Hyperventilation is the excessive rate and depth of respiration which reduces the amount of carbon dioxide in the blood.
Hyperventilation can impair the pilot’s judgment and increase anxiety or stress aggravates the situation. Hyperventilation seldom leads to unconsciousness, but the symptoms include dizziness, tingling in the lips, hands or feet, headache, weakness, fainting and seizures. The systems of hyperventilation are similar to hypoxia so correct diagnosis is required.
The treatment for hyperventilation involves restoring the proper carbon dioxide level in the body. Breathing normally is both the best prevention and the best cure for hyperventilation. In addition to slowing the breathing rate, breathing into a paper bag or talking aloud helps to overcome hyperventilation.
FAA-H-8083-25B Pilots Handbook of Aeronautical Knowledge pg. 17-4