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NURA 641 Intro to Nurse Anesthesia > Week 5 Review Chem/Phys > Flashcards

Week 5 Review Chem/Phys Flashcards

1
Q

Mnemonic for relating gas laws with the variable and constant.

A

Could These Guys Possibly Be Violent?

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2
Q

What is Fick’s Law?

A
  • Fick’s law is an application of Graham’s law in physiologic states
  • Fick’s law for diffusion of a gas across a tissue plane is an encompassing law that accounts for molecular weight, concentration gradient, solubility, and membrane interactions
  • The rate of diffision of a substance across a membrane is directly proportional to:
    • ​concentration gradient (partial pressure difference of gas across the membrane)
    • membrane surface area
    • diffusion coefficient (solubility)
  • and inversely proportional to
    • thickness of the membrane
      • molecular weight

Vgas = Area x Solubility x Partial pressure difference

Molecular Wt x Distance

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3
Q

Name 3 factors that change flow from laminar to turbulent.

A
  1. increased velocity
  2. bend > 20 degrees
  3. irregularity in the tube
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4
Q

Describe how viscosity and density relate to laminar and turbulent flow.

A
  • Viscosity is a determinant of flow when flow is laminar (low flow rates)
  • Density is a determinant of flow when flow is turbulent (high flow rates)
    • D=mass/volume
    • Determines rate of flow in flow meters when rate of gas flow is high through variable orifice flow meter
    • i.e. Heliox
      • Heliox is used to improve ventilation in patient’s with narrow airways. It has lower diffusability, able to get better oxygenation by using carrier of helium
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5
Q

1 bar = ____ psi

A

14.7 psi

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6
Q

Discuss a few Clinical Applications of Fick’s Law.

A

**Allows determination of pulmonary gas exchange**

  • 2nd gas effect
    • Nitrous can almost act like a carrier gas
    • the rapid uptake of high concentrations of nitrous at induction of inhalation anesthesia produces an increase in alveolar concentrations of oxygen and the accompanying volatile anesthetic agent
  • Diffusion hypoxia
    • more likely to displace oxygen
    • during emergence from nitrous, rapid elimination of nitrous from the lungs dilutes other alveolar gases, producing alveolar “diffusion hypoxia.” (This phenomenon is driven by the same mechanism as the second gas effect—-but in reverse direction)
  • COPD - reduced alveoloar surface tension
    • ​slower induction
    • indirectly proportional relationship of membranes
  • placental drug transfer - of drugs and oxygen
    • Fick’s describes passive diffusion of molecules down a concentration gradient
  • expansion of endotracheal tube cuff (when nitrous is in use)
  • expansion of air pockets (when nitrous is in use)
    • N2O is 34x more soluble in blood than nitrogen
      • Therefore, volume of nitrous oxide diffusing IN > volume nitrogen OUT
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7
Q

What is critical temperature?

A

The temperature above which a gas cannot be liquefied regardless of how much pressure is applied

A gas cannot be liquefied if the ambient temperature is greater than critical temperature

A gas can be liquefied if sufficient pressure is applied at ambient temp below the critical temperature

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8
Q

Describe Charle’s Law and give a practical application.

A

Volume of a gas is directly proportional to the temperature (K)

Pressure remains constant

So, as temp increases, volume increases

Application: LMA cuff ruptures in an autoclave

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9
Q

Effects of 1 mA.

A

Macroshock

skin tingling/perception

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10
Q

Effects of 10-20 mA.

A

Macroshock

let go of source

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11
Q

Effects of 50 mA.

A

Macroshock

pain, LOC, mechanical injury

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12
Q

1 atm = ____ mmHg = ____ torr = ____ bar = ____ kPa = ____cm H20 = _____ psi

A

1 atm = 760 mmHg = 760 torr = 1 bar = 100 kPa = 1020 cm H2O = 14.7 psi

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13
Q

Effects of 100-300 mA.

A

Macroshock

V fib, resp intact

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14
Q

1 atm = _____ torr

A

760 torr

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15
Q

Formula for O2 delivery

A

DO2 = CO x [(1.34 x hgb x SpO2) + (.003 x PaO2)] x 10

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16
Q

Effects of 5 mA.

A

Macroshock

maximal “harmless” current

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17
Q

Describe Adiabatic Cooling.

A
  • occurs when matter changes phase
  • the term adiabatic implies a change in temperature of the matter without gain or loss of heat
  • Clinical Application: N2O cylinder opened fully - frost can form on the outlet due to cooling
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18
Q

What is the solubility coefficient for O2?

