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70 Cards in this Set

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What is the oil:gas partition coefficient of a gas in relation to anesthesia?
It gives an indication of the gas' relative solubility in fat (lipid membranes), which is then directly related to it's *potency. A high oil:gas coefficient means a small amount is highly soluble in brain tissue membranes.
What is the relationship between solubility of an anesthetic agent and onset of action?
Highly soluble = slow onset.
Low solubility = fast onset.

Remember: soluble drugs quickly suck up the drug and deliver it to all tissues but it has to saturate the blood AND the tissue to achieve anesthetic effect. Low solubility drugs don't have to saturate the entire blood volume and so achieve a very rapid tissue saturation. As soon as this gas is turned off the gas "pops" back out into the lungs and quickly unloads from the brain leading to rapid waking. The highly soluble drug has to empty all the blood and THEN the tissues and it takes much longer.

***NOTE: this is the best I can do to conceptualize this at this point in time. I welcome clarification/chastisement so I can correct this info if necessary.
What is the relationship between blood:gas partition coefficient and onset of anesthetic?
Low blood:gas = rapid onset.
High blood:gas = slow onset.

(relatively speaking)
What is the relationship between blood:gas partition coefficient and solubility?
They are directly related.
High b:g = high solubility.
Low b:g = low solubility.
What might the bourdon gauge read (psig) for the tank pressure of a full O2 tank on the back of the anesthesia machine?
1900 psig O2
What might the bourdon gauge read (psig) for the *line pressure for O2 on the back of the anesthesia machine?
45-55 psig
What does the pressure reducing valve (first stage regulator) between the O2 E-cylinder and the anes machine reduce the pressure to?
40-45 psig (just below whatever the line pressure is set at).
Why is the O2 line pressure higher than the first stage regulator pressure?
So that wall gas will be preferentially used over the e-cylinder.
Where is the O2 supply low pressure alarm usually located in respect to the internal piping of the machine?
Usually right after the common gas INLET
Immediately after the common gas INLET, what are the two paths that O2 can flow?
One way is to the O2 flush valve and the other is to the second stage O2 pressure regulator, the OFPD/failsafe valve, vent driving gas circuit.
What is a failsafe valve? What is the problem with this device?
*OHMEDA specific:
an on/off style valve that is open when the O2 system is *pressurized (usually set at 25 psig), theoretically to ensure that N2O (or other gas) isn't flowing if O2 is off and creating a hypoxic mixture for the pt. This valve only ensures adequate O2 *pressure but NOT O2 *flow. You can still run pure N2O if your gas line is pressurized but your O2 flowmeter is OFF.
What is an OFPD? How does it work? Is this safer than the failsafe valve?
*Drager specific:
Oxygen Failure Protection Device. It is a valve that limits N2O (or other gas) flow in proportion to the pressure of the O2 line. When O2 psig drops below 12 psig the OFPD valve is totally closed. The same risks exist with the OFPD as the failsafe valve. If the line is *pressurized then N2O can flow. O2 line pressure does not mean that O2 is actually *flowing to the pt. The could be getting a hypoxic mixture !
What is the essential difference between the failsafe valve and OFPD designs?
failsafe is on/off at 25 psig. The OFPD is gradual valve closure in relation to dropping O2 line pressures and turns off at 12 psig.

Failsafe valve is Ohmeda.
OFPD is Drager.
What is N2O *cylinder pressure as it enters the machine?
745 psig
What is N2O pipeline/wall line pressure as it enters the machine?
45-55 psig (same as O2).
To what end pressure is the N2O tank pressure downregulated at the first stage regulator?
40-45 psig (just below the wall supply pressure) so that the wall supply is preferentially used over the tank.
What pressure does the second stage pressure regulator downregulate O2 and N2O pressure to?
14 psig (1 atm)for O2


