Which condition may contribute to diffusion limitations in CO2 exchange?

• A. Excessive hydration
• B. Pathology
• C. Acclimatization
• D. Rest

Answer: (B)

Diffusion limitations in carbon dioxide (CO2) exchange can occur when there are conditions that impair the transport of gases across the alveolar-capillary membrane. One significant factor contributing to these limitations is the presence of pathology, which can include various lung diseases and conditions that affect gas exchange, such as chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, or asthma.

These pathological states may lead to changes in the structure and function of the alveoli or the blood vessels surrounding them, resulting in thickening of the alveolar membrane, reduced surface area for gas exchange, or alterations in ventilation-perfusion ratios. As a consequence, the efficiency of diffusion of CO2 from the blood into the alveoli could be diminished, leading to accumulation of CO2 in the blood and potential respiratory acidosis.

In contrast, excessive hydration might lead to edema, affecting gas exchange but it is not typically cited as a direct cause of diffusion limitations in CO2. Acclimatization, on the other hand, usually refers to adaptations of the body to changes in environment (such as high altitude) and does not inherently lead to diffusion limitations. Lastly, being at rest typically does not interfere with CO2 diffusion; in fact, it may facilitate efficient gas exchange when