Which condition is NOT a cause of respiratory alkalosis?

Respiratory alkalosis occurs when there is an excess loss of carbon dioxide from the body, leading to an increase in blood pH. To understand why pneumonia is not a cause of respiratory alkalosis, it's important to consider how pneumonia affects respiratory function.

Pneumonia is a lung infection that typically leads to impaired gas exchange and reduced oxygenation. In cases of pneumonia, the patient's ability to expel carbon dioxide effectively is compromised, often resulting in hypoventilation rather than hyperventilation. When hypoventilation occurs, carbon dioxide levels in the blood increase, leading to respiratory acidosis instead of alkalosis.

In contrast, the other conditions listed all contribute to respiratory alkalosis through different mechanisms. Increased temperature can lead to hyperventilation, which lowers carbon dioxide levels. Aspirin toxicity can stimulate the respiratory center, causing increased respiration and subsequent carbon dioxide loss. Controlled mechanical ventilation may also be set to cause a patient to hyperventilate, artificially lowering carbon dioxide levels.

Thus, pneumonia is not a cause of respiratory alkalosis; it is more closely associated with respiratory acidosis due to its negative impact on ventilation and gas exchange.