There are two concepts of lung protection, broad and narrow. Narrow lung protection refers to the protection of the donor lung during lung transplantation or heart-lung transplantation so that it can still perform normal lung function after transplantation in the recipient. Lung protection in the broad sense is the proactive prevention and treatment of impending lung injury from various causes in order to maintain the patient’s lung function and promote early recovery. Surgical perioperative lung protection belongs to the category of broad lung protection. The lung is the only organ in the body that receives all the cardiac output, and is also a giant filter through which venous blood must pass throughout the body; at the same time, the lung is also an open organ, and the alveoli are connected to the outside world through all levels of bronchi and trachea. This makes the lungs vulnerable to damage by endogenous and exogenous harmful factors. Preoperative risk factors, surgery, anesthesia, blood transfusion, cardiopulmonary transfer, and other medical measures can cause certain damage to the lungs during the perioperative period, resulting in various perioperative pulmonary comorbidities and, in severe cases, respiratory insufficiency, threatening the life of the patient. Therefore, perioperative lung protection measures to prevent and treat perioperative pulmonary complications are very important and are a strong guarantee for the rapid recovery of surgical patients. Wang Chuanqing, Department of Thoracic Surgery, Shandong Chest Hospital “Rapid recovery surgery” refers to the application of various proven methods to reduce surgical stress and complications before, during and after surgery, and to accelerate the recovery of patients after surgery, which is the synergistic result of a series of effective measures. Rapid rehabilitation surgery must be a multidisciplinary collaborative process that includes not only surgeons, anesthesiologists, rehabilitation therapists, nurses, but also the active participation of patients and their families. More importantly, rapid recovery surgery relies on the integration and good integration of important perioperative therapies. For thoracic surgery, perioperative lung protection is precisely the key to reducing postoperative pulmonary complications. In recent years, the Chinese Medical Association Thoracic and Cardiovascular Surgery Branch and the Chinese Physicians Association Thoracic Surgeons Branch have reached the following consensus on perioperative lung protection for the reference of fellow surgeons, based on the organization of academic exchanges on perioperative management and rapid recovery surgery, and after many discussions among relevant experts. Common perioperative pulmonary complications and their associated risk factors I. Common perioperative pulmonary complications Postoperative pulmonary complications are one of the important components of the risks of thoracic surgery. In the perioperative period, common pulmonary complications in patients include pulmonary atelectasis, pulmonary edema, pneumonia, bronchitis, bronchospasm, respiratory failure and even ARDS, and exacerbation of underlying chronic lung disease. Studies have shown that the incidence of postoperative pulmonary complications after upper abdominal surgery is as high as 35%, with pneumonia accounting for 16.6%, bronchitis for 15%, and 1.7% each for pulmonary atelectasis and pulmonary embolism. Postoperative pneumonia is usually nosocomial acquired pneumonia, which has a morbidity and mortality rate of 10% to 30%, and postoperative pulmonary complications result in an average prolonged hospital stay of 1 to 2 weeks. The incidence of perioperative bronchospasm is increased in the presence of concomitant respiratory disease such as chronic obstructive pulmonary disease (COPD). The incidence of intraoperative bronchospasm in patients with a history of asthma is about 10%. The incidence of bronchospasm is higher in patients undergoing thoracic and abdominal surgery than in other surgeries. Risk factors for perioperative pulmonary complications The main risk factors for perioperative pulmonary complications include those related to the patient’s underlying condition and those related to surgery. (Smoking: Smoking can lead to cilia oscillation disorder and increased secretion in the respiratory tract. Trials have confirmed that the relative risk of pulmonary complications in smokers is 1.4 to 4.3 times greater than in nonsmokers. Even in patients without chronic lung disease, smoking can increase the risk of pulmonary complications. Quitting smoking for more than 8 weeks before surgery can reduce the incidence of postoperative complications. The higher the ASA classification, the greater the risk of postoperative pulmonary complications. Those with increased pulmonary fluid due to preoperative malnutrition and low plasma protein have a significantly increased chance of developing pulmonary comorbidities. 3. Underlying lung disease: COPD is not an absolute contraindication to any thoracic surgery, but studies have confirmed that patients with COPD have an elevated risk of postoperative pulmonary complications. Pulmonary function tests are the gold standard for COPD diagnosis, and patients with COPD whose symptoms and airflow limitation and exercise tolerance have not been effectively improved should be given aggressive preoperative treatment; for patients undergoing elective surgery, surgery should be postponed if an acute exacerbation of COPD occurs. Early studies have shown that the overall incidence of postoperative complications is higher in patients with asthma than in patients without asthma. 