Physics and Chemistry POA

Boyle’s Law

(V₁P₁=V₂P₂)

Pressure is inversely proportional to volume at a constant temperature.

As the volume decreases, the pressure of the gas inside it increases, and vice versa

Charles’ Law

(V₁/T₁ = V,/T₂)

Volume is directly proportional to absolute temperature at a constant pressure.

As the temperature of a gas increases, its volume will also increase, and conversely, as the temperature decreases, its volume will decrease (at constant pressure)

Gay-Lussac’s Law

(P1/T1 = P2/T2): Pressure is directly proportional to absolute temperature at a constant volume.

At a constant volume, an increase in the gas's temperature will cause a corresponding increase in its pressure, and vice versa

Avogadro's Hypothesis

one mole of any gas contains exactly the same number of molecules, which is 6.023 x 10²³

Specifically, one mole of any ideal gas at standard temperature (0℃) and standard pressure (1 atm) will always expand to occupy exactly 22.4 Liters of volume.

Dalton’s Law of Partial Pressures

The total pressure of a gas mixture equals the sum of the partial pressures of each individual gas.

Ptotal = P1 + P2 + P3 + P4 +...

atmospheric pressure of 760 mmHg
Partial pressure of Nitrogen: 760 mmHg x 0.79 = 600.4 mmHg.

Partial pressure of Oxygen: 760 mmHg x 0.21 = 159.6 mmHg.

Henry’s Law

At a constant temperature, the amount of gas dissolved in a liquid is directly proportional to the partial pressure of that gas over the liquid.

• Key component: gas solubility in a liquid is inversely related to temperature - explains why hypothermic pts have delayed emergence (decreased temperature = increased gas solubility in blood).

Allows calculations of the amount of O2 and CO2 dissolved in blood

Multiply PaO₂ by 0.003 to find dissolved oxygen, and PaCO₂ by 0.067 to find dissolved carbon dioxide.

Fick’s Law of Diffusion

examines the entire system: diffusion rate is directly proportional to the partial pressure gradient, membrane surface area, and gas solubility, but inversely proportional to membrane thickness and molecular weight.
Ex: Diffusion hypoxia, the concentration effect, and placental drug transfer.

Graham’s Law

isolates the specific physical properties of the molecule. 

It states the rate of diffusion is inversely proportional to the square root of the gas's molecular weight. (r = 1/ √mw)

Simply put, smaller molecules diffuse faster. Explains the rapid uptake of smaller molecules in the second gas effect

Ohm’s Law (V = IR)

Flow (Current) equals the Pressure Gradient (Voltage) divided by Resistance.

(Hemodynamics): fluid flow is driven by a pressure gradient.
Fluids move from an area of higher pressure to lower pressure, and this flow is inversely affected by the resistance or friction it encounters along the tube (or blood vessel)

SVR

SVR = (MAP-CVP)/CO x 80

Hagen-Poiseuille Law

(Laminar Flow): Fluid flow is directly proportional to the pressure gradient and the radius to the fourth power (r ⁴), and inversely proportional to viscosity and tube length.

Reynolds Number (Re)

index used to predict whether the flow of fluid (or gas) laminar or turbulent.

It is directly proportional to fluid density, velocity, and tube diameter, and inversely proportional to viscosity. Laminar Flow < 2300 < Turbulent Flow

Heliox lower density, rough surfaces vascular bruits

Bernoulli Principle

describes the fundamental relationship between a fluid's velocity and pressure. As fluid/gas flows through a constriction (narrowing) in a tube, its velocity increases and its pressure decreases

Venturi Effect

If the pressure drop at the constriction falls below atmospheric pressure, it acts as a vacuum and entrains (sucks in) surrounding air or fluid

Law of Laplace

relationship between wall tension (T), internal pressure (P), and radius (r).

Law of Laplace: Cylinders

(T=Pr) Tension is directly proportional to the radius

as the structure expands (increased radius), the tension (force) in the wall of the structure will increase. A dilated aorta or an aneurysm (larger radius) experiences significantly more wall tension

Law of Laplace: Spheres

wall tension in a sphere is half that of a cylinder of the exact same radius

pressure is inversely proportional to the radius (P=2T/r)