Physics Review

Question 1

Describe Solids

Answer 1

Closely approximated atoms due to lattice and greatly influenced by intermolecular forces. Non-compressible and have volume, shape, and limited motion. If you add heat, the lattice structure breaks down, and molecules move further apart. Ex- Ice melting.

Question 2

Describe Liquids

Answer 2

Molecules exert weaker forces on each other, known as Van der Waals forces. Allows molecules to flow and move throughout the substance. A decrease in the force between molecules enable them to take the shape of a container while still having volume. Have more kinetic energy than solids.

Question 3

What are Van der Waals forces?

Answer 3

A weak force exists between molecules in a liquid state. Allows for molecules to flow.

Question 4

Describe Gases

Answer 4

Molecules are independent of each other and constantly moving, hitting the side of their container. No definite shape or volume. Pressure can be generated by the compression of gas in a chamber and is measured by flowmeters or respirometers. This pressure is the force exerted by the gas on the chamber walls.

Question 5

What is the pressure exerted by vapor when, ay any one temperature, an equilibrium is reached at which the same number of molecules are vaporizing as are returning to liquid?

Answer 5

Saturated Vapor Pressure

Question 6

What is the temperature at which vapor pressure becomes equal to atmospheric pressure and at which all liquid changes to gas?

Answer 6

Boiling point

Question 7

Describe the relationship between vapor pressure and boiling points.

Answer 7

They are inversely related. The lower the boiling point, the higher the vapor pressure. This is why there are specific vaporizers needed for specific anesthetic gases.

This means vapor pressure is temperature dependent.

Question 8

Is vapor pressure a function of volume, temperature, or pressure?

Answer 8

Temperature

Question 9

What are the vapor pressures for gases at 20 degrees C?

Answer 9

Sevoflurane, 170 mmHg
Isoflurane, 240 mmHg
Halothane, 244 mmHg
Desflurane, 669 mmHg

Question 10

Describe Force

Answer 10

Force is what changes or tends to change the state of rest or motion of an object. This is measured in N (newton).

N- gives a mass of 1 kg an acceleration of 1 m/s^2

Equation: F=ma
This is mass multiplied by acceleration (Newton’s second law)

Ex- gravity, force of air through valves in ventilator, force of fluid through IV, force of ETT on surrounding tissue.

Question 11

Describe Pressure

Answer 11

Pressure is the force applied over a surface area. It is measured in pascal (Pa). This is the pressure of 1 newton acting over 1 square meter - N/m^2

Question 12

What do we typically use to measure pressure?

Answer 12

The kPa or the kilopascal. This is used because the pascal is too small of a number to be manageable.

psi is pounds per square inch and is also used to measure pressure. (British)

Question 13

Atmospheric Pressure = 1 bar

Provide the remaining conversions

Answer 13

= 100 kPa
=760 mmHg
=1034 cmH2O
=14.7 psi

1 kPa = 7.5 mmHg
= 10.34 cmH2O
=0.147 psi

Question 14

What is absolute pressure?

Answer 14

This equals gauge pressure plus atmospheric pressure. (gauge pressure is the important parameter in most cases)

Ex- gas-cylinder pressures (psig or pounds per square inch gauge). When a cylinder is empty, it will say 0 psi or 0 bar. This does not mean that it is truly empty, but the O2 is equal to atmospheric pressure (14.7 psi or 1 bar), and no more gas can be removed.

Question 15

What is important to remember with gas laws?

Answer 15

Temp must be measure in Kelvin for gas laws. Remember Kelvin = Celcius + 273. There is no degree sign.

Absolute zero 0 K or -273 degrees C
1 unit K is 1 degree C

Question 16

What is Boyle’s Law?

Answer 16

At a constant temperature, the volume of a given gas varies inversely with the absolute pressure.

Equation: P1 x V1 = P2 x V2

If volume goes up, pressure goes down. Ex- squeezing ambu bag raises pressure and decreased volume. OR with inspiration, intrapulmonary pressure falls and volume increases. During expiration, intrapulmonary pressure increases and volume decreases.

Question 17

What is Charles’ Law?

Answer 17

At a constant pressure, the volume of a given gas varies directly with the absolute temperature. Increasing temperature causes molecules to increase movement and thus take up more volume.

Equation: V1/T1 = V2/T2

A direct relationship means that as one increases, the other increases also.
Ex- Helium balloons shrink in the cold.