4. Age: With age, the lung parenchyma changes, fibrous connective tissue increases, lung elasticity decreases, alveoli collapse, resulting in decreased lung compliance and increased respiratory resistance resulting in decreased pulmonary ventilation and hyperventilation. 5. Obesity: obese patients have significantly reduced pulmonary compliance in the supine position, and the ventilation/blood flow ratio is out of balance; at the same time, obese patients have hypoxemia and hypercapnia due to the posterior convexity of the thoracic spine, anterior convexity of the lumbar spine, excessive intra-abdominal fat, and reduced thorax and its mobility due to the elevation of the diaphragm, which is often seen in typical cases of patients with sleep apnea syndrome. Although obesity is often thought to increase the risk of pulmonary complications, most studies have not found an intrinsic link between the two. 6. prolonged bed rest: prolonged bed rest can lead to atrophy of the mucosa and glands of the upper respiratory tract, weakening the warming and humidifying effect of inhaled gases, which can impair the defense function of the lower respiratory tract; atrophy of the lymph glands of the pharynx, reduced airway immune function, so that the self-barrier function of the respiratory tract is reduced; reduced respiratory muscle strength, making coughing weak, small airway narrow and easy to collapse, resulting in the retention of secretions; degeneration of the mucosa of the pharynx. The mucous membrane of the pharynx degenerates, the sensation is dulled, and the swallowing reflex decreases with age, making it easy for bacteria in the pharynx to be inhaled or choked into the lower respiratory tract, causing pneumonia. Prolonged bed rest can also lead to posterior base of the two lungs to fall edema and fall pneumonia. 7. Diabetes: Studies have shown that lung tissue is also a target organ for diabetes damage. The older the patient with type 2 diabetes, the longer the disease duration, and the more microvascular complications, the greater the likelihood that pulmonary diffusion will be impaired. In addition, diabetes affects the local defense function of the lungs. The airway defense reflexes and mucociliary clearance are reduced in patients with diabetes mellitus combined with autonomic neuropathy. Diabetes mellitus is an independent risk factor for lower respiratory tract infections and the severity of these infections. (ii) Surgery-related risk factors 1. Site of surgery: Chest and upper abdominal surgery are the most important surgery-related risk factors. Studies have shown that surgical site affects pulmonary infections in the following order: cranial > thoracic > upper abdomen > lower abdomen > other. 2. Anesthesia: The type of anesthesia, drug selection, and mode of operation are all surgery-related risk factors. General anesthesia tracheal intubation can destroy the respiratory barrier and even induce bronchospasm; diaphragm elevation and reduced functional residual air volume (FRC) can lead to pulmonary atelectasis; mechanical positive pressure ventilation can lead to loss of negative pressure in the thoracic cavity, increased physiological nullification and shunt, improper mechanical ventilation can lead to pulmonary air pressure injury, mostly seen in large tidal volume, high airway pressure mechanical ventilation; prolonged inhalation of high oxygen concentration can lead to pulmonary expansion insufficiency. Inhaled anesthetics can attenuate the pulmonary hypoxic pulmonary vasoconstrictor response, alter the ventilation/blood flow ratio, and reduce alveolar surface active substances, which can seriously affect patients’ intraoperative lung function and increase the incidence of postoperative pulmonary comorbidities; opioid analgesics in anesthetic drugs (such as fentanyl, pethidine hydrochloride, morphine hydrochloride, etc.) have an inhibitory effect on the respiratory center, especially in pediatric surgical patients; residual effects of muscle relaxants Can lead to reduced ventilation, affecting respiratory function; intravenous anesthetics have a certain inhibitory effect on the circulation and respiratory system. 3. surgical operation: after opening the chest, the thoracic cavity on that side is opened, and the lung pulling expansion effect due to negative intrathoracic pressure disappears, leading to alveolar atrophy and a sharp decrease in alveolar ventilation area (even by about 50%), as well as an increase in pulmonary circulatory resistance. Intraoperative damage to the chest wall, bronchi and lung tissue results in reduced respiratory motion; excessive squeezing or pulling of lung tissue damages healthy lung tissue. Open thoracotomy can limit the magnitude of respiratory motion due to chest wall softening, phrenic nerve injury, pleural effusion and gas accumulation, pain, and tight dressing wrapping, which affects the patient’s ventilatory function and induces bronchospasm. 