Respiratory System

Respiratory Tract Embryology Stages {EPCSA}

  • Embryonic
  • Pseudoglandular
  • Canalicular
  • Saccular
  • Alveolar

Lung Volumes and Measurements

Indices Methods
IRV
TV
ERV
Spirometry
RV Helium dilution method
Plethysmography

Perfusion and Diffusion Limited Pulmonary Circulation

Ventilation/Perfusion (V/Q) Ratio

Ratio Conditions
0 Shunt
Low Lung base
High Lung apex
Dead space

Dead Space

Parameter VD = VT × (PaCO2 - PECO2) ÷ PaCO2
VD Dead space
VT Tidal volume
PaCO2 Arterial CO2 pressure (mmHg)
PECO2 Expired Air CO2 pressure (mmHg)

Diffusion Rate

Parameter G × A ÷ T
G A-a gradient
A Area
T Thickness

Alveolar Gas Equation

Parameter PAO2 = PIO2 - PaCO2 ÷ RQ
PAO2 Alveolar O2 pressure (mmHg)
PIO2 Inspired Air O2 pressure (mmHg)
PaCO2 Arterial CO2 pressure (mmHg)
RQ Respiratory quotient