Anesthesia Equipment Ch. 16 Nagelhout
Exam Questions With Correct Answers
A Vapor is composed of - answer✔molecules (in the gaseous state) of a substance that is a
liquid at room temperature and 1 atmosphere of pressure
What prevents the vaporization cooling and slowing the rate of further vaporization -
answer✔Cooper bc it has high thermal conductivity and high thermal capacity
The rate of vaporization depends on 3 things - answer✔1- the temperature
2- the vapor pressure of the liquid
3- the partial pressure of the vapor above the evaporating liquid
PP- Dalton's law (the total pressure of a mixture of gases is equal to the sum of the partial
pressures of the component gases
3- Amount of carrier Gas (N20 & O2) used
Boiling point - answer✔Vapor pressure equals atmospheric pressure, all liquid is in the vapor
phase
Latent Heat of Vaporization - answer✔Heat required to change liquid into a vapor
Comes from liquid and environment
Vapor pressure - answer✔Pressure exerted on walls of a container by molecules that broke
away from the liquid surface. Equilibrium will be achieved if temperature remains constant. All
volatile anesthetics have a specific vapor pressure. The concentration can be calculated from
the vapor pressure above the liquid
Volumes percent (Vol %) - answer✔the volume of gas carried per 100 volumes of blood
"the number of units of volume of gas in relation to a total of 100 units of volume for the total
gas volume
"Liquid inside closed container"
At constant temperature: (2) - answer✔1- number of molecules entering and leaving liquid are
equal
2- number of molecules in vapor phase stays constant
Saturated Vapor Pressure (SVP) - answer✔Pressure created when molecules "BOMBARD" the
walls of container
When the gas phase on top of the liquid phase is saturated by the molecules of vapor (it
contains as much vapor as it can handle)
Volatile Anesthetic Agent (VAA) - answer✔Liquid that has tendency to change to a vapor at
standard temperature and pressure
Higher volatility = - answer✔stronger tendency to change to vapor = higher SVP
Know SVP for Methoxyflurane, Sevo, Enflurane, Iso, Halo, Des - answer✔Methoxyflurane- 23
mmhg
Sevo-160
Enflurane- 175
Iso-238
Halo-243
Des- 660
SVP and Temperature Changes
Heat increases SVP (2)
What happens in the gas and liquid phase - answer✔Gas phase: more molecules enter gas
phase
Less molecules "re-enter" liquid phase
Cooling decreases SVP
What happens in the gas and liquid phase - answer✔gas phase: less molecules enter gas phase
More molecules "re-enter" liquid phase
when the practitioner turns on the vaporizer, What happens to SVP when carrier gas (N2O &
O2) passes over the liquid in the vaporize and picks it up to deliver VAA to patient? -
answer✔SVP decreases
What is needed continuously to vaporize anesthetic agents and maintain constant SVP -
answer✔Heat
The liquid agent (e.g. Iso) generates more vapor as an "inherent attempt" to keep SVP constant
and this leads to - answer✔heat being lost, and decreased vaporizer output
Concentration calibrated
(Variable bypass) - answer✔-AUTOMATIC
-total carrier gas flow automatically divided into two paths
- one path flowing through vapor above liquid anesthetic
-the other bypassing the vapor chamber
-the two flows meet and mix at the outflow tract. The concentration of the anesthetic
determined by the flow ratio
3 MOST common variable bypass - answer✔Datex Ohmeda Tec 3,4, and 5
Now, list all Variable-bypass Vaporizer - answer✔Tec, 3,4,5,7
SevoTec
Aladin (Aisys, Avance)
Vapor 19
Vapor 2000 & 3000
Method of Vaporization for Variable-bypass Vaporizers - answer✔Flow over (including the
Aladin for Des, which does not require added heat like the Tec 6)
Temperature compensation for Variable-bypass Vaporizers - answer✔Automatic temperature
compensation mechanism
Calibration for Variable bypass - answer✔Calibrated, agent specific
Position of Variable bypass - answer✔Out of circuit
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