A decrease in oxygen (hypoxia) triggers what change in respiratory rate?

• A. Increase
• B. Decrease
• C. No change
• D. Variable

Answer: (A)

When oxygen levels fall, the body's oxygen-sensing system raises the drive to breathe. Peripheral chemoreceptors in the carotid bodies detect the drop in arterial O2 and send signals to the medullary respiratory centers. In response, both the rate and depth of breathing increase to raise minute ventilation, improving O2 uptake and delivery to tissues. This is why the typical reflex to hypoxia is an increased respiratory rate. Decreasing ventilation or keeping it the same would not help restore oxygen levels, and “variable” isn’t the standard response in a healthy, acute hypoxic situation.