Question 18

What is Gay Lussac’s Law?

Answer 18

Also known as the 3rd perfect gas law.

At a constant volume, the absolute pressure of a given mass of gas varies directly with the absolute temperature.

Equation: P1/T1 = P2/T2

Meaning that if temperature lowers, the pressure lowers; if temperature increases, the pressure increases. Like tire pressure in summer and winter.

Application: The lower the atmospheric pressure, the lower the boiling point.

Question 19

What is Dalton’s Law of Partial Pressures?

Answer 19

In a mixture of gases, the pressure exerted by each gas is the same as that it would exert if it were alone in the container.

Ex- in a cylinder of air with a pressure of 100 kPa, the O2 would exert 21% or 21 kPa, and nitrogen would exert 79% or 79 kPa.

Partial pressure exerted by any single gas in a combination of gases is directly proportional to its % composition of the gas mixture.

Equation: P1 + P2 + P3 = P total

Question 20

What is partial pressure?

Answer 20

The pressure exerted by a single component of a mixture of gases.

In the atmosphere at sea level, partial pressures are
O2, 160 mmHg (21%)
N2, 600 mmHg (79%)
Total is 760 mmHg.

In the mountains where the atmospheric pressure is 550 mmHg:
O2, 550 mmHg x 21% = 116 mmHg
N2, 550 mmHg x79% = 434 mmHg.

Application: what is the partial pressure of CO2 if its concentration in the end-tidal gases is 5%? 5% x 760 mmHg = 38 mmHg

Question 21

What is Avogadro’s Hypothesis?

Answer 21

Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules (a mole).

We have to discuss gas molecules in moles instead of masses, because gas molecules have different molecular weights. So if one mole of any gas at STP occupies 22.4 L, that means 2 gm hydrogen or 32 gm Oxygen or 44 gm CO2, or 44 gm nitrous oxide occupies 22.4 L.

Question 22

What is Avogadro’s number?

Answer 22

6.022 x 10^23

It is the number of atoms/molecules in one mole.

Question 23

What is STP?

Answer 23

This is standard temperature and pressure. At STP, one mole of any gas occupies 22.4 liters. STP is 0 degrees C, 760 mmHg, dry (no H2O vapor).

22.4 L = 44 g.
44g = 1 mole

Application: a nitrous oxide container is full and contains 3.4 kg of the gas. If the measurements are made at STP, what volume of nitrous oxide is obtained from this cylinder?

44g (1 mole) of N2O is 22.4 L at STP.
X liters/3400 g = 22.4 L/44 g
X = 1730 liters

Question 24

What is Universal Gas Constant?

Answer 24

This is the gas laws combined with Avogadro’s hypothesis.

Constants: PV, V/T, P/T

PV/T = universal gas constant (nR)

PV = nRT (n is the number of moles)

Question 25

Explain why the pressure gauge does not act as a content gauge for nitrous oxide.

Answer 25

Nitrous in a cylinder is a liquid with the pressure measuring the vapor above the liquid. Unlike O2 or air, which lowers in pressure as it empties, nitrous pressure remains constant as long as liquid remains in the container. This is why nitrous pressure will remain the same until the liquid is gone, moving from full to empty instead of gradually decreasing.

Applying avodadro’s number can be done to determine amount of nitrous left.

Question 26

Universal Gas Law (ideal gas law)

Answer 26

PV = nRT

In application to a cylinder of gas, V is constant, R is a constant (R is universal gas constant), T is held constant, so P is directly proportional to n.

So as moles decrease, the pressure decreases.

Question 27

What is critical temperature?

Answer 27

The temperature above which no amount of pressure can liquify a gas

This is important for nitrous

Question 28

What is critical pressure?

Answer 28

The pressure to liquify a gas at its critical temperature.

Gas can liquify at its critical temperature but not at a temperature any higher. The critical temp of nitrous is 36.5 C. because it is stored below that temp, it is in liquid form.

Question 29

What does solubility depend on?

Answer 29

Partial pressure of a gas
Temperature
Gas
Liquid

Question 30

What is a solution?

Answer 30

A homogenous mixture of a solute (gas) in a solvent (liquid)

Application: we think of this in terms of the gas content in the blood through the alveoli. The pressure gradient determines how much gas goes into the blood.

Question 31

What is saturated vapor pressure?

