Question

Describe how gravity alters ventilation and especially perfusion in the lungs.

Answer 1

Total ventilation is a product of regional ventilation and alveolar regional volume.

Both measurements therefore have a direct relationship with lung volume.

• In the left lateral position the dependent lung has smaller volume than than in the right lateral position.
• And the magnitudes of the vertical gradients of blood flow and ventilation are less.

relatively small variation in blood flow and ventilation with gravity does no compensate for the greater loss of lung volume in this position.

Thus total blood flow and alveolar ventilation in the dependent lung is less than the non-dependent lung In The left lateral position.

BECAUSE THE DECREASE IN LUNG volume outweigh ANY GRAVITY DEPENDENT increase in VENTILATION AND PERFUSION.