Iatrogenic tracheal and main bronchus injury

　　First, etiology

　　Airway injuries caused by tracheal intubation include laryngeal injury caused by oropharyngeal intubation, injury caused by tracheotomy or cricothyroidotomy, and compressive necrosis of the tracheal wall caused by excessive intubation balloon pressure.

　　Second, pathogenesis

　　1. Tracheal intubation can cause various injuries, the earliest of which is necrosis caused by pressure, the nasal cartilage can also be involved, the vocal cords in the larynx can become edematous and granulomas can form due to stimulation, the posterior part can be damaged, leading to local scar fusion, and tracheal intubation can cause mucosal injury at the level of the cricoid cartilage, leading to subglottic stenosis. Most children and adults can repair the laryngeal injury caused by tracheal intubation over time. Some believe that cricothyroidotomy can avoid the complications of tracheotomy, but can cause severe subglottic stenosis. Local use of hormones is beneficial for reducing complications and the prognosis of injuries.

　　2. Tracheotomy is an ancient surgery, the indications for tracheotomy are upper tracheal obstruction and clearance of tracheal secretions, especially in cases with nervous system defects. Generally, in such cases, a tracheostomy tube is also placed simultaneously for use when the patient needs long-term respiratory support. Tracheotomy and placement of tracheostomy tube can usually be retained for 1 week or longer. A large number of literature has described the immediate and early complications of tracheotomy, including cardiac arrest caused by hypoxia during the operation; injury to adjacent structures such as the recurrent laryngeal nerve, esophagus, and large blood vessels, pneumothorax, bleeding during or shortly after the operation, etc.

　　3. At the site of the tracheostomy orifice, granulomas often form during the process of interstitial healing, the lighter granulomas at the site of the tracheostomy orifice can be removed by bronchoscopy, and they can also be without obvious clinical symptoms. However, the loss of the anterior wall of the trachea at the site of the tracheostomy orifice can cause stenosis due to scar healing and granulation tissue hyperplasia. Other important causes of tracheal stenosis include:

　　① During the initial tracheotomy surgery, the orifice is intentionally or unintentionally made too large;

　　Organic defects caused by necrotizing infection;

　　The external force lever action of the connection system of the breathing device compresses the tracheal wall and causes necrosis, the last factor is very important. Andrews and Pearson argued for this point in 1971, they believe that replacing the rigid connection pipe of the auxiliary breathing device can significantly reduce the incidence of tracheostomy stenosis. Similarly, Geillo et al. used lighter connection tubes in the early stage of tracheostomy-assisted breathing, which significantly reduced the incidence of tracheal stenosis, while many cases showed inevitable segmental stenosis.

　　4. Another cause of horizontal obstruction at the level of tracheotomy stoma is the tissue flap formed by the pressure of the tracheotomy tube on the surrounding tissue of the stoma, which is mostly located above the tracheotomy stoma. This kind of injury can cause necrosis and inflammatory changes in the cricoid cartilage and subglottic larynx, therefore, it should be avoided to damage the first cartilage ring during the initial tracheotomy to prevent subglottic stenosis. In addition, if the tracheotomy stoma is lower, it may cause injury to the无名 artery or stenosis of the trachea above the carina. If certain pressure is applied to the tracheal wall at the edge of the tracheotomy stoma, causing the tracheotomy tube to abut the tracheal wall, it will cause necrosis of the tracheal wall. The triggering factors are various, such as hypotension, bacterial infection, toxicity of the material used to make the tracheotomy tube, and the manufacturing process of the plastic tube, but clinical experience and laboratory materials have confirmed that the direct cause of tracheal compressive necrosis is the high pressure around the tracheotomy stoma. Since the pressure on the edge of the tracheotomy stoma is circumferential, the injury is also circumferential. If the deep tissue is involved, the scar formed during healing will be circumferential stenosis, which can even cause complete obstruction of the trachea, leading to death of the patient. If the pressure on the tracheotomy stoma is great and lasts for a long time, tracheoesophageal fistula or tracheal-innominate artery fistula may occur, and the mortality rate of both types of injuries is high.

　　5. One of the late complications of tracheotomy is the non-closure of the stoma 3 to 6 months after the removal of the tracheotomy tube. This situation usually occurs in patients with a longer tracheotomy tube placement, or those with malnutrition, long-term use of high-dose corticosteroids, or infection around the tracheotomy stoma. In such patients, the epithelial layer of the skin has connected with the tracheal epithelium at the edge of the tracheotomy stoma. If the tracheotomy incision does not heal after a sufficient long observation period, surgical methods can be used to close the tracheotomy stoma. The non-healing of the tracheotomy stoma is disliked by patients, affects speech, causes an increase in tracheal secretions, and may become a source of infection.