26 psig for N2O.
Why is there such a gradient between the 1st and 2nd stage reducing valves from 45 psig to 14/26 psig?
This ensures that fluctuations in line pressure before the 2nd stage regulator don't reduce O2 *flow and cause hypoxic gas delivery to the pt.
What are the 4 conceptual "zones" or systems of the anesthesia machine?
high pressure system, low pressure system, circle system, vent circuit.
What is the path of gas from the flowmeter to the common gas outlet?
flowmeter, vaporizers, past pressure relief valve, through outlet check valve to common gas outlet.
What does the pressure *relief valve do?
It prevents back-pressure in the low pressure system from damaging the vaporizers (only some Datex-Ohmeda machines).
What does the outlet *check valve do?
It is a constriction of the line that essentially creates a pressure gradient that inhibits back-pressure generated from the breathing circuit to flow retrograde past the valve. Essentially, it's a pressure INCREASING valve at that point only due to the constriction.
What are the characteristics of the *IDEAL anesthetic gas in terms of blood:gas coeff and brain:gas coeff?
It would have a low blood:gas coeff (low blood solubility) to allow for a higher alveolar concentration gradient to develop. It would have a *HIGH oil:gas coeff which means that it would be easily soluble in the brain tissue.
What are the factors that determine how long an anesthetic "wash out" time will be?
The blood gas partition coefficient is important to a certain extent, as once the drug is in the blood, the lower the BGPC, the quicker the drug is excreted through the lungs. However, every tissue in the body has its own tissue-blood partition coefficient and as the tissues act as a reservoir for anaesthetic gas, the rate at which this diffuses back from the tissues ultimately determines how quickly the patient wakes up. The combination of the tissue-blood and blood-gas partition coeff determines how quickly the patient wakes up.
On an O2 tank the embedded stamp that reads "AA" means what?
AA means medical grade gas.
How are medical gas cylinders tested to ensure that they can handle their pressures?
hydrostatic testing.
What is the mechanism on gas cylinders that protects from explosion if the content's pressure increases?
Woodsmedal disk or frangible disk.
What is the best way to determine what gas is in a tank?
Read the label.
Don't go by the color of the tank.
What is vol% mathmatically?
SVP/atm pressure mmHg x 100
What is the Pmac1 superior to vol% when determining MAC sedation?
It converts MAC to *pressure values. Alveolar pressure gradients partially determine anesthetic onset time.
How do you convert vol% to Pmac1?
Pmac1=(vol%)x(760mmHg) / 100
How is vol% calculated?
vol%= (Palveolar)/ (Patm) x (100)
With anesthesia machine turned on and flowmeter off, what is the flow of O2 to the pt?
When you want to use O2 from the O2 tank on the machine, how can you be sure you're using the tank O2 and not the wall O2?
Unplug the wall O2.
What are several mechanisms that are designed to prevent hypoxic gas delivery to pts?
-manufacturer precautions (right gas/right tank)
-DIS/PIS (diameter/pin index system
-failsafe valve/OFPD
-Link25/ORMC (ox ration monitor control)
-FIO2 analysis in CGO
-"always on" 200cc O2 flow
-O2 as last gas flowmeter
What is the vapour pressure of water?
What is specific heat?
The amount of heat required to raise the temp of 1kg of a substance 1 degree kelvin.
What is latent heat?
the amount of heat required to convert 1 kg of a substance from one phase to another at a given temp? Expressed in J/kg.
What is the second gas effect?
the second gas diffuses faster into the blood at the alveocap mem, so the relative concentration of the other gases in the alveoli are increased.
What is the phenomenon called when N2O is bleeding out of the blood into the alveoli and causing hypoxia?
diffusion hypoxia.
Draw an entire diagram of a Datex-Ohmeda anesthesia machine.
Yeah, the WHOLE thing baby...
CO2 e-cyl
1590 L
O2 e-cyl
1900 psig
660 L
N2 e-cyl
1900 psig
610 L
Air e-cyl
1900 psig
625 L
N20 e-cyl
745 psig
1590 L
He2 e-cyl
1600 psig
500 L
CO2 H-cyl
doesn't exist
O2 H-cyl
2200 psig
6900 L
N2 H-cyl
2200 psig
6400 L
Air H-cyl
2200 psig
6550 L
N2O H-cyl
745 psig
What is an acronym to remember gas tanks and their Press/L?
c-o-n-a-n H

(like Conan the Barbarian)
What are the differences between Datex-Ohmeda and Drager regarding O2/N2O flow protection valve?
D-O: failsafe valve, all or nothing, off at <25psi

Drager: OFPD, proportional to O2 pressure, off at <12 psi
What are differences between Ohmeda and Drager regarding pop-off valve?
D-O: has pop off valve, 135 psi
Drager: no press relief valve, the vaporizer compensates for pumping effect
What is difference between Datex-Ohmeda and Drager regarding outlet check valve?
D-O has a check valve.
Drager has no check valve, the vaporizer compensates for pumping effect.
Describe the Link-25 system in detail and which brand machine uses it:
29 cogs on O2 and 14 on N2O flowmeter knobs. Maintains a minimum 25% FIO2. N20 can "float" down and O2 can float up without engaging the teeth, but if the ratio is later adjusted the teeth will engage to maintain FIO2 >25% at all times. Link 25 is a Datex-Ohmeda design.
What is the ORMC system and (in detail) how does it work? Which brand has this?
Drager Narcomed uses this. Flow of O2 through flowmeter meets a resistor which pressurizes a diaphragm and moves the bar to the left opening the N2O slave control valve. N2O must pass through the slave control valve to reach the flowmeter, so it can only flow if sufficient O2 pressure is being generated. If the N20 pressure increases, it's diaphragm push back against the bar and the O2 diaphragm thereby closing the slave control valve.

***there are no 2nd stage O2/N2O pressure regulators with ORMC's.
What are the differences between Datex-Ohmeda and Drager regarding 2nd stage O2/N20 reducing valves?
D-O has them.
Drager does not.
What is the difference in pneumatic vent circuits between Datex-Ohmeda and Drager?
D-O is proximal to main on/off so it can run the vent when machine is OFF. If you're on tank O2 it can be sucked dry very quickly.

"Drager is distal" to on/off switch so machine must be ON to use the vent.
Draw a detailed diagram of a Drager anesthesia machine.
oooooohhhhh yeeeeaaaaahhhhh.

fun times...
What is the only way to check the low pressure system for leaks on a Datex-Ohmeda system (except Modulus 2+ or Modulus CD)?
the LOW VOLUME neg pressure bulb test
What are the two ways to test for leaks from the flowmeters to the CGO on Drager machines?
the LOW VOLUME negative pressure bulb test or the positive pressure LOW volume using the rigid short bypass tubing substituted for the Y tubing on the breathing circuit.
What is the Fa/Fi ratio:
alveolar O2/inspired O2 ratio
What is MAC?
the vol% of an agent that prevents movement to stim in 50% of patient. It is agent specific. Better to use Pmac1 though.
Why is Pmac1 superior?
it gives the partial pressure of the agent at the alveolar level that prevents movement in 50% of patients. You can compare between agents more easily this way.
How do you convert vol% to Pmac1?
vol% x 760 / 100 = Pmac1
What is the definition of osmotic pressure?
the pressure that would need to be applied to a system to prevent H2O from diffusing across a semi-perm membrane.
At zero degrees C, 1 GMW of a substance disolved in 22.4 liters of water will exert what osmotic force?
1 atm.
At zero degrees C, 22.4 L of water is exerting an osmotic force of 1 atm. How much of the solute is disolved in solution?
1 GMW.