Gas laws, formulas, and conversion rates

Absolute Humidity

The actual amount of water vapor in the air in mg/L

Saturation point

Maximum amount of water vapor that air can hold at any temperature between 0C and 100C

Relative Humidity (RH)

The water content in a gas compared with the gas’s capacity for water content at that temperature

Relative humidity formula

%RH = Absolute humidity / Saturation point

Isothermic Boundary (RH 100% at body temp)

RH at 37C = 44mg/L or 47 mmHg water vapor pressure

1 tsp to ml

1tsp = 5ml

Unit Conversion mmHg to Torr

1 mmHg = 1 torr

Unit Conversion mmHg to cmH2O

1 mmHg = 1.36 cmH2O

Unit Conversion atm to mmHg

1 atm = 760 mmHg

Unit Conversion Fahrenheit to Celsius

C = (F-32) * 5/9

Unit Conversion Celsius to Fahrenheit

F = 32+ (C*9/5)

C to Kelvin

K = C +273

Boyle’s Law

Constant Temperature. Volume and Pressure inversely related. V1 x P1 = V2 x P2

Charles’s Law

Constant Pressure, Volume and temperature Directly Related V1/T1 = P2/T2

Gay- Lussac’s Law

Constant Volume. Temperature and pressure directly related. P1/T1 = P2/T2

Ideal Gas Law

(P1*V1)/T1 = (P2*V2)/T2

Dalton’s Law

All partial pressures in a mixed gas equal the total pressure. Ptotal = p1 + p2 +p3 etc

Henry’s Law

The amount of gas that can dissolve in a liquid. Varies with the solubility coefficient and the partial pressure

Fick’s Law

Gas diffusion through a membrane.

(Concentration gradient x surface area x permeability) / (Particle Size x membrane thickness)

CaO2 Formula

CaO2 = ((Hb*1.34)*SaO2) + (PaO2×0.003)

COHb Half Lives

Half life Room Air: 5hr

Half life 15 LPM non-rebreather mask: 75 min

Half Life FiO2 100% at 3atm = 30 min