A

.003 ml/100ml blood/mmHg partial pressure

**CO2 is 20 more soluble in blood than O2**

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19
Q

How do stereoisomers differ from structural isomers?

A
  • structural isomers
    • have the same molecular formula, but their atoms are located in different places
    • i.e. enflurane and isoflurane
    • truly different molecules with differing physical and chemical properties
  • stereoisomers
    • molecules that have a similar geometric arrangement of atoms but differ in their spatial position
    • may be enantiomers or diastereomers
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20
Q

What is a concentration solution?

A

grams per ____ cc

i.e. 1:100,000 Epinephrine = 1 gram per 100,000 cc

= 1 gram Epi in 100,000 mL
= 1000 mg in 100,000 mL

= 1 mg in 100 mL

= 1000 mcg in 100 mL

= 10 mcg in 1 mL

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21
Q

What is a clinical application of Beer’s law and how does it work?

A
  • Clinical Application
    • spectroscopy - pulse oximetry
  • 2 LEDs
    • one (RED) - emits light at 660 nm
      • deoxy Hgb at 660 nm
    • one (INFARED) - emits light at 940 nm
      • oxy Hgb at 940 nm
    • shine across a pulsatile tissue bed
    • measure the absorption on opposite side
    • Compare RED vs INFARED light
    • calculate oxygen saturation
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22
Q

7.5 mmHg = _____ cm H2O

A

10.2 cm H2O

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23
Q

What is a percentage solution?

A

grams per 100 mL

i.e. 2% Lidocaine = 2 grams of Lidocaine per 100 mL

= 2000 mg in 100 mL

= 20 mg in 1 mL

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24
Q

Describe a few clinical applications of Bernoulli and Venturi.

A
  • lateral pressure of rapidly flowing fluid in a constricted tube can be subatmospheric, hence a sidearm on that portion of the tube can be used to aspirate another fluid into the tube
  • nebulizers
  • venturi oxygen masks (24-40%)
  • Jet ventilation
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25
Q

Name 3 clinical applications of La Place’s Law.

A
  1. normal alveoli and the need for surfactant during expiration
  2. vascular pathology - aneurysm rupture due to increased wall tension
  3. ventricular volume and work of the heart - a dilated ventricle has greater tension in its wall (end diastolic pressure rises)
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26
Q

What is Avogadro’s Hypothesis and Number?

A

6.02 x 1023 molecules = 1 mole

Hypothesis: If you have 2 different gas containers containing 2 different gases at the same temp and pressure, then they contain the same number of molecules

1 mole is 1 gram multiplied by the molecular weight:

i.e. 1 mole O2 = 32 grams

1 mole of any substance occupies 22.4 L, so 6.02 x 1023 molecules of O2 = 32 grams and occupies 22.4 L

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27
Q

Explain Dalton’s Law of Partial Pressures.

A

Total pressure of a gas mixture is the sum of the partial pressure of each gas

In a mixture of gases, the pressure exterted by each gas is the same as that which it would exert if it alone occupied the container

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28
Q

1 torr = _____ mmHg

A

1 mmHg

29
Q
A
30
Q

Describe errors/sources of artifact in pulse oximetry.

A
  • Artifact
    • ambient light
    • low perfusion
    • motion
    • dyshemoglobins
  • Dyshemoglobins
    • carboxyhgb: falsely high
    • methgb: Sat ~85%
    • polythycemia: no effect
    • methylene and isosulfan blue: falsely low
    • blue nail polish: falsely low
31
Q

50 - 100 microamps of a microshock can cause…..

A

V fib

32
Q

How is Poiseuille’s Law applied with Laminar Flow?

A
  • Describes the relationship between rate of flow and
    • pressure gradient across the length of tube - direct
    • radius4 of the tube (r4) - direct
    • length of the tube (L) - inverse
    • viscosity of the fluid (n) - inverse

Q = π r4 “delta P” / 8 n L

33
Q

1020 cm H2O = _____ kPa

A

100

34
Q

Explain how a bourdon gauge works.

A
  • contain a coiled tube that expands as pressure is applied
  • linkage connects the coil to a rotating arm that records the pressure
  • gauge pressure is zero referenced to atmospheric pressure and reads 0 at 760 mmHg at sea level
  • Gauge pressure = absolute pressure minus atmospheric pressure
35
Q

How do enantiomers differ from diastereomers?