Answer 31

partial pressure exerted by a vapor over a liquid in a closed container when equilibrium has been met between the liquid and the vapor.

Molecules of the gas will dissolve into the liquid and an equilibrium will be attained where as many molecules of gas are entering the liquid as leaving the liquid. This is a saturated solution.

Question 32

What is Henry’s Law?

Answer 32

At a certain 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.

ex- breathing air under pressure as scuba divers cause more nitrogen into solutions in tissues.

Henry like to scuba dive.

When you increase O2 concentration, you are increasing the partial pressure and this aids diffusion into the blood. “over pressuring”

Question 33

Given an anesthesia example of Henry’s law

Answer 33

Increasing the concentration of isoflurane in the blood involves increasing the concentration or partial pressure. This is utilized at induction of anesthesia when a higher concentration of the anesthetic than necessary for maintenance is given as a loading dose is delivered to speed uptake. This is concentrating effect or over pressuring.

Ex- sevoflurane indiction 4-8% while maintenance is 1-4%.

Question 34

Describe Le Chatelier’s Principle

Answer 34

A change in any of the factors in determining an equilibrium causes the system to adjust or reduce or counteract the effect of the change.

Solubility increases with decreasing temp. As the temperature of the liquid increases, the amount of gas dissolved decreases. This is because gas becomes a liquid in cooler temps, increasing the ability to dissolve in liquid, but converts back to a gas in higher temps.

Question 35

What happens if a patient is cold at the end of an anesthetic?

Answer 35

The inhaled anesthetic will be more soluble in the blood, causing the patient to wake up more slowly.

Question 36

What is solubility coefficient?

Answer 36

The volume of gas which dissolves in one unit volume of the liquid at the temperature concerned.

Question 37

What is partition coefficient?

Answer 37

The ratio of the amount of substance present in one phase compared with another ( the two phases being of equal volume and in equilibrium)

Question 38

How does gas affect solubility?

Answer 38

The solubility coefficient of a gas at body temperature explains how dissolvable a gas is.

Ex. Oxygen = 0.024 and carbon dioxide is 0.57 at body temperature. This shows that CO2 is 20 times as soluble as O2. In anesthesia, we look at the partition coefficient as a ratio and it is stated for 37 C unless stated otherwise.

Ex. if 1 liter of nitrous oxide above 1 liter of blood at 37 degrees C, the volume of nitrous oxide dissolved in the blood is 0.47 liters. So blood-gas partition coefficient is 0.47.

Order listed is important. blood-gas is 0.47 to 1, gas blood is 1 to 0.47.

Question 39

What is the blood-gas partition coefficient?

Answer 39

This reflects the proportion of the anesthetic that will be absorbed in the blood vs the amount of anesthetic that will leave the blood to dissolve into tissues.

We can use this to compare different anesthetic agents. The lower this b-g coefficient, the faster the induction. Low b-g coefficient means poorly soluble. Equilibrium between gas and blood and brain is reached rapidly.

Inhaled agents with low solubility cause buildup in alveoli, producing the rapid induction of anesthesia.

Question 40

What is the oil-gas partition coefficient?

Answer 40

The ratio of a gas present in oil vs in the gas state.

Indicates how efficiently a gas can access and affect the sites of action.

The higher the oil-gas coefficient (lipid-solubility) the more potent the anesthetic gas.

Fat is an important substance in cell membranes and neurons. Solubility of gases can be measured in oil, which is similar to fat in tissues.

Question 41

What is the most and least potent gas? What does this mean about their solubility?

Answer 41

Halothane is the most potent, it has the highest oil-gas coefficient. Nitrous is the least potent, it has the lowest oil-gas coefficient.

Question 42

Diffusion is the continual movement of molecules among each other in liquids and gases. Which way do they move?

Answer 42

From high to low concentration

Question 43

Diffusion can happen across …

Answer 43

gas-liquid barrier, gas-filled area, and membranes.

Gas can diffuse through into other gases

Question 44

Discuss diffusion and what it is directly or indirectly proportional to in gases.

Answer 44

Diffusion is directly proportional to the pressure gradient, surface area, and solubility of the gas. It is indirectly proportional to the thickness of the membrane and the size of the molecule.

More soluble, more diffusion.

Bigger (more of) a molecule or thickness of membrane, less diffusion.