4. operation time: the lungs may be squeezed and twisted for a long time during the operation, and there are different degrees of pulmonary edema in the lung tissue on the open side, which affects the exchange of gas in the alveoli. The risk of pulmonary complications is higher when the duration of surgery is >3 h. 5. Fluid balance: During thoracic surgery, the overall blood loss may be small, but there is a potential risk of large blood loss in a short period of time; surgical operations may compress or pull the heart and large blood vessels in the thoracic cavity, which may interfere with the circulation. In addition, improper control of intraoperative rehydration amount and rehydration rate leads to: excessive fluid intake, increased pulmonary water or even pulmonary edema, resulting in diffusion disorders and hypoxia; too little fluid output, airway dryness, difficulty in airway cilia to discharge sputum, sputum obstruction or even occurrence of pulmonary atelectasis. 6. Analgesia: (1) imperfect analgesia: pain affects the patient’s sleep and rest, leading to fatigue and decreased physical strength; at the same time, it makes the patient afraid to breathe deeply and cough hard, which is not conducive to the discharge of respiratory secretions and can lead to pulmonary insufficiency and pneumonic pneumonia. (2) Excessive analgesia: patient drowsiness, decreased respiratory sensitivity, and weakened cough reflex, which can easily lead to aspiration when vomiting occurs. Strategies and measures for perioperative pulmonary protection The purpose of perioperative pulmonary protection is to maintain lung function and prevent pulmonary complications, so that patients can safely pass through the perioperative period and safeguard surgical outcomes. Therefore, perioperative pulmonary protection measures should begin preoperatively and continue throughout the intraoperative and postoperative periods. I. Preoperative assessment (a) Careful history taking Preoperative history should be reviewed in detail to understand the diagnosis and treatment process of the disease. Particular attention should be paid to the following points: (1) Whether the cough is chronic, the nature of the cough and the diurnal changes. (2) Understand the coughing sputum, including the volume, color and viscosity of the sputum, whether it is easy to cough up, and whether changing the position is helpful for sputum excretion; whether there is blood in the sputum, and if there is hemoptysis, the amount of hemoptysis should be understood. Find out whether there is a history of frequent coughing up yellow pus sputum with foul odor. (3) The nature of dyspnea (inspiratory, expiratory, mixed), and whether dyspnea occurs at rest. If so, it suggests poor cardiopulmonary compensation and poor tolerance of both anesthesia and surgery. (4) Smoking history: For smokers, the amount of daily smoking, the number of years of smoking, and the time to stop smoking before surgery should be known. (5) Disease triggering and remitting factors: for example, whether the patient with asthma has specific allergens. (6) Treatment history: antibiotics, bronchodilators, and glucocorticoid applications, including specific dosage usage, and the patient’s response to medications. (2) Detailed physical examination 1. Body shape and appearance: Patients with obesity and scoliosis are prone to pulmonary atelectasis and hypoxemia due to reduced lung volume (FRC, total lung volume) and decreased pulmonary compliance; patients with malnutrition and hyperhydrosis have weak respiratory muscle strength and decreased immunity, and are prone to co-infection. Observe whether there is cyanosis in the mouth, lips and nail bed. COPD patients may have barrel-shaped chest; if there is chest wall asymmetry, there may be pneumothorax, pleural effusion or solid lung changes. 2. Respiratory condition: respiratory rate >25 times/min is a sign of early respiratory failure; expiratory effort suggests airway obstruction; as the diaphragm and intercostal muscle load increases, the role of auxiliary respiratory muscles is enhanced; the presence of paradoxical breathing suggests diaphragm paralysis or severe dysfunction. 3. Chest auscultation: The importance of chest auscultation should be particularly emphasized. In patients with obstructive pulmonary disease, the expiratory phase is prolonged and the breath sounds are low; when sputum is retained, a rough, wet sound can be heard; in the case of sputum retention, a slightly deceitful hospital can be heard; in the case of a solid lung, a turbid sound can be heard. 5. Others: In cases of combined pulmonary hypertension, pulmonary heart disease, and right heart insufficiency, there may be jugular venous anger, hepatic? Jugular regurgitation sign (+), heart auscultation may be heard and 2 heart sounds split. (C) Preoperative pulmonary function assessment Pulmonary function tests help to understand the nature and severity of lung disease and whether the lesions are reversible, predict the efficacy of surgery and the occurrence of postoperative pulmonary complications, and help in the selection of the type and extent of chest surgery. Pulmonary function tests need to be routinely performed in patients undergoing open-heart surgery and in non-open-heart surgery patients aged >60 years with lung disease and a history of smoking. (IV) Laboratory tests and auxiliary examinations 1. Routine blood tests: in addition to the general significance, hemoglobin > 160 g/L and hematocrit > 60%, in the absence of special circumstances (such as true erythrocytosis, etc.), often suggest chronic hypoxia. 