Bernoulli Effect (Daniel Bernoulli)
As velocity increases, lateral pressure (the force applied to the sides of the tube) decreases
As gas flows through a stricture (obstruction), its velocity increases and lateral pressure decreases
Magnitude of pressure drop is proportional to the increase in the square of the velocity.
Lung pathophysiology – COPD: increased mucus in airways can cause partial obstruction, the increased velocity of gas passing by the narrowing causes a decrease in lateral pressure, and combined with the destructive changes in the lung tissue, augments airway collapse and air trapping on exhalation.