What is the primary mechanism causing respiratory alkalosis?

The primary mechanism causing respiratory alkalosis is hyperventilation. In this condition, there is an increase in the rate and depth of breathing, which leads to an excessive expulsion of carbon dioxide (CO2) from the lungs. When CO2 levels decrease, it results in a higher blood pH, creating a state of alkalosis. Hyperventilation may occur due to various physiological or psychological factors, such as anxiety, pain, or metabolic issues, but regardless of the trigger, the key outcome remains the same: a reduction in CO2 concentration resulting in increased blood pH.

In contrast, the other options pertain to conditions that do not primarily drive respiratory alkalosis. Deficient alveolar diffusion and deficient pulmonary perfusion can lead to respiratory acidosis or hypoxemia due to inadequate gas exchange, rather than creating an alkalotic state. Parasympathetic inhibition may affect respiratory rates, but it is not a direct mechanism leading to respiratory alkalosis. Thus, hyperventilation is the most direct cause of this condition.