Lectures on respiratory physiologyLectures on respiratory physiology

Pulmonary Gas Exchange IPulmonary Gas Exchange I

Perfect Lung

PO2 cascade in a hypothetical perfect lung

Effect of hypoventilation

All the expired CO2 comes from the All the expired CO2 comes from the alveolar gasalveolar gas

Alveolar Ventilation Equation using PCO2

Alveolar Gas Equation

F R

COP - OP OP

22

AI2A

Using the Alveolar Gas Equation

100 OP0.8

40 - 150 OP

F R

COP - OP OP

2A

2A

AI2A

22

Alveolar gas equation for hypoventilation

50 OP0.8

80 - 150 OP

F R

COP - OP OP

2A

2A

AI2A

22

What inspired O2 concentration is required to return the alveolar PO2 to normal?

2

2

22

2

2

22

28% ion concentrat O Inspired

0.28 713

200 OF

713 OF OP

200 OP

F0.8

80 - OP 100

F R

COP - OP OP

I

II

I

I

AI2A

Causes of hypoventilation

PO2 cascade showing a diffusion step

Time courses for PO2 in the capillary

Thickened blood-gas barrier

PO2 cascade showing addition of shunt

O2 concentrations with a shunt

Deriving the shunt equation

The shunt equation

Shunt causes a low arterial PO2 with 100% O2