Question

Explain why pressure falls as gas flows from alveoli to airway opening during a forced exhalation maneuver.

Answer 1

The pressure gradient at the onset of forced expiration is created by the release of inspiratory muscles, which results in unopposed elastic tensile stress throughout the pulmonary parenchyma, the elastic recoil. Because the parenchyma is indirect contact with the air in the alveoi ,this stress is transmitted to the air And is the alveolar pressure.

During a forced expiration, the pressure outside the airway remains relatively constant. Whilst the pressure inside the airway decreases from the peripheral airways to the mouth resulting in airway compression. With a forced exhalation, a wave of equal pressure points move peripherally into smaller airways as the lung volume decreases and the pressure within the airway falls.