Anesthesia Delivery Physics Flashcards
Dalton’s Law
Total pressure = P1 + P2 + P3
Henry’s Law
The amount of gas that will dissolve in a solution is proportional to the partial pressure of the gas in contact with the solution
Universal Gas Law
PV = nRT
Cylinder safety device
Woods metal
- Composed of bismuth, lead, tin, cadmium
- Melts at 200 degrees
Pin Index Safety System (and positions for O2, air, N2O)
PISS -Safety system on ECylinders, connects to yoke O2: 2, 5 Air: 1, 5 N2O: 3, 5
Boyle’s Law
P1xV1 = P2xV2
T is constant
Charles’s Law
V1/T1 = V2/T2
P is constant
Gay-Lussac’s Law
P1/T1 = P2/T2
V is constant
Dr Henry Boyle
Came up with original anesthesia machine concept in 1917
- Flow meters
- Vaporizing bottles
Critical temperature
The temperature a gas must be at or below for it to be liquefied by pressure only
O2: -119 C
N2O: 97 F
Prevention of pipeline O2 supply problems
- 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
Bourdon
Pressure gauge used to measure cylinder and pipeline pressure
Full O2 tank psi and liters
2000 psi
660 L
Full N2O tank psi and liters
745 psi
1590 L
Full tank = 8.8 kg / 20 lb
Empty tank = 5.9 kg / 14 lb
ASA closed claims project database frequent cause
Lack of familiarity with equipment or failure to check AM function is more frequent cause (2%)
SPDD
Supply, processing, delivery, and disposal of gasses
-Model to describe gasses to and from the OR
Hanger Yoke functions
- Orient/support cylinders
- Provide unidirectional flow to the machine
- Ensures a gas tight seal
Check valve
Unidirectional
- Allows cylinders to be changed during use
- Minimizes leaks if yoke is empty
- Minimizes transfilling between cylinders
Pressure reducing device
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
O2 failsafe
- 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
5 tasks of O2
- Pressure failure alarm
- Pressure failure device (failsafe)
- Flowmeter
- Flush valve
- Ventilator drive gas (GE machines)
Oxygen flush valve
“CRNA panic button”
- Gets O2 from pipeline or cylinder reducer to the common gas outlet (after the vaporizers)
- 50psi
- 35-75LPM
Second-stage pressure regulator
- In GE Datex-Omeda machines
- Before flow control valves: Keeps flow constant
- Reduces pipeline or cylinder pressure to: N20-26psi, O2-14psi
Reynolds Number
= (Density x Diameter x Velocity) / Viscosity
- Low flow (<2000) = Laminar flow
- High flow (>2000) = Turbulent flow
Turbulent flow is dependent on ____
Gas density
Graham’s Law: Diffusion is directly proportional to molecular weight
Laminar flow is dependent on ____
Gas viscosity
Poiseulle’s equation: Flow is directly proportional to the r^4
O2 flowmeter placement on the manifold
On the right side, downstream from other flowmeters
Proportioning system/Hypoxia Prevention safety device
- 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
Oxygen analyzer
Only device that evaluates the integrity of low pressure circuits and ensures that O2 is present
-In the inspiratory limb
