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*Anesthesia Concepts 2 > Gas Laws :( > Flashcards

Gas Laws :( Flashcards

1
Q

What is the molecular theory of matter?

A

matter is made of molecules that can exist in solid, liquid, gas

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2
Q

What is the kinetic theory of matter?

A

molecules are in constant (random) motion and have attraction between them (van der waals forces)

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3
Q

What is Avagrado’s hypothesis and number?

A

-2 diff containers containing 2 diff gas at same temp and pressure = same number of molecules
1 mole = 6.02 x10^23 molecules

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4
Q

How do you determine a mole?

A

1 mole = 1 gm x molecular weight

i.e. 1 mole of O2 = 32 g

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5
Q

How many liters does 1 mole of ANY substance occupy?
How many molecules would 1 mole of O2 have and how many liters would it occupy?
(Avagadro)

A

22.4 liters

therefore 6.02 x 10^23 molecules of O2 = 32 g and occupies 22.4 l

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6
Q

How are vaporizers calibrated?

A

using Avagadro’s hypothesis:
-i.e. Sevoflurane = 200 g
1 mole of sevo is 200 g and occupies 22.4 l at S.T.P (standard temperature and pressure)
-so if only putting 20 g of sevo into vaporizer then = 0.1 mole, it will occupy 2.24 l when it all vaporizes

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7
Q

What is Boyle’s gas law?

A

as pressure increases, volume decreases
(when temp is constant)
V = 1/P

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8
Q

What is an example of Boyle’s law in anesthesia?

  1. reservoir bag
  2. E cylinder
  3. spontaneous breathing
  4. bellows
A
  1. applying pressure (squeezing) reservoir bag decreases volume
  2. a full E cylinder of O2 = 625 L (small volume is at high pressure of 2000 PSI), as you open tank, pressure decreases and volume increases
  3. (inspiration) when intrapulmonary (lungs) pressure becomes more negative (decreases), intrapulmonary volume increases
  4. as pressure increases, volume within bellows decreases
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9
Q

What is Charles’ gas law?

A

as temperature increases, volume increases

V/T = constant (when pressure is constant)

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10
Q

What is Gay-Lussac’s gas law?

A

as temperature increases, pressure increases (when volume is constant)
P/T = constant

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11
Q

What is an example of Gay-lussac’s law regarding a gas cylinder?

A

full cylinder of gas moves from air conditioned hospital (70 degrees F) to loading dock (100 degrees F), pressure will increase

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12
Q

What is the universal gas law?

A

PV = nRT

n =  # of moles of gas (Avagadro)
R = universal gas constant
T = absolute temp
P = pressure
V = volume
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13
Q

What is an example of the universal (ideal) gas law regarding cylinders?

A

PV = nRT
-as cylinder of compressed gas empties, pressure falls
-cylinder has a constant volume
-# of moles (n) decreases as gas exits cylinder = pressure decreases
(P = n)

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14
Q

What is Dalton’s law?

A

-total pressure of gas mixture = sum of partial pressure of each gas
total P = P1 + P2 + P3
-in mixture of gas, pressure of each gas is same as if it were alone in the container

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15
Q

What is an example of Dalton’s law regarding the gas mixture of air?

A 
O2 = 21% > 760 mmHg x .21 = 160 mmHg
N = 79% > 760 mmHg x .79 = 600 mmHg
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16
Q 
Determine the partial pressures of each for a mixture of inhalation anesthetic:
50% N2O
44% O2
6% Desflurane
total = 100% to patient
A

N2O > 760 x .50 = 380 mmHg
O2 > 760 x .44 = 334 mmHg
Desflurane > 760 x .06 = 46 mmHg

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17
Q

What is Fick’s Law of Diffusion?

A

rate of diffusion across membrane is directly proportional to:
1. concentration gradient (pp diff of gas)
2. surface area of membrane
3. solubility
and indirectly proportional to
4. thickness of membrane
5. molecular weight
V (gas) = SA x solubility x pp diff/ mol wt x distance

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18
Q

How does Fick’s law apply to anesthetic gases?

  1. N2O as a second gas
  2. N2O concentration
  3. alveolar-capillary membrane
  4. air pockets
  5. ETT cuff
  6. placental transfer
A
  1. 2nd gas effect - high concentration of first gas (N2O) accelerates uptake of 2nd gas
  2. concentration effect - uptake of high volumes of N2O concentrates remaining 2nd gas
  3. diffusion of gas across alveolar-capillary membrane (diffusion hypoxia - gradient that is driven by hypoxia = high to low)
  4. expansion of air pockets - with N2O (34x more soluble than N in blood) - N2O diffusing in is > N going out
  5. expansion of ETT cuff with N2O use
  6. placental transfer of drugs and O2
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19
Q

What is Graham’s law?

