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Chem/Physics- Hannah > Exam 3: Gas Laws & Cylinders > Flashcards

Exam 3: Gas Laws & Cylinders Flashcards

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1
Q

Dalton’s Law

A

the total pressure of a gas is equal to the sum of the pressures of the individual gases in a mixture
P1+P2+P3=total pressure

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2
Q

What are the implications of Dalton’s Law to anesthesia?

A

We have to make sure the patient is breathing in a minimum of 21% fiO2 with our other gases
-vapor pressure as a percent of atmosphere

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3
Q

Calculating the PP of unmeasured gas in a mixture:

Ptotal is 200 mmHg, gas 1 is 50 mmHg, gas 2 is 40 mmHg; what is gas 3?

A

Gas 3 is 110 mmHg

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4
Q

Calculate the total pressure if pressure in mmHg is 40 for gas 1, 30 for gas 2, and 100 for gas 3.

A

170 mmHg

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5
Q

At sea level agent monitor says ETiso= 8 mmHg. What is volume % for isoflurane?

A

1%

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6
Q

At sea level agent monitor says ETsev=2%. What is PP for sevoflurane?

A

15.2 mmHg

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7
Q

Describe atmospheric pressure, barometric pressure, and ambient pressure

A

Atmospheric pressure is the weight of atmosphere pushing against an object; at sea level it is 760 mmHg
atmospheric pressure can be used interchangeably with barometric pressure
Ambient pressure is the pressure of the surrounding medium on you or an object. If you are underwater, the ambient pressure= atm + water (hydrostatic) pressure

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8
Q

If an object is sitting out in room air, then

A

ambient pressure=atmospheric pressure

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9
Q

What is the alveolar gas (Air) equation?

A

PAO2= PiO2 - (PaCO2/RQ) + F
F is a correction factor that is usually ignored
PIO2 is the partial pressure of O2 in inspired air and equals PIO2= FiO2 x PB-PH20 (alveolar)
RQ is the respiratory quotient and is typically 0.8

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10
Q

Why is the alveolar gas equation useful?

A

it can tell us if there is a diffusion problem since we have the calculation PAO2 and can measure PaO2

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11
Q

RQ- Respiratory Quotient is reflective of

A

8 CO2 molecules are produced for every 10 O2 molecules burned so our ratio is 0.8

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12
Q

What is the alveolar-arterial oxygen gradient?

A

(PAO2-PaO2)
This is not as good when dealing with high FiO2
Normal range is 5-15 mmHg

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13
Q

What alveolar-arterial calculation should be utilized when dealing with high fiO2?

A

PaO2/PAO2

ratio should be 0.75 or greater if there is no diffusion problem

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14
Q

What are normal reasons for alveolar arterial oxygen diffusion differences?

A

regional VA/Q mismatch (largest influence)

Normal anatomic shunt of the blood (Thebesian circulation of the bronchial and circulatory system)

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15
Q

What are reasons for pathological A-a O2 differences?

A
  • Significant VA/Q mismatch
  • Intrapulmonary shunts
  • A-v-cap membrane diffusion block
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16
Q

What is an additional way to calculate arterial-alveolar ratio?

A

PaO2/FiO2 ratio
normal >200
<200 observed in ARDS

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17
Q

Henry’s Law

A

the amount of gas dissolved in a liquid is directly proportional to the pressure applied to the gas as it overlies the liquid

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18
Q

Henry’s Law formula

A

Cgas= Pgas/Kh
where C= dissolved gas concentration
Kh= solubility constant of gases leaving the solution
Pgas= partial pressure of the gas above the liquid and represents gas molecules entering the liquid

19
Q

What is the solubility of CO2 compared to O2?

A

CO2 is 22x more soluble than O2

20
Q

How many times more diffusable is CO2 compared to O2?

A

20x more diffusable

21
Q

What is the amount of oxygen delivered to the tissues?

A

= O2 content x cardiac output

22
Q

What is the oxygen content equation?

A

Arterial O2 content= (1.34 mL O2/gm hgb x 15 gm hgbb/ 100 ml blood x % saturation) + (0.003 x PaO2)

23
Q

How would our venous O2 content calculation differ from our arterial O2 content?

A

the % saturation would be about 75%

24
Q

How much oxygen should we expect to carry in 1 deciliter of blood?

A

20.4 mL

25
Q

What is Boyle’s Law?

A

P1V1=P2V2
at a constant temperature, pressure of a gas is inversely proportional to volume
Must assume two things: constant temperature & closed container (so number of moles is constant)

26
Q

What is Charles’ Law?

A

V1/T1=V2/T2
At a constant pressure, the volume of a gas is directly proportional to its absolute temperature
Must have constant pressure and constant # of moles (i.e. closed container)
Temperature is in Kelvin

27
Q

What does the combination of Charles’ & Boyle’s Law yield?

A

P1V1/T1= P2V2/T2

28
Q

What is Gay-Lussac’s Law?

A

P1/T1=P2/T2
at a constant volume, the pressure of a gas is directly proportional to its absolute temperature
as temperature increases–> pressure increases

29
Q

Avogadro’s law

A

if we have increase n or number of moles, we have increase volume
V1/n1=V2/n2

30
Q

According to Avogadro, 1 mole of gas at STP

A

has 6.02 x 10^23 molecules and occupies 22.4 L

31
Q

What makes a gas ideal?

A

zero IMF between gas molecules

32
Q

What is the ideal gas law?

A

PV=nRT
where n= number of moles of gas
R= ideal gas constant at STP

33
Q

What is a key difference between O2 gas cyclinders and nitrous oxide?

A

The O2 is all compressed gas whereas the N2O can be highly pressurized into a liquid

34
Q

If you have a 5L tank at sea level, how many L of gas can you put into the tank if you apply a pressure of 2 atm?

A

10 L

35
Q

If we have a tank of oxygen, the amount of O2 in the tank is directly proportional

A

to the pressure

it is a linear relationship

36
Q

Expansion of a gas will

A

make things cold
if a gas is under pressure and it expands, expansion takes work and work requires energy
therefore heat is taken from the environment- endothermic process

37
Q

Compression of a gas will

A

make things warm

If a gas is being compressed, has to have less energy, so energy given off to environment will be an exothermic process

38
Q

Describe adiabatic conditions

A

will feel the heat gained or loss (heat or coolness) because it occurs so rapidly that it cannot dissipate or the area where this occurs is so insulated that it cannot be dissipated

39
Q

What are two gas effects that determine how quickly anesthesia is distributed in blood and brain?

A
  • Concentration effect

- second gas effect

40
Q

What is the concentration effect?

A

-accelerating the rate of rise of the alveolar concentration of a gas by an increasing the inspired concentration (Fa/Fi) or fraction alveolus/fraction inspired
the optimal ratio is 1

41
Q

What is the second gas effect?

A

if you are giving oxygen, and nitric oxide and then you give a 3rd gas, it will help to accelerate the rate of gas and will also suction in more of the anesthetic in the airways this is because nitric oxide is very soluble and so crosses quickly and leaves a void which brings more gas down into alveoli
-allows us to anesthetize patients more quickly

42
Q

What is the maximum operating pressure and volume for a tank of O2?

A

1900 psi & 660 L

43
Q

What is the maximum operating pressure and volume for a tank of N2O?

A

1590 L and 745 PSI

44
Q

The second gas effect has two functions:

A

concentrates remaining gases (other than N2O b/c a void is left) and it suctions other gases into lungs

Chem/Physics- Hannah (9 decks)

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