Anesthesia machine/PHYSICS

Question 1

what’s radius effect when TURBULENT flow?

Answer 1

r^5 (vs laminar r^4)

Question 2

viscosity vs density?

Answer 2

viscosity represents frictional coefficient

DENSITY - impedes process of forward flow

Question 3

5th difference between DRAGER and DATEX machines??

Answer 3

1 -
2 - 
3 - 
4 - 
5 - DATEX uses chain-linked sprockets to control O2:N2O ratio; DRAGER uses pneumatic interlock system

Question 4

what should proportion of nitrous to O2 be?

Answer 4

3:1

Question 5

how does O2 relate to other gases mixed in machine, as far as SEQUENCE of when it’s mixed?

Answer 5

it’s the LAST GAS IN THE SEQUENCE!! (minimize the risk of hypoxic mixture if leak happens)

Question 6

N2O cylinder’s Pressure gauge won’t decrease until vol of liquid within gets to what vol?

Answer 6

400

full = 1600; deplete 75% before it shows

Question 7

how are vaporizers characterized?

Answer 7

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

Question 8

vaporizer (variable bypass) works how?

Answer 8

1) volume of liquid anesthetic; wic dropped in and saturated - emanates vaporous molecules in the vaporizer; gas blows by and re-enters main line

Question 9

vapor pressure is defined HOW?

Answer 9

closed container, pressure from gas phase of molecules inside

Question 10

vapor press primarily depends on what?

Answer 10

TEMPERATURE

Question 11

with incr temp, how vapor press change?

Answer 11

curvilinear

swoop upward

Question 12

which two sets of volatiles are similar in Temp/VaporPress?

Answer 12

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

Question 13

temp probe in vaporizer, and then turn it on. what happens to temp inside vaporizer?

Answer 13

DROPS; endothermic rxn. have to add energy to get gas.

comes from warmth of OR and temp of system itself

Question 14

latent heat of vaporization?

Answer 14

calories to change 1gm of liquid to gas WITHOUT change in temp

Question 15

what compensates for constant drop in temp from gas vaporization?

Answer 15

-temp compensation mechanism from bi-metalic strip

two different metals

Question 16

efficiency by which a metal transfers heat?

Answer 16

thermal conductivity

Question 17

LOW fresh gas flow rate effect on Vaporizer output of inhaled anesthetics?

Answer 17

output DECREASE

Question 18

HIGH fresh gas flow rate on vaporizer output?

Answer 18

output will DECREASE

Question 19

when convert from O2 to N2O, what happens to vaporizer output?

Answer 19

some of nitrous that enters vaporizer gets dissolved in the liquid of vapor; so get less carrier gas; TRANSIENT DECREASE in vapor output

Question 20

machine tipped?

Answer 20

flush for 30min to at high flow rate

Question 21

difference between vapor pressure and boiling point?

Answer 21

vapor pressure so high that starts to compete with atmospheric pressure

Question 22

what’s the function that prevents simultaneous agent administrations?

Answer 22

VAPOR INTERLOCK SYSTEM

Question 23

how detect a leak

Answer 23

high or low pressure leak test

Question 24

how does Desflurane vaporizer differ from VARIABLE BYPASS vaporizer

Answer 24

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.

Question 25

DES vaporizer

(filled with liquid) is heated why?

Answer 25

-gets TWICE its boiling point, so ALL liquid des is then gas (100% des gas); so then fuel injects into fresh gas flow

Question 26

what’s name of des vaporizer?

Answer 26

Tec 6

Question 27

other things about Tec 6?

Answer 27

• electrically heated; -thermostatically controlled
• constant temp
• pressurized
• electrochem coupled
• dual circuit
• gas-vapor blender

Question 28

HIGH altitude vaporizer…..what do you do to get 1MAC of desflurane?

Answer 28

set dial HIGHER than 1MAC

Question 29

HIGH altitude; 1MAC ISOFLURANE?

Answer 29

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]

Question 30

at sea level, different from high altitude?

Answer 30

SEA: 2%(760 torr) = 15.2torr

HIGH: 4% (380 torr) = 15.2torr

end up with same partial pressure in brain

Question 31

however, DES is DIFFERENT?

Answer 31

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