Physics Final Flashcards
Human tissue heat capacity is ____ that of water
0.85
Define specific heat capacity
amount of heat required to raise temperature of 1 kg of a substance 1 K
Define heat capacity
amount of heat required to raise the temperature of a given object by 1 K
What is the specific heat capacity of water?
4.18 kJ kg-1
1 kcal kg-1
1 Cal/g
What is the SI unit of heat capacity?
J/K
1 calorie = ? Joules
4.18
1 Calorie = ? calories
1000 calories
What is the specific heat of blood?
0.86 cal/ (gm x *C)
You administer 4 L of IV fluids @ 21*C for a 70 kg patient. What effect will this have on the patient’s temperature?
lower it by approx. 1*C
Vapor pressure is dependent on what?
temperature and substance
Do you lose energy or gain energy when vaporizing water?
Lose energy
What is HME?
Heat moisture exchanger
Why do we need humidification?
- maintain function of cilia
- maintain surfactant properties
- reduce drying of secretions
What type of humidifier is the most efficient?
ultrasonic nebulizer
What is the difference between absolute and relative humidity?
Absolute: mass of water vapor in a given volume of air
Relative: Absolute vs. amt required to saturate that given vol. (ex. weather - usually %)
What is difference between hydrophobic and hygroscopic?
Hydrophobic hates water (pore membranes)
Hygroscopic loves water (wool and foam coated membranes)
What does HMEF stand for?
Heat Moisture Excange Filter
What does the S beside the number on HME mean?
Means a sample port available on filter
What does the number on the side of the HME represent?
How much tidal volume can accurately be put through humidifier
What are some hazards of HME’s?
Excessive breathing circuit resistance which could limit spont breathing
Weight could cause kinking of ETT which causes airway obstruction
Can aspirate HME material
Increased dead space rebreathing
Another site for airway disconnection
What effect do HME’s have on dead space and airway pressure?
A. None
B. Increase, Decrease
C. Decrease, Increase
D. Increase Both
E. Decrease Both
D. Increase both ANNA DID YOU MEAN D INCREASE BOTH???????
YES!!!!!!! FORGOT TO CHANGE THE ANSWER AFTER I ADDED A 2ND PART TO THE QUESTION
Maximum deposition occurs in the alveoli for particles with what diameter?
3 micrometers
What is the relative humidity of the trachea and the HME?
- 77 trachea (77%)
- 57 HME (57%)
What is Henry’s Law?
At a particular temperature the amount of a given gas dissolved in a given liquid is DIRECTLY proportional to the PARTIAL PRESSURE of the gas in equilibrium with the liquid.
Gases are (more/less) soluble at higher temperatures?
LESS!!!
ANNA I HAVE THAT GASES ARE LESS SOLUBLE IN MY NOTES???
I SHOULDN’T TRY TO STUDY WHILE FALLING ASLEEP
What is the Otswald solubility coefficient?
the volume of gas which dissolves in one unit of the liquid at the temperature concerned (is independent of pressure)
What is the Main difference between Otswald solubility coefficient and Bunsen solubility coefficient?
Otswald is used more in Anesthesia and does not have to correct for temp. and pressure
What is the standard temperature used when determining Ostwald coefficients?
37* C
Define partition coefficient
Ratio of the amt of substance present in one phase compared with another, the two phases being of equal volume and in equilibrium
What is the blood-gas partition coefficient for N2O?
0.47
What is the blood-oil partition coefficient for N2O?
0.34
What is the oil-blood partition coefficient for N2O?
2.98
When determining partition coefficients, what must be accounted for?
The order of the phases you wish to determine.
EX gas-blood partition coefficient (1L / 0.47L) much different than blood-gas coefficient (0.47L / 1L)
List the path/order a gas takes to enter body.
Machine –> lungs
Lungs –> blood
blood –> fat (brains most important for us)
The Oxygen content equation is
CaO2 = 1.36 x (SaO2/100) x 0.0031 x PaO2
What is the normal range for CaO2?
16-22 ml O2 / dL
What is the formula for uptake of inhalational agents?
Uptake = Solubility x CO x (Pa-Pv)
What is a MAC?
Minimum Alveolar Concentration in
Percent at equilibrium, at 1atm, at which 50% of test subjects will not respond to noxious stimuli
What is the determining factor of whether the patient has reached a proper MAC value and anesthesia has been produced?
Partial pressure of anesthetic agent in the brain
What is the partial pressure in the brain for an agent @ MAC of 2%?
What is partial pressure that produces anesthesia for an agent at MAC of 1%?
(0. 02 x 760mmHg) = 15.2mmHg
7. 6 mmHG
What is the MAC of Sevo for a 24 year old?
How does it change per decade?
2.6%
Decreases 0.2%
Gases with a (lower/higher) solubility will reach pressures faster
lower
Anesthesia is produced by what?
the partial pressures of the anesthetic agents in the brain tissue
Concentration has what effect on induction?
