GasLaws, Physics, and Math Flashcards
Molecular Theory of Matter
states that matter is made of minute particles called molecules, that exist in various states (solid, liquid, or gas).
Kinetic Theory of Matter
states that molecules are in constant motion (random motion) and have a degree of attraction between them called van der waals forces.
Critical Temperature
the temp. above which a gas cannot be liquefied regardless of how much pressure is applied
Avagadro’s Hypothesis
Avagadro hypothesized that if you had 2 different containers containing 2 different gases at the same temp and pressure, then they contain the same number of molecules
Avagadro’s Number
1 mole - contains 6.02 x 10^23 molecules
What is one mole equivalent to?
One mole is one gram multiplied by the molecular weight: e.g. 1 mole 02 = 32 grams.
One mole of any substance occupies how many liters?
22.4 liters so: 6.02 x 1023 molecules of 02 = 32 grams and occupies 22.4 L.
Calibration of vaporizers are done using what?
Give an example using sevo
Avagadro’s Hypothesis
- Molecular weight of Sevoflurane is 200, so 200 g Sevo is 1 mole, and would occupy 22.4L at s.t.p.
- If we put 20g of Sevo (0.1 mole) into a vaporizer, and allow it all to vaporize, it would occupy 2.24 liters
Universal Gas Constant
By combining the perfect gas laws with Avagadro’s hypothesis we arrive at the following equation:
PV/T = Constant (k4), for any given quantity of gas
Boyle’s Law
The volume of an ideal gas is inversely proportional to the pressure—Thus as pressure ↑ the volume ↓
V = 1/P
temperature held constant
Application of Boyle’s Law with a reservoir bag
Applying pressure (squeezing it) causes the volume to decrease
Application of Boyle’s Law with an E cylinder
The relatively small volume of gas in the cylinder is at high pressure. When it is released to the atmosphere where there is a relatively low pressure, a large volume results
Pressure ↓ and Volume ↑
Application of Boyle’s Law with spontaneous breathing
When intrapulmonary pressure becomes negative (decreases), intrapulmonary volume increases
Application of Boyle’s Law with bellows on the ventilator
As pressure increases, the volume within the bellows decreases
Charles’ Law
Charles’s Law states that the volume of a given gas is directly proportional to the Kelvin Temperature provided the amount of gas & the pressure remains constant : V/T
temperature ↑ the volume ↑
Gay-Lussac’s Law
At constant Volume, the pressure of a gas sample is directly proportional to the Kelvin Temperature.
Thus as the temperature ↑ the pressure ↑
Application of Gay-Lussac’s Law
A full cylinder of compressed gas is moved from the air conditioned hospital (70 degrees) to the loading dock (100 degrees Fahrenheit)- What happens to the pressure in the cylinder???
-increased pressure
What remains constant in Boyle’s Law?
temperature
What remains constant in Charles’?
pressure
What remains constant in Gay-Lussac’s Law?
volume
Universal (Ideal) Gas Law
PV = nRT
Application of the Ideal Gas Law with a cylinder
As a cylinder of compressed gas empties, the pressure falls-
The cylinder has a constant volume. The number of moles (n) of gas decreases as gas exits the cylinder, so Pressure decreases
Dalton’s Law
states that 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.
Application of Dalton’s Law using air
760 mmHg x 21% = 160mmHg, this is the partial pressure of Oxygen in the container
What is the partial pressure for nitrogen?
760mmHg x 79% = 600mmHg
Application of Dalton’s Law using a combination of inhaled anesthetic
Commonly used agents might be:
50% N20 .5x760
+ 44% O2 .44x760
+ 6% Desflurane .06x760
100% Mix to patient = 1.0 x760
What is MAC
the concentration of the vapor (measured as a percentage at 1 atmosphere, i.e the partial pressure) that prevents the reaction to a standard surgical stimulus in 50% of subjects.
What is physiologically important, the partial pressure or concentration?
