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116 Cards in this Set
- Front
- Back
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vapor
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composed of molecules in gasous phase of substance that is liquid at room temp and 1 atomoshpere of pressure
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factors affect rate of vaporization
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-physical characteristics of vaporizing liquid
- temperature |
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latent heat of vaporization
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for each substance a specifc amt of heat must be supplied to vaporize a given quality.
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rate of vaporization depends on:
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-temp
-VP of liquid -parial pressure of vapor above the evaporating liquid |
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vaporizers
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blend the combined flow of fresh gases from the flowmeters with sufficient vapor to form clinically useful concentrations
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3 types of vaporizers
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1- variable bypass
2- measured-flow (vernitrol) 3- Tech 6 (des specific) |
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splitting ratio
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is automatically determined in a variable bypass vaporizer by the internal resistance to flow
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wicks and baffles
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ensures full saturation of the carrier gas
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tempature-compensation device
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built in so that more gas is directed into the vaporizing chamber as the vaporizer cools
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patient outlet
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saturated FGF mixes with nonsaturated FGF
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vernitrol
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obsolete
used overseas/by military can be used with multiple agents |
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tech 6
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heated, dual circuit vaporizer
FGF never comes in contact with liquid agent |
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control point 1 on tech 6
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the setting on the concentration control dial
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second control point on tech 6
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keyed to a transducer that is responsive to the amt of FGF
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tech 6 heated to
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39degrees C produces VP of 1500mmHG
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variable-bypass splitting ratio
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vaporizer determines carrier gas split
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tech 6 injector splitting ratio
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carrier gas is not split
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Method of vaporization for
VB |
flow-over
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Method of vaporization for injector
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Gas/vapor blender(heat produces vapor which is injected into FGF
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Temp compensation for VB
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automatic Temp compensation mechanism
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Temp compensation for Injector
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electrically heated to constant 39degrees C
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Calibration for VB
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calibrated, agent specific
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calibration for injector
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calibrated, agent specific
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interlock system
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prevents administration of more than 1 agent
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VP Sevo
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160 mmHG
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VP Ether
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175 mmHG
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VP Iso
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238 mmHG
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VP Halothane
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241 mmHG
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VP des
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664mmHG
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Boiling point Sevo
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58.5
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Boiling point Ether
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56.5
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Boiling point Iso
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48.5
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Boiling point Hal
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50.2
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Boiling point Des
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23.5
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MAC Sevo
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1.7%
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MAC Iso
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1.15%
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MAC ether
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1.7%
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MAC Halo
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0.77%
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MAC Des
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6%
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sevo bottle
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yellow
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des bottle
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blue
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iso bottle
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purple
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formula
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%concentration=
VP agent/BPx100 |
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specific heat
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number of calories reuqired to increase the temp of 1g of a substance by 1degree C.
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thermal conductivity
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measure of the speed at which heat flows through a substance.
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MAC
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minimum alveolar concentration of inhaled anesthetic required to prevent 50% of subjects from gross purposeful movement in response to skin incision
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flow over
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refers to the method of vaporization
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VB vaporizers deliver gases:
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halo, enflurane, isoflurane, sevoflurane
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compenents of VB vaporizer
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concentration dial
-bypass chamber -vaporizing chamber -filler port -filler cap |
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final concentration of inhaled anesthetic
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ratio of the flow of inhaled anesthetic to the total gas flow
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expansion element
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directs a portion of the gas flow through the bypass chamber as temperature increases
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bimetallic strip
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temp compensating valve that directs gas flow through bypass chamber on Ohmed Tec vaporizer
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pumping effect increased with:
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rapid resp rate
-high peak inspired pressures -rapid drops in pressure during expiration |
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desflurane
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MAC 4-9X higher than other gases, has low blood-gas soluability coefficient and recovery from anesthesia is more rapid
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2004
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FDA approved Drager of its version of Tech 6 desflurane vaporizer
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Tech 6 plus
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has enhanced audible alarm system
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pressure regulating valve
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downregulates the pressure from about 2.0-1.1atm absolute (74mmHG gauge) at FGF rate of 10L/min
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Tech 6 interfaced through
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differential pressure transducers
-control electronic system -pressure-regulating valve |
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control electronic system
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regulates the pressure regulating valve so that pressure in teh vapor circuit equals the pressure in the FG circuit
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tech vaporizer
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electrically heated
-thermostatically controlled -constant temp -pressurized -electromechanically coupled dual circuit -gas-vapor blender |
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Datex Ohmeda Aladin
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designed to deliver 5 diff inhaled anesthetics: halothane, isoflurane, enflurane, sevoflurane,desflurane
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Aladin
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made up of bypass chamber and vaporizing chamber
-cassette |
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unique in Aladin
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prevents retrograde flow of vapor back into the bypass chamber, crucial when delivering Des if room temp if >BP 23.5C
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fan activation in Aladin
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desflurane induction
-sevo induction |
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Key type filling device
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-lessens chance of filling wrong agent
-fits a specific inhalational agent -fits a specific vaporizer |