A
  • enantiomers
    • mirror images of one another
    • cannot be superimposed on each other
    • possess similar chemical and physical properties
    • optically active and can rotate polarized light in a clockwise fashion (denoted by the prefix + or dextro)
    • or counterclockwise fashion (denoted by the prefix - or levo)
  • diastereomers
    • not mirror images
    • may have differing physical and chemical properties
36
Q

What is an isomer?

A
  • molecules that have the same chemical formula, but different structures
  • the number and type of atoms and bonds are the same in isomers, but the arrangement of the atoms is different
  • two types
    • structural isomers
    • stereoisomers
37
Q

What is Graham’s Law?

A
  • A gas diffuses at a rate that is inversely proportional to the square root of its molecular weight
  • As molecular weight increases, the rate of diffusion decreases
  • Smaller molecules diffuse faster
38
Q

Describe gas solubility in liquids in terms of pressure and temperature.

A
  • Inversely related to temperature
    • as temperature increases, less gas is able to dissolve into a liquid
    • increased temperature represents greater kinetic energy → greater kinetic energy allows dissolved gas molecules to escape and prevents further dissolving
    • lower temperature slows the kinetic energy of the gas molecules, allowing them to dissolve in liquids
    • i.e. hypothermic patients receiving volatile agent general anesthetic
      • slower wake up
  • directly proportional to pressure
39
Q

Explain what the Beer-Lambert law states.

A
  • absorption of radiation by a given thickness of a solution of a given concentration is the same as that of twice the thickness of a solution of half of the concentration (Beer)
  • Each layer of equal thickness absorbs an equal fraction of the radiation that passes through it (Lambert)
40
Q

Describe two application’s of Ohm’s law.

A
  • Strain gauges in pressure transducers
  • thermistors
41
Q

Name an application of Dalton’s Law.

A

Air = 21% O2 and 79% N2; atmospheric pressure is 760mmHg

Calculate the partial pressue of each gas:

Partial pressure of nitrogen is 79% x 760 mmHg = 600 mmHg

Partial pressure of oxygen is 21% x 760 mmHg = 160 mmHg

42
Q

Explain the difference between microshock and macroshock.

A
  • Macroshock
    • current distributed through the body
    • culprit: faulty wiring, improper grounding
  • Microshock
    • current applied in or near the heart
    • culprit: pacing wires, faulty equipment during cardiac cath
43
Q

Effects of 6000 mA.

A

Macroshock

complete physiologic damage

44
Q

Nitrous oxide diffuses into air filled cavities. What are some scenarios in which nitrous is either contraindicated or not preferred in particular types of surgery?

A
  • contraindicated in patients with pneumothorax or where air filled cavity expansion is undesirable
    • middle ear surgery
    • retinal surgery
    • long bowel cases - think of bowel distension
    • neurosurgeries
  • nitrous oxide can diffuse into endotracheal cuffs, increasing volume, and cause tracheal mucosal damage
45
Q

What is a racemic chemical composition?

A
  • contain 50% of the levo form of the isomer and 50% of the dextro form of the isomer
  • i.e. racemic epinephrine used to treat laryngeal edema
46
Q

What is the solubility coefficient for CO2?

A

.067ml/100ml blood/mmHg partial pressure

**CO2 is 20x more soluble in blood than O2**

47
Q

1 kPA = ____ cm H2O

A

10.2 cm H2O

48
Q

How does the standard set up of the OR put the patient at risk for burns in the OR?

A
  • Metal is a good conductor, your patient is lying on a metal bed, surgery causes bleeding, blood is wet, the room is full of electrical equipment → RISK TO THE PATIENT → BURNS
  • Electrocautery
49
Q

Explain how a thorpe tube works at high and low flows.

A
  • Thorpe Tube is an older term for flowmeters
  • At low flows
    • annular shaped orifice around the float is relatively tubular so (according to Poiseuille’s Law) flow is governed by viscoisity
  • At high flows
    • (indicated on the wider top part of the float tube), the annular opening is more like an orifice, and density governs flow
50
Q

Describe 2 applications of critical temperature.

A

Critical temp of O2 = -119 C

Therefore, O2 cannot be liquefied at room temp no matter how mjch pressure is applied to it.

**Main supply of O2 in a hospital is in liquid oxygen stores. Huge quantities can be stored in this way and is more economincal. The containers are insulated from the outside and the temperature is kept at -160 C**

Critical temp of Nitrous = 39.5 C

Room temp = ~25 C

Therefore, pressure can be applied to liquefy nitrous at room temp, Hence, nitrous is stored at pressure of 745 mmHg and at room temp.

51
Q

1 atm = _____ mmHg

A

760 mmHg

52
Q

What is the molecular theory of matter?