The partial pressure (mm Hg), not the concentration. This is important to remember because atmospheric pressure changes. The concentration may change to keep the same partial pressure of an agent at a different atmospheric pressure
Fick’s Law of Diffusion
Vgas=
Area x Solubility x Partial pressure difference/
Molecular Wt x Distance
Clinical application of Fick’s Law - 2nd gas effect
high inspired concentration of a first gas (N2O) accelerates uptake of a companion gas
Clinical application of Fick’s Law - Concentration Effect
Uptake of high volumes of N2O concentrates the remaining 2nd gas
Graham’s Law
A gas diffuses at a rate that is inversely proportional to the square root of its molecular weight
Thus as molecular weight ↑ the rate of diffusion ↓
Henry’s Law
The amount of gas dissolved in a liquid is directly proportional to the partial pressure of the gas in contact with the solution
What is an application of Henry’s Law?
Allows calculation of O2 and CO2 dissolved in blood.
What is the solubility coefficient of O2? (its a constant)
.003ml/100ml blood/mmHg partial pressure
What is the solubility coefficient of CO2? (its a constant)
.067 ml/100ml blood/mmHg partial pressure
ABG: pH 7.44, PaO2 600mmHg, PaCO2 35mmHg, HCO3 25
How much O2 and CO2 is dissolved in blood?
Multiply PaO2 x constant (.003) 600 x .003 = 1.8ml/100ml blood
Multiply PaCO2 x constant (.067) 35 x .067 = 2.35 ml/100ml blood
*application of Henry’s Law
How can you estimate the PaO2?
when delivering certain amount of oxygen and multiplying FiO2 x 5.
Let’s say you have 21% O2, estimate the PaO2 and the dissolved O2 in the blood.
21 x 5 = 105mmHg
105mmHg x .003 = .315 ml/100ml blood.
Your delivering 40% FiO2 via face tent, estimate the PaO2 and the dissolved O2 in the blood.
40 x 5 = 200 mmHg;
200 mmHg x .003 = .6ml/100ml blood.
Critical Temperature
The temp above which a substance goes into gaseous form in spite of how much pressure is applied.
T/F: A gas cannot be liquefied if the ambient temperature is greater than critical temperature
True
A gas cannot be liquefied if sufficient pressure is applied at ambient temp below the critical temperature
False; A gas CAN be liquefied if sufficient pressure is applied at ambient temp below the critical temperature
What is the critical temperature of oxygen?
-119 degree C
Can oxygen be liquified at room temperature? (25 degree C)
O2 cannot be liquefied at room temp no matter how much pressure is applied to it
Recall: A gas can be liquefied if sufficient pressure is applied at ambient temp BELOW the critical temperature
How does the hospital store oxygen?
Liquid form; The containers are insulated from the outside and the temperature is kept at -160 degress C.
What is the critical temperature of nitrous oxygen?
39.5 degree C
Can nitrous oxide be liquified at room temperature? (25 degree C)
Yes; pressure can be applied to liquefy N2O at room temp
Adiabatic Cooling
The term adiabatic implies a change in temperature of the matter without gain or loss of heat
What is an example of adiabatic cooling?
N2O cylinder opened fully-> frost can form on the outlet due to cooling
Joule-Thompson Effect
Expansion of a gas causes cooling
What is an example of Joule-Thompson Effect?
As gas leaves a cylinder, the expansion cools the surrounding air causing condensation of moisture on the cylinder
Poiseuille’s Law
Q = pie r4 delta P / 8nL
Poiseuille’s Law is associated with what kind of flow?
Laminar
Give some clinical examples of Poiseuille’s Law?
IV Flow
Airways
Vascular flow – Polycythemia vs. Anemia
Thorpe Tubes – at low flows
Density is a determinant of flow when it is..
turbulent
Viscosity is a determinant of flow when flow is..
laminar (low flow rates)
Reynolds number
velocity ∙ density ∙ diameter/viscosity
What number is associated with turbulent flow?
> 2000
Thorpe tube - low flow
the annular-shaped orifice around the float is tubular so (according to Poiseuille’s Law) flow is governed by viscosity.
Thorpe tube - high flow
(indicated on the wider top part of the float tube), the annular opening is more like an orifice, and density governs flows.
