sujata sahu msc tutor

2. Presented by
Sujata sahu
Lecturer
APPLICATION OF
PRESSURE IN NURSING

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.
Osmotic Pressure

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.