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1: Intro to Anesthesia > Chemistry & Physics > Flashcards

Chemistry & Physics Flashcards

1
Q

Are fluids compressible?

A

Fluids have little to no compressibility

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2
Q

Are gases compressible?

A

Compressible and easily change volume w/ changes in pressure and temp

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3
Q

What type of bonds does H2O have? Why is this property important?

A

polar covalent - makes it a good solvent for other polar substances but not oils

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4
Q

How does gas solubility in a liquid relate to temperature? Why?

A

Inversely, ex hypothermic pts receiving volatiles wake up slowly bc gas is more soluble in tissues when cold. Higher temps increase kinetic energy of gas and therefore molecules escape and prevent further dissolving.

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5
Q

How does gas solubility in a liquid relate to pressure?

A

Directly, increase pressure, increase solubility

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6
Q

What is Henry’s Law?

A

Gas dissolved in a liquid proportional to pp (partial pressure) of gas in contact w/ solution

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7
Q

What is the solubility coefficient of O2? Of CO2? Why is more soluble in blood and by how much?

A

0.003 mL/100mL blood/mmHg pp 0.067 mL/100mL blood/mmHg CO2, 20x

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8
Q

If PaO2 600 mmHg and PaCO2 35 mmHg how much of each dissolved in blood?

A

600 x 0.003 = 1.8 mL/100mL blood 35 x 0.067 = 2.35 mL/100mL blood

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9
Q

Increasing FiO2 is an application of what law?

A

Henry’s Law Increasing concentration of oxygen helps fix hypoxemia

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10
Q

How do you calculate O2 delivery? (DO2)

A

DO2 = CO x (1.34 x Hb x SpO2) + (PaO2 x 0.003) x 10 CO = HR x SV

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11
Q

Is most O2 in blood bound to Hb or dissolved in blood?

A

bound to Hb

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12
Q

Overpressuring vaporizer is an example of application of what law?

A

Henry’s Law Increasing pressure of volatile gas increases the speed of delivery of gas to blood and then the brain

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13
Q

How does temperature affect solubility of gas?

A

increased temp, decreased solubility decreased temp, increased solubility

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14
Q

What is Graham’s law?

A

Gas diffuses at rate that is inversely proportional to square root of its molecular wt. Therefore, as molec wt increases, rate of diffusion decreases. Smaller molecules diffuse faster.

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15
Q

What property of N2O can lead to complications? Examples (3)?

A

N2O can diffuse into air filled cavities ex. pneumo or air filled cavity expansion likely and bad - brain, abd, middle ear ex. in ett cuff, may cause tracheal mucosal damage ex. bowel distention w/ N2O delivery

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16
Q

What is apneic oxygenation?

A

Continual passive diffusion of O2 into blood via a gradient created by O2 diffusing into alveoli ventilator circuit when the pt is apneic

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17
Q

When can apenic oxygenation be used? What does it do? Hows it done?

A

obese pts, pts w/ compromised FRC - helps to increase safe apnea time NC w/ HF O2, w/ preoxy

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18
Q

What is Fick’s Law?

A

diffusion of gas across a membrane is directly proportional to: pp/concentration gradient, diffusion coefficient - solubility, membrane surface area and inversely proportional to: membrane thickness and MW of gas

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19
Q

What is Fick’s Law of Diffusion formula?

A

Vgas = area x solubility x pp difference / MW x distance

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20
Q

What are some clinical applications of Fick’s Law? (6)

A

determining pulm gas exchange, diffusion hypoxia, COPD-reduced alveolar surface tension = slower induction, placental drug transfer - drugs, O2, expansion of air pockets, expansion of ETT/LMA cuff

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21
Q

What is diffusion hypoxia?

A

Opposite of second gas effect. Happens on emergence when using N2O, because of its rapid diffusion out of the blood into the alveoli, it dilutes the concentration of other gases like O2 causing hypoxia

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22
Q

N2O is how many times more soluble in blood than N2? Whats that mean when N2O used?

A

34, volume of N2O diffusing in > volume of N2 diffusing out

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23
Q

1 torr = 1 kPa = 1 atm =

A

1 torr = 1 mm Hg 1 kPa = 10.2 cm H2O = 7.5 mmHg 1 atm = 760 mmHg = 760 torr = 1 bar = 100 kPa = 1020 cm H2O = 14.7 psi

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24
Q

Bourdon gauge measure what and how? How are they referenced?

A

high pressure from gas cylinders, zeroed to atmosphere, therefore reads 0 at 760 mmHg at sea level measure pressure via coiled tube that expands when pressure applied, linkage connects it to an arm that records pressure

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25
Q

Bourdon gauge pressure =?

A

= absolute pressure - atmospheric pressure mmHg

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26
Q

Boyle’s Law is? Whats constant? Whats the formula?