2. Blood urea nitrogen: blood urea nitrogen >7.5 mmol/L can be a risk factor predicting postoperative pulmonary complications. 3. Serum serum protein: Studies have shown that low levels of serum serum protein (30-39 g/L) are an important predictor of postoperative pulmonary complications, and serum serum protein <35 g/L is the most effective and patient-relevant predictor of postoperative pulmonary complications. 4. Chest X-ray: Preoperative frontal and lateral chest X-rays should be routinely performed. The presence of tracheal deviation, barrel chest or stenosis, airway obstruction, etc. is an important guide for the choice of anesthesia. 5. ECG: Those with obvious pulmonary dysfunction may have ECG changes, such as right deviation of the electrical axis, pulmonary P waves, right ventricular hypertrophy and right bundle branch conduction block, which may suggest pulmonary hypertension and pulmonary heart disease. Myocardial ischemia and enlarged heart can be estimated to be poorly tolerated by anesthetics. 6. Blood gas analysis: Blood gas analysis is a valuable index to evaluate pulmonary function, reflecting the ventilation, acid-base balance, oxygenation and hemoglobin content of the body, thus reflecting the severity of the patient's lungs and disease and the urgency of the disease. PaCO2>45 mm Hg (1 mm Hg=0.133 kPa) is associated with a significant increase in postoperative pulmonary complications. Preoperative preparation (a) Routine preparation 1. Quit smoking or smoking ban: For long-term smokers, they should quit smoking as much as possible before surgery, and the earlier the better. It is very difficult to quit smoking clinically, but smoking should be prohibited for at least 2 weeks before surgery in order to reduce airway secretions and improve ventilation. 2. Respiratory exercise: Instruct patients to perform respiratory exercises. When chest breathing is no longer effective in increasing pulmonary ventilation, deep and slow abdominal breathing should be practiced. Respiratory exercise, voluntary deep breathing, and coughing will help discharge secretions and increase lung capacity, reducing the incidence of postoperative pulmonary complications. 3. Nutritional support: improve the general nutritional status, and actively correct severe anemia and water-electrolyte imbalance caused by long-term malnutrition and protein depletion. 4. Others: For those with combined hypertension, coronary atherosclerotic heart disease, diabetes mellitus, arrhythmia, conduction block, liver and kidney insufficiency, consult the appropriate department for comprehensive treatment and actively create conditions for surgery. In case of combined pleural effusion, if the amount of effusion is large and affects FRC, thoracentesis to release fluid or placement of drainage device is feasible. In the case of tension pneumothorax, closed chest drainage should be placed, and the drainage tube should not be removed 24 h before general anesthesia. (B) Respiratory preparation 1. Clean the respiratory tract: Before thoracic surgery, the patient’s respiratory tract should be kept open and the secretions in the respiratory tract should be cleared in a timely manner. At present, the main drugs used for respiratory tract cleaning are mucus secretion promoting drugs and mucus lysing drugs. The efficacy of mucus secretion promoting drugs (ammonium chloride) is difficult to be sure, especially when the sputum is thick and almost ineffective; mucus dissolving drugs are represented by amiloride, which is the effective product of bromoxyn in the body, and can promote the dissolution of mucus sputum, reduce the adhesion of sputum and cilia, and increase the discharge of respiratory secretions, and the dosage of amiloride can be increased appropriately for patients with high risk factors. In addition, fluid infusion, nebulized inhalation to wet the airway, nebulized bronchodilator, postural drainage, and chest and back tapping are all beneficial to the discharge of respiratory secretions. 2. Release airway spasm: Bronchospasm is one of the most common complications during the perioperative anesthesia period. Especially during the period of surgical anesthesia, once the patient has severe bronchospasm, if not treated in time, it can lead to severe hypoxia and CO2 accumulation, and even endanger life. Bronchospasm can be induced by anesthetic drugs and tracheal intubation during surgery, and the mortality rate can be as high as 70%. In acute asthma attacks, when bronchospasm has not been eliminated, any elective surgery should be postponed until the asthma is effectively controlled. Preoperative application of bronchodilators (e.g. ipratropium bromide) can significantly reduce pulmonary resistance, improve pulmonary compliance, and prevent the occurrence of bronchospasm. In addition, for elderly, COPD and asthmatic patients, preoperative application of rapid-acting bronchodilators is beneficial to improve the basal lung function and improve the patient’s oxygen saturation, which can further improve the quality of preoperative preparation. (C) Anti-infection For acute upper respiratory tract infection elective surgery should be performed after the treatment has improved. Those with large amounts of sputum should be operated after 2 weeks of sputum reduction. In cases of combined chronic respiratory diseases, antibiotics should be routinely applied 