Hyperventilation syndrome (Hyperventilation syndrome), is a physiological and psychological reaction caused by acute anxiety. During the attack, the patient will feel rapid heartbeat, palpitations, sweating, and speed up breathing because he cannot feel breathing, resulting in carbon dioxide being continuously expelled with too low a concentration, causing symptoms such as secondary respiratory alkalosis. Hyperventilation is excessive breathing, which causes respiratory alkalosis, resulting in numbness of the hands and feet, and in severe cases, the limbs can be convulsed. To increase blood PCO2, a paper bag or long tube bag can be placed over the nose and mouth to increase the dead space of the respiratory tract and reduce the expiration and loss of CO2. Oxygen containing 5% CO2 can also be inhaled to achieve symptomatic treatment.4. Calcium can be given intravenously in appropriate amounts to increase plasma [Ca++] for hand and foot twitching (slow injection of 10% calcium gluconate 10ml). Etiology 1. Psychogenic hyperventilation This is a common cause of respiratory alkalosis, but it is usually not serious. In severe cases, there can be dizziness, abnormal sensation, and occasional convulsions. It is commonly seen in patients with hysterical episodes. [1] 2. Abnormal metabolic processes In hyperthyroidism and fever, etc., ventilation can significantly increase beyond the amount of CO2 that should be expelled. It can lead to respiratory alkalosis, but it is also usually not severe. However, both indicate that the amount of ventilation does not depend solely on [H+] and Pco2 in body fluids, but is also related to the intensity of metabolism and oxygen demand. Hyperventilation at this time may be caused by increased pulmonary blood flow through a reflex response.3. Hypoxic hypoxia Hyperventilation in hypoxic hypoxia is a compensation for hypoxia, but at the same time it can cause excessive CO2 excretion and respiratory alkalosis. It is common in people who enter plateau, high mountain or high altitude; patients with thoracic and pulmonary lesions such as pneumonia, pulmonary embolism, pneumothorax, pulmonary stasis, etc., which cause reflex ventilation increase due to stimulation of thoracic, pulmonary vascular or afferent nerve of lung tissue; in addition, some patients with congenital heart disease, hypotonic hypoxemia due to increased right-to-left shunt can also appear hyperventilation. In addition, in some patients with congenital heart disease, hypotonic hypoxemia due to increased right-to-left shunt can also lead to hyperventilation. These all cause a decrease in plasma H2CO3 and respiratory alkalosis. 4. 5. Salicylic acid poisoning Salicylic acid can directly stimulate the respiratory center to increase its excitability and sensitivity to normal stimuli. In patients with Gram-negative bacillus sepsis, hyperventilation can be evident before there is a change in body temperature and blood pressure, and Pco2 can be as low as 17 mmHg. This change is very helpful in the diagnosis. The mechanism is not clear, as this phenomenon has not been successfully replicated in animal experiments. [Hyperventilation can occur in cirrhosis of the liver with ascites and elevated blood NH3. It may be caused by the stimulating effect of NH3 on the respiratory center. Of course, ascites also has a stimulating effect on respiration by elevating the transverse septum, but non-cirrhotic patients with ascites do not respond to hyperventilation.9. Metabolic acidosis is suddenly corrected For example, when NaHCO3 is used to correct metabolic acidosis, the concentration of extracellular fluid [HCO3-] rises rapidly to normal, but passes through the blood-brain plasma barrier very slowly, about 12-24 hours, at which time the brain is still metabolic acidosis, so hyperventilation still persists. This results in respiratory alkalosis with low H2CO3.10. Pregnancy [4] has a moderate increase in ventilation, which exceeds CO2 production and is now thought to be due to the stimulatory effect of progesterone on the respiratory center, which is also seen in some synthetic progesterone preparations. Ketoacidosis can occur during the gestational reaction period due to vomiting and inadequate diet, and respiratory alkalosis after the gestational reaction period, sometimes causing hand and foot convulsions.