Physics & Chemistry Flashcards
Is vapor pressure a function of volume, temp, or pressure?
Temp
If isoflurane is added to a flask of oxygen, what is the % oxygen and % isoflurane in the flask above the liquid?
*Dalton's Law VP of Iso = 240 760-240 = 521 for O2 240/760 x100 = 31.5% 521/760 x100= 68.6%
Adding Volatile Agent to the Wrong Vaporizer
Agent - vaporizer - output HLH LHL H: Isoflurane, Halothane L: Sevoflurane, Enflurane
Desflurane Vaporizer
Heated to 39 deg C
Vapor pressure - 2 atm, 1500 mmHg
Unit Conversions
1 atm = 760 mmHg = 14.7 psi = 101 kPa = 1 bar
1 mmHg = 1.36 cmH2O = 1 torr
Bourdon Gauges
High pressures (cylinder)
Pressure relative to atmospheric
NOT the absolute pressure
If gauge reads 0…pressure = atm
Law of LaPlace
Cylinder - T = P x r
Ex: blood vessels, LV
Spheres - T = (P x r )/2
Ex: alveoli
Why will a capillary wall withstand a pressure of 100 mmHg far better than a vein?
B/c the capillary has a tiny radius - so the tension in the wall of the capillary is extraordinarily smaller than in the vein
*Law of Laplace - T= P x r
Frank-Starling Law
Greater the tension in the ventricular wall at end-diastole — the greater the SV
What law states that the greater the filling of the LV the greater the tension in the ventricular wall?
Law of LaPlace
Tension and Pressure Relationship for Soap Bubbles (Liquid-Air Interface) & Surfactant-Deficient Alveoli
T = (P x r)/2 Tension does not change Tension is independent of radius Smaller radius = greater pressure Smaller bubbles/alveoli with high pressure will empty into larger bubbles/alveoli with lower pressure
Tension and Pressure Relationship for Normal Alveoli
T = (P x r)/2
Surfactant
Pressure does not change
Smaller radius = less tension
Hagen-Poiseuille’s Law
F = pie r4 change in pressure /
8 viscosity length
R = 8 viscosity length/
pie r4
*Laminar Flow
What is the property of fluid that determines flow when flow is laminar? Turbulent?
Laminar - viscosity
Turbulent - density
Flow becomes turbulent if…
Velocity of flow is high Tube wall is rough There are kinks, bends, narrowing, branches Fluid flows through an orifice Angle > 25 deg
Reynolds #
velocity diameter density/
viscosity
>2000 = turbulent flow
Venturi Effect & Bernoulli’s Principle
When fluid flows through a constricted region
The velocity of flow increases
The lateral pressure decreases
Ex: nebulizer, jet ventilator, injector
Which law permits the calculation of dissolved O2 and dissolved CO2 in the blood?
Henry’s Law
Amount of gas that dissolves in a liquid is proportional to the partial pressure of the gas in the gas phase
PaO2 x 0.003
PaCO2 x 0.067
Boyle’s Gas Law
Pressure is inversely proportional to volume
Constant temp
P1V1 = P2V2
Ex: pressurized cylinder is opened slowly (so temp doesn’t change), Ambu bag, breathing, FRC measurement
Charles’ Gas Law
Volume is directly proportional to the absolute temp (K) Constant pressure V1/T1 = V2/T2 K = 273 + C Ex: LMA expands in autoclave
Gay-Lussac’s Law
Pressure is directly proportional to the absolute temp (K)
Volume is constant
P1/T1 = P2/T2
Ex: cylinder of gas is moved from the loading dock to OR
Ideal/Universal Gas Law
PV = nRT
n= moles of gas
R = universal gas constant
Ex: as gas is released from a cylinder of compressed gas, pressure inside the cylinder decreases
van der Waal’s Relationship
Deviation from the ideal state
Gas molecules have finite volumes
Gas molecules attract one another
Dalton’s Law of Partial Pressures
In the atmosphere at sea level, the partial pressures are…
O2 160 mmHg (21%)
N2 600 mmHg (79%)
Total 760 mmHg (100%)
Avogadro’s #
Describes the relationship b/t the amount of gas and volume of gas
1 mole = 6.022 x 10 23 molecules
1 mole of gas = 22.4 L
Critical Temp
A gas cannot be liquified if the temp is above the critical temp
Critical temp of O2 = -110 deg C - O2 cannot be liquified at room temp no matter how much pressure is applied
Adiabatic
Constant heat process
Cylinder of compressed gas is opened into a closed space - the pressure and temp will rise rapidly - flame/explosion
Change occurs so quickly, heat cannot be dissipated
Joule-Thompson Effect
Compressed gas is allowed to escape freely into space the process is adiabatic and cooling occurs
Ex: cryoprobe
N2O Cylinders
As gas escapes Liquid N2O vaporizes Heat is lost (latent heat of vaporization) Temp falls (Joule-Thompson) Pressure decreases
When cylinder is turned off, the pressure will be restored as the cylinder regains heat
Always reads 745 psi
Pressure gauge does NOT correlate with volume until all liquid is consumed
When the gauge starts to fall, only 25% remaining (about 400 L). Change tank!
Cylinder Calculations
N2O - 1590 L, 745 psi (3-5)
O2 - 660 L, 2200 psi (2-5)
Air - 625 L, 2200 psi (1-5)
Fick’s Law of Diffusion
(P1 – P2) X area of membrane x solubility
(membrane thickness) (square root of MW)
Explains: concentration effect, second gas effect, diffusion hypoxia, why N20 expands spaces
Fick’s Principle: calculation of CO from A-V O2 or A-V CO2 difference
Graham’s Law
1/square root of MW
Explains why smaller substances diffuse in greater quantities
Exception:
CO2 is larger than O2 BUT CO2 diffuses 20x faster
CO2 is 20x more soluble in fluid than O2
What are the 3 main factors determining diffusion rate across membranes for non-gases?
- Concentration gradient
- Lipid solubility
- Size
What law is the basis for pulse oximetry?
Beer’s Law
Routes of Heat Loss
Radiation
Convection
Conduction
Evaporation
Does relative humidity increase or decrease as temp falls?
Increases
What is the partial pressure of saturated water vapor at 37 C?
47 mmHg
Soda Lime
94% Ca(OH)2 5% NaOH 1% KOH Silica - increase hardness and reduce dust 4-8 mesh size - compromise b/t absorptive capacity and resistance Hydration 14-22% Exothermic Neutralization rxn
Baralyme
80% Ca(OH)2
20% Ba(OH)2
No silica
Amsorb
5% CaCl2
80 % Ca(OH)2
13-18% H2O
Facts about CO2 absorber.
Air space in CO2 absorber should be 2-3x tidal volume
Canister = 50% airspace + 50% absorbent
1000 g canister can absorb 200 L of CO2
Each 100 g granules absorbs as much as 15 L of CO2
Average production of CO2 by an anesthetized adult = 12-18 L/hr
Each canister of absorbent can last 8-10 hours
Ohm’s Law permits the calculation of what?
SVR
Density
Mass/Volume
Solubility increase or decrease with changes in temp…solid? gas?
Solid - solubility increases with increasing temp
Gas - solubility decreases with increasing temp
*Le Chatelier’s principle
Is electrical equipment in the OR grounded or isolated?
Isolated