Question 45

What affects diffusion in/through gases?

Answer 45

Thickness of the membrane (d)
size of the molecule (MW)
surface area of the membrane (A)
solubility of the gas (S)
Pressure gradient (P1-P2 or delta P)

Question 46

What is Fick’s Law?

Answer 46

The rate of diffusion of a substance across unit area is proportional to the concentration gradient

Ex. Overpressuring for induction or increasing the FiO2 to increase PaO2.

This explains concentration effect, second gas effect, diffusion hypoxia, and expanded air-filled spaces with nitrous.

Question 47

What is Graham’s Law?

Answer 47

The rate of diffusion of a gas is inversely proportional to the square root of its molecular weight.

So increased MW, decreased diffusion.

Another concerning factor is the membrane- its area, thickness, and makeup.

Question 48

Discuss second gas effect of nitrous oxide

Answer 48

this is a theoretical situation because nitrous would not render someone unconscious unless it were at 104%. It is used as a carrier gas for the other gases because it helps build alveoli content up faster.

Question 49

Why is there diffusion hypoxia when using nitrous oxide?

Answer 49

Nitrous has a low solubility, so it comes out of the blood rapidly. This rush of nitrous from the lungs will overwhelm the oxygen concentration in the alveoli. We give 100% O2 when turning off the nitrous to counter this.

Question 50

Why is nitrous avoided in certain surgeries?

Answer 50

Nitrous has a blood-gas coefficient of 0.47 which is 34 times greater than nitrogen at 0.014. Thus, nitrous can leave the blood to enter an air-filled cavity 34 times faster than nitrogen can leave the cavity to enter the blood. If there is a compliant wall, the volume of gas will expand. ex. pneumothorax, intestinal gas. Additionally if there are noncompliant walls, such as a surgical graft in the middle ear, the nitrous can cause the ear drum or graft to burst.

Question 51

What are the 2 components of fluid flow?

Answer 51

Cohesion and Adhesion

Question 52

Explain cohesion (fluid flow)

Answer 52

internal attractive forces between like molecules trying to stick together in the smallest shape possible.

ex. liquid pulling on itself; mercury

Question 53

Explain Adhesion (fluid flow)

Answer 53

The attractive forces between unlike molecules trying to stick to something different

ex. attracted to the container; water

Question 54

Explain surface tension

Answer 54

Cohesive factors at the surface of a liquid that tend to keep liquid in its most compact form.
ex. dome at the top of a full glass.

Question 55

What does heating do to surface tension?

Why does this matter to us?

Answer 55

Heating lowers surface tension.

This matters to us because of alveoli and surfactants. The alveoli would collapse due to surface tension of the liquid, but surfactant reduce the surface tension and prevents that collapse when the walls of the alveoli come together during expiration. When the surfactant is absent, alveoli collapse can occur (premature neonates)

Question 56

Formula for pressure in liquids

Answer 56

P = hdw
height of column x density weight of liquid

If it is static, it is not moving or at rest. This also means that pressure is the same in all directions at any given point.

Question 57

Explain pressure in liquids

Answer 57

Remember that pressure is equal to force per unit area

Force in a liquid is from the column of liquid of a specific density and height above the point of measurement- from the weight of the liquid column.

In a closed system, any change in pressure is equally transmitted to all parts of the system.

Question 58

Manometer for H2O and Hg

Answer 58

Density of H2O = 1 gm/cc
Density of Hg = 13.6 gm/cc

Compare 7.5 mmHg = 10.2 cm H2O

Converting cm H2O to mmHg: 0.74x

Converting mmHg to cm H2O: 1.36x

The densities are different. Conversions do not change much, but remember changing from cm to mm

Another difference is the reaction of the liquid in the manometer. H2O adhesive forces to the side of the column. Mercury has surface tension to itself.

Ex. MAP 50 mmHg v 68 cm H2O

Question 59

Explain Flow

Answer 59

The quantity of a fluid passing a point in a given time.
F=Q/t
Q = quantity
t = time

P1-P2
Has to have a pressure gradient. Meaning there has to be a difference in pressure between the starting point and ending point of the flow. Once flow is established, it is either laminar or turbulent.

Question 60

How is static fluid pressure determined?

Answer 60

depth of the fluid, the density of the fluid, and any outside pressure exerted on it.