Greater concentration = faster induction
The more soluble an agent is in fat, the more _______ that agent is as an anesthetic agent.
POTENT
Low solubility in the blood = ____ induction and recovery
fast
What age population has the highest MAC values?
1 - 6 months old
What is the partial pressure of N2O at 1 ATM?
800 mmHg (helps explain why MAC is 105%) (its above 760 mmHg)
GENERALIZATIONS
Anything that increases delivery of anesthetics to the alveoli, thus increasing partial pressure will hasten (speed up) anesthesia
Conversely, anything that enhances removal from the lungs, increasing systemic uptake, will lower alveolar pp and thus delay anesthesia
For inhaled anesthetics, increasing the total Cardiac Output does what to the onset of general inhalational anesthesia?
slows it
increases O2 demand, so pulls gas from alveoli delaying equilibrium
In tissues, what is order of uptake of the 3 main compartments?
Vessel rich group (VRG)
Muscle group
Fat group
What are the Blood-Gas partition coefficients for:
Desflurane
Nitrous Oxide
Sevoflurane
Isoflurane
Halothane
Ether
Desflurane 0.42
Nitrous Oxide 0.47
Sevoflurane 0.68
Isoflurane 1.4
Halothane 2.3
Ether 12.1
What is the second gas effect?
when potent agents are administered with nitrous oxide so that the potent agent will be delivered in increased amounts to the alveoli
What is the concentration effect?
when nitrous is administered in high concentrations during induction. it is taken up rapidly and more gas rushes in to take its place, increasing alveolar ventilation
What are the Vapor Pressures and MAC values for Halothane?
VP @ 20* C = 243
MAC 0.75%
What are the Vapor Pressures and MAC values for Isoflurane?
VP @ 20* C = 238
MAC 1.2%
What are the Vapor Pressures and MAC values for Desflurane?
VP @ 20* C = 664
MAC 6-7.25 %
What are the Vapor Pressures and MAC values for sevoflurane?
VP @ 20* C = 160
MAC 1.6-2.6 %
What is the opposite of the concentration effect?
diffusion hypoxia: high rate of transfer of anesthetic from blood and tissues to alveoli, thus diluting alveolar oxygen
(lessoned by administration of supplemental oxygen)
How much total flow will come out of the vaporizer if running 5L flow and want 1% agent of Halothane?
Halothane VP 240. This is 1/3 of atmosoheric pressure.
At 5000ml flow, 1% of this is 50 mL. This means we need 50ml of agent.
Since agent is 1/3 of atm, 50/(1/3) will give total flow. Equates to 150mL flowing out of vaporizer.
This means 100 ml (150-50) will need to flow into flowmeter
5000ml FGF, 100 O2 into flowmeter, 50ml Agent, 150 ml out of flowmeter
What kind of vaporizer uses a fractioning or splitting valve to control amount of flow into flowmeter?
Plenum vaporizer
Which anesthetic agent is the most variable in patients?
Sevoflurane
What is the Vaporizer equation? And whose law does it encompass?
(Va / Vo2) = (Pa / Po2) = (Pa / {Pb -Pa})
Encompasses daltons law
Given Vo2 = 100 ml / min
Pb = 760mmHg
Pa = 200mmHg
What is Va?
(Va / Vo2) = (Pa / Po2) = (Pa / {Pb -Pa})
So (Pa / Pb-Pa)= 200/ 760-200 = 0.357
Since Va/Vo2 = (Pa / Pb-Pa) , then Va/Vo2 = 0.357
Solving for Va = 100 ml / min x 0.357 = 35.7 ml / min
What is the boiling point of a liquid?
The temperature at which the vapor pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding environmental pressure
What kind of vaporizer does desflurane require?
A measured flow vaporizer
What is a variable bypass vaporizer?
When the carrier gas flow is split so that only a portion passes through the vaporizer (this portion picks up the saturated agent) then leaves the vaporizer to mix with remainder of gas flow that did not enter vaporizer.
Using a adjustable valve, you can alter the final concentrations of agent by varying the splitting ratio between bypass gas and vaporizer gas flows
To turn on more agent, which way do you turn the dial on top of the vaporizer?
Counter-clockwise
TRUE OR FALSE: All fresh gas goes through all modern vaporizers?
TRUE
Temperature controlled valves are used in some vaporizers to adjust the flow through the vaporizing chamber automatically. Name 3 kinds of temperature controlled valves:
Bimetallic strip
Bellows
Metal rod
Larger amounts of fresh gas goes into agent when the temperature is ______.
down/lower
When the temperature is up/higher, _______ amounts of fresh gas goes into the agent.
Smaller
The Tec 5 type vaporizer is a variable degree vaporizer, what does this mean?
That variable amounts of gas are allowed to flow through the vaporizer chamber
The principle of injection of a liquid anesthetic agent requires P1 > P2. Explain how this works in the vaporizer.
Adjusting the throttle valve(dial on top of vaporizer) creates a forced greater pressure of P1 that is into anesthetic agent chamber. This increase causes agent to be shot out of nozzle leading to gas flow out of vaporizer. Greater the pressure of P1, the more agent is injected into flow out of vaporizer, resulting in greater concentration of agent.
