Emergency Medical Technician (EMT) Intermediate Practice Exam

What acid-base derangement initially occurs in a tachypneic patient without a physiologic demand for increased oxygen?

1. Respiratory acidosis

2. Respiratory alkalosis

3. Metabolic acidosis

4. Metabolic alkalosis

The correct answer is: Respiratory alkalosis

In a tachypneic patient who does not have a physiological demand for increased oxygen, the initial acid-base derangement that occurs is respiratory alkalosis. Tachypnea, which is rapid breathing, leads to an increased rate of expiration, resulting in a decreased concentration of carbon dioxide (CO2) in the blood. This lowering of CO2 levels causes a shift in the acid-base balance, specifically an increase in blood pH, leading to respiratory alkalosis. Respiratory alkalosis may occur in various situations, such as anxiety, pain, or other factors that may not necessarily require the body to demand more oxygen but provoke an increase in the respiratory rate. Other forms of acid-base disturbances, such as respiratory acidosis or metabolic imbalances, would generally require different underlying physiological processes to initiate, which are not present in this scenario. For instance, respiratory acidosis involves retaining CO2 due to inadequate ventilation, while metabolic acidosis and metabolic alkalosis relate to imbalances in acid and base levels in the body's metabolism rather than directly resulting from changes in respiratory capacity. Thus, the altered state of breathing leading to less CO2 and subsequently higher pH characterizes the respiratory alkalosis seen in tachypneic patients without a physiologic need