Question 61

Explain laminar Flow

Answer 61

This is fluid movement in smooth layer with no turbulence. Typically a straight channel at low rates of flow.

Flow is greatest at center and slower at walls of channel.

This flow has the least resistance and the movement of air in the respiratory tract is a great example. The air movement is mostly laminar, but changes to turbulent during speaking, coughing, or deep breathing when velocity is increased.

Question 62

Explain turbulent flow

Answer 62

Flow is no longer smooth and has swirls and eddies.

Laminar flow changes to turbulent when critical velocity is reached, the direction is changed, or flow is obstructed. Resistance to flow is increased.

Energy is lost- this requires a greater pressure gradient.

Examples of when this happen is a kink in tubing, y connector sites. Anything that increases the resistance decreases the flow and requires an increase in pressure.

Question 63

Explain factors affecting resistance

Answer 63

The factors include:
diameter of the channel (r)
length of the channel (L)
nature of the flow (laminar v turbulent)
viscosity of the fluid (n)

Question 64

Discuss viscosity

Answer 64

Viscosity is the fractional forces between layers within a fluid. cohesive forces which weaken as temperature increases. It is influenced by temperature: increase temp = decrease viscosity. decrease temp = increase viscosity

more viscosity, more thickness. blood is more viscous than water.

Crystalloid IV fluids have lower viscosity than blood. In the clinical setting, the viscosity of blood is influenced by the hematocrit, pt age (increases with age), smokers (increased), and can be lowered by the molecular wt dextran.

Question 65

Discuss Hagen-Poiseuille equation derivative

Answer 65

This is an equation that explains the factors that affect flow.

Resistance = 8nL/(pie)r^4

n is viscosity which is directly proportional to resistance
L is the length of the channel, which is directly proportional to resistance.

r is the radius of the channel which is inversely proportional to the resistance to the fourth power.

If you double the radius of the channel, the resistance to flow decreases 16x

Application: flow through different sized IV catheters or ETTs.

Physiological application: muscular work increases demand for blood flow while the heat generated slightly decreased blood viscosity making it flow easier.

Question 66

Poiseuille’s Law formula

Answer 66

P1-P2 = resistance x flow

or

flow = p1-p2/8nL/(pie)r^4

Question 67

Describe poiseuille’s law

Answer 67

This looks at the flow rate in relation to resistance and the pressure gradient if you have ideal fluid with no turbulence.

For this equation, flow is directly proportional to pressure. The radius or diameter of channel has the greatest effect on flow. Once turbulence occurs, this law can no longer be used to predict resistance.

To maintain flow rates, the pressure gradient must increase or the turbulence must be removed.

Question 68

What is the Bernoulli Effect?

Answer 68

Given a channel with a narrowing which then increases, the pressure measured along the channel is lowest at the narrowest point, often below atmospheric.

This narrowing causes increased velocity, thus increased kinetic energy. To maintain unchanged sum of energy, the potential energy must decrease.

If an opening is located at the narrowing where the pressure is lower than atmospheric, entrainment could occur. This type of system is called the venturi system.

Another type of entrainment where O2 moving at high speed picks up air into flow to reduce O2 concentration.

Question 69

What forms of energy are contained in fluid?

Answer 69

Potential energy associated with pressure and kinetic energy associated with its flow.

energy can neither be created nor destroyed. The sum of energy must remain unchanged.

Question 70

Explain Laplace’s Law

Answer 70

Relationship of wall tension, pressure, and radius of cylinders (vessels) and spheres (ventricles and alveoli)

Clylinders: T = Pr
Spheres: 2T = Pr

Aneurysm in aorta- in aneurysm with greater radius, wall tension increases (direct relationship of tension to radius) P = T/r

Question 71

How does surfactant affect Laplace’s Law?

Answer 71

Surfactant lowers the surface tension in the alveoli and prevents the effects of this law.

Question 72

Equations for normal aorta and aneurysm in regards to Laplace’s Law

Answer 72

Normal Aorta: 100 mmHg (P) x 2 cm (r) = T
Aneurysm: 100 mmHg (p) x 4 cm (r) = T x 2

Question 73

What is heat?

Answer 73

The kinetic energy of molecules of substance

Question 74

What is calorie (cal)?

What is kcal?

Answer 74

Calorie is the energy needed to increase temperature of one gram of H2O 1 degree C.

1kcal = C = 4184 joules = energy to increase temperature of 1 kg H2O 1 degree C.