A

Volume of a gas is inversely proportional to pressure. Temp is constant. As pressure increases, volume decreases. P1V1 = P2V2

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27
Q

Example of Boyle’s Law? (3)

A

squeezing reservoir bag, storage of O2 in e cylinder (660L at 2000 psi) - small volume in tank, when released to atmosphere (lower pressure) gas expands, spont breathing - when pressure in lungs negative, volume increases

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28
Q

What’s Charle’s Law? Whats constant?

A

Volume of a gas is directly proportional to temp (in K), while pressure is constant. Therefore as temp increases so does volume.

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29
Q

What is Gay-Lussac’s Law? What is constant?

A

Pressure is directly proportional to temp (in K), w/ a constant volume. Therefore as temp increases, pressure increases.

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30
Q

What is an application of Gay-Lussac’s Law?

A

cylinder of gas moved from cold hospital to hot loading dock, pressure in cylinder increases

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31
Q

What is the Universal/Ideal Gas Law?

A

PV = nRT pressure volume mol of gas gas constant = 0.0821 L-atm/K/mole temp (K)

32
Q

How many molecules are in a mole?

A

6.02 x 10^23 molecules

33
Q

What’s Avagadro’s Hypothesis?

A

2 diff containers w/ 2 diff gases at same temp and pressure, will have same number of molecules

34
Q

How many L in one mole?

A

22.4 L, therefore 1 mole of O2 occupies 22.4 L

35
Q

Whats the molecular weight of sevoflurane? How is this concept used in vaporizers?

A

200 g/mole, occupies 22.4 L at STP 20g of sevo (0.1 mole) in vaporizer will occupy 2.24 L

36
Q

What’s Dalton’s Law?

A

Total pressure of gas mixture = PP of each gas. Also, pressure exerted by each gas is the same that it would exert if it alone occupied the container.

37
Q

Calculate the PPs of the gases in room air.

A

atmospheric pressure = 760 mmHg Air = 21% O2, 79% N2 21% x 760 = 160 mmHg 79% x 760 = 600 mmHg 160 + 600 = 760

38
Q

How much is a MAC of desflurane?

A

6%

39
Q

What is a MAC?

A

the concentration of volatile gas (as a percentage at 1 atm aka pp) that prevents the reaction to standard surgical stimulus in 50% of patients

40
Q

What is more important: PP of volatile or its concentration? Why?

A

PP, because of atmospheric pressure, affects how much is being given. Lower barometric pressure, increases vapor given.

41
Q

What is the critical temperature?

A

temp above which a substance goes into gaseous form regardless of the pressure its under therefore gas cant be liquefied if ambient temp > critical temp gas can be liquefied if sufficient pressure applied at ambient temp below critical temp.

42
Q

Whats the critical temp of O2? Whats the significance? How is O2 stored in hospital?

A

-119 C, can’t be liquefied at room temp no matter how much pressure applied. Huge quantities can be stored in liquid form at -160 C.

43
Q

What is critical temperature of N2O? Whats the significance?

A

39.5 C, bc critical temp higher than ambient temp, N2O can be stored as a liquid under enough pressure

44
Q

What is adiabatic cooling? Give an example.

A

change in temp of matter w/out gain or loss of heat when matter changes phase N2O cylinder opened fully, frost forms on outlet d/t cooling

45
Q

Describe the Joule-Thompson effect. Give an example.

A

Expansion of gas causes cooling. When gas leaves cylinder, expansion cools the surrounding air causing condensation of moisture on cylinder.

46
Q

Describe Poiseuille’s Law. What is the most significant factor, why?

A

The rate of flow is directly proportional to: radius of tube***, pressure gradient across length of tube inversely proportional to: length of tube, viscosity Most significant is radius of the tube, because is ^4.

47
Q

What is Poiseulle’s formula?

A

Q = pi x r^4 x delta P / 8 x n x L Q = flow r = tubing radius P = pressure n = viscosity L = length

48
Q

What are applications of Poiseuille’s Law? (4)

A

IV flow, aws, vascular flow (polycythemia vs anemia), Thorpe tubes - low flows

49
Q

What is a determinant of flow when flow is laminar?

A

Viscosity is a determinant at low flow

50
Q

What is a determinant of flow when it is turbulent? Whats the significance, w/ an example?

A

Density Heliox (70:30 He: O2) used in asthma exacerbations. Because He is less dense that air and increasing viscosity you can achieve higher flows w/ less turbulent flow and subsequently less pressure. Heliox decreases large aw resistance.

51
Q

What happens to viscosity of gas as temperature increases? Why?

A

Viscosity increases. More gas molecule collisions.

52
Q

What is Reynold’s number and whats the calculation?

A

RN = V x p x D / n v = velocity p = density D = diameter n = viscosity RN > 2000 = turbulent flow

53
Q

Describe Thorpe tubes.

A

Type of flow meter. It is a tapered glass tube that has a float inside that has an annular space in between the sides of the float and the glass tube that allows gas to travel to top of tube. At low flows the gas has a laminar flow and is determined by viscosity. As flows increase, density begins to determine flow.

54
Q

What are factors that change laminar flow to turbulent flow? (3)

A

increased velocity, bend >20 degrees, irregularity in tube

55
Q

Describe Bernoulli’s Theorem.