What are three factors of that change flow from laminar to turbulent
Increased velocity
Bend >20 degrees
Irregularity in the tube
Bernoulli’s Theorem
The lateral wall pressure is LEAST at the point of greatest constriction and the speed is the GREATEST
Thus, flow will be faster through the constricted portions and slower at the wider portions of a tube
What is an application of Bernoulli’s Theorem?
Venturi tube
Explain the principle of the venturi tube
as the tube narrows, velocity of the fluid increases, thus dropping pressure - hence a sidearm on that portion of the tube can be used to aspirate another fluid into the tube.
Beer’s Law
Absorption of radiation by a given thickness of a solution of a given concentration is the same as that of twice the thickness of a solution of half the concentration
Lambert’s Law
Each layer of equal thickness absorbs an equal fraction of the radiation that passes through it
Clinical application of Beer-Lambert’s Law
pulse ox
Carboxyhgb
FALSE HIGH reading
Methgb
If SaO2 > 85% FALSE LOW
If SaO2 < 85% FALSE HIGH
HgbF, HgbS, Polycythemia
No Effect
Methylene & Isosulfan Blue
FALSE LOW reading
Indocyanine Green & Indigo Carmine
slight decrease
Blue Nail Polish
FALSE LOW reading
Law of La Place
T=Pr
What are three clinical applications of LaPlace’s Law?
- Normal Alveoli and the need for surfactant during expiration
- Vascular Pathology- Aneurysm rupture due to increased wall tension
- Ventricular volume and work of the heart- a dilated ventricle has greater tension in its wall (end diastolic pressure rises)
Ohm’s Law
E (Voltage) = I(current flow or amp) R(resistance)
E=IR
What are two applications of ohm’s law?
- Strain Gauges in Pressure Transducers
- Thermistors
How is a patient in the OR at risk for burns?
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
Macroshock
Current distributed through the body, culprit: faulty wiring, improper grounding
Microshock
Current applied in or near the heart, culprit pacing wires, fault equipment during cardiac cath
What are the amounts of amps and injuries associated with them in reference to macroshock
- 1 milliamp skin tingling/perception
- 5 milliamps maximal “harmless” current
- 10-20 milliamps let go of source
- 50 milliamps pain, LOC, mechanical injury
- 100-300 milliamps V-Fib, resp intact
- 6000 milliamps complete physiologic damage
How many amps is required to cause harm with microshock?
50 - 100 microamps V-Fib
2% Lidocaine
2 grams of Lidocaine in 100 mL
2000 mg in 100 mL
20 mg in 1 mL
1% Lidocaine
1 gram in 100 mL
1000mg in 100 mL
10 mg in 1 mL
0.75% Bupivicaine
- 75 grams in 100 mL
- 0 mg in 100.0 mL
- 5 mg in 1 mL
1:100,000 Epinephrine
1 gram Epinephrine in 100,000 mL 1000 mg in 100,000 mL 1mg in 100 mL 1000 mcg in 100 mL 10 mcg in 1 mL
1: 1000 Neostigmine
1 gram in 1000 mL
1000mg in 1000 mL
1mg/mL
Epinephrine 1: 10,000
1 gram in 10,000 mL 1000 mg in 10,000 mL 1mg in 10mL 1000 mcg in 10mL 100 mcg/mL (OR 0.1 mg/mL)
Epinephrine 1: 200,000
1 gram in 200,000 mL 1000mg/200,000 mL 1mg/200mL 1000 mcg/200mL 10 mcg/2mL = 5 mcg/mL
2% Lidocaine with Epinephrine 1:200,000
What is in EACH mL??
2% means 2 grams per 100 mL
2000 mg/100 mL = 20 mg/mL
1:200,000 means 1 gram per 200,000 mL
1000 mg/200,000 mL= 1mg/200 mL = 1000 mcg/200 mL =
10 mcg/2mL = 5 mcg/mL
2% Lidocaine with Epinephrine 1:200,000
How much is each in 5ml?
EACH ml contains 20 mg Lidocaine AND 5 mcg Epinephrine
100mg Lido and 25mcg of Epi
