Maintaining Pulmonary Diffusion Gradients: The Role of Alveolar Ventilation

Efficient gas exchange in the lungs depends on maintaining steep concentration gradients between alveolar air and pulmonary capillary blood. This is achieved through continuous alveolar ventilation—the regular replacement of air in the alveoli with fresh, oxygen-rich air and removal of carbon dioxide-rich air.

How It Works

• Oxygen Gradient: Fresh air brings high O₂ concentration into alveoli, creating a strong gradient for O₂ diffusion into the blood.
• Carbon Dioxide Gradient: Expired air removes CO₂, keeping alveolar CO₂ low, which maintains a gradient for CO₂ to diffuse from blood into alveoli.

Without this constant "air freshening" (ventilation), gradients would flatten, and gas exchange would slow or stop. Breathing rhythm and depth are precisely regulated to match metabolic demand and preserve these gradients.