# 0. Physiology Equations Flashcards

What are the equations for calculating whether or not respiratory acidosis is acute or not?

Acute:

HCO3 = 24 + (PaCO2 - 40)/10

Chronic:

HCO3 = 24 + 4(PaCO2 - 40)/10

What is the equation for calculating whether or not a patient is compensated adequately for metabolic alkalosis?

Expected change in PaCO2 = (.5 to 1.0) change in HCO3

What is the equation for calculating whether or not a patient is compensated adequately for metabolic acidosis?

PaCO2 = 1.5(HCO3) + 8 +/- 2

What are the equations for calculating whether or not respiratory alkalosis is acute or not?

Acute

Expected HCO3 = 24 - 2(40 - PaCO2)/10

Chronic:

Expected HCO3 = 24 - 5(40 - PaCO2)/10

What is the equation for calculating anion gap?

Anion gap = [Na] - ([Cl] + [HCO3])

What is the equation for minute ventilation?

Tidal volume x frequency

What is the equation for minute alveolar volume?

(Tidal Volume - Dead space) x frequency

What is the equation for blood pressure in terms of cardiac output?

BP = CO x Resistance (pulmonary or peripheral)

What is the equation for the respiratory quotient?

Volume of CO2 produced / Volume of O2 consumed

OR

Minute ventilation CO2 / Minute ventilation O2

What is the (solvable) equation for alveolar O2 given arterial PaCO2?

PAO2 = P_{I}O_{2} - [PaCO2/RQ]

P_{I}O_{2} = Pressure of air (760 at sea level) - Pressure of water (47) x percentage of oxygen (21 in room air)

What is the equation for airway resistance?

8nL/r^{4}

n = viscosity

L = length of the tube

r = radius of the tube

What is the relationhip between pressure and surface tension?

LaPlace’s law

Pressure = 2(tension)/radius