In V/Q mismatch, what does a low V/Q ratio indicate?

A low V/Q ratio indicates poor ventilation relative to blood flow. This means that while there may be adequate blood flow to a lung region, there isn't enough air getting into the alveoli for effective gas exchange. When ventilation is reduced in relation to perfusion, the oxygen levels in the blood decrease because not enough oxygen can diffuse into the bloodstream to match the volume of blood being supplied to those alveoli. This mismatch can occur in various conditions such as asthma, chronic obstructive pulmonary disease (COPD), or pneumonia, where airway obstruction hampers the delivery of air into parts of the lungs, resulting in inefficient oxygenation of the blood.

The other statements do not accurately capture the significance of a low V/Q ratio in the context of respiratory mechanics.