A

as molecular weight increases, rate of diffusion decreases

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20
Q

What is Henry’s law?

A

increased amount of gas dissolved = increased partial pressure

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21
Q

How do you apply Henry’s law to ABGs if

PaO2 = 600 mmHg and PaCO2 = 35 mmHg

A 
1. Henry's law allows calculation of O2 and CO2 dissolved in blood
O2 constant = 0.003 ml/100ml/mmHg pp
CO2 constant = 0.067 ml/100ml/mmHg pp
PaO2 = 600 x 0.003 = 1.8 ml/100ml blood
PaCO2 = 35 x 0.0067 = 0.23/100 ml blood
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22
Q

How do you apply Henry’s law to PaO2 when delivering O2?

A
  • Multiply FiO2 x 5 (because 21% = 1/5 of 100%)
  • if 21% RA > 21x5 = 105 mmHg x 0.003 = .315 ml/100 ml blood
  • if deliver 40% FiO2 > 40 x 5 = 200 mmHg x 0.003 = 0.6ml/100 ml blood
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23
Q

What is critical temperature?

A
  • temp before substance converts to gas despite pressure applied
  • gas if ambient (room) temp is ABOVE critical temp
  • liquid if sufficient pressure is applied at ambient (room) temp BELOW critical temp
24
Q

What is the critical temp for O2? What is its risk for becoming liquified?

A
  • -119 degrees Celsius (-182 degrees F)
  • O2 cannot be liquefied at room temp regardless of pressure applied
  • room temp = 25C
25
Q

What is the critical temp for N2O? What is room temp?

What is its risk for becoming liquified? How is it stored?

A
  • 39.5 Celsius, room temp is 25 Celsius
  • with pressure, N2O can be liquified at room temp
  • stored as liquid in 745 PSI in cylinder
26
Q

What is adiabatic cooling?

A

caused when substance changes phases > change in substance temp without + or - heat

27
Q

What is Joule-Thompson effect?

A

expansion of gas = cooling

i.e. as gas exits cylinder (expands) > surrounding air cools = condensation from moisture in cylinder

28
Q

What is Poiseuille’s law?

A

laminar flow (low flow rates)
Flow = (P1-P2)r^4/viscosity x length
flow increases if pressure gradient and/or radius increases
flow decreases if length of tube and/or viscosity of fluid increases

29
Q

How does Poiseuille’s law apply to anesthesia? (4)

A
  1. IV flow (radius of needle, viscosity)
  2. airway
  3. vascular flow (polycythemia (viscous) vs anemia (low viscosity)
  4. gas flow - thorpe tubes aka flow meters
30
Q

What is an influence of flow when it is laminar?

Use flow meter as example.

A

viscosity

-at low flow in flow meters = located in annular-shaped orifice (tube) around float&raquo_space; flow is influenced by viscosity

31
Q

What is an influence of flow when it is turbulent?

Use flow meter as example.

A

density (D = m/v)

-at high flow in flow meters = located in wider top part of float tube&raquo_space; flow is influenced by density

32
Q

What is Reynold’s number? What is Reynold’s number when flow is turbulent?

A 
Rn = v x d x D / n
# = velocity x density x diameter/viscosity
> 2000
33
Q

What is Beroulli’s theory?
What effect does this have on pressure and flow in the middle (narrow diameter) vs outer (wider diameter) portions of tube?

A
  • flow is faster thru constricted portions (middle) and slower at wider portions (by wall of tube)
  • narrow diameter = decreased lateral wall pressure = increased speed
  • wider diameter = increased lateral wall pressure = decreased speed
34
Q

How does Bernoulli’s theory apply to Venturi tubes?

A

-venturi tubes have varying diameters&raquo_space; as tube narrows, velocity increases, dropping pressure

35
Q

Name 3 things in anesthesia that apply to Bernoulli’s theory and venturi tubes.

A
  1. nebulizers
  2. venturi O2 mask (24-40% O2)
  3. jet ventillation
36
Q

What is Beer’s (Beer-lambert) law?

A
  • radiation absorbed of a solution of a concentration = same amount absorbed of 2x’s thickness of solution at 1/2 concentration (beer)
  • each equally thick layer absorbs same fraction of radiation that passes thru it (lambert)
37
Q

What is an example of Beer’s law in anesthesia? How does it work?