The Tec 6 type vaporizer is a heated and pressurized vaporizer used only for Desflurane. It is a kind of liquid injection vaporizer. What temperature and pressure is desflurane inside the vaporizer?
39* C
2 atm = 1520 mmHg
Does barometric pressure and altitude ultimately change the concentrations of anesthetic we set on the vaporizer?
Ultimately no. (Anna if you want to clear this up to make more sense please do, this was hard to explain this late at night)
While barometric pressure has decreased (thus increasing the amount of agent being delvered in the circuit compared to what has been dialed-in), the physiological conditions have also been altered in a way that the body needs more agent to achieve anesthetic depth.
So while volume % has increased, potency of MAC has been decreased, thus actually needing the increased volume.
ANSWER: NO WE DO NOT ADJUST BASED ON BAROMETRIC PRESSURES DUE TO LOCATION
What is the maximum agent concentration that can be achieved?
Vapor pressure of agent
Barometric pressure
What organization is in charge of vaporizers and standards?
American society for testing and materials
What organization oversees the halogenated agents?
FDA
What is minimal FGF for SEVO?
2L of flow for 2 hours
Using minimal flow for SEVO, At 1/2 MAC, how many hours can you run at 1L flow?
4 hours
Using the minimal flow for SEVO, running 1L flow for 1 hour will give what MAC?
2 MAC
What drives diffusion?
Molecular motion
What is the diffusion equation?
dM / dt = V x C
dM = rate of change
dt = change in time
V = volume per time
C = concentration
Rate of diffusion equation
dM / dt = dP / dx
dP = change in pressure
dx = distance traveled change
What is Ficks Law?
dM / dt = dC / dx <———————> dM / dt = dP / dx
Rate of diffusion of a substance across a unit area is proportional to concentration gradient
The greater the solubility of the gas in the a liquid, the _________ will be the concentration gradient between the surface layer of the liquid and its deeper layers.
greater
True or False: A more soluble gas diffuses into the deeper layers of the liquid more rapidly?
TRUE
What gas should never be used in laparoscopic cases because of its tendency to settle into holes/cavities in the body?
Nitrous Oxide b/c its flammable and using bovie could spark and explosion inside pt
What law states that the rate of diffusion of a gas is inversely proportional to the square root of its molecular weight?
Graham’s Law
What is osmotic pressure?
The hydrostatic pressure that is needed to overcome a concentration gradient of that solution
An osmotic pressure of 101.325 kPa (1 atm, 760 mmHg) is produced when ___ mol solute is dissolved in 22.4 L of solution at 0*C ?
1 mol
How many moles does NaCl apply towards osmotic pressure?
How many does Glucose?
2 mol
1 mol
Molarity is?
Moles of solute
Liters of solution
What is: moles of solute
Kilogram of solvent
Molality
Using what kind of solution will cause a lysing of the cells?
Hypo-osmotic
Calculate the mmole / L of Normal Saline 0.9%
NaCl molecular weight = 23 + 35.5= 58.8 gm/mole
NS 0.9% = 0.9 gm/dl
- 9 / 58.5 = 0.0154 mole/dl = 15.4 mmole/dl
- 4 mmole/dl X 10 dl/L = 154 mmole/ L
What is the osmotic pressure of plasma?
~ 300 mmole / L
Why is NS “normal” and why do we use it during surgery?
It is normal b/c of its osmolarity. This osmolarity means you will not have a net movement of fluid into or out of the cells
Explain how NS 0.9% has an osmolarity of 154 mmole / L yet has no net movement of fluid with blood plasma that has an osmotic pressure of ~ 300 mmole/ L
When NaCl dissociates, it becomes 2 mol, thus doubling the number of mmole/L, bringing the total to appoximately 300 mmole/ L, which is the same as plasma
What is potentially fatal side effect of giving too much NS?
Hyperchloremic acidemia
What is the osmolarity of LR?
278 mmol / L
Define oncotic pressure
Osmotic pressure generated by plasma proteins in the capillaries
What is the net osmotic pressure generated in the capillary loop?
3.5 kPa
What agecy controls the vaporizers’ standards?
ASTM American Society for Testing and Materials
Arterial pressure generated by plasma proteins is what in the capillaries?
7 kPa or 52.5 mmHg
Glomerular filtrate is approx how many mosmol/L?
300 mosmol/L
After fluid reabsorption, what is osmolarity of urine?
1000 mosmol/L
What is the osmotic pressure of blood colloids?
4 kPa (30 mmHg)
What is the min blood pressure that is required for efficient kidney perfusion and function?
70 mmHg
(30 mmHg from osmotic pressure of blood colloids, 30-40 mmHg of pressure required to overcome resistence of kidney tubules)
Who’s law states that the depression or lowering of vapour pressure of a solvent is proportional to the molar concentration of the solute?
Raoult’s Law
