The document discusses different types of pressure and methods used to measure them in the human body. It defines pressure and its units, and describes typical pressures in the body. Methods covered include measuring arterial, central venous, intraocular, and intracranial pressures. Devices discussed include sphygmomanometers, transducers, manometers, tonometers, and ICP monitoring catheters and bolts. Key concepts explained are Pascal's law applications, osmosis, and atmospheric and hydrostatic pressures.

2. Presented by
Sujata sahu
Msc Tutor

3. Introduction
We use pressure in different contexts

4. Definition
Pressure is the force on a
unit surface area
If the force F is acting a
surface of area A, the
pressure is given by
P=F/A
The pressure exerted by
fluids is called fluid pressure

5. Unit of pressure
 SI unit of pressure is pascal (“Pa”)
 The traditional unit for pressure in
medical community is “mmHg” which
correspond to pressure at the bottom of a
column of mercury “Hg” of certain
height “h”
 The pressure of column of liquid can be
calculated as P= hdg
Where d=density of liquid
g=acceleration due to gravity
h= height of liquid column

6. Typical pressure in normal human body

7. Hydrostatic pressure
 A very important property
of all fluids.
 When pressure is applied
on a confined fluid, it is
transmitted uniformly
throughout its volume
 “Any change in pressure
applied at any point in an
enclosed fluid at rest is
transmitted
undiminished &
uniformly to all its
parts.” (Pascal’s law)

8.  It consists of 2 hollow cylinders, one large & one small that
are connected & filled with a fluid as oil.
 Each cylidner has a piston that fits closely at the top.
 In small cylinder a handle is attached to the piston
Hydraulic Jack

9.  When a force is applied to this handle ,the force is
transmitted throughout the oil to large piston
 A check valve prevents the fluid from flowing back when
handle is raised a 2nd time.
 The force is sufficient to raise a heavy object supported on
the large piston
Hydraulic Jack

11. • The dentist’s chair work on
the hydraulic jack principle.
The seat of the chair is
placed over the large piston
& smaller piston is operated
by a foot pedal.
• Heavy lids of some
sterilizers are lifted by
utilizing the same principle .
Application of Pascal’s law

12. Application of Pascal’s law
• Ordinary bed are having many uneven pressure points.
 The heavier part of body press against the mattress, &
the mattress in turn presses upward more firmly against
these parts of the body .
 The ch. ill pt develop ulcer at these uneven points of
pressure

13. A water/air mattress is ideal for patient
• Enclosed fluids provides equal pressure on all parts of
the body.
• Both wt of patient & the area that he covers influence
the pressure of the fluid within the mattress.
• Since the pressure is exerted against the surface of an
enclosed fluid , the pressure is transmitted equally
through out the fluid & therefore equally on the surface
of patient’s body.
Application of Pascal’s law

14. CONT…
• Nursing depart use alternating pressure mattress for
the prevention of decubitus ulcers.
• Alternate rows of pockets are emptied & filled at short
interval by an electrical driven air pump.
• Cells are inflated & deflated every 3 min, pressure
against pt are changed constantly.
• Encourage local blood circulation & prevent ulcer

15. Cont…
• Amniotic fluid sac enclosing
the fetus in ut is filled with
amniotic fluid.
• It is confined fluid & serves
as protection to the fetus .
• Any pressure exerted the
abdominal wall will be
transmitted to the amniotic
fluid & to all surfaces of fetus.

16. Cont…
• There is possibility that
continued unequal pressure
may produce fetal
deformity.
• For this reason pt is
cautioned against wearing
tight clothing/garments
during pregnancy.

17. Cont…
 LP or spinal fluid flow test to locate the
blockage of in flow of CSF is also based on this
principles.
 In spygmomanometer, the mercury manometer
operates on the Pascal’s law.
 Medicine droppers & rubber bulp syringes
enclose a fluid also work on the principle of
Pascal’s law.