　　6. The etiology of tracheal stenosis caused by high-pressure cuff of tracheal intubation has been confirmed in post-mortem examination materials of patients assisted by ventilators before death. At the same time, the results of these studies are consistent with the findings of surgical resection specimens, and such injuries have been further confirmed in experimental animal models. Currently, in clinical practice, high-compliance low-pressure cuffs are used to ensure that the trachea is not subjected to excessive pressure when it is sealed. Grillo et al. reported in 1971 that since the clinical application of tracheal intubation with low-pressure cuffs has been continuously used at the Massachusetts General Hospital in the United States, there has been no case of tracheal injury due to tracheal cuff. At the Toronto General Hospital in Canada, the same low-pressure cuff is used, and the incidence of tracheal stenosis in 100 patients is zero. Conversely, the incidence rate of complications due to the use of standard tracheal cuffs is 9%. Another method to solve the problem of tracheal injury-related stenosis is to intermittently deflate and reinflate the cuff during the process of assisted breathing. Children do not use the cuff during assisted breathing, but the tip of the tube can be raised to abut the anterior wall of the trachea, which can also cause necrosis.

　　7. Tracheal softening is another complication of intubation injury, which can occur in several segments. The most common site is the tracheal segment between the tracheotomy incision and the tracheal intubation cuff. It is obvious that even if the trachea is kept as clean as possible, there are still many secretions accumulated here, and the inflammatory changes make the tracheal cartilage thin. Although there is no ulceration of the mucosa, the local tracheal segment becomes soft, causing tracheal collapse and functional tracheal obstruction, which is especially obvious when the patient exerts force in breathing. Short-segmental tracheal softening usually occurs at the high-pressure cuff of the tracheal intubation. It is a common site of tracheal stenosis caused by tracheotomy and tracheal intubation.

　　8. After tracheotomy, sputum aspiration through tracheotomy tube can cause tissue edema, ulceration, and even severe bleeding due to the constant friction and aspiration of the tracheal mucosa near the tip of the tracheotomy tube. Clinically, it is necessary to prevent this, and the aspiration action should be gentle. Before aspiration, the trachea should be flushed with 5% NaHCO3. In case of bleeding, a few drops of adrenaline or ephedrine can be dripped into the tracheotomy tube to stop the bleeding, while actively aspirating the blood and clot in the trachea to prevent blood from flowing into the distal end and causing pneumonia or obstruction, resulting in difficulty in ventilation.

　　7. The onset of tracheal stenosis is relatively slow, and only when the tracheal lumen is blocked by more than 50% to 70%, obvious自觉 symptoms appear. It can also be accelerated due to secondary infection, and severe tracheal obstruction or asphyxia may occur within one month after the injury.

　　Post-traumatic bronchial rupture after chest trauma is mainly manifested clinically as difficulty breathing, subcutaneous or mediastinal emphysema, pneumothorax or tension pneumothorax, hemothorax. After the pneumothorax patient has the thoracic drainage tube placed, due to the direct overflow of inhaled gas from the chest tube, the difficulty breathing may worsen. Bronchial injuries are always accompanied by varying degrees of bleeding, and most patients' bronchial bleeding has stopped or has not been expectorated when they arrive at the emergency room. Only when there is massive bleeding do patients present with hemoptysis symptoms. The above clinical symptoms depend on the location, size of the tear, whether the bronchial blood vessels are torn, and whether the mediastinal pleura is intact.

　　1. Most of the various injuries mentioned earlier manifest as obstruction of the injury cross-section. Clinically, patients present with extreme difficulty breathing, wheezing, and even a small amount of mucus in the tracheal lumen can cause obstruction. In radiological examinations, the lung fields of most of these patients are normal, therefore, they are often misdiagnosed as 'asthma'. Many patients have received medication, including high-dose corticosteroids, and a few patients present with unilateral or bilateral pneumonia in clinical settings. It must be remembered that any patient with symptoms of airway obstruction, such as a history of tracheal intubation in the recent past, should consider the possibility of tracheal injury before confirming the presence of other diseases.

　　2. Obstruction after tracheal injury can cause respiratory failure in patients based on the primary disease site, although the tracheal lesion will not further develop, the degree of tracheal stenosis can reach the extreme before the onset of difficulty in breathing, both clinically and experimentally confirmed. In the tracheal diameter

　　3. Tracheoesophageal fistula caused by tracheal intubation cuff compression, the patient presents with difficulty in breathing, gastric dilation, a large amount of secretions retained in the tracheobronchial tree, and the patient develops pneumonia, bronchopneumonia, and lung abscess. After eating or swallowing food and dyes containing methylene blue, the food and dyes will enter the trachea and cough out.

