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
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about the BORING gas laws..?
whether it will last for the entire surgical procedure or not..?
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
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?
“Wt of N2O in the cylinder/ Wt of H2O,the cylinder can hold”
PRESSURE IN N2O CYLINDERS
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
if N2O leaks through it?
When a compressed gas is allowed free expansion
through a narrow opening, the temperature of the
surrounding falls rapidly.
pressures. What do you mean by that..?
Daltons law of partial pressure
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.
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.
In a mixture of gases, each constituent exerts the same
Proportion of total pressure as its volume is to the
What happens in an alveoli?
O2 – 100
CO2 – 40
H2O – 47
N2 - 573
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.
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?
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
What will you do?
1.Put a wider gauge canula
2.Increase the drip stand height
3.Use a rapid infusion bag
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
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
“Viscosity affects laminar flow,whereas density affects the
2. Insect sprayer
3. Venti oxygen mask
6. Bunsen burner
Flow meter by incorporating a bifurcator in the line:
Will both the patients get equal amount of O2?
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?
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
1.Boyle’s law 2.Charles law
3.Gay-Lussacs law 4.Avagadro hypothesis
5.Daltons law 6.Law of thermodynamics
7.Venturi principle 8.Joule-Thomson effect
9.Laplace law 10.Hagen-Poiseuille formula