Anesthesia Delivery Physics

Question 1

Dalton’s Law

Answer 1

Total pressure = P1 + P2 + P3

Question 2

Henry’s Law

Answer 2

The amount of gas that will dissolve in a solution is proportional to the partial pressure of the gas in contact with the solution

Question 3

Universal Gas Law

Answer 3

PV = nRT

Question 4

Cylinder safety device

Answer 4

Woods metal

• Composed of bismuth, lead, tin, cadmium
• Melts at 200 degrees

Question 5

Pin Index Safety System (and positions for O2, air, N2O)

Answer 5

PISS
-Safety system on ECylinders, connects to yoke
O2: 2, 5
Air: 1, 5
N2O: 3, 5

Question 6

Boyle’s Law

Answer 6

P1xV1 = P2xV2

T is constant

Question 7

Charles’s Law

Answer 7

V1/T1 = V2/T2

P is constant

Question 8

Gay-Lussac’s Law

Answer 8

P1/T1 = P2/T2

V is constant

Question 9

Dr Henry Boyle

Answer 9

Came up with original anesthesia machine concept in 1917

• Flow meters
• Vaporizing bottles

Question 10

Critical temperature

Answer 10

The temperature a gas must be at or below for it to be liquefied by pressure only
O2: -119 C
N2O: 97 F

Question 11

Prevention of pipeline O2 supply problems

Answer 11

• Inlets have a filter to trap debris
• One-way check valve prevents reverse flow
• High pressure relief valve if pressure > 95-110 psi in regulator failure
• DISS

Question 12

Bourdon

Answer 12

Pressure gauge used to measure cylinder and pipeline pressure

Question 13

Full O2 tank psi and liters

Answer 13

2000 psi

660 L

Question 14

Full N2O tank psi and liters

Answer 14

745 psi
1590 L
Full tank = 8.8 kg / 20 lb
Empty tank = 5.9 kg / 14 lb

Question 15

ASA closed claims project database frequent cause

Answer 15

Lack of familiarity with equipment or failure to check AM function is more frequent cause (2%)

Question 16

SPDD

Answer 16

Supply, processing, delivery, and disposal of gasses

-Model to describe gasses to and from the OR

Question 17

Hanger Yoke functions

Answer 17

• Orient/support cylinders
• Provide unidirectional flow to the machine
• Ensures a gas tight seal

Question 18

Check valve

Answer 18

Unidirectional

• Allows cylinders to be changed during use
• Minimizes leaks if yoke is empty
• Minimizes transfilling between cylinders

Question 19

Pressure reducing device

Answer 19

AKA: Regulator

• In each cylinder
• 2000 psi -> 45 psi (<50 to prevent use if accidently left open)
• Manifold has valves to do this
• Has a filter before

Question 20

O2 failsafe

Answer 20

• Threshold alarm when O2 pipeline pressure is <30psi
• Pneumatic device that stops N2O when O2 pressure is <20psi
• Doesn’t prevent a hypoxic mixture if there’s crossover

Question 21

5 tasks of O2

Answer 21

• Pressure failure alarm
• Pressure failure device (failsafe)
• Flowmeter
• Flush valve
• Ventilator drive gas (GE machines)

Question 22

Oxygen flush valve

Answer 22

“CRNA panic button”

• Gets O2 from pipeline or cylinder reducer to the common gas outlet (after the vaporizers)
• 50psi
• 35-75LPM

Question 23

Second-stage pressure regulator

Answer 23

• In GE Datex-Omeda machines
• Before flow control valves: Keeps flow constant
• Reduces pipeline or cylinder pressure to: N20-26psi, O2-14psi

Question 24

Reynolds Number

Answer 24

= (Density x Diameter x Velocity) / Viscosity

• Low flow (<2000) = Laminar flow
• High flow (>2000) = Turbulent flow

Question 25

Turbulent flow is dependent on ____

Answer 25

Gas density

Graham’s Law: Diffusion is directly proportional to molecular weight

Question 26

Laminar flow is dependent on ____

Answer 26

Gas viscosity

Poiseulle’s equation: Flow is directly proportional to the r^4

Question 27

O2 flowmeter placement on the manifold

Answer 27

On the right side, downstream from other flowmeters

Question 28

Proportioning system/Hypoxia Prevention safety device

Answer 28

• Integration of N2O/O2 flow control valves
• Automatically keeps O2 at at least 25%
• N2O : O2 = 3 : 1
• Not fool proof if there is a leak downstream or crossover

Question 29

Oxygen analyzer

Answer 29

Only device that evaluates the integrity of low pressure circuits and ensures that O2 is present
-In the inspiratory limb