Physics/ Math Flashcards
Molecular Theory of Matter
Matter is made of minute particles called molecules, that exist in various states (s, l, g)
Kinetic Theory of Matter
Molecules are in constant (random) motion and have a degree of attraction b/w them called van der waals forces
Critical Temperature
temp, above which, a gas cannot be liquified regardless of how much pressure is applied
Avogadro’s Hypothesis
if you had 2 different containers containing 2 different gases (@ the same T and P), they contain the same # of mlcs
Avogadro’s Number
1 mole = 6.02 x 10^23 mlcs
1 mol = 1g x molecular wt
1 mol of any substance = 22.4 L
Avogadro & anesthesia
Calibration of vaporizers uses Sevo mlc wt = 200g = 1 mole so occupy 22.4L @STP 20g of sevo = .1 mol into vaporizer, should occupy 2.24 L
Boyle’s Law
Constant = PV (k1) P & V relationship, T contant V = 1/P Vol of ideal gas inverse proportional to P Ex: Reservoir Bag
Universal Gas Constant
PV/T = constant (k4) for gas
Applying Boyle’s Law
Full E cylinder of O2 will empty large vol into atmosphere 625-650L (low P = high Vol)
Spontaneous breathing
Bellow in Vent
Charles’ Law
V proportional to T
P stay constant
V/T = constant
Ex: Tec 6, balloon bust on hot day
Guy-Lussac’s Law
P and T proportional
V constant
EX: gas cylinder full & moved to hot room
Universal Gas Law
PV = nRT
EX: cylinder P decreases as gas empties, mol decreases too
Dalton’s Law
Total P of gas mix is sum of the partial Ps of each gas
Pressure exerted by each gas is same as if it was alone in container
Fick’s Law
Rate of diffusion of substance across membrane r/t: Directly by: 1) Concentration gradient 2) SA of membrane 3) Solubility Inversely by: 4) thickness of membrane 5) Molecular Wt
Vgas = Area x Solubility x PP diff
/ Mlc Wt x Distance
Ficks Application
2nd Gas Effect:
high inspired concentration of 1st gas (N2O) accelerates uptake of companion gas
Concentration Effect: high vol of N2O concentrates remaining 2nd gas
Diffusion Hypoxia: Diffusion of gas across alveolo-capilary membrane
Ficks Application 2
Expansion of Air Pockets
-N2O 34x more soluble in blood than N2 =
>Vol N2O diffusing in than N2 Vol out
Expansion of ET cuff w/ N2O in use
Placental transfer of drugs & O2
Graham’s Law
Gas diffuses at rate inversely proportional to square root of its mlc wt
> ml wt = < diffusion rate
Henry’s Law
Amount of gas dissolved in liquid directly proportional to partial P of gas in contact w the solution
Application of Henry’s Law
Calculate O2 & CO2 dissolved in blood
Constants:
O2: .003ml/100ml blood/ mmHg partial pressure
CO2: .067 ml/100ml blood / mmHg partial pressure
Multiply PaO2 x constant to get mls in 100mls of blood
Multiply FiO2 by 5 to get mm Hg, then multiply by .003 to get mls in 100mls of blood
Critical Temperature
Temp above which a substance goes into gaseous form in spite of how much pressure is applied
If temp > critical temp can’t liquify gas
Critical Temp of O2
-119 degree C
so can’t liquify @ room temp
-keep main hospital O2 supply @ -160 degrees C as liquid
Critical Temp of N2O
39.5 degrees C
P can liquefy N2O @ room temp (25 C)
Adiabatic Cooling
occur when matter changes phase
Change in temp of matter w/o gain/loss of heat
-frost forms d/t cooling when N2O opened fully
Joule Thompson Effect
Expansion of a gas causes cooling
-gas leave cylinder, expansion cools air = condensation
Poiseuille’s Law
& laminar flow
Describe relationship b/w rate of flow and:
DIRECT:
1) Pressure gradient across length of tube
2) radius^4 of the tube
INVERSE
3) length of the tube
4) viscosity of fluid
Applications of Poiseuille’s Law