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breathing system (circuit)
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large, bore, corrugated hose that provides flexible, low resistance, lighweight connection from one part of the system to another
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breathing circuit
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extends from point of FG inlet to point at which gas escapes to atmosphere or scavenging system
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functions of breathing system
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-receives gas mixture from AM
-delivers gas to pt -removes CO2 -allows continuous flow from AM to be converted to intermittent flow -allows spontaneous, controlled, or assisted respiration -gas sampling -airway pressure -flow -volume monitoring |
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4 classification of breathing circuits
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open
-semi-open -semi-closed -closed |
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MV
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minute volume
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Ve
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minute ventilation
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APL
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adjustable pressure limiting valve
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nonrebreathing systems
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those in which the exhaled gases containing the carbon dioxide are removed from the system
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rebreathing systems
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inhalation of previously respired gases from which CO2 may or may not have been removed
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mechanical (apparatus) dead space
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is the volume in a breathing circuit occupied by gasses that are rebreathed without any change in composition
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advantages of rebreathing
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-increase in tracheal warmth
-increase in humidity -decrease in potential for exposure of waste gases |
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rebreathing of CO2
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-avoid
-not desirable -produces respiratory acidosis |
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higher FGF during emergence
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reduces the discrepancies from desired and actual concentrations
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avoid hypercarbia
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minute ventilation must be increased
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dry gases
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avoids internal corrosion
and bacterial colonization |
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in the lungs
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gases flow down their concentration gradients, interchanging with pulmonary and blood gases
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features of nonrebreathing circuits
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-lack unidirectional valves
-lack soda lime CO2 absorption -amt of rebreathing is highly dependent on FGF in all -amt of resistance is low in all |
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mapleson systems
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-facemask
-spring loaded pop-off valve -reservoir tubing -fresh gas inflow tubing -reservoir bag |
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3 grps of Mapleson systems
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-A
- BC - DEF |
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mapleson B&C
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APL valve fully open
-excess gas is vented during exhalation with spontaneous ventilation -excess gases vented during inspiration with controlled/assisted ventilation |
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Mapleson D, E, F
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T-piece group
-requires 2.5x Ve, more efficient than BC |
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Mapleson E
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-convenient method of switching between mapleson A and D/E
-easy to perform IPPV |
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mapleson F
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-referred to as Jackson-Rees
-very low resistance to breathing -used for any age:premies, infants to adults -2-3x Ve to prevent rebreathing -minimum 5L/min of FGF |
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some factors affecting CO2 rebreathing with mapleson systems
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-fg flow rate
-minute ventilation -mode of ventilation -tidal volume -respiratory rate -CO2 sample site -inspiratory to expiratory ratio -duration of expiratory phase.... |
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mapleson system efficiency during spontaneous vent:
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A>DEF>BC
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prevention of rebreathing during controlled vent:
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DEF>BC>A
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Bain circuit
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in US most popular representative from DEF group
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bain system
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-aka modified mapleson D
-gives inhaled gases great heat and humidity -used for spontaneous and controlled vent. -rate to prevent rebreathing is 2.5x Ve |
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Pethick's test
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detects faulty inner tubes in co-axial bain circle
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advantages of NRB system
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-lightweight
-convenient -easily sterilized and scavenged -exhaled gases in corrugated limb may give heat and humidity to inhaled gas |
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disadvantage of NRB system
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-unrecognized disconnection or kinking of FG hose
-pollution and increased cost of agents and gases d/t higher flows -loss of heat from patient -can be reassembled improperly |
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circle breathing system
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-"universal F" or "single limb circuit"
-prevent rebreathing of CO2 by use of CO2 absorbents, allows partial rebreathing of other gases -can be semi-open, semi-closed or closed |
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3 rules to follow to prevent rebreathing of CO2 in circle breathing system
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1-unidirectional valve must be ocated between the pt and the reservoir bag on both insp and exp limbs
2-FG inflow cannot enter the circuit between the expiratory valve and the pt 3-overflow (APL) valve cannot be located between the pt and insp valve |
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7 components circle breathing system
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1-fresh gas inflow source
2-insp and exp unidirectional valves 3-insp and exp corrugated tubes 4-Y-piece connector 5-overflow or APL valve 6-Reservoir bag 7-canister containing CO2 absorbent |
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advantages of circle system
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1-constant inspired concentrations
2-conservation of resp tract & heat 3-minimal OR pollution 4-useful for closed-system, low-flow and semi-open configurations 5-low resistance |
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disadvantages of circle system
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1-relatively complex
2-opportunities for misconnect/disconnect 3-malfunctioning unidirectional valves cause serious probs 4-open:rebreathing 5-closed: occlusion 6-less portable 7-increased DS |
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causes for circle system obstruction
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1-manufacturing defects
2-debris 3-patient secretions 4-particulate obstruction from other sources: albuterol nebulization |
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FGF circle system
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0.3-0.5L/min provides near total rebreathing and full reliance on absorbent for prevention of rebreathing CO2
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correct response to hypercarbia
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increase FGF-chg absorbent at end of case
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2 commonly used absorbents
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1-soda lime
2-calcium hydroxide lime (amsorb) |
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Fx of absorbent
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eliminate CO2 from breathing circuite
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composition of soda lime
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80% calcium hydroxide
15% water 4% sodium hydroxide 1% potassium hyroxide |
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what does silica do?
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produce calcium and sodium salicate, makes a harder more stable pellet and reduces dust formation
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sodium hydroxide
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a catalyst for CO2 absorbent properties of soda lime
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barylime
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mixture of 20% barium hydroxide and 80% calcium hydroxide
-may produce fires when used with sevo |
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newest absorbent
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calcium hydroxide
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adv of calcium hydroxide lime over others
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lack of strong bases sodium and potassium hydroxide
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disadv of calcium hydroxide lime
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less absorbent capacity
generally higher cost per unit |
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4-8 mesh
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size at which absorptive surface area and resistance to flow are optimized
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factors leading to increase conc of compound A with Sevo:
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-low flow or close circuit anesthesisa techniques
-use of barylme rather than soda lime -higher absorbent temps -fresh absorbent -higher sevo in anesthesia circuit |
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limit of Sevo for 2 MAC hrs at what flow rates
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<2L/min
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