Final answer:
V/Q mismatch occurs when ventilation (V) and perfusion (Q) in the lungs are not properly balanced, which can result from anatomical or physiological issues, affecting gas exchange. It often presents in conditions like fibrosis, asthma, or emphysema, and is compensated for by the body through adjustments in arteriole and bronchiole sizes.
Step-by-step explanation:
V/Q mismatch occurs when there is an imbalance between the amount of air (ventilation, V) and the amount of blood (perfusion, Q) in the lungs. This imbalance can be caused by a variety of factors, including physiological shunts, anatomical deformities, or changes in lung compliance and resistance due to diseases such as fibrosis, asthma, or emphysema, leading to issues in gas exchange. Anatomical dead space, or an anatomical shunt, is when the impairment is due to physical structure issues, whereas physiological dead space, or physiological shunt, is when the problem arises from functional changes within the lung or its blood vessels.
For example, in pulmonary edema or infection, the airways may become obstructed, leading to a decrease in ventilation but not necessarily affecting perfusion. Conversely, altered resistance or compliance in lung tissues can also affect gas exchange by trapping air in the lungs and making breathing more difficult. The lung has mechanisms to compensate for these mismatches by adjusting the diameter of arterioles and bronchioles to correct the imbalances.