Important Formulas

Question 1

Flow Equation

Answer 1

Δ Pressure / Resistance = Flow

Question 2

Law of LaPlace

Answer 2

2T (surface tension) / r (alveolar radius) = P (collapsing pressure)

Question 3

Alveolar Pressure

Answer 3

Alveolar Pressure (PA) – Pleural Pressure (PPl) = Lung Recoil Pressure (Pl)

Question 4

Poiseuille’s Law

Answer 4

Flow Rate (Q) = π△Pr4 / 8ηL

Question 5

Minute Ventilation Equation

Answer 5

Tidal Volume (VT) x Respiratory Frequency (f) = Minute Ventilation (VE)

Question 6

Gas Diffusion (Two equations)

Answer 6

VCO2 = (PACO2 - PVCO2) × A/T

AND

VO2 = (PAO2 - PVO2) × A/T

Question 7

Alveolar Gas Equation

Answer 7

PIO2 – PACO2 / R = PAO2