EXPLAINING FLOW FROM A BOOK ABOUT ANAESTHESIA PHYSICS,OF PARBROOK BY ONLY TWO SLIDES

1. Fluid Flow
MOHAMED ANWER
RIFKY
2-FLUID FLOW:
A-WHAT IS THE TYPE OF FLOW THAT OCCURES IN AN ORFICE ?AND
WHAT ARE THE FACTORS AFFECTING THAT FLOW?
B-( G.R )LAMINAR FLOW IS USUALLY PRESENT IN THE LOWER
RESPIRATORY TRACT.
C-IN PREMATURE INFANTS,SURFACTANT MAY NOT YET BE
PRESENT,THUS PROBLEMS MAY ARISE.(EXPLAIN)
D-( G.R )THE VISCOSITY OF BLOOD IS ANOMALOUS.
E-SOME EQUIPMENTS MAY INCLUDE A TUBE WITH A
CONSTRICTION.(EXPLAIN IN FULL DETAILS)
F-( G.R ) ENTRAINMENT OCCURS IN THE VENTURI MASK.
G-( G.R ) THE UNEVEN DISTRIBUTION OF GAS FLOW TO ALVEALI
WHERE THERE HAS BEEN A SLIGHT NARROWING OF THE
BRONCHIOLE BEFORE IT DIVIDES.
G.R=GIVE REASONS

2. Fluid Flow 1- (GAS OR LIQUID ) 3- (Mass or volume, passing a point in
unit time. )
2- --(Small dot above the Q
?)
1-LAMINAR FLOW: a-No eddies or turbulence (Steady).
b-Flow approaches zero at the wall
3-Hagen-Poiseuille
equation:
Greek letter eta (η)
Measure resistance by this device.
2-TURBULENT FLOW: a-Fluid velocity increasing. b-Flows swirls in eddies. c-Relationship of pressure to flow is no longer
linear.
e-The resistance is higher than for the same
laminar flow
Greek letter rho(p)
d-The behaviour
of turbulent is not straightforward so no
simple formula can be given.
e-
3-ONSET OF TURBULENT FLOW: v = linear velocity of
fluid
a-If Reynolds
number exceeds about 2000, then turbulent flow is likely to be
present.
b-It can be seen from this formula that for a fixed set of conditions there
is a critical velocity at which Reynolds number has the value of 2000.
d-Turbulent flow is often
present where there is an orifice, a sharp bend or some other
irregularity.
4-CLINICAL ASPECTS OF FLOW: (Based on the velocity of the
gas)
a-Typical anaesthetic mixture of 60% nitrous oxide in
oxygen and
also for air at an ambient temperature of 20°C.
b-Humidified gases, contain carbon dioxide and are at a
temperature of
34 to 37°C. The critical flow for the humidified warmed
anaesthetic mixture in the patient could be 10% higher than the
figures
for dry gases at 20°C
c-Rise in critical flow,in situation of a
and b.
d-The gas in a 9 mm internal diameter endotracheal tube becomes turbulent
when flow exceeds about 9 litre min-1, the flow in a 15 mm diameter trachea is turbulent at flows over 15 litre min-1. 22
mm internal
diameter tubing.!!!
e-with peak flows over
50 litre min"1, turbulent flow usually
predominates.
f-laminar flow is usual present in the lower respiratory
tract.
.
The 30 mm
diameter
(scavenging
tubing).!!!
g-In quiet breathing, the flow within the respiratory tract is principally
laminar, but during speaking, coughing or taking a deep breath,
turbulent. --What about the lining mucus?
Helium and density. !!

3. g-Similar considerations apply to the circulation.
(Bruit)
.
5-TENSION:
(Blood vessels and bronchi, are not rigid tubes but have a variable radius).
(The smooth muscle and elastic tissue and the fluid pressure in the tube) .Instability
may occour.
Laplace's
law.
a- fall in pressure in an arteriole>>>
smooth muscle in the wall MAINTAINS TENSION. But instability can occur>>>
closure of the vessel.
b-critical closing pressure is also present in the airways on expiration.
6-SURFACE TENSION: When the radius of the alveolar ducts and alveoli diminish during expiration, the pressure across the wall tends to rise
(Laplace's law)
Laplace's law (in a sphere) a-_The surface tension of the fluid lining the alveoli, renders the
tension variable.
b-In premature infants, surfactant may not yet be present in the alveoli and consequently problem
may arise.
7-VISCOSITY:
(in a tube )
b- Viscosity increases at low temperature, with patient age and with cigarette. smoking. c-while treatment with low molecular weight dextran
reduces it.
.
a-If a patient's haemoglobin or fibrinogen level is raised >>>in viscosity reduces blood flow, giving a risk of vascular
occlusion.
d-The viscosity of blood is anomalous. e-A viscometer is used to measure viscosity(cone-shaped cup—rotate-controlled temperature-torsion wire support-
dragged by the viscosity-torque generated-light beam on a scale-) f-Other viscometers determine viscosity by
measuring
the time taken for a sample of liquid to flow down a vertical tube.( photo cell ).
8-FLOW THROUGH A VENTURI: 1-Tube with a constriction. 2-The cross section gradually decreases and then
increases.
3-Pressure along the tube is
measured.
4-This fall of pressure at a constrictionin a tube is named after its discoverer, (Bernoulli)
5-Flowing fluid contains energy in two forms, potential energy
associated with its pressure and kinetic energy associated with its
flow.
6-Marked fall of pressure occurs at B.7-Heat energy LOSS by friction
The driving fluid entrains
fluid
The driving fluid enters by the centre
tube.
a-Entraing (1 l.o2---9 l.air )
air into the oxygen flow.b-what is
Ent.RATIO ?
b-Friction between
the oxygen moving at high speed and the air pulls more air along with the flow
of oxygen,
9-THE COANDA EFFECT:
1- The stream is held against the wall. flow tends to cling to one side.It may explain
some
cases of myocardial infarction. 2-The fluid logic,( switch ) may be incorporated in
ventilators (no moving parts )
(Two planes of curvature)