Physics and Math

Question 1

Definition: Molecular Theory of Matter

Answer 1

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

Question 2

Definition: Kinetic Theory of Matter

Answer 2

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

Question 3

Definition: Critical Temperature

Answer 3

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

O2 is gas

Question 4

Avagadro’s Hypothesis and Number

Answer 4

mole-numbering system

1 mole= 6.02 x 10^23 molecules

Hypothesis: 2 different containers containing 2 different gases at the same temp and pressure= same number of molecules

1mole= 1gram x molecular weight

ex) 1mole occupies 22.4L
6. 02x10^23 molecules of O2=32g occupies 22.4L

Question 5

Physics in Context

Answer 5

Calibration of vaporizers is done using Avagadro’s hypothesis

ex) Sevo =200g=1mole=22.4L at stp

Question 6

Gas Laws

Answer 6

-Boyle’s
-Charles
-Gay Lussac
I-deal Gas Law

Question 7

Universal Gas Constant for Boyle, Charles, Gay Lussac, and Ideal Gas Law

Answer 7

Boyles: PV= Constant (k1)
Charles: V/T= Constant (k2)
Gay Lussac: P/T= Constant (k3) (3rd Law)

Perfect gas law + Avagadro’s hypothesis:
PV/T= Constant (k4), for any given quantity of gas

Question 8

Boyle’s Law

Answer 8

• PV : Volume of an ideal gas is inversely proportional to the pressure (V=1/P)
• Temperature is constant
  ex) Squeezing (pressure) Reservoir bag causes the volume to decrease
  ex) A full E cylinder of oxygen will empty 625-650 L into the atm (Pressure decreases, Volume increases)
  ex) spontaneous breathing- intrapulmonary pressure becomes negatiive (decreases), intrapulmonary volume increases
  ex) Bellows on ventilator- As pressure increases, the volume of the bellows decreases

Question 9

Charle’s Law

Answer 9

• V/T: Volume is proportional to temperature(Kelvin)
• Pressure remains constant
  ex) Balloons burst on hot days

Question 10

Gay Lussac’s Law

Answer 10

• P/T: Pressure is proportional to Temperature(Kelvin)
• Volume is constant
  ex) Tec 6- increasing temperature surrounding the gas which gave the false increasing atmosphere-boils
  ex) Full cylinder of compressed gas moved from the air conditioned hospital (70degrees) to loading dock (100degrees), the pressure increases

Question 11

Charles + Gay-Lussac’s Law

Answer 11

For given mass, at constant pressure, the volume is directly proportional to the temperature
V=CT
C= Constant pressure

Question 12

Universal (Ideal) Gas Law

Answer 12

PV=nRT

• Combines Boyle’s, Charles’, and Gay Lussac’s Law + Avagadro’s law
• n= # moles of gas
• R= universal gas constant
• T= temperature (Kelvins)
• P= pressure
• V= volume

ex) Cylinder of compressed gas empties, the pressure falls - cylinder has constant volume, the # of moles decrease as gas exits, so pressure decreases

Question 13

Mole

Answer 13

A mol of a pure substance: mass(g)= molecular mass (amu). A mol of any material will contain Avogadro’s number of molecules.
ex) C (atomic mass 12.0amu): 1 mol C= 12g

Question 14

General Gas Law

Answer 14

• Dalton’s Law
• Fick’s Law of Diffusion
• Graham’s Law
• Henry’s Law

Question 15

Dalton’s Law

Answer 15

Total P= P1 +P2 + P3 (Total pressure= sum of partial pressure)

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

ex) atm pressure is 760mmHg, O2 21%, N 79%
P Oxygen = 159mmHG
P Nitrogen= 600.4

ex) 50% N2O + 44% O2 + 6% Desflurane = 100% mix to pt =
(.5x760) + (.44x760) + (.06x760) = 1.0x760

Question 16

Ficks Law of Diffusion

Answer 16

Rate of diffusion of a substance across a membrane is related to:

1) Concentration gradient (pp difference of gas across the membrane- Directly proportional
2) SA of membrane- Directly proportional
3) Solubility- (Directly proportional)
4) Thickness membrane- Inversely proportional
5) Molecular Weight- Inversely proportional

Vgas= (Area x Solubility x PP difference)/(Molecular Wt x Distance)

Effects:

• 2nd gas effect: high inspired concentration of 1st gas(N2O), accelerates uptake of companion gas -Uptake and Distribution of Anesthetic Gases
• Concentration effect- Uptake of high volumes of N2O concentrates the remaining 2nd gas
• Diffusion hypoxia- Diffusion of gases across the alveoli-capillary membrane
• Expansion of air pockets- when using N2O (N2O is 34x more soluble in blood than N2; therefore volume N2O diffusing in > volume N out)
• Expansion of ET cuff- N2O diffuses accross plastic as well
• Placental Transfer- durgs and O2

Question 17

Graham’s Law

Answer 17

A gas diffuses at a rate that is inversely proportional to the square root of its molecular weight

• Molecular weight increases, rate of diffusion decreases

Question 18

Henry’s Law

Answer 18

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
KNOW:
O2: .003ml/100ml blood/mmHg PP
CO2: .067ml/100ml blood/mmHg PP

• Can estimate PaO2 when delivering certain amounts of oxygen by multiplying FiO2 x 5

Question 19

General Laws

Answer 19

• Critical Temperature
• Adiabetic Heat Process
• Joule-Thompson Effect
• Poiseuille’s Law
• Bernoulli and Venturi
• Beer’s Law
• Law of La Place
• Ohm’s Law

