Acute respiratory failure (acute respirator failure, ARF, hereinafter referred to as respiratory failure) is a serious clinical syndrome. Where the respiratory organs and (or) respiratory center of the various diseases, resulting in pulmonary oxygenation and (or) alveolar ventilation affects gas exchange, can cause respiratory failure, manifested as hypoxemia or hypoxemia and hypercapnia coexist. I. Etiology The primary disease is mainly respiratory system disease, followed by central nervous system disease. The pathophysiological changes of dyspnea type I expiratory failure are dominated by the gas diffusion between alveoli and blood and the dysregulation of ventilation/blood flow ratio (V/Q), and there is only hypoxemia without carbon dioxide retention in the early stage. Ventilation-impaired expiratory failure, i.e., type II expiratory failure, is mainly due to low alveolar ventilation. Blood gas measurements show a decrease in PaO2, an increase in PCO2, and a decrease in pH. Clinical manifestations: In addition to primary symptoms, the main respiratory system and symptoms of hypoxemia and hypercapnia. (1) Respiratory symptoms: (1) dyspnea: accelerated respiratory rate and nasal flaring, increased activity of auxiliary respiratory muscles; respiratory rhythm disorders, tidal respiration, sighing respiration, sobbing respiration, and jaw respiration, which is often caused by the involvement of the respiratory center. (2) Respiratory depression: it can be caused by neurological disorders and poisoning by sedative and sleeping drugs. There are respiratory center inhibition, cranial nerve damage and respiratory muscle paralysis and other manifestations. 2.Symptoms of hypoxemia and hypercapnia. (1) Hypoxemia: ① Cyanosis: it is one of the main symptoms of hypoxia. Cyanosis is one of the main symptoms of hypoxia. It is obvious in lips, perioral area and nail bed. But severe anemia, hemoglobin less than 50g / L may not appear cyanosis. ② cardiovascular dysfunction: acute hypoxia early blood pressure rise. Heart rate increases and cardiac output increases. Later, due to severe hypoxia, heart rate slows down, heart rate irregularity, cardiac output decreases, and shock occurs. Neuropsychiatric symptoms: early irritability, agitation, blurred vision, followed by apathy, drowsiness, impaired consciousness, and in severe cases, increased intracranial pressure and brain hernia. Gastrointestinal symptoms: Gastrointestinal bleeding is a serious complication of respiratory failure, often coexisting with encephalopathy and shock. When the liver is severely deprived of oxygen, lobular center necrosis, elevated aminotransferases and changes in liver function may occur. ⑤ Renal dysfunction: protein, red and white blood cells and tubular pattern, oliguria or anuria may appear in urine, or even renal failure. (6) Cellular metabolic disorder and acid-base electrolyte disorders: when severe hypoxia, PO220~30mmHg, energy metabolism of mitochondria is blocked, anaerobic glycolysis increases, pyruvic acid can not enter the tricarboxylic acid cycle, lactic acid increases, resulting in metabolic acidosis; sodium pump malfunctions, intracellular acidosis, extracellular potassium increases, electrolyte and acid-base imbalance is more serious. When cell death exceeds a certain threshold, organ failure will occur. (2) Hypercapnia: when PCO2 is higher than normal by 5~10mmHg, common symptoms include sweating, head shaking, restlessness, impaired consciousness; skin flushing, pupil narrowing, pulse rate, elevated blood pressure, and increased pulse pressure difference; when PCO2 is higher than normal by more than 15mmHg, lethargy, limb trembling, increased heart rate, and bulbar conjunctival congestion are manifested; convulsions are seen if PCO2 continues to be elevated, If PCO2 continues to increase, convulsions, coma and optic nerve papillae edema will occur; if PCO2 increases, respiratory acidosis will occur, and if pH<7.20, circulatory function and cellular metabolism will be seriously affected. Diagnosis: Early diagnosis is mainly based on clinical manifestations, primary diseases and blood gas analysis. 1.History:understand the primary diseases and triggers of expiratory failure, especially the history of respiratory tract infection and neurological diseases. 2.Clinical manifestations of hypoxemia or hypercapnia 3.Blood gas analysis: It is more reliable to make a diagnosis based on arterial blood (or arterialized capillary blood) blood gas analysis. At sea level, at rest, breathing room air, PaO2<8kPa(60mmHg), PaCO2>6kPa(45mmHg), SaO2<0.90, respiratory insufficiency; PaO2≤6.65kPa(50mmHg), PaCO2≥6.65kPa(50mmHg), SaO2<0.85, respiratory failure. Respiratory failure. According to the results of blood gas analysis, acute respiratory failure can be divided into the following two types: Type I: i.e., hypoxemic respiratory failure PaO2 ≤ 6.65kPa (50mmHg), PaCO2 normal. Type II: hypercapnia respiratory failure, PaO2≤6.65kPa(50mmHg), PaCO2≥6.65kPa(50mmHg). Treatment: The basic principle is to treat the original disease and remove the causative factors; prevent and control infection; improve respiratory function, improve oxygenation and promote carbon dioxide discharge; maintain the heart, brain, kidney and other organs function; correct the acid-base imbalance and electrolyte disorders. 