　　4. Trachea-无名动脉瘘 is characterized by a sudden large amount of blood entering the tracheobronchial tree, occasionally with bleeding precursors, which may indicate that a trachea-无名动脉瘘 is about to occur. If the fistula is caused by tracheal intubation cuff compression, there may be an opportunity to control bleeding, that is, to reinsert a tracheal intubation with a high-pressure cuff to block the fistula. If the injury is caused by the tracheal intubation itself compressing the无名动脉, immediate surgery should be performed. In such cases, it must be distinguished from bleeding caused by severe tracheitis.

       The airway injury caused by tracheal intubation in this disease includes laryngeal injury caused by orotracheal intubation, injury caused by tracheotomy or cricothyroidotomy, and tracheal wall necrosis caused by excessive intubation balloon pressure. Therefore, when tracheotomy intubation is performed, attention should be paid to the size of the incision, and the balloon pressure should not be too high. Careful observation according to the regular operation process can prevent the occurrence of this disease.

　　1. X-ray examination
　　The main X-ray changes in the early stage of main bronchus rupture are large amounts of pneumothorax, subcutaneous and mediastinal emphysema, deep neck emphysema, upper chest rib fractures, main bronchus truncation or discontinuity, atelectasis of the lung坠征 and lung floating sign. The upper edge of the atelectatic lung descends below the hilum level. In the late stage, diagnosis mainly relies on bronchial bifurcation tomography and bronchial iodine oil contrast, which can clearly show blind pouch-like bronchial proximal or narrowed bronchial segments.
　　2. Tracheal CT tomography
　　It can discover direct signs of tracheal rupture, deformation and discontinuity of the tracheal transparent band, and even signs of displacement.
　　3. Fiberoptic bronchoscopy examination
　　It can clearly identify the location and degree of tracheobronchial rupture and stenosis, which has definite diagnostic value for both early and late cases. Negative examination results can exclude the presence of bronchial rupture. Severe hemoptysis symptoms after chest injury should not be ignored, and bronchoscopy should be considered immediately even if there are no other signs of tracheobronchial disconnection.

　　Eat more foods that can relieve coughing, asthma, expectoration, warm the lungs, and strengthen the spleen, such as white sesame seeds, lily, kelp, and nori.
　　Avoid cold, salty, sweet foods, and spicy and刺激性 items. Avoid smoking and drinking to prevent symptoms from worsening.
　　Avoid seafood and greasy foods to prevent the generation of fire and phlegm. Do not rush to take tonics, as they are not suitable during the acute attack phase or when there is a lot of phlegm and a greasy tongue coating. Otherwise, chest tightness and shortness of breath may worsen, and the condition may worsen. It is recommended to use a comprehensive therapy of traditional Chinese medicine for treatment, and combining traditional Chinese medicine acupoint treatment is currently the latest and most effective method.

　　1. Treatment

　　The treatment of tracheal obstruction caused by tracheal intubation is a complex issue. For patients with progressive tracheal stenosis and severe tracheal obstruction, if the tube has been removed or no longer receives ventilation support, general surgery is usually required. On the other hand, conservative treatment can also be accepted, such as expanding the narrowed segment of the trachea or performing a tracheotomy again, and placing a finer tracheal tube through the stenosis, and opening a window on the tube so that the patient can speak. In this way, the patient can maintain life with a tracheal T-tube. This measure allows the patient to safely have time to schedule for surgical treatment. If the tracheal stenosis is just above the carina, this method is not suitable, because the tracheal tube may slip back above the stenosis. For such patients, although the condition is severe, active surgical exploration should also be carried out.

　　For some patients whose lesions have not eroded the deep wall of the trachea and there is no severe narrowing, conservative therapy such as repeated expansion and local injection of hormones can be used to wait for the regression of scar tissue. The specific method is: 40mg of prednisolone acetate is injected into 4 points of the narrowed area each time, 10mg at each point.

　　At the same time, expand once a month. Sometimes laser, electrocautery, and cryotherapy methods can also be used. The immediate efficacy is still good. The nickel-titanium alloy stent also has a certain effect. When the nickel-titanium alloy stent is cooled, its shape can be stretched into a fine wire, placed in the narrowed segment of the trachea, and the nickel-titanium alloy stent rises to more than 30℃ due to body temperature, restoring its spiral stent shape and expanding the narrowed segment of the trachea. In addition, a finer silicone T-shaped tracheal tube can also be placed for a long time, waiting for the narrowing to stabilize or regress, and finally remove the stent, so that the trachea can at least partially open and ensure its ventilation function. Some patients have been wearing metallic tracheal tubes for several months or even years. If the tracheal tube is removed, the tracheal lumen will close within a few minutes. For such patients, in order to restore normalcy, a comprehensive and carefully planned surgical tracheal reconstruction must be implemented.