Question 75

What is temperature?

Answer 75

The parameter used to describe the amount of heat possessed.

Question 76

What are the temperature conversions?

Answer 76

T celcius = 5/9 (T fahreheit -32 degrees) F to C
T fahre = 9/5 (T celcius + 32 degrees) C to F
T kelvin = celcius + 273 C to K

Question 77

Discuss the Kelvin

Answer 77

This is the necessary unit for calculations in gas laws.

The kelvin is the same as the celcius unit, so at times these are interchanged.

Kelvin is not recorded in degrees. 0K is the absolute zero because at this temperature, all atomic motion ceases.

Question 78

What is the triple point

Answer 78

The temperature at which water, ice, and water vapor are all at equilibrium. This is 0 degree celcius or 273.15 K.

Question 79

First law of thermodynamics

Answer 79

Heat is a form of energy and can be converted to other forms of energy, but neither created or destroyed

Question 80

Second law of thermidynamics

Answer 80

Heat always flows from warmer to cooler. There must exist a difference in temperature and the two things must be in contact.

Question 81

What are the 4 methods of heat transfer?

Answer 81

Conduction
Radiation
Convection
Evaporation

Question 82

Discuss conduction

Answer 82

Heat movement through a substance by the transfer of kinetic energy from molecule to molecule.

Metal is a good conductor. Air gas poor conductivity qualities.

This form of heat loss is not a real factor in the heat loss of an anesthetized pt as they are only in contact with the foam pad and it is a thermal insulator. (2%)

Question 83

Discuss Radiation

Answer 83

Heat is transferred from warmer to cooler objects by emission and absorption of energy radiated in varying wavelengths.

Objects do not have to touch.

This accounts for the largest percentage of normal heat loss from the body. (40%)
-this can be minimized by surrounding the body with warm objects and accelerated by surrounding it with cooler objects.

The difference in temp of the objects determined the rate of heat transfer.

Question 84

Discuss convection

Answer 84

Heat transfer occurs by moving fluid (liquid or gas)

air adjacent to the body is warmed, it expands and moves away, and it carries heat with it.

-this is why we warm gas or blood when it is delivered to the patient. This type causes 32% of heat loss in the anesthetized pt. Reduce this by using cotton blankets, surgical drapes, plastic sheeting
-a single layer to trap air reduced heat loss by about 30%.
-have to consider the amount of skin surface covered. popular misconception that a large amount of heat is lost in adults through the head, this is however true in neonates and infants due to the head being a a high percentage of body surface area.
-can also occur in respiratory tract. warmed air is the prevention.

ex- wind chill and convection air current. heat rises, cool air lowers.

Question 85

Explain evaporation

Answer 85

This is the loss of latent heat of vaporization of moisture on the skin’s surface.

If evaporation occurs (latent heat of evaporation), the remaining liquid loses heat.

This accounts for 28% of heat loss in anesthetized pts.

Can occur in surgical wounds and respiratory tract.

Question 86

what is latent heat of vaporization

Answer 86

The heat required to turn liquid into vapor.

If temp is decreased, vaporization is decreased. This is why some vaporizers have heaters.

Question 87

What two factors influence evaporation?

Answer 87

Difference in vapor pressure between skin surface and surrounding air (amount heat lost can be increased ten times by sweating)

The amount of surface exposed.

Question 88

What is specific heat capacity?

Answer 88

The amount of heat required to raise the temperature of 1 kg of a substance by 1 kelvin.

H2O is the standard: 1 cal/g/degree celcius = 1kcal/kg/degree celcius

1 cal = 4.18 joules

joules is the energy required.

Question 89

Discuss specific heat capacity

Answer 89

Temp changes more gradually for materials with a high specific heat than those with a low specific heat

The materials chosen for vaporizers need to have higher specific heat capacity so that they cool off slower.

We also need to know the specific heat of the volatile anesthetic agent, so we know how much heat to apply to increase its temperature to the point of vaporization

Question 90

Discuss Heat Capacity

Answer 90

The amount of heat required to raise the temp of an object by 1 kelvin.

This is calculated by multiplying the mass of the object by the specific heat capacity.

ex. 70 kg pt trying to increase his temp from 36 to 37 C, how many minutes of shivering would it take?
-Basal heat production is 50 W/m^2 (average man 80W)
-shivering can increase production up to 4 times. (320W)
-shivering also increases the amount of O2 that the myocardium needs.

knowing heat capacity of an object allows us to calculate the effect of changes in heat production.

