Anesthesia Equipment Ch. 16 Nagelhout
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
- 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
Capacity of Tec 4,5, Vapor 19, Aladin 250 - ANSWER-Tec 4 : 125
Tec 5: 300 1 / 3
Vapor 19: 200
Aladin: 250
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
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
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 2 / 3
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
What type of Vaporizer has a Dual circuit where carrier gas is not split - ANSWER-Tec 6 (Desflurane)
Method of vaporization of Tec 6 - ANSWER-Gas/Vapor blender (heat produces vapor, which is injected into the Fresh gas flow)
Temperature compensation of Tec 6 - ANSWER-Electronically heated to a constant temperature (39 degrees C; thermostatically controlled)
Calibration of Tec 6 - ANSWER-calibrated, agent specific
Position of Tec 6 - ANSWER-out of circuit
capacity of Tec 6 - ANSWER-390 ml
Variable bypass The concentration of the anesthetic agent in this gas is therefore known from what? - ANSWER-from its saturated vapor pressure, so when this gas is mixed with the anesthetic-free bypass gas, the concentration of anesthetic in the gas leaving the vaporizer is also known
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