Unit 12: Miscellaneous Topics Flashcards
Define an ionic bond, covalent bond, and polar covalent bond
Ionic Bond: complete transfer of valence electrons from one atom to another
- leaves one atom w/ a negative charge and the other w/ a positive charge
- metals, acids, and bases tend to form ionic bonds
Covalent Bond: equal sharing of electrons (strongest type of bond)
- single bond is created when 1 pair is shared, double bond = 2 shared
Polar Covalent Bond: an “in-between” type of bond
- atoms share electrons but electrons tend to remain closer to one atom than the other
- one area of the molecule is relatively positive and the other is relatively negative
What are Van der Waals forces?
Very weak intermolecular force that hold molecules of the same type together
-weakest type of molecular attraction
What is Dalton’s Law? List several examples of how it can be used in the OR
Dalton’s Law of Partial Pressures = total pressure is equal to the sum of the partial pressures exerted by each gas in the mixture
P total = P1 + P2 + P3
Ways to apply it:
-calculate partial pressure of an unmeasured gas
-calculate total pressure
-convert partial pressure to volumes percent
-convert volumes percent to a partial pressure
At sea level, the agent monitor measures the end-tidal Sevo as 3%. What is the partial pressure of Sevo in the exhaled tidal volume?
Partial Pressure = Volumes % x Total Pressure
0.03 x 760 mmHg = 22.8 mmHg
*application of Dalton’s Law
What is Henry’s Law? List several examples of how it can be used in the OR
At a constant temperature, the amount of gas that dissolves in a solution is directly proportional to the partial pressure of that gas over the solution
-the higher the gas pressure, the more of it will dissolve into a liquid (assuming constant temp)
Increased Temp = Decreased Solubility
Decreased Temp = Increased Solubility
Application:
-anesthetic emergence is prolonged in the hypothermic pt
-dissolved O2 in the O2 carrying capacity equation
What is Fick’s Law of Diffusion?
Describes the transfer rate of gas through a tissue medium
Rate of Transfer is Directly Proportional To:
-partial pressure difference (driving force)
-diffusion coefficient (solubility)
-membrane surface are
Inversely Proportional To:
-membrane thickness
-molecular weight
What are the clinical examples of Fick’s Law of Diffusion?
-Diffusion hypoxia
-Pt w/ COPD has a reduced alveolar surface area and therefore has a slower rate of inhalation induction
-Calculation of CO
-Drug transfer across the placenta
What are Boyle’s, Charles’s, and Gay-Lussac’s Laws?
Boyle’s Law: P1 x V1 = P2 x V2 – inverse relationship
Charles’s Law: V1/T1 = V2/T2 – direct relationship
Gay-Lussac’s Law: P1/T1 = P2/T2 – direct relationship
What are the clinical examples of Boyle’s Law?
Pressure x Volume – (constant = temp)
-Diaphragm contraction increases tidal volume
-Pneumatic bellows
-Squeezing an Ambu bag
-Using the bourdon pressure gauge to calculate how much O2 is left in a cylinder (assumes a given flow rate)
What are the clinical examples of Charles’s Law?
Volume / Temperature – (constant = pressure)
-LMA cuff ruptures when placed in an autoclave
What are the clinical examples of Gay-Lussac’s Law?
Pressure / Temperature – (constant = volume)
-Oxygen tank explodes in heated environment
What is the function of the ideal gas law?
Ideal Gas Law unifies all 3 gas laws into a single equation: PV = nrT
P = pressure
V = volume
n = # of moles
r = constant 0.0821 L-atm/K/mole
T = temperature
What is Ohm’s Law?
Current passing through a conductor is directly proportional to the voltage and inversely proportional to the resistance
-can adapt to understand fluid flow
Current = Voltage Difference / Resistance
OR
Flow = Pressure Gradient / Resistance
How is Poiseuille’s Law related to Ohm’s Law?
Poiseuille’s law is a modification of Ohm’s law that incorporates vessel diameter, viscosity, and tube length
Q = πR^4ΔP / 8 nL
Q - blood flow
R - radius
ΔP - arteriovenous pressure gradient (Pa - Pv)
n - viscosity
L - length of tube
How do changes in radius affect laminar flow?
Altering radius of the tube exhibits the greatest impact on flow
R = 1^4: 1x1x1x1 = 1
R = 2^4: 2x2x2x2 = 16
R = 3^4: 3x3x3x3 = 81
R = 4^4: 4x4x4x4 = 256
How can we apply Poiseuille’s law to the administration of a unit of PRBCs?
PRBCs can be delivered faster if we:
-increase the radius w/ a large bore IV
-increase the pressure gradient w/ a pressure bag and/or increase height of IV pole
-decrease viscosity by diluting blood w/ 0.9% NS and/or running it through a fluid warmer
-decrease the length by not using longer tubing than you really need
What does Reynold’s number tell you?
Predicts the type of flow (laminar, turbulent, and transitional) that will occur in a given situation
Re < 2000: laminar flow is dependent on gas viscosity (Poiseuille’s Law)
Re > 4000: turbulent flow is dependent on gas density (Graham’s Law)
Re 2000-4000: transitional flow
Reynolds’ # = Density x Diameter x Velocity / Viscosity
**in status asthmaticus – airway resistance is increased, thus increases turbulent flow and WOB (treat w/ Heliox to improve Reynold’s # by reducing density)
What is Bernoulli’s principal?
Describes the relationship between the pressure and velocity of a moving fluid (or gas)
-if fluid’s velocity is high – pressure exerted on the walls of the tube will be low
-if fluid’s velocity is low – pressure exerted on the walls of the tube will be high
*ex: think of a river:
- wide river = water moves slowly
- narrow river = water moves faster –> slow water exerts more pressure on riverbank than fast narrow river
What is the Venturi effect? Give examples
Application of the Bernoulli principle
- as airflow in a tube moves past the point of constriction, the pressure at the constriction decreases (Bernoulli principle) and if the pressure inside the tube falls below atmospheric pressure, then air is entrained into the tube (Venturi effect)
- adjusting diameter of the constriction allows for control of the pressure drop and the amount of air that is sucked into the tube
Ex: jet ventilator, Venturi, and nebulizer
What is the Coanda effect? Give examples
Describes how a jet flow attaches itself to a nearby surface and continues to flow along that surface even when the surface curves away from the initial jet direction
Ex: wall-hugging jet of mitral regurgitation and water that follows the curve of a glass
How do you calculate the law of Laplace for a sphere? How about for a cylinder?
Sphere: Tension = (Pressure x Radius) / 2
-examples: alveolus, cardiac ventricle, saccular aneurysm
Cylinder: Tension = Pressure x Radius
-examples: blood vessels, aortic aneurysm
*Law of Laplace illustrates the relationship between the wall tension, internal pressure, and radius
What is the yearly maximum for radiation exposure? How does this change if someone is pregnant?
Yearly Max Exposure = 5 rem
-eye and thyroid are most susceptible to injury
Pregnant Yearly Max Exposure = 0.5 rem or 0.05 rem/month for the fetus
-fetus is most susceptible to injury
What are 3 ways to protect yourself from radiation exposure?
Distance – minimum safe distance is 6ft
Duration
Shielding
How can we apply the inverse square law to radiation exposure?
The amount of exposure is inversely proportional to the square of the distance of the source
Intensity = 1 / Distance^2
Can quantify the amount of exposure at two different locations with the following equation:
Intensity1 = Distance2^2
Intensity 2 = Distance1^2