Anesthesia machine/PHYSICS Flashcards
what’s radius effect when TURBULENT flow?
r^5 (vs laminar r^4)
viscosity vs density?
viscosity represents frictional coefficient
DENSITY - impedes process of forward flow
5th difference between DRAGER and DATEX machines??
1 - 2 - 3 - 4 - 5 - DATEX uses chain-linked sprockets to control O2:N2O ratio; DRAGER uses pneumatic interlock system
what should proportion of nitrous to O2 be?
3:1
how does O2 relate to other gases mixed in machine, as far as SEQUENCE of when it’s mixed?
it’s the LAST GAS IN THE SEQUENCE!! (minimize the risk of hypoxic mixture if leak happens)
N2O cylinder’s Pressure gauge won’t decrease until vol of liquid within gets to what vol?
400
full = 1600; deplete 75% before it shows
how are vaporizers characterized?
1) variable bypass
- 2 circuits in parallel; one pics up vapor and fresh gas in other
2) FLOW OVER
- out of circuit and gas flows over and picks up gas
- agent specific
- temp specific
vaporizer (variable bypass) works how?
1) volume of liquid anesthetic; wic dropped in and saturated - emanates vaporous molecules in the vaporizer; gas blows by and re-enters main line
vapor pressure is defined HOW?
closed container, pressure from gas phase of molecules inside
vapor press primarily depends on what?
TEMPERATURE
with incr temp, how vapor press change?
curvilinear
swoop upward
which two sets of volatiles are similar in Temp/VaporPress?
1) enflur/Sevo (for set temp, lower VP)
2) halo/iso (somewhat higher VP for set temp)
DES is DIFF; WAY higher vapor pressure for set temp
temp probe in vaporizer, and then turn it on. what happens to temp inside vaporizer?
DROPS; endothermic rxn. have to add energy to get gas.
comes from warmth of OR and temp of system itself
latent heat of vaporization?
calories to change 1gm of liquid to gas WITHOUT change in temp
what compensates for constant drop in temp from gas vaporization?
-temp compensation mechanism from bi-metalic strip
two different metals
efficiency by which a metal transfers heat?
thermal conductivity
LOW fresh gas flow rate effect on Vaporizer output of inhaled anesthetics?
output DECREASE
HIGH fresh gas flow rate on vaporizer output?
output will DECREASE
when convert from O2 to N2O, what happens to vaporizer output?
some of nitrous that enters vaporizer gets dissolved in the liquid of vapor; so get less carrier gas; TRANSIENT DECREASE in vapor output
machine tipped?
flush for 30min to at high flow rate
difference between vapor pressure and boiling point?
vapor pressure so high that starts to compete with atmospheric pressure
what’s the function that prevents simultaneous agent administrations?
VAPOR INTERLOCK SYSTEM
how detect a leak
high or low pressure leak test
how does Desflurane vaporizer differ from VARIABLE BYPASS vaporizer
boils at room temp; energy absorbs changing from liquid to gas when it boils is DRAMATIC, that temp plummets, and bi-metalic strips can’t keep up.
DES vaporizer
(filled with liquid) is heated why?
-gets TWICE its boiling point, so ALL liquid des is then gas (100% des gas); so then fuel injects into fresh gas flow
what’s name of des vaporizer?
Tec 6
other things about Tec 6?
- electrically heated; -thermostatically controlled
- constant temp
- pressurized
- electrochem coupled
- dual circuit
- gas-vapor blender
HIGH altitude vaporizer…..what do you do to get 1MAC of desflurane?
set dial HIGHER than 1MAC
HIGH altitude; 1MAC ISOFLURANE?
set vaporizer SAME
[if pressure drops by half, then iso vaporizes MORE; so twice as much vaporizes; BUT has to do with pressure in brain]
at sea level, different from high altitude?
SEA: 2%(760 torr) = 15.2torr
HIGH: 4% (380 torr) = 15.2torr
end up with same partial pressure in brain
however, DES is DIFFERENT?
closed des system to atmosphere. doesn’t know what’s happening outside of system; gives SAME percentage.
1) AT SEA:
6% (760)=45
2) HIGH:
6%(380)=23
—so INCREASE dial above sea level