1.Treatment of etiology: analyze the causes and triggers of respiratory failure, and deal with them in time. 2, prevention and treatment of infection: lung infection is a common cause of respiratory failure, other causes of respiratory failure often complicate respiratory infections, should be done in a timely manner for bacterial culture and drug sensitivity test, the selection of appropriate antimicrobial agents. 3.Improve respiratory function: (1) Keep the airway open: suction, turn over, pat the back, strengthen the nebulization. Insufficient humidification of inhaled oxygen can cause airway epithelial degeneration and necrosis, affecting the cilia function, the water temperature in the oxygen cylinder should be maintained at about 60 ℃, so that the inhaled oxygen temperature humidification. Ultrasonic nebulization of fog particles small, easy to reach the deep respiratory tract, each 15min, several times a day. Nebulized liquid can be added with antispasmodic, phlegm, anti-inflammatory drugs, which is conducive to ventilation and expectoration. Suctioning is very important to keep the airway open. Do not insert the suction tube under negative pressure, the action of suction should be gentle, should be backed up while suctioning, a suction time of no more than 5 s. In tracheal intubation, in order to avoid damage to the tracheal prominence and bronchial tubes, suction tube insertion to reach the end of the tracheal tube: pay attention to the aseptic operation in order to prevent contamination: before and after suctioning should be given for a short period of time to avoid hypoxia of 100% pure oxygen ventilation: pay attention to the monitoring of the heart rate and the clinical symptoms, such as cardiac tachycardia, if there is a cardiac tachycardia, the heart rate and clinical manifestations of the heart rate. If bradycardia or clinical deterioration occurs, suction should be stopped immediately and high concentration of oxygen should be given until the heart rate recovers and the clinical symptoms improve. (2) Oxygen therapy: children with spontaneous respiration are usually given oxygen by nasal catheter (oxygen flow 0.5~1L/min, FiO20.25~0.30), if hypoxia symptoms are not relieved after oxygen inhalation, oxygen can be given by mask or face mask (or nasal plug) under pressure (oxygen flow 3~5L/min, FiO20.5~0.8). Severe hypoxia, emergency rescue can be 100% pure oxygen, but not more than 4~6h is appropriate, suction FiO20.6 oxygen not more than 24h, to prevent oxygen poisoning. Prolonged use of high concentration of oxygen, can make the premature baby crystal after fibrous tissue proliferation, resulting in blindness: can make the lung surface active substance reduction, pulmonary atelectasis, interstitial fibrosis, and even bronchopulmonary dysplasia (BPD). (3) Mechanical ventilation: If there are no contraindications such as tension pneumothorax, large amount of pleural effusion or multiple pulmonary alveoli, and if there is severe ventilation insufficiency and it is difficult to maintain gas exchange by oneself, then respiratory therapy can be applied. The indications are: ① respiratory rate is only one half of normal; ② extremely critical respiration, breath sounds in the whole lung range is reduced; ③ frequent or long as more than 10s apnea; ④ cyanosis which is difficult to be relieved despite the use of high concentration of oxygen; ⑤ the condition is deteriorating rapidly and the above treatment is ineffective. Blood gas analysis is an important reference value for the decision of using ventilator. In acute expiratory failure, if the PCO2 is above 8~9kPa (60~70mmHg), and the partial pressure of arterial oxygen is lower than 8kPa (60mmHg) when 60% of the oxygen is inhaled, the use of ventilator can be considered. In particular, it should be pointed out that, due to the central nervous system or thoracic muscles and other pathologies caused by expiratory failure need to be combined with the clinical decision of whether to apply the ventilator, such as severe cerebral edema, frequent convulsions or coma children, even if the blood gas is still good, but also to immediately intubate the application of mechanical ventilation. In short, the ventilator should be applied according to the specific situation before the organ function is damaged by hypoxemia and acidosis caused by expiratory failure. (4) Maintenance of cardiovascular, cerebral, renal and other organ functions: ① application of respiratory stimulants: central respiratory failure has a certain effect, but is ineffective in respiratory failure caused by neurological and muscular diseases. Commonly used drugs are Aramin, Lobelin and Kisulin. Only with respiratory stimulants do not improve airway obstruction, increase respiratory function and aggravate respiratory