A

states that matter is made of minute particles called molecules that exist in various states (solid, liquid gas, or plasma)

53
Q

Describe Boyle’s Law and name a few practical applications.

A
  • P1V1=P2V2
  • volume is inversely proportional to pressure
  • temperature constant
  • As pressue increases, volume decreases
  • APPLICATIONS
    • squeezing resevoir bag on anesthesia machine
      • apply pressure (squeezing it), volume decreases
    • A full E Cylinder will empty 625-650 L into the atmosphere
      • the relatively small volume of gas in the cylinder is at high pressure. When it is released to the atmosphere where there is a relatively low pressure, a large volume results
    • Spontaneously breathing
      • when intrapulmonary pressure becomes negative (decreases), intrapulmonary volume increases (taking a breath in)
    • Bellows on a ventilator
      • as pressure increases, the volume within thin the bellow decreases
54
Q

Explain Bernoulli’s Therom.

A
  • Relates pressure and velocity and how they interact
  • the lateral wall pressure is LEAST at the point of greatest constriction and the speed is the GREATEST
  • Thus, flow will be faster through the constricted portions and lower at the wider portions of a tube

Narrow diameter = decreased lateral wall pressure = increased speed

Wider diameter = increased lateral wall pressure = decreased speed

55
Q

What is the Joule-Thompson Effect? Relate a clinical application.

A
  • Expansion of a gas causes cooling
  • Clinical Application: as gas leaves a cylinder, the expansion cools the surrounding air causing condensation of moisture on the cylinder
56
Q

Name a practical application of Avogadro’s law.

A

Calibration of vaporizers is done using Avagadro’s hypothesis.

57
Q

Explain how a venturi tube is an application of Bernoulli’s equation to meausure fluid flow.

A
  • fluid flows through different cross sectional areas in different portions of the tube
  • as tube narrows (V2), velocity of fluid increases, thus dropping pressure
  • Velocity of the fluid can be found by measuring the pressure
58
Q

What is the kinetic theory of matter?

A

states that molecules are in constant motion (random motion) and have a degree of attraction between them called van der waals forces.

59
Q

What is Henry’s Law and describe a practical application.

A
  • At constant temperature:
    • The amount of gas dissolved in a liquid is directly proportional to the partial pressure of the gas in contact with the solution.
  • allows calculation of O2 and CO2 dissolved in blood
  • Increasing FiO2 is an application of Henrys law
    • recall - most oxygen in the blood is bound to hgb rather than dissolved in the blood
  • overpressurizing the vaporizer is another example
    • we increase the concentration set on the vaporizer to speed up delivery to the blood, and therefore, the brain
60
Q

Describe the relationship of tension, radius, and pressure in the Law of La Place.

A
  • pressure gradient across the wall of a SPHERE or TUBE/CYLINDER (blood vessel, ventricle, alveolus) is related to
    • wall tension (T) - directly
    • radius (r) - inversely
61
Q

1 kPa = ____ mmHg

A

7.5 mmHg

62
Q

1 bar = ____ kPa

A

100 kPa

63
Q

Name a few clinical applications of Pouiseuille’s Law.

A
  • IV flow
    • gauge (r4)
    • shorter/longer catheter (L)
    • viscosity of fluid
  • Airways
  • Vascular flow
    • polythycemia vs anemia
  • thorpe tubes
    • at low flows
64
Q

What is Reynold’s Number is relation to turbluent flow?

A

Reynolds Number = velocity x density x diameter

viscosity

Reynold’s Number > 2000 = Turbulent Flow

65
Q

Describe Ohm’s Law.

A

That resistance which will allow one ampere of current to flow under the influence of a potential of one volt

W (resistance) = Potential (volt) / Current (ampere)

or

E (Voltage) = I (current flow or amp) x R (resistance)

66
Q

What is Gay Lussac’s Law and what is a practical application?

A

Pressure of a gas is directly proportional to the temperature (K)

So, as temperature increases, pressure increases

Application: full cylinder of compressed gas is moved from air conditioned hospital (70 degrees) to the loading dock (100 degrees F) → pressure in the tank increases!

67
Q

760 mmHg = _____ torr

A

760 torr

68
Q

Explain the concept of diffusion during apneic oxygenation.

A
  • Continual diffusion of oxygen into the blood is driven by a concentration gradient that continually diffuses oxygen into the alveoli via the ventilator circuit
  • When ventialtion is absent, we are dependent on this continual diffusion of oxygen
  • This is the principle behind apenic oxygenation

NURA 641 Intro to Nurse Anesthesia (10 decks)

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