　　For patients with poor respiratory reserve function, if the tracheal reconstruction surgery is completely extrapleural, at the end of the operation, under anesthesia, respiratory maintenance is relatively normal, and postoperative ventilation support may not be necessary.

　　1. Indications for surgery

　　Different from patients with normal trachea and early tracheal tumors, iatrogenic tracheal injury has a heavier inflammatory response around the narrowed segment of the trachea, with a large amount of fibrous tissue appearing during the repair process of inflammation. The blood supply is relatively poor, and the tissue elasticity is also low, so the length of the tracheal narrowed segment is

　　2. Preoperative Preparation

　　Before surgical treatment, it is necessary to evaluate the length of the trachea involved, the function of the larynx, and exclude conditions such as tracheal wall softening, neurogenic glottic dystonia, and airway burns.

　　Routine fiberoptic bronchoscopy should be performed before surgery, during which, in addition to paying attention to the position of the stenotic segment and the degree of lumen stenosis, it is also necessary to understand the function of the glottis and vocal cords. The tracheal anteroposterior and lateral oblique tomographic images, CT scan, and MRI examination should be performed if possible, in order to understand the length, location of the tracheal stenosis, and the relationship between the tracheal stenosis and mediastinal tissues, organs, and large blood vessels from different angles. Through these examinations, a full judgment and estimation of the local condition of the lesion, the difficulty of surgical treatment, and the prognosis of surgical treatment can be made.

　　3. Surgical Treatment

　　For patients with a long-term unclosed tracheotomy incision, the surgical treatment method is to use the edge of the incision as the base of the primary skin flap.

　　Make a circular incision around the tracheotomy incision stoma, lift the edge of the skin flap without damaging the blood supply, then flip the skin ring and close the stoma with subcutaneous sutures. The skin surface of this circular flap is smooth and facing the trachea internally, and then use a short, small incision extending laterally to free the muscle bundles and pull them to the center to fill the defect, then suture the platysma, and close the skin horizontally with intradermal sutures. By巧妙成形术关闭气管切开造口，使气管内面完整光滑，although in many cases, the use of a muscle flap alone also has the same effect, but occasionally there are interstitial surfaces in the trachea that form granulomas and require further repair.

　　If the tracheal stenosis caused by the tracheotomy incision affects the patient's ventilation, surgical treatment is necessary. The surgical method is to excise the stenotic segment of the trachea and reconstruct the bronchus. This type of surgery can usually be completed by a collar incision of the neck, occasionally the neck incision can be slightly higher, around the tracheotomy incision, and a horizontal incision can also be made, and the subcutaneous incision is also in the horizontal direction, but not on the same plane as the skin incision. If there is a stenosis below the incision, the skin may not need to be separated from the incision, in this case, the tracheotomy incision can be used as an atraumatic point after surgery, and it may close spontaneously later. However, when extensive excision of the trachea is necessary, the skin must be separated from the incision to achieve a flat surface, in this case, a re-tracheotomy should be performed and allowed to heal spontaneously. If the tracheotomy is located behind the sternum and it is difficult to return the skin, a pedicled muscle flap can be used to close it, and it should be fixed in the appropriate position.

　　The difficult problem is the tracheal stenosis caused by a tracheotomy under the cricoid cartilage, in this case, the lower part of the cricoid cartilage should be incised obliquely first, and the trachea sutured to the larynx, its basic technique is the same as the tracheal anastomosis technique, and the mucosa should be sutured as much as possible. Some sutures may not penetrate the full thickness of the cricoid cartilage, but the upper oblique angle should be embedded in the midpoint of the lower incision, and the needle should be passed through the mucosa under the larynx to come out from the cavity, and then suture the trachea to make the two close together. Many patients have varying degrees of submucosal fibrosis in the larynx, which can cause stenosis of the lumen, and in this case, the anastomosis cannot be very satisfactory.

　　Tracheal stenosis caused by tracheostomy involving the subthyroid cartilage is generally more extensive, and the reconstruction of the trachea is also more difficult. The results of complex staged surgical procedures are not very satisfactory. Grillo reported in 1982 on 18 cases of such tracheal stenosis, using a single-stage surgical correction, that is, resecting the lower anterior part of the larynx and the stenotic trachea, and anastomosing the distal part of the trachea with the thyroid cartilage, of which 16 cases achieved good results.