IV Flow,
Airways
Vascular Flow
Thorpe Tubes (@ low flowso
Determinate of flow when:
low flow rates-
high flow rates
Low flow rate determinant is viscosity
High flow rates (turbulent gas) determined by density (heliox)
Reynold’s Number
Reynold’s # = velocity * density * diameter
/ viscosity
R# >2000 = Turbulent flow
Thorpe Tube
Low flow = annular orifice around float is tubular so flow determined by viscosity
High flow = annular opening more like orifice & density governs flow
3 Factors that change flow from
Laminar –> Turbulent
1) > Velocity
2) Bend >20 degrees
3) Irregularity in the tube
Bernoulli’s Theorem
Relate P & velocity
-Lateral wall P is least @ point of:
greatest constriction & speed
=faster flow
Bernoulli’s Theorem
Narrow Diameter =
Small diameter =
< Lateral wall P = > speed
Bernoulli’s Theorem
Wider Diameter =
Wider Diameter =
> Lateral Wall P = < speed
Venturi Tube
application of Bernoulli’s
- as tube narrows, velocity increases thus dropping the pressure
- so we can find velocity by measuring pressure
Clinical Applications of
Bernouilli and Venturi
Nebulizers
Venturi Oxgen Masks (20-40% O2)
Jet Ventilation
Lateral P of rapidly flowing fluid in constricted tube can be sub-atmospheric, so
Side arm on that part of tube can be used to aspirate another fluid into the tube
Beer’s Law
aka Beer-Lambert Law
absorption of radiation of a solution (of a given concentration and thickness) is same as 2x that of a solution w/ x2 thickness and 1/2 convcentration
Each layer of thickness absorbs an equal fraction of radiation that passes through it
Beer’s Law
Clinical Applications
Pulse Oximetry -2 LEDs, -Red emit light @ 660nm -Infrared emit light @ 940nm compares 2 types of light absoprbed & calculates oxygen saturation
OxyHgb 940nm (IR light) DeoxyHgb 660nm (Red Light)
Errors in Pulse Oximetry (6)
- Artifact: low perf, ambient light, motion
- Alternate Species of Hgb
Carboxyhgb: false high
MethHgb: >85% false low, <85% false high
HgbF and HgbS: No Effect - Polycythemia: no effect
- Methylene & Isosulfan Blue
false low - Indocyanine Green & Indigo Carmine
slight decrease - Blue Nail Polish: false low
Law of La Place
Pressure gradient across the wall of a sphere (alveolus) or tube/cylinder (blood vessel/ ventricle) is r/t to:
Wall Tension (T) directly
&
Radius (r) inversely
T=Pr
La Place’s Law
Clinical Applications 3
- Normal alveoli & surfactant need during expiration
- Vascular Pathology:
aneurysm rupture d/t > wall tension - Ventricular vol & work of the heart
dilated ventricle has >tension in wall
Rise in end-diastolic pressure
Ohm’s Law
Resistance which will allow 1 ampere of current to flow under influence of potential of 1 volt
W = Potential(volt)/current (amp)
E= IR
Ohm’s Law 2
Clinical Application of
- Strain gauges in pressure transducers
- Thermistors
Electricity in the OR
4
- Burns from metal
-metal bed, blood wet, electrical equipment = burns - Macroshock
current distributed througn body
by faulty wiring, bad grounding - Microshock
current applied in or near heart
by pacing wires, faulty equipment during cardiac cath - Electrocautery
Macroshock
1 milliamp --> tingling/perception 5 --> max harmless current 10-20 milliamps --> let go 50 milliamps --> pain/LOC./ mech injury 100-300 milliamps --> V-fib, resp intact 6000 milliamps --> complete physiologic damage
Microshock
50-100 microamps –> V-fib
Percentage Solutions
grams per cent/100
2% Lidocaine = 2g in 100mls
or 20mg per ml
To get mg in 1 ml, move decimal to R x1 of the %
Concentration Solutions
grams per x ccs
1:100,000 Epi =
1g per 100,000 cc
FYI: 1mg=1000mcg
1g = 1000mg
