Professional and Linguistic Assessments Board (PLAB) Practice Exam

What is typically seen in a patient who hyperventilates?

1. Metabolic acidosis

2. Respiratory alkalosis

3. Respiratory failure

4. Metabolic alkalosis

The correct answer is: Respiratory alkalosis

Hyperventilation refers to an increased rate and depth of breathing, which leads to an excessive loss of carbon dioxide (CO2) from the body. As CO2 levels drop, the blood pH rises, resulting in a condition known as respiratory alkalosis. This occurs because the carbonic acid-bicarbonate buffer system becomes disrupted; lower levels of CO2 lead to a decrease in carbonic acid, thus raising the pH of the blood. In respiratory alkalosis, the primary problem arises from the respiratory system's function, where excessive ventilation causes the imbalance. Patients who hyperventilate may experience symptoms such as lightheadedness, tingling in the extremities, and even muscle cramps, all stemming from the consequent temporary abnormalities in blood chemistry due to the reduction of CO2. While metabolic acidosis and metabolic alkalosis relate to disturbances in the body's metabolism and can involve different pathophysiological processes, they do not directly result from hyperventilation. Respiratory failure signifies a scenario where gas exchange cannot occur adequately, resulting from various causes, but it is not a typical outcome of hyperventilation itself. Therefore, the most accurate representation of a patient who hyperventilates is the development of respiratory alkalosis.