Pulmonary gas pressures

• The pressure of outside air
• The partial pressures of inspired oxygen and carbon dioxide
• The rates of total body oxygen consumption and carbon dioxide production
• The rates of alveolar ventilation and perfusion

  Partial pressures

Partial pressure of oxygen (at sea level)

• Firstly, as the air enters the lungs, it is humidified by the upper airway and thus the partial pressure of water vapour reduces the oxygen partial pressure to about 150 mmHg.
• The rest of the difference is due to the continual uptake of oxygen by the pulmonary capillaries, and the continual diffusion of CO₂ out of the capillaries into the alveoli.

Partial pressure of carbon dioxide

Pathology