UNIT 12 Miscellaneous Topics Flashcards
what is an ionic bond?
complete transfer of valence electrons from one atom to another, leaving one atom w/ a negative charge and the other w/ a positive charge
metals tend to form ionic bonds
- also common w/ acids and bases
what is a covalent bond?
equal sharing of electrons. Sharing is Caring! = Covalent. This is the strongest type of bond
- single bond = 1 pair e- is shared
- double bond = 2 pairs
- triple bond = 3 pairs
what is a polar covalent bond?
polar covalent bonds are an “in-between” type of bond
Atoms share electrons but the 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
define Dalton’s law. list several examples of how it can be used in the OR.
daltons law of partial pressures says that total pressure is equal to the sum of the partial pressures exerted by each gas in the mixture.
Ptotal = P1 + P2 + P3 + ..
applications:
- calculate partial pressure of unmeasured gas
- calculate total pressure
- convert partial pressure to volumes percent
- convert volumes percent to 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 Tv?
application of Dalton’s law of partial pressures
PP = volumes % x total pressure
0.03 x 760mmHg = 22.8mmHg
define Henry’s law. List several examples of how it can be used in the OR.
at constant temp, the amount of gas that dissolves in solution is directly proportional to the partial pressure of the gas over the solution. (the higher the gas pressure, the more that will dissolve into a liquid)
increase temp = decrease solubility
decrease temp = increase solubility
Ex:
- 1) anesthetic emergence is prolonged in the hypothermic patient
- 2) dissolved oxygen in the oxygen carrying capacity equation (CaO2)
- 3) Overpressurizing vapor pressure
- 4) Measuring PaO2
describe Fick’s law of diffusion, what increases it? What decreases it?
transfer rate of gas through a tissue
rate of transfer increases with:
- partial pressure difference
- diffusion coefficient
- membrane surface area
rate of transfer decreases with and is indirect with:
- membrane thickness
- molecular weight
list clinical examples of Fick’s law of diffusion.
1) diffusion hypoxia 2) COPD = reduced alveolar SA 3) slower rate of inhalation induction 4) CO calculation 5) drug transfer across placenta
list several examples of how Boyle’s law can be applied in the OR.
(PV)
- diaphragm contraction increases Tv
- pneumatic bellows
- squeezing an Ambu bag
- using Bourdon pressure gauge to calculate how much O2 is left in a cylinder
list an example of how Charle’s law can be applied in the OR
V/T
- LMA cuff ruptures when placed in an autoclave VOLUME OF CUFF
list an example of how Gay-Lussac’s law can be applied in the OR.
P/T
- oxygen tank explodes in heated environment
what is the function of the ideal gas law
unifies all 3 gas laws into a single equation
PV= nRT
R = constant 0.0821 Latm/Kmol
define Ohm’s law
the current passing through a conductor is directly proportional to the voltage and inversely proportional to the resistance
Q = change in pressure / resistance
It can relate to noninvasive blood pressure
how is Poiseuille’s law related to Ohm’s law?
Poiseuille’s law is a modification of Ohms law that incorporates vessel diameter, viscosity, and tube length.
Q = blood flow R = radius deltaP = arteriovenous pressure gradient "n" = viscosity L = length of the tube
Q = (piR^4deltaP)/(8”n”L)
how do changes in radius affect laminar flow (x1, x2, x3, x4, and 5)
altering the radius of the tube exhibits the greatest impact on flow
R = 1^4 = 1 R = 2^4 = 2x2x2x2= 16 doubled R = 3^4 = 3x3x3x3 = 81 tripled R = 4^4 = 4x4x4x4 = 256 quadruple R = 5^4 = 5x5x5x5 = 625
how can we apply Poiseuille’s law to the administration of a unit of PRBCs?
we can deliver PRBCs faster if we:
- increase the radius w/ a large bore IV
- increase the pressure gradient w/ a pressure bag or increasing IV pole height
- decrease viscosity by diluting blood w/ NS 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?
There are three types of flow: laminar, turbulent, and transitional
Reynolds number allows us to predict the type of flow that will occur in a given situation
Re <2000 = laminar flow is dependent on gas viscosity (Poiseuille’s Law)
Re 2000-4000 = transitional flow
Re >4000 = turbulent flow is dependent on gas density (Graham’s law)
Re = (density x diameter x velocity)/viscosity
explain how understanding Reynold’s number helps you treat status asthmaticus.
increased airway resistance, and this increases flow turbulence and the work of breathing.
- bc turbulent flow is primarily dependent on gas density, we can improve flow by having the patient inhale a lower density gas
- oxygen/helium mixture (Heliox) improves Reynold’s number by reducing density
- the key here is that we are converting turbulent flow to laminar flow. Helium doesn’t improve flow if it’s already laminar
Explain Bernoulli’s principal, and discuss it in the context of a river.
- describes the relationship b/n the pressure and velocity of a moving fluid (or gas)
- if the fluid’s velocity is high, then the pressure exerted on the walls of the tube will be low
explain the Venturi effect, and give some examples.
an application of the Bernoulli principal.
As air flow in a tube moves past the point of constriction, the pressure at the constriction DECREASES and if the pressure inside the tube falls below atmospheric pressure, then air is entrained into the tube (venturi effect)
adjusting the diameter of the constriction allows for control of the pressure drop and the amount of air that is sucked into the tube. The key here is air entrainment!
Example is jet ventilator, nebulizer, Venturi mask
explain the Coanda effect and give some 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 regurg and the water that follows the curve of a glass.
how do you calculate the law of Laplace for a sphere? for a cylinder?
sphere:
T = PR/2
ex: alveolus, ventricle, saccular aneurysm
cylinder
T = PR
ex: blood vessels, aortic aneurysm
what is the yearly maximum for radiation exposure? How does this change if someone is pregnant?
nonpregnant:
- 5rem max
- eye, thyroid = most susceptible
pregnant
- 0.5rem max for fetus or 0.05rem/month
- fetus = most susceptible
how can we apply the inverse square law to radiation exposure?
intensity of exposure
1/distance ^2
minimum safe distance from radiation source is 6ft