Download Daltons law of partial pressure

GAS LAWS
Dr.R.Selvakumar
Asst.Professor,
G.R.H.,Madurai.
Is it necessary for an Anesthetist to study
about the BORING gas laws..?
Yes.,of course…..
•Better understanding of the behavior of anesthetic gases
•Smooth conduct of anesthesia
•For the proper use of Boyles machine
•To escape from an explosion…!
An new oxygen cylinder is being opened.How do you know
whether it will last for the entire surgical procedure or not..?
Knowing the contents of the cylinder…
Relationship between the volume,pressure and temperature
O2
N2O
Boyle’s law
Charles law
Gay-Lussac’s law
Boyle’s law: At constant temp, volume is inversely proportional
to its absolute pressure.
Charles law: At constant press, volume is directly proportional to
Its absolute temp.
Gay-Lussacs law: At constant volume, pressure is directly
proportional to its absolute temp.
PiVi/Ti = PfVf/Tf
Try this calculation…!
An O2 cylinder indicates a pressure of 132 atm while
being transported in hot weather when the temp is 44C.
What pressure will be indicated when it is placed in a
cool operation theatre when the temp is 20C?
N2O CYLINDERS:
0.67
•Filling ratio
•Critical temperature
•Why older machine doesn’t have
a pressure gauge..?
“Wt of N2O in the cylinder/ Wt of H2O,the cylinder can hold”
51 atm
25 atm
18 atm
75atm
94atm
20C
-10C
-20C
37C
45C
PRESSURE IN N2O CYLINDERS
ADIABATIC COMPRESSION:
When a gas is subjected to sudden compression,heat energy
is produced rapidly. If there is no time for dissipation of this
heat, the temperature of the system rises enormously.
First law of thermodynamics
Have you seen ice crystal formation over a cylinder valve
if N2O leaks through it?
Joule-Thomson effect
Joule-Thomson effect:
When a compressed gas is allowed free expansion
through a narrow opening, the temperature of the
surrounding falls rapidly.
We often talk about partial pressure when we refer gaseous
pressures. What do you mean by that..?
Daltons law of partial pressure
Daltons law of partial pressure
0
0
0 X/4
x
X+x/4
Daltons law:
In a mixture of gases having no chemical interaction
between them,each constituent gas exerts the same
pressure which it would have exerted if it alone had
occupied the volume of the mixture,provided the
temperature be the same as that of the mixture.
Daltons law:
It follows that in a mixture of gases, the pressure exerted
by each gas is the partial pressure and the pressure of a
mixture of gases is the sum of the partial pressures of its
constituents.
Daltons law:
In a mixture of gases, each constituent exerts the same
Proportion of total pressure as its volume is to the
total volume
What happens in an alveoli?
alveolus
O2 – 100
CO2 – 40
H2O – 47
N2 - 573
O2- 40 vein
CO2- 46
H2O- 47
N2- 627
Pulmonary capillary
artery O2- 100
CO2- 40
H2O- 47
N2- 573
On the Mount Everest…
Altitude – 8800 m ( 29,000 ft )
Atm. Pressure – 240 torr
Alveolar O2 – 23 torr
PVO2– 40 torr
Life is possible only when 100% O2 is supplemented, when
PAO2 becomes 153 torr.
Try this calculation…!
Recently filled D-type N2O cylinder weighs 53.45 kg with
Its contents. The tare weight of the cylinder is 24.48 kg.
How long will it last if the anesthetist draws 2 lpm of N2O?
Avagadros hypothesis
Avagadros hypothesis:
One gram molecular weight of any gaseous substance
will occupy a volume of 22.4L at S.T.P and will contain
6.023 x 1023 number of molecules
If you want to give blood rapidly…
What will you do?
1.Put a wider gauge canula
2.Increase the drip stand height
3.Use a rapid infusion bag
Hagen-Poiseuille formula
Hagen-Poiseuille Law:
When a fluid flows through a tube, then the quantity of the flow(Q) is
1. Proportional to the pressure difference between the two ends of the tube
2. Proportional to the fourth power of the radius of the tube
3. Inversely proportional to the viscosity of the fluid
4. Inversely proportional to the length of the tube
Q = π r4 (P1- P2)/ 8ηl
Try to answer these questions..!
1.Why acute bends in the breathing circuits are avoided?
2.What is the rationale behind in giving Helium-O2 mixture
for the patients with partial upper respiratory tract
obstruction?
Flow through tubes…
•LAMINAR FLOW
•TURBULENT FLOW
Reynold’s number
“Viscosity affects laminar flow,whereas density affects the
Turbulent flow.”
What is the common factor among the following..?
1.Gas stove
2. Insect sprayer
3. Venti oxygen mask
4. Nebuliser
5. Ventilator
6. Bunsen burner
Have you used a Bunsen burner?
Bernoulli’s theorem
Clinical application of Bernoulli’s theorem:
0
-
+
0
0
DIFFUSER ( VENTURI TUBE )
In the IRCU, you’ve taken O2 for 2 patients from one
Flow meter by incorporating a bifurcator in the line:
Will both the patients get equal amount of O2?
COANDA EFFECT
COANDA EFFECT:
"That we have written an equation does not
remove from the flow of fluids its charm or
mystery or its surprise." --Richard Feynman
[1964]
• Coanda Effect
Try to reason out…!
1.Why the rain water takes a globular shape?
2. When the lung decreases in size during expiration
how the alveoli remain patent without getting emptied
into nearby alveoli?
Laplace law
Laplace law:
The excess pressure inside a spherical gas-liquid
interface is equal to twice the co-efficient of surface
tension divided by the radius of the interface
ΔP= 2γ/ r
I think I’ve confused you enough about:
1.Boyle’s law
3.Gay-Lussacs law
5.Daltons law
7.Venturi principle
9.Laplace law
2.Charles law
4.Avagadro hypothesis
6.Law of thermodynamics
8.Joule-Thomson effect
10.Hagen-Poiseuille formula