching the cuff and tubing.

Posture
Routine - seated
Standing in patients with symptoms or diabetic (diabetic
nephropathy) and the elderly
Supine position unnecessary, inconvenient and cuff position often
below the heart.

BP measurement – patient
Anxiety and unfamiliarity
Animated discussion about the latest news
Ambient temperature
Full bladder!
Postural hypotension
Difference between arms.

Patient
Consent is taken as read when patient rolls up sleeve
Explain the procedure, that it may be a little uncomfortable and that
several readings will be taken
Seated, relaxed, not speaking
Tight arm clothing removed
Arm supported (not hyper extended)with cuff level with the heart.

Explanation to the patient
Tell the patient their blood pressure reading
Write BP down – use co-operation cards
Give relevant leaflets/booklets on life style issues (not too many at a
time)
Reassure patient that this is a risk factor not a disease (unless left
untreated)
Do not lose to follow-up.

‘White coat’ hypertension
Effective method of diagnosing a rise in blood pressure
associated with having blood pressure measured
Maybe from anxiety
10-20% of subjects labelled ‘hypertensive’ may have
‘white coat’ effect.

THANK YOU

Stethoscope and BP apparatus (Sphygmomanometer)

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