　　For the segmental resection of tracheal stenotic segments and the specific methods of tracheal reconstruction and end-to-end anastomosis, as well as the requirements for anesthesia, please refer to the relevant chapters on tracheobronchial tumors. The resection range of the tracheal stenotic segment does not need to be too extensive, just close to the edge of the stenotic segment, and it is not necessary to resect too much normal tissue. However, the anastomosis should be as close to the normal tissue as possible. If there is residual scar tissue, it is easy to cause recurrence of stenosis at the anastomosis.

　　For stenotic segments >4cm, based on the specific condition of the patient, the advantages and disadvantages of the surgical method are weighed to decide the treatment plan. Sometimes, it is necessary to perform tracheal stenotic segment resection and tracheal anastomosis, which will inevitably cause excessive tension at the anastomosis, resulting in more postoperative complications and poor prognosis.

　　Most patients with long-segment tracheal stenosis can be maintained with a windowed extended tracheostomy tube or T-shaped silicone tube to maintain ventilation. This can provide a relatively safe airway with no mortality, and it can also expand the stenotic segment for a long time. After 6 to 8 months, it is estimated that epithelialization is complete, and then consider extubation. Subsequently, regular bronchoscope dilatation or placement of a memory alloy support frame can be performed.

　　If there are two narrowings, and the two narrowings are also at a certain distance from each other, it would be too可惜 to resect the normal trachea between them. At the same time, it also increases the difficulty of tracheal reconstruction. The clinical implementation of staged resection of the narrow segments and staged reconstruction of the trachea is very difficult. Grillo adopted the method of segmental circumferential resection and separate reconstruction of the trachea, which preserved the normal tracheal segments and resected the two narrowings separately, and had been successful in clinical practice many times.

　　Acute tracheo-subclavian artery fistula is a fatal injury, and its mechanism is mostly due to the damage of the tracheal intubation cuff through the tracheal wall, involving the无名动脉. The emergency treatment method is to temporarily use a high-pressure cuff of the tracheal intubation to compress.

　　Generally, the resection of the segment of the无名动脉 involved in the process is relatively safe. The proximal and distal ends are tightly sutured with fine, non-absorbable arterial suture materials, and the thymus, fat, and muscle can be placed around the anastomosis to protect it. In lesions caused by the balloon, the trachea is also damaged at the point of compression, so it is best to perform segmental resection of the trachea at the same time and then perform end-to-end anastomosis. Although the reconstruction of the artery is very good, in the case of infection, the replacement of artificial vessels or autologous grafts often results in more postoperative complications.

　　For acute tracheoesophageal fistula, if the patient no longer requires ventilator assistance, it can be repaired. The technique is to plug the hole in the trachea with a muscle flap and then suture the opening on the esophagus with a single suture. However, due to the circular injury of the trachea caused by the cuff, patients with tracheoesophageal fistula generally have a tendency to cause tracheal stenosis, so segmental resection of the trachea should be considered.

　　If an attempt to repair the tracheoesophageal fistula is made on a patient who is still being assisted by a ventilator, it will always fail. The management of such patients should be to remove the already inserted nasogastric tube, place a low-pressure cuff tube into the trachea, insert a gastric drainage tube to prevent reflux, and maintain nutrition through jejunal feeding. After fasting, the repair of the trachea and esophagus is completed in one stage, the fistula is closed in layers, surrounded by pedicled muscle flaps, the damaged segment of the trachea is excised, and the trachea is re-anastomosed, with good results.

　　II. Prognosis

　　Generally speaking, the treatment results of benign tracheal stenosis are very satisfactory. Dr. Grillo reported that he treated 208 patients with tracheal injury after tracheal intubation, including the excision of the stenotic segment of the trachea and reconstruction of the trachea. Among them, 33 had previously undergone tracheal reconstruction surgery, many patients had laryngeal injury, 9 had tracheoesophageal fistula, 1 had trachea-axillary artery fistula, 216 underwent tracheal reconstruction, 8 had re-stenosis of the trachea after the first excision, including 13 cases through the cervical mediastinal approach, 1 case through the thoracic approach with tracheal skin tube reconstruction, the longest excision length was 7cm. In this group of patients, 5 died (2%), 9 failed (5%), and 93% of the patients obtained good or satisfactory results after surgery. Granuloma on the suture line requiring fiberoptic bronchoscopy is the most common phenomenon, and now the use of polymeric suture materials basically excludes this complication.