A

Lateral wall pressure is least at the smallest portion of the tube and speed is the highest there. Therefore narrow diameter = lower lateral wall pressure, higher speed. And wider diameter = higher pressure, slower speed.

56
Q

Give an example of Bernoulli’s Theorem. (4)

A

Venturi tubes. Velocity of fluid can be found by measuring pressure. Nebulizers Venturi O2 masks (24-40%) Jet ventilation

57
Q

Describe the Beer-Lambert Law.

A

Absorption of radiation is directly proportional to concentration of a solution.

58
Q

Describe a clinical application of Beer-Lambert Law.

A

Pulse Oximetry. 2 LEDs, one red at 660 nm and an infrared at 940 nm, shines across tissue bed, absorption measured on other side, calculates oxygen saturation of Hgb. O2Hb - 940 nm deO2Hb - 660 nm

59
Q

What can cause errors in pulse oximetry?

A

artifact (motion, ambient light, low perf), alt. Hb species (metHb - false low if >85% SaO2, false high<85% SaO2, COHb - false high), dyes - false low

60
Q

How does metHb affect pulse oximetry? Why?

A

If SaO2 > 85% false low If SaO2 < 85 % false high, It increases absorption of light at both 660 nm and 940 nm.

61
Q

How does COHb affect pulse oximetry? Why?

A

false high bc it absorbs light at a similar wavelength to O2Hb

62
Q

What dyes affect pulse oximetry? How?

A

methylene and isosulfan blue - low indocyanine green & indigo carmine - slight decrease blue nail polish - low

63
Q

Describe Law of La Place. What’s the formula?

A

pressure gradient (P) across wall of a sphere/tube/cylinder (blood vessel/ventricle/alveolus) is proportional to wall tension (T) and inversely proportional to radius (r) Therefore wall tension increases w/ vessel radius. T = P x r

64
Q

Clinical applications of La Place’s Law? (3)

A

alveoli needing surfactant, aneurysms - rupturing d/t increased wall tension, ventricular volume and work of heart - dilated ventricle has greater tension and end diastolic pressure increases

65
Q

Why do alveoli need surfactant?

A

Helps reduce surface tension, needed to lower work of breathing and prevent alveolar collapse on end-exhalation

66
Q

Describe Ohm’s Law. Formula is?

A

Current through a conductor between two points is directly proportional to the voltage across the two points. W (resistance) = Potential (volt)/ Current (ampere) or Voltage (E) = current flow/amp (I) x resistance (R)

67
Q

Two clinical applications of Ohm’s Law?

A

thermistors, strain gauges in pressure transducers

68
Q

What is the difference between macro and micro shocks? And what causes each.

A

macro: current through body, usually from faulty wiring, improper grounding micro: current at or near heart, usually from pacer wires, faulty equipment during cardiac cath

69
Q

Describe levels of different macroshock.

A

1 ma = skin tingle 5 ma = max harmless current 10-20 ma = let go 50 ma = pain, LOC, mech injury 100-300 ma = vfib, resp intact 6000 ma = complete physiological dmg

70
Q

How many MICROamps required in a microshock to cause vfib?

A

50-100 microamps

71
Q

What does 2% lidocaine mean? Whats the significance?

A

2g of lido in 100 mL. Therefore: 2000mg / 100mL or ***20mg / 1 mL***

72
Q

What does 0.75 % Bupivicaine mean? Whats the significance?

A

0.75 g in 100 mL. Therefore: 750 mg in 100 mL or ***7.5 mg in 1 mL***

73
Q

What is the ratio of g to mL of epinephrine? Whats the significance?

A

1:100,000, 1g per 100,000 mL Therefore: 1000 mg in 100,000 mL, 1 mg in 100 mL, 1000mcg in 100 mL, ***10 mcg/1 mL***

74
Q

What is ratio of g to mL in Neostigmine? Whats the significance?

A

1:1000, 1 g per 1000 mL Therefore: 1000 mg in 1000 mL ***1 mg/ mL***

75
Q

What is the per mL dose of 1:10,000 epinephrine?

A

1 g per 10,000 mL 1000mg per 10,000 mL 1 mg per 10 mL/ 1000mcg per 10 mL ***100 mcg / 1 mL or 0.1 mg/mL***

76
Q

What is the per mL dose of 1:200,000 of epi?

A

1 g 200,000 mL 1000 mg 200,000 mL 1 mg per 200 mL 1000 mcg per 200 mL 10 mcg per 2 mL ***5 mcg per 1 mL***

77
Q

What is the per mL dose of 2% lidocaine w/ 1:200,000 epi?

A

2% lido: 2 g 100 mL or 2000 mg 100 mL or 20 mg/mL 1:200,000: 1000 mg 200,000 mL or 1 mg 200 mL or 1000 mcg 200 mL or 10 mcg /2 mL or 5 mcg/mL ***20 mg lido, 5 mcg epi***

1: Intro to Anesthesia (12 decks)

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