3 d before surgery to prevent and control pulmonary infections. The pathogenic microorganisms of pulmonary infections include bacteria and viruses, and the rational application of antibiotic therapy is the key. The combination of sputum or airway secretion culture of pathogenic bacteria and drug sensitivity test can help in the selection of antibiotics. The ideal anesthesia method and drug selection principles are: less respiratory and circulatory disturbances; good sedation, analgesia and muscle relaxation; satisfactory blockage of adverse surgical reflexes; fast recovery from postoperative awakening; and few complications. The effective solution to the respiratory and circulatory disturbances caused by dissection is endotracheal intubation and the application of inotropic drugs to control breathing, so general thoracic surgery are used for general anesthesia. Intraoperative management 1. Shorten anesthesia and operation time: choose incisions (such as transverse incision) and simple and practical operation styles that have little effect on the strength of abdominal muscles and light postoperative pain. 2. Promote minimally invasive surgical operations: anesthesia intubation should be as non-invasive as possible. Surgery should be performed with as much care as possible for lung tissue, avoiding excessive pulling, squeezing and twisting of lung tissue, and intraoperative hemostasis should be tightened. When lung cancer patients undergo lung resection, two major principles must be observed: maximum removal of tumor and maximum preservation of lung tissue. Thoracic integrity should be ensured, especially in the management of severe thoracic trauma and large resections of chest tumors and chest wall tissues. The integrity of the recurrent laryngeal nerve and vocal cords should be protected; bilateral recurrent laryngeal nerve injury will lead to serious consequences. Protect the phrenic nerve and diaphragm integrity; prevent phrenic nerve injury and diaphragmatic hernia from occurring. Timely detection and management of tension pneumothorax and related post-thoracic surgery complications (such as hemothorax, celiac disease, pulmonary embolism, etc.). 3. Ensure airway patency and maintain adequate ventilation: ensuring airway patency is the most important aspect of thoracic surgical anesthesia, so that adequate oxygen supply and good CO2 expulsion can be achieved. However, PaCO2 <35 mm Hg for a long time should be avoided, otherwise it may cause cerebral vasospasm and insufficient blood supply. 4. Maintain circulatory stability: avoid excessive high or low blood pressure, prevent cardiac arrhythmias, and correct shock in a timely manner. 5. Standardize intraoperative infusion: ensure at least two intravenous accesses: one access can rapidly infuse blood and fluids; one access can monitor central venous pressure and give cardiovascular active drugs. The total amount of rehydration should be limited and the infusion rate per unit of time should be controlled to avoid intraoperative or postoperative pulmonary edema and heart failure due to excessive circulatory load. 6. Other: handle negative venous pressure carefully to prevent air embolism; for those who need long-term indwelling gastric tube for decompression, it is advisable to make a gastrostomy instead to avoid affecting cough and sputum; handle fractures gently to avoid fat embolism; for those who have a higher possibility of postoperative pulmonary infection, the abdominal incision should be closed with reduced sutures to prevent cracking. Intraoperative application of bronchodilator can prevent bronchospasm. V. Postoperative treatment 1. Keep the respiratory tract unobstructed: encourage patients to actively cough, breathe deeply, pat the chest wall, combine with postural drainage, and assist patients to expectorate. Powerful expectoration after surgery can make sputum thinner, less viscous and easy to cough up, or accelerate the function of respiratory mucous membrane cilia and improve the function of sputum transfer. Ambroxol is an effective pharmacological treatment to prevent postoperative pulmonary complications (especially pulmonary atelectasis, acute lung injury, hypoxemia, ARDS, etc.), and the dose can be increased appropriately if necessary. Start nebulized inhalation as early as possible to humidify the airway, so that secretions can be easily discharged and edema and bronchospasm can be relieved. Bronchodilators dilate the airway and are combined with expectorant therapy to facilitate sputum expulsion and release edema and bronchospasm. Stimulated spirometry is the main means to prevent mucus plug and prevent postoperative pulmonary atelectasis. 2. effective analgesia: effective postoperative analgesic measures can promote patients' early diaphragmatic movements, coughing and sputum excretion, and reduce complications of pulmonary co-infection that impair lung function. However, the dosage of analgesic drugs should be individualized, especially for elderly patients, and the dosage should be appropriately controlled, and postoperative anesthesia visits should be strengthened to avoid excessive sedation or respiratory depression. 3. Other: postoperative nasal catheter oxygen in COPD patients with a flow rate of <3 L/min; maintenance of fluid balance; measures to reduce abdominal distension, timely removal of the gastric tube; reasonable application of effective antibiotics.