failure, must be used with caution. ② cardiotonic and vasoactive drugs: when the combination of heart failure, should be given cardiotonic. The myocardial hypoxia in expiratory failure, sensitive to digitalis preparations, easy to digitalis poisoning, should be given rapid digitalis preparations such as cediran, digoxin, etc., and the dosage should be small or prolong the saturation time. Dobutamine is a kind of B1 and B2 adrenergic receptor stimulant, which can also be applied to enhance myocardial contractility when combined with heart failure. Vasoactive drugs can improve microcirculation, reduce the anterior and posterior load on the heart, improve cardiac function: reduce pulmonary hypertension, pulmonary stasis and pulmonary edema; relieve bronchospasm, improve pulmonary ventilation: for toxic intestinal paralysis, it can reduce intestinal wall edema, promote intestinal peristalsis. Phentolamine 0.3~0.5mg/kg each time, the maximum dose can be 1mg/kg each time, as appropriate, several times a day. In addition, scopolamine or 654-2 can be used; different doses of dopamine act on different receptors, which can be applied according to the clinical situation. ③ Application of dehydrating agents and diuretics: treatment of cerebral edema is an important part of interrupting the vicious circle of ventilatory failure, respiratory acidosis and cerebral edema. Commonly used dehydrating agent is mannitol 0.5~1.0g/kg, 3~4 times/d. Tachycardia 0.5~1.0mg/kg, can be. Combined with mannitol or used alternately. Application of tachycardia can also prevent pulmonary edema. Adrenocorticotropic hormone: it can increase the children's stress capacity, reduce inflammation and exudation, relieve bronchospasm, improve ventilation; reduce cerebrovascular permeability, reduce cerebral edema. Commonly used drugs are dexamethasone, 0.5~1mg/kg each time, 3~4 times/d. (5) Correct acid-base imbalance and electrolyte disorders: (1) rehydration: appropriate rehydration should be done in the case of exhalation failure, and rehydration should be limited in the case of concurrent cerebral edema, the principle is "and take off and replenish", "fast take off and replenish". The principle is "to take off and replenish" and "to take off quickly and replenish slowly", the general fluid replenishment is 60~80ml/kg, and 30~60ml/kg per day in the case of combined cerebral edema. If fever, diarrhea, etc., can be increased as appropriate. ② Electrolyte supplementation: high blood potassium, low blood sodium, low blood chloride, etc., often after correction of expiratory failure hypokalemia, should be dealt with in a timely manner. Correct acidosis: acid-base imbalance in expiratory failure is mainly respiratory acidosis, which can be corrected by improving ventilation. Mixed acidosis or metabolic acidosis can be supplemented with alkaline drug 1.4% sodium bicarbonate. Sodium bicarbonate solution can only correct acidosis under good ventilation, otherwise it will increase carbon dioxide retention and aggravate acidosis. (6) New progress in the treatment of respiratory failure: ①Pulmonary surface active substance (PS): PS has become a routine treatment for neonatal RDS in developed countries, which can reduce alveolar surface tension and improve oxygenation. Recently, domestic and foreign is carrying out PS applied to the treatment of RDS other than breath failure such as meconium aspiration syndrome, severe pneumonia, acute respiratory distress syndrome and other clinical trials. ② high-frequency oscillatory ventilation (HFOV): severe expiratory failure, conventional mechanical ventilation is ineffective or combined with pneumothorax and other barotrauma can be changed to high-frequency oscillatory ventilation, it is low tidal volume, low airway pressure, high respiratory rate of gas exchange, which can reduce the barotrauma, less impact on cardiac output. Nitric oxide inhalation (NO): Nitric oxide can be inhaled when severe hypoxemia occurs in the combination of expiratory failure and pulmonary hypertension, which can dilate the pulmonary artery and improve oxygenation. (4) Extracorporeal membrane lung therapy (ECMO): when the child is ineffective in conventional mechanical ventilation and the new therapies mentioned above, ECMO can undertake the task of gas exchange, so that the lungs are in a state of rest, and buy valuable time for the patient's recovery. Similarly, when the heart function is seriously impaired, blood pump can replace the blood transfusion function of the heart to maintain blood circulation. ⑤ Other respiratory support techniques: e.g., tracheal lung inflation (TGI) and liquid ventilation (LV). ⑥ Permissible hypercapnia: During mechanical ventilation, in the absence of severe metabolic acidosis, cardiac insufficiency and cranial hypertension, apply small tidal volume, limit the peak inspiratory pressure, use relatively high respiratory rate, adopt permissible hypercapnia, and maintain moderate ventilation, so that the PCO2 reaches 45~60mmHg and pH>7.25, and minimize the lung injury as much as possible.