Question 91

70 kg pt trying to increase his temp from 36 to 37 C, how many minutes of shivering would it take?

Answer 91

tissue specific heat capacities can be approximated to a mean of 3.5 kJ/kg/degree celcius
-for a 70 kg pt, it would be 245 kJ/degree celcius.

The additional heat production from shivering is 240W or 240 x 60 joules/min. This is 14.4 kJ/min. If 245 kJ are needed to increase temperature 1 degree C, then it will take 245/14.4 minutes or 17 minutes of shivering.

Question 92

What is specific latent heat?

Answer 92

energy required to convert 1 kg of a substance from one phase to another at a given temp. (J/kg)

Question 93

what is latent heat of fusion?

Answer 93

The heat required to change a solid to a liquid.

Question 94

What is latent heat of vaporization?

Answer 94

heat required to change a substance from a liquid to a gas at a constant temp

ex- when N2O cylinder is allowed to empty rapidly, the cylinder becomes very cold and the water vapor from the surrounding air freezes on the cylinder. (this is the joule-thompson effect)

if a vaporizer had lower temps, the liquid would be less volatile, and the amount of agent vaporized would decrease

Question 95

Discuss atomic structure

Answer 95

atoms are comprised of protons (+), neutrons(-), and electrons(-). The element is determined by the number of protons. The number of neutrons determines the isotope and the stability of the nucleus.

Question 96

Discuss unstable isotopes

Answer 96

unstable isotopes may emit beta particles (electrons). The nucleus may attract and capture an electron. Alpha particle is lost consisting of two protons and two neutrons. The nucleus may split into several parts.

After the isotope has decayed, it is common that it will emit an electromagnetic wave or gamma ray.

Question 97

discuss Ionizing electromagnetic radiation

Answer 97

releases energy by removing electrons from atoms in tissues.

Creating ions that are very chemically reactive and very hazardous. included xrays and gamma rays released by radioactive isotropes.

this can be harnessed and used as medical xrays.

Question 98

Discuss non-ionizing electromagnetic radiation

Answer 98

discharges its energy without creating ions or removing electrons from atoms in tissues.

This included infrared radiation, visible light, ultraviolet radiation as utilized with lasers.

LASER- light amplification by stimulated emission of radiation.

Question 99

Protection- ionizing radiation

Answer 99

Distance is the intensity of scattered radiation in inversely proportional to the square of the distance from the source.

Distance is the best form of protection: at least 3 feet away. 6 feet of air is the equivalent of 9 inches of concrete or 2.5 mm lead.
- 0.25 to 0.5 mm lead sheeting blocks most scattered radiation.

Time- minimize time around radiation
shielding- use barriers, like lead aprons.

Question 100

What is the greatest source of radiation in the OR?

Answer 100

fluoroscopy. (used by ortho, neuro, uro, general, and vascular surgery.)

Exposure is due to x-rays scattered by both patient and other surfaces. (it bounces off reflective surfaces like light)

Question 101

What is needed for protection during fluoroscopy procedures

Answer 101

a lead apron with 0.35 mm lead thickness equivalence should be sufficient for most procedures. For high workload, a wrap around apron with 0.25 led equivalence that overlaps on the front to provide 0.5 mm (.25 to .25) and 0.25 mm on the back would be ideal.

Question 102

Radiation exposure stats

Answer 102

Max yearly occupational exposure is no more than 5 rem or 5000 mrem.

One chest xray is 25 mrem

routine fluoroscopy exposure may be greater than 8000 mrem.

monitoring shows that one person rarely absorbs more than 50 mrem a year.

actively dividing cells are affected by radiation, making tumors and fetuses susceptible.

Question 103

Discuss protection for non-ionizing radiation

Answer 103

eyewear- must have lenses that filter the specific wavelength of the laser in use. instruments should be non-reflective. distance does NOT help.

The wavelength matters.

reflected radiation injuries include cornea burns, optic nerve injury, and cataract formation.

A properly fitting filter mask is important to prevent intake of plumes, vapor, and cellular debris. Debris sizes range from 0.1 to 0.8 micrometer (um)
-intact DNA of HPV and HIV proviral DNS found in plume.