Question 20

Critical Temperature

Answer 20

Definition: temp above which a substance goes into gaseous form in spite of how much pressure is applied

• Gas cannot be liquefied if the ambient temperature is greater than critical temperature
• Gas can be liqufied if sufficient pressure is applied at ambient temp below the critical temperature

O2: Critical Temp: -119C

N2O: Critical temp 39.5 C, therefore, N2O is stored as a liquid at pressure of 745mmHg and at room temp

Question 21

Adiabatic Cooling

Answer 21

• Occurs when matter changes phase
• Implies a change in temperature of the mattter w/o gain or loss of heat

ex) N2O cylinder opened fully-> frost can form on the outlet due to cooling

Question 22

Joule-Thompson Effect

Answer 22

Expansion of gas causes cooling

ex) as gas leaves a cylinder, the expansion cools the surrounding air causing condensation of moisture on the cylinder

Question 23

Poiseuille’s Law Applied with Laminar Flow

Answer 23

Describes rate of flow and:

1) Pressure gradient across length of tube- Direct
2) Radius^4 of tube- Direct
3) Length of tube- Inverse
4) Viscosity of fluid- Inverse

Q= (pi x r^4 x delta x P)/8nL

ex) IV flows, Airways, Vascular flow (Polycythemia vs Anemia), Thrope Tube (low flows)

Question 24

Laminar to Turbulent

Answer 24

Viscosity- determinant of flow when flow is laminar (low flow rates)

Density- determinant of flow when its turbulent. Ratio of mass to volume. D=m/v. Determines the rate of flow meters when rate of gas flow is high through variable orifices flow meter.
ex) Heliox

Reynold’s number= (velocity x density x diameter)/ viscosity

Raynold’s Number >2000= Turbulent flow

Question 25

Thorpe Tubes

Answer 25

Thorpe Tubes= Flowmeters - Low flow- the annular-shaped orifice around the float is tubular(Poiseuille's Law) flow is governed by viscosity - High flow- (wider top part of the float tube), the annular opening is more like an orifice and density governs flows

Question 26

Factors that Change Flow from Laminar to Turbulent

Answer 26

1) Increased velocity 2) Bend >20degrees 3) Irregularity in the tube 4) Reynolds # > 2000

Question 27

Bernoulli's Theorem

Answer 27

- Pressure and velocity - Lateral wall pressure is LEAST at point of greatest constriction and speed is the GREATEST - Flow will be faster through the constricted portions and slower at the wider portions of tube Narrow Diameter= Decrease LWP = Increase speed Wider Diameter= Increase LWP = decrease speed

Question 28

Bernoulli and Venturi- Venturi Tube and Application

Answer 28

Venturi Tube- application of Bernoullis equation to measure fluid flow - fluid flows through diff cross sectional areas in different portions of the tube - As tube narrows, velocity of fluid increases thus dropping pressure - Velocity of the fluid can be found by measuring the pressure - 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 ex) Nebulizers, Venturi O2 Masks (24-40% O2), Jet Vent

Question 29

Beer's Law (Beer-Lambert Law)

Answer 29

- Absorption of radiation by a given thickness of a solution of a given concentration is the same as that of 2x the thickness of a solution of half the concentration (Beer) - Each layer thickness absorbs an equal fraction of the radiation that passes through (Lambert)

Question 30

Pulse Oximetry (Beer's Law Application)

Answer 30

``` 2 LEDs: 1) One (Red) emits light at 660nm 2) One (Infrared) emits light at 940nm Shines across pulsatile tissue bed Measures absorption on opposite side Compare Red vs Infrared light Calculate O2 sat ``` ``` OXYHGB 940nm (IR light) DEOXYHGB 660nm (Red light) ```

Question 31

Errors in Pulse Oximetry

Answer 31

-Artifact (ambient light, low perfusion, motion) - Alt. Species of Hemoglobin Carboxyhgb: False High Methgb: SaO2>85%: False Low SaO2<85%: False High HgbF: No Effect HgbS: No Effect -Polycythemia: No Effect -Mythylene & Isossufan Blue: False Low -Indocyanin Green & Indigo Carmine: Slight Decrease -Blue Nail Polish: False Low

Question 32

La Place

Answer 32

Pressure gradient across the wall of a SPHERE or TUBE/CYLINDER (vessel, ventricle, alveolus) is rt: 1) Wall tension (T)- Directly 2) Radius (r)- Inversely T=Pr ex) Normal Alveoli and the need for surfactant during expiration ex) Vascular Pathology- Aneurysm rupture d/t increased wall tension ex) Ventricular volume and work of the hear-a dilated ventricle has greater tension in its wall (end diastolic pressure rises)

Question 33

Ohm's Law

Answer 33

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) R(resistance) ex) Strain Gauges in Pressure Transducers ex) Thermistors

Question 34

Electricity in the OR

Answer 34

1) 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 pt=BURNS 2) Macroshock: Current distributed through the body, culprit: faulty wiring, improper grounding 3) Microshock: Current applied in or near the heart, culprit pacing wires, fault equipment during cardiac cath 4) Electrocautery

Question 35

Macroshock

Answer 35

- 1 milliamp= skin tingling/perception - 5 milliamps =maximal "harmless" current - 10-20 milliamps= let go of source - 50 milliamp = pain, LOC, mechanical injury - 100-300 milliamps= V-Fib, resp intact - 6000 milliamps= complete physiological damage

Question 36

Microshock

Answer 36

50-100 microamps= V-FIb