A
  • pulse ox
  • 2 LEDs: 1 red emits light at 660 nm and 1 infrared emits light at 940 nm
  • LEDs shine across pulsatile tissue bed and measures absorption on opposite side
  • compared red vs infrared and calculate O2 sat
38
Q

Which of these is the red light and infrared light of the pulse ox?
oxyhgb
deoxyhgb

A

oxyhgb 940 nm = infrared

deoxyhgb 660 nm = red

39
Q

What things can cause errors in pulse ox?

A
  1. artifact
  2. alternate types of hgb
  3. injections/chemicals
  4. nail polish
40
Q

What kind of errors will the following have on pulse ox?

  1. polycythemia
  2. methylene and isosulfan blue
  3. indocyanine green and indigo carmine
  4. blue nail polish
A
  1. none
  2. methylene and isosulfan blue - false low
  3. indocyanine green and indigo carmine - slightly false low
  4. blue nail polish - false low
41
Q

What kind of errors will the following have on pulse ox?

  1. carboxyhgb
  2. methgb
  3. hgbF (fetal)
  4. hgbS (sickle cell)
A
  1. false high
  2. if SaO2 > 85%, false low; if SaO2 < 85%, false high
  3. none
  4. none
42
Q

What is La Place’s law?

A

T (tension) = P (pressure) x r (radius)

increasing pressure or decreasing radius = increases tension

43
Q

What are 3 examples of La PLace’s law?

A
  1. alveoli - require surfactant to decrease tension
  2. blood vessels (aneurysms) - rupture due to increase pressure causing increase tension
  3. ventricle - dilated (increased pressure) ventricle = higher wall tension
44
Q

What is Ohm’s law?

A

resistance will allow 1 amp of current to flow under the potential of 1 volt
W (resistance) = volt/current
or
E (voltage) = I (current/amp) x R (resistance)

45
Q

How does Ohm’s law apply to anesthesia?

A
  1. strain gauges in pressure transducers

2. thermistors (a resistor)

46
Q

What is macroschock?

What are potential causes?

A
  • current through body

- faulty wiring, improper grounding

47
Q

What is microshock?

What are potential causes?

A
  • current in/near heart

- pacing wires, faulty equipment during cardiac cath

48
Q

Describe the following symptoms of macroshock levels:

  1. 1 milliamp
  2. 5 mAmp
  3. 10-20 mAmp
  4. 50 mAmp
  5. 100-300 mAmp
  6. 6000 mAmp
A
  1. skin tingling
  2. max harmless current
  3. let go of source
  4. pain, LOC, mechanical injury
  5. Vfib, resp still intact
  6. complete physiologic damage
49
Q

At what level of microshock does v-fib occur?

A

50-100 microAmps

50
Q

What do percentage solutions indicate?

A

grams per 100 ml

-convert to mg per ml

51
Q

What does 2% lidocaine mean?

What is the final concentration per ml?

A
  • 2% lidocaine = 2 g of Lido in 100 ml
  • 2000 mg per 100 ml
  • 20 mg per 1 ml
52
Q

What is 0.75% bupivicaine mean?

What is the final concentration per ml?

A
  • 0.75 g of bupivicaine per 100 ml
  • 750 mg per 100 ml
  • 7.5 mg per 1 ml
53
Q

What do concentration solutions indicate?

A

grams per # of ml

54
Q

What does 1:100,000 epi mean?

What is the final concentration per ml?

A
  • 1 gram of epi in 100,000 ml
  • 1 mg in 100 ml&raquo_space; 1000 mcg in 1 ml
  • 10 mcg per 1 ml
55
Q

What does 1:10,000 epi mean?

What is the final concentration per ml?

A
  • 1 gram of epi per 10,000 ml
  • 1000 mg per 10,000 ml
  • 0.1 mg per 1 ml (or 100 mcg/ml)
56
Q

What does 1:200,000 epi mean?

What is the final concentration per ml?

A
  • 1 g of epi per 200,000 ml
  • 1000 mg per 200,000 ml = 1 mg per 200 ml
  • 1000 mcg per 200 ml = 10 mcg per 2 ml
  • 5 mcg per ml
57
Q

What is in each ml of 2% lidocaine with 1:200,000 epi?

How much is in 5 ml?

A

-2 g lidocaine per 100 ml
-2000 mg per 100 ml = 20 mg per ml
-1 g epi per 200,000 ml
-1000 mg per 200,000 = 1 mg per 200 ml
-1000 mcg per 200 m = 10 mcg per 2 ml
-5 mcg per ml
=20 mg of lido + 5 mcg of epi in 1 ml
20 x 5 = 100 mg, 5 x 5 = 25 mcg
= 100 mg of lido + 25 mcg of epi in 5 ml

*Anesthesia Concepts 2 (6 decks)

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