The stethoscope is a medical device used to listen to internal sounds of the body. It works through multiple reflections of sound waves in tubing from the chestpiece to the ears. There are acoustic and electronic types, with electronic amplifying sounds electronically. Stethoscopes vary in price from 300 to 40,000 rupees. A sphygmomanometer, also known as a blood pressure meter, measures blood pressure using an inflatable cuff and measuring unit. It detects the systolic and diastolic pressures as the cuff pressure is released and blood flow is heard through a stethoscope. Sphygmomanometers vary in price from 600 to 6000 rupees.

1. STETHOSCOPE
•The stethoscope(also known as Aala) is an acoustic
medical device for auscultation, or listening to the
internal sounds of an animal or human body
• It is also used to listen to intestines and blood flow in
arteries and veins.

2. •Construction:-A binaural stethoscope(commonly used)
consists :-
of earplugs, binaural pieces,
flexible tubing, a stem, and a chestpiece.

3. •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.

4. Specifications
Stethoscope Head Specifications
•The head of a stethoscope is the metal end that is placed on the chest to listen to the
lungs and heart. 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.

5. Type OF Stethoscope:-
•ACOUSTIC stethoscope
o Acoustic stethoscopes are familiar to most people
o operate on the transmission of sound from the
chestpiece, via air-filled hollow tubes, to the listener's ears
o Demerit:-Demerit of acoustic stethoscopes was that the
sound level is extremely low.

6. •Electronic stethoscope
oAn electronic stethoscope (or stethophone) overcomes
the low sound levels by electronically amplifying body
sounds
o The simplest and least effective method of sound
detection is achieved by placing a microphone in the
chestpiece.
o 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 ₹300 to ₹
40,000.

7. Sphygmomanometer
A sphygmomanometer, blood pressure meter, or blood
pressure gage (also referred to as a sphygmometer) is a
device used to measure blood pressure.
It is always used in conjunction with a means to determine
at what pressure blood flow is just starting, and at what
pressure it is unimpeded.

9. Construction:-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.

10. 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).

11. 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.

12. Technical Specification
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. The leak rate
should not exceed 10 mm of mercury per minute.
7 The manometer scale markings and graduations should be permanent and
clearly visible and filled with pigments.
8 The internal diameter of the manometer glass tube should be 4.1 ± 0.1 mm
and the thickness not less than 2 mm.
9 All plastic parts, if any used should not crack, flake, peel or disintegrate in
normal use.
10 The inflating rubber bag should be capable of withstanding an internal
pressure of 450 mmHg without leaking.
11 The inflating bulb should be soft and should not have any joints or ridges.
.

13. TYPES:-
Manual sphygmomanometers : It require a stethoscope
for auscultation . They are used by trained practitioners. It is
possible to obtain a basic reading through palpation, but this
only yields the systolic pressure.
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

14. •Aneroid sphygmomanometers (mechanical 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
mountedon walls or stands are less susceptible to this particular problem.
•Digital: Digital sphygmomanometers are automated, providing blood pressure
readingwithout needing someone to operate the cuff or listen to the blood flow
sounds. However digital types are less accurate. Some healthcare providers use
digital forscreening but use manual sphygmomanometers to validate readings in
some situations.
 Price:-The price of sphygmomanometer vary from ₹ 600 to ₹ 6000.