There is no harm in moderate deep breathing, but excessive and frequent deep breathing can easily trigger hyperventilation syndrome and respiratory alkalosis. Moderate deep breathing is good for health, allowing more alveoli to participate in breathing, and can exercise lung function. However, excessive excessive frequent deep breathing, will make more carbon dioxide dissolved in the blood, breathlessness, chest tightness, chest pain and other symptoms, further development can be caused by the mouth, hands and feet numbness, etc., and in severe cases, muscle spasms, hand and foot convulsions, consciousness disorders and so on. When these symptoms occur due to tension, anxiety and deep breathing, you can use a plastic bag or a paper bag to cover the mouth and face, and inhale the exhaled gas into the lungs again to increase the concentration of carbon dioxide, so that the state of respiratory alkalosis can be improved.