18. Osmosis Pressure

19. Osmosis
 Normal osmosis
 Reverse pressure

20. Osmotic pressure of a solution is proportional to the
concentration of the solute particle that can’t cross the
membrane.

21. Osmosis In Animal
Cell
 Any solution in which a cell,e.g-a
red cell maintains its normal
shape & volume is an isotonic
solution
 In hypotonic solution the cell will
swells
 In hypertonic solution the cell will
shrink

22. Application of osmotic pressure
 Blood albumin helps to maintain the colloidal pressure of
blood. If a patient loses blood albumin which may happen
in nephrosis , the colloidal osmotic pressure will drops &
fluid remains in the tissues. This results in edema .
 Sometimes infusion of a hypertonic solution is useful to
treat patient who have cerebral edema. It relives such fluid
overload by causing osmosis of water from interstitial fluid
in to blood
 hypotonic solution can be used by iv/oral,to treat
dehydration . The water in hypotonic solution moves from
blood in to interstitial fluid & then in to the body cells to
rehydrate them.

23. Atmospheric pressure
 The air around you has weight, and it
presses against everything it touches.
That pressure is called atmospheric
pressure, or air pressure.
 It is the force exerted on a surface by
the air above it as gravity pulls it to
Earth.
.

24. Measuring the atmospheric pressure
 Atmospheric pressure is commonly
measured with a barometer.
 Barometer is made up glass tube closed
at one end & it is filled up mercury &
inverted in to a bowl of mercury
 When the atmospheric pressure
increases, the level of mercury column
in tube rises, when pressure decreases
the level of mercury falls
 a column of mercury in a glass tube rises
or falls as the weight of the atmosphere
changes.

25. Toricelli experiment
 Torricelli's experiment was
invented in Pisa in 1643 by the
Italian scientist Evangelista
Torricelli (1608-1647).
 The purpose of his
experiment is to prove that
the source of vacuum comes
from atmospheric pressure.

26.  He took a long glass tube open at
one end & filled it with mercury
 He closed the open end of the tube
with his finger & inverted it in a
vessel containing mercury.
 When he removed his finger , he
observed that level of mercury
dropped to certain height (76 cm
)leaving the space at the top.
Toricelli experiment

27.  Space at top of mercury is
vacuum
 Toricelli reasoned that
atmosphere pressed downward
on the surface of mercury in
the container & supported
mercury in the glass tube
 In other words, the rise of
mercury is due to the
atmosphere pressing down on
the mercury in the open
container
Toricelli experiment

29. Application of atmospheric pressure
 It is employed during surgical operation
for the removal of blood &
serosanguineous fluids from the region of
human body being operated.
 Many kinds of aspirators in hospital words
work on the application of controlled
suction.
 Water-sealed drainage used after thoracic
operation work on controlled suction &
gravity.

30.  Water-sealed drainage used after thoracic operation
work on controlled suction & gravity.
Application of atmospheric pressure

31. Cont…

32. MEASUREMENT
OF
PRESSURE
IN THE BODY

33. Measuring arterial pressure
 Arterial pressure is measured by BP cuff on upper arm
 Systolic & diastolic pressure represent the pressure
within brachial artery
 This pressure is slightly different than the pressure
found in aorta .
 The aortic pressure pulse travels down the aorta & into
distributing arteries.
 So there are characteristics changes in the systolic
pressure , diastolic pressure & in mean pressure

34. Measuring arterial pressure
 The systolic pressure rises & the diastolic pressure
falls,
 Therefore the pulse pressure increases, as the pulse
pressure travels away from the aorta.
 As the Arterial BP also can be measured by the placing
an intra-arterial catheter and directly attaching it to a
monitor through a transducer

35. Measuring central venous pressure
 CVP can be measured by either manometer or
electronically transducer.
 In either case CVP must be “zeroed” at the level of right
atrium
 The iv pressure are measured to the atmospheric pressure
at the middle of Rt atrium.
 This usually taken to the level of 4th intercostal space in
the mid-axillary lines while patient is in supine position
because the middle of Rt atrium is present in this level .

