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 |