Ninety percent of thyroid cancer is highly differentiated cancer, which is low malignant and can have a high survival rate if properly treated. However, if the tumor invades the trachea, the patient can be suffocated and die. Patients with respiratory distress caused by thyroid cancer invading the trachea often consult internal medicine departments, which may lead to misdiagnosis or omission of diagnosis if the doctors are not familiar with the disease or are not alert to it. Correct management of thyroid cancer that has invaded the trachea and caused respiratory distress, especially the choice of anesthesia tracheal intubation method and tracheal revision and repair after tumor resection, is crucial to improve the survival rate. The author retrospectively analyzed 23 cases of thyroid cancer invading into the trachea and causing obvious dyspnea admitted to our hospital from 1995 to 2003, and hereby reports as follows: 1. Materials and Methods (1) Clinical data: Among the 23 cases of thyroid cancer invading into the trachea and causing obvious dyspnea, 9 cases were accompanied by intermittent coughing up of blood or blood in the sputum, and 13 cases were accompanied by hoarseness of voice. Eight of these cases were first seen in the internal medicine department. The diagnosis relied on careful inquiry of medical history, physical examination and imaging examination, including X-ray film, CT, B ultrasound, etc. Combined with intraoperative observation, among the 23 patients, there were only 10 cases of invasion of the tracheal epithelium and compression of the trachea resulting in tracheal displacement and stenosis of the trachea, 7 cases of invasion of the tracheal cartilage resulting in tracheal collapse, and 6 cases of invasion of the whole trachea and protruding into the lumen. (2) Anesthesia selection: general anesthesia was performed in all cases. According to the scope of tracheal invasion and the degree of respiratory distress, there were three methods of anesthesia intubation: 13 cases of transoral tracheal intubation under wakefulness; 4 cases of low tracheotomy followed by tracheal intubation, 2 cases of high tracheotomy followed by tracheal intubation, and 4 cases of laryngeal intubation followed by laryngeal slit. (3) Selection of surgical methods: different treatments were used according to the degree of tracheal invasion. If thyroid cancer only invaded the outer membrane of the trachea and compressed the trachea resulting in tracheal displacement and stenosis, the softened and collapsed trachea would be suspended from the surrounding soft tissues or from the hyoid flap of the sternocleidomastoid muscle of the appropriate size while the tumor was completely resected in the operation. For those who invaded the tracheal cartilage or invaded the whole layer of trachea and protruded into the lumen, the whole layer of the affected part was resected, and in 4 cases, the whole section of the invaded tracheal ring was resected (i.e., tracheal sleeve resection) and then the trachea was anastomosed end to end; in 6 cases, anterior cervical musculocutaneous flaps were used to flip and repair the tumors; and in 3 cases, insular sternocleidomastoid musculocutaneous flaps were used for the repair. 2. Results The 23 patients were intubated with different methods of surgical anesthesia, and no accident occurred in one case. In 19 cases, the tracheal tube was removed at 26d~5 months after surgery; 4 cases were intubated for a long time. After more than 3 years of follow-up, except for 2 patients who died of lung metastasis 2 years after surgery, the remaining 21 patients had good respiration and phonation. 3, Discussion Thyroid cancer, especially highly differentiated thyroid cancer, is slow-growing and has a long course, which can invade the tracheal lining and the tracheal wall, causing tracheal pressure, narrowing and deformation, or the tumor protrudes into the lumen causing dyspnea, which may be accompanied by coughing up blood or sputum with blood. Patients may present with dyspnea alone without symptoms of nerve compression such as hoarseness or Horner’s syndrome, and often seek medical attention. The possibility of thyroid cancer invading or compressing the trachea should be considered for unexplained respiratory obstruction. In this group of cases, 8 cases had been treated by internal medicine. It was not difficult to make a diagnosis after a detailed history and physical examination, combined with X-ray film, CT and fiberoptic bronchoscopy. Preoperative fiberoptic bronchoscopy can understand the scope and degree of invasion of thyroid cancer into the trachea, which can provide a basis for the surgical method and also help in the choice of anesthesia. However, bronchoscopy can irritate the wall of the tube, causing spasm and even asphyxiation, so it should not be practiced for people with severe respiratory distress. Before surgery, the key lies in the rational choice of anesthesia intubation to ensure a smooth airway. As the use of inotropes will aggravate tumor compression of the softened trachea, respiratory obstruction or asphyxiation may occur. Therefore, for those suspected of tracheal softening, awake intubation under airway surface anesthesia or tracheostomy should be chosen as appropriate. For those with respiratory distress occurring predominantly with tracheal compression variant, the mucosa of the tracheal lumen is generally smooth, and awake intubation under airway surface anesthesia is more often chosen. In our experience, for those with preoperative I~II dyspnea and can tolerate the stimulation of intubation, awake tracheal intubation can be chosen. The diameter of the tracheal tube should be appropriate to ensure smooth passage through the stenosis, and the catheter should be lined with a metal ring guidewire that is not easily deflated. As the tumor compresses the trachea to make the airway S-shaped change, the patient’s position should be slightly adjusted to the healthy side, which can significantly improve the success rate of one-time intubation. Thirteen of the 23 patients in this group successfully completed tracheal intubation while awake. Airway obstruction due to endotracheal tumor is different from tracheal stenosis caused by extrinsic compression. When performing endotracheal tube intubation, it is easier to damage the tumor tissue and cause bleeding, or the tumor tissue is dislodged and causes airway obstruction. We experience that for those who have more severe dyspnea (II~III.) and cannot guarantee the smooth passage of the stenosis via nasal or orotracheal intubation in a short time, firstly, high pressure oxygen is given by mask, and according to the site of tracheal involvement, low tracheotomy, high tracheotomy or laryngeal lysis can be selected, and the catheter lined with metal ring guide wire that is not easy to deflate can be rapidly inserted into the trachea (connecting with the high-frequency jet ventilator) under the direct visualization. For tumor invasion of the trachea causing tracheal stenosis resulting in severe respiratory distress, and can not tolerate tracheal intubation or laryngeal lysis operation stimulation, local anesthesia to establish the right femoral vein femoral artery, the left femoral vein diversion of extracorporeal circulation, to ensure that the body’s