Physics Laws Flashcards
Identify the law:
The total pressure of a mixture is equal to the sum of the partial pressures exerted by each gas in the mixture
Dalton’s Law
Calculate P3:
Ptotal= 100 mmHg
P1= 20 mmHg
P2= 20 mmHg
P3= x mmHg
x= 60 mmHg
Calculate Ptotal:
P1= 30 mmHg
P2= 40 mmHg
P3= 50 mmHg
Ptotal= 120 mmHg
At sea level, the agent monitor measures the end-tidal isoflurane as 8 mmHg. Convert this to volumes percent.
1%
At sea level, the agent monitor measures the end-tidal sevoflurane as 2%. What is the partial pressure of sevoflurane in the exhaled tidal volume?
15.2 mmHg
Identify the law:
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 it will dissolve into a liquid (at a constant temperature)
Henry’s Law
How does partial pressure affect solubility?
Directly proportional (Henry’s Law)
How does temperature affect solubility?
Inversely proportional (Henry’s Law)
Identify the law application:
Anesthetic emergence is prolonged in the hypothermic patient.
Henry’s Law
What is the oxygen solubility coefficient?
0.003 mL/dL/mmHg
What is the carbon dioxide solubility coefficient?
0.067 mL/dL/mmHg
How is dissolved oxygen in the blood calculated?
By multiplying the PaO2 by 0.003 mL/dL/mmHg (the solubility coefficient)
Henry’s Law
How is dissolved CO2 in the blood calculated?
By multiplying the PaCO2 by 0.067 mL/dL/mmHg (the solubility coefficient)
Henry’s Law
What is the formula for oxygen delivery?
DO2 = CO x [(1.34 x Hgb x SpO2) + (PaO2 x 0.003)] x 10
Identify the law:
The rate of transfer of a gas through a tissue medium is directly proportional to the partial pressure difference (driving force), diffusion coefficient (solubility), and membrane surface area. The rate of transfer is inversely proportional to the membrane thickness and molecular weight.
Fick’s Law
Identify the law application:
Diffusion hypoxia
Fick’s Law
Identify the law application:
A patient with severe COPD has reduced alveolar surface area and therefore has a slower rate of inhalation induction
Fick’s Law
Identify the law application:
Calculation of cardiac output
Fick’s Law
Identify the law application:
Drug transfer across the placenta
Fick’s Law
Identify the law:
The molecular weight of a gas determines how fast it can diffuse through a membrane.
The rate of diffusion of a gas is inversely proportional to the square root of the gas’s molecular weight.
Smaller molecules diffuse through a membrane faster than larger molecules
Graham’s Law
Identify the law application:
Second gas effect
Graham’s Law
Identify the law application:
Pneumatic bellows used for positive pressure ventilation
Boyle’s Law
Identify the law application:
Diaphragm contraction increases tidal volume
Boyle’s Law
Identify the law application:
LMA cuff ruptures when placed in than autoclave
Charles’s Law
Identify the law application:
Oxygen tank explodes in a hot environment
Gay-Lussac’s Law
What is the equation for Boyle’s Law?
P1 x V1= P2 x V2
What is the equation for Charles’s Law?
V1/T1 = V2/T2
What is the equation for Gay-Lussac’s Law?
P1/T1 = P2/T2
Identify the law application:
Squeezing a bag valve mask
Boyle’s Law
Identify the law application:
Using the bourdon pressure gauge to calculate how much O2 is left in the cylinder
Boyle’s Law
What is the equation for the Ideal Gas Law?
PV = nrT
n: number of moles
r: constant of 0.0821 liter-atm/K/mole
May be reduced to P = T/V
Identify the law:
The current passing through a conductor is directly proportional to the voltage and is inversely proportional to resistance; flow is directly proportional to the pressure gradient and inversely proportional to resistance.
Ohm’s Law
What is the equation for Ohm’s Law?
Q = ∆P/ R
Q: flow (cardiac output)
∆P: MAP- CVP
R: SVR
How is Poiseulle’s Law different from Ohm’s Law?
Poiseulle’s Law uses the same concept as Ohm’s Law, but incorporates vessel diameter, viscosity, and tube length
What is the equation for Poiseulle’s Law?
Q = [(πR^4) (∆P) /8 (viscosity) L
Q: blood flow
R: radius
∆P: arteriovenous pressure gradient (Pa-Pv)
Eta: viscosity
L: length of tube
What are the relationships between temperature, viscosity, and resistance?
A fluid’s viscosity is inversely proportionate to its temperature.
A fluid’s viscosity is proportionate to resistance.
Identify the law application:
PRBCs can be delivered faster with a large bore IV, a pressure bag or increased height of IV pole, diluting the blood with 0.9% NS through a fluid warmer, and decreasing tubing length.
Poiseuille’s Law
Identify the law application:
Polycythemia reduces microvascular flow
Poiseuille’s Law
Identify the law application:
Carotid stenosis reduces flow through the carotid artery
Poiseuille’s Law
What is the equation for Reynold’s number?
Reynold’s number = (density x diameter x velocity) / viscosity
Identify the law application:
Laminar flow is dependent on gas viscosity
Poiseuille’s Law
Identify the law application:
Turbulent flow is dependent on gas density
Graham’s Law
What are the properties of laminar flow?
Re <2,000
All molecules travel in a parallel pattern
Molecules in the center of the tube travel at the fastest rate, while molecules near the walls of a tube travel at a slower rate
Identify flow as laminar, turbulent, or transitional:
Airflow in the terminal bronchioles
Laminar flow
Identify flow as laminar, turbulent, or transitional:
Blood flow in the systemic circulation
Laminar flow
Identify flow as laminar, turbulent, or transitional:
Flow through the glottis
Turbulent flow
Identify flow as laminar, turbulent, or transitional:
Airflow through medium-sized bronchi
Turbulent flow
What are the properties of turbulent flow?
Re> 4,000
All molecules travel in a chaotic pattern
Produced by: an orifice, high gas flow, acute angle in tube, or branching the tube
How does adding helium to oxygen improve airflow?
Because turbulent flow is primarily dependent on gas desnity, Heliox will only improve airflow if it is turbulent.
What are examples of conditions that may be treated with Heliox?
Status asthmaticus
Acute epiglottitis
What is Bernoulli’s principle?
If the velocity of a fluid or gas is high, the pressure exerted on the walls of the tube will be low. If the velocity of a fluid or gas is low, then the pressure exerted on the walls of the tube will be high.
What does the Venturi effect add to Bernoulli’s priniciple?
If pressure inside a tube falls below atmospheric pressure, then air is entrained into the tube.
Identify the concept application:
Jet ventilation
Venturi effect
Identify the concept application:
Nebulizer
Venturi effect
Identify the concept application:
Application of air entrainment
Venturi effect
What is the Coanda effect?
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.
What is the equation for the law of Laplace for a cylinder?
tension = pressure x radius
What is the equation for the law of Laplace for a sphere?
tension = (pressure x radius) /2
Identify the law/ concept:
Type two pneumocytes produce surfactant which decreases surface tension and prevents alveolar collapse
Law of LaPlace
Identify the law/ concept:
Patient with systemic hypertension compensates with left ventricular hypertrophy
Law of LaPlace
Describe the relationship between wall stress and intraventricular pressure, radius, and ventricular thickness.
Wall stress is inversely proportionate to ventricular thickness and directly proportionate to intraventricular pressure and radius. Wall Stress = (Intraventricular pressure x Radius)/ Ventricular Thickness