36. Measuring central venous pressure
Using Manometer
 A 3 way tap is used to connect
the manometer to an intravenous
drip set on one side, via
extension filled with fluid &
other side connect to patient.
 There should be no air bubbles
in the tube
 There should be no block in the
CVP catheter tube

37. Using manometer
 The 3 way tap is then turned , so that
it is open to the fluid bag &
manometer but closed to the patient,
allowing the manometer column to fill
with fluid.
 Once the manometer has filled
adequately
 The 3 way tap is turned so that it open
to patient & manometer but closed to
fluid bag.
 The fluid level within the manometer
column will fall to the level of CVP

38. Using manometer
 The value can be read on manometer
scale which is marked in cm.
 There fore the value for the CVP is
cm of water (cm H2O).
 The fluid level will continue to rise &
fall slightly with respiration .
 The average reading should be
recorded.

39. Using manometer
 The value can be read on manometer
scale which is marked in cm
 There fore the value for the CVP is
cm of water (cm H2O.
 The fluid level will continue to rise &
fall slightly with respiration
 The average reading should be
recorded

40. Using transducer
 The transducer is fixed at the level of right atrium &
connected to patient’s CVP catheter , via fluid filled
extension tubing.
 Avoid the air or kinks in the fluid tube & in the CVP
catheter tube respectively.
 The transducer is then zeroed to atmosphere pressure by
turning its 3-way tap so that it is open to the transducer
& to room air ,but closed to the patient
 Then 3 way tap is turned so that it is now closed to room
air & open between the patient & the transducer
 A continuous CVP reading, measured in mmHg rather
than cmH2O, can be obtained.

41. Using transducer

42. Intraocular Pressure
 IOP is the fluid pressure inside the eye.
 IOP is measured by tonometer
 Tonometry is the measurement of tension or pressure
within the eye
TYPES OF TONOMETRY
 Applanation Tonometry
 Pneumatonometry

43. Applanation Tonometry
There are many different ways to measure eye pressure.
 One such method is a painless procedure, called
“applanation tonometry.”
 The term applanate means to flatten.
 In most ophthalmologist’s offices, eye pressure is
measured using “Goldmann applanation tonometry,”
and this is considered a “gold standard” eye pressure
measurement.

44.  In this test, the eyes are a small amount of non-toxic
dye is placed in the eye.
 Ophthalmologist will instruct Patient to position your
head into a device called the slit lamp.
 Then, a small tip gently touches the surface of the eye
and the eye pressure is measured.
 The eye pressure is measured based on the force
required to gently flatten a fixed area of the cornea.
Applanation Tonometry

45. Pneumatonometry
 Alternative measurement methods include
pneumatonometry, which is particularly useful in
cases of scarred corneas.
 The pneumatonometer will also print out a tracing so
that the quality of the measurement can be assessed.
 Pneumatonometry is thought to be less influenced by
corneal thickness.

46. ICP monitoring
How the Test is Performed
 There are three ways to monitor ICP.
Intraventricular catheter
 The intraventricular catheter is the most accurate
monitoring method.
 To insert an intraventricular catheter, a hole is drilled
through the skull.
 The catheter is inserted through the brain into the lateral
ventricle.
 The catheter may be hard to get into place when the
intracranial pressure is high.

47. ICP monitoring
Subdural screw (bolt)
 This method is used if monitoring needs to be done
right away.
 A hollow screw is inserted through a hole drilled in the
skull.
 It is placed through the membrane that protects the
brain and spinal cord (dura mater).
 This allows the sensor to record from inside the
subdural space.

48. ICP monitoring
Epidural sensor
• An epidural sensor is inserted between the skull and
dural tissue.
• The epidural sensor is placed through a hole drilled in
the skull.
• This procedure is less invasive than other methods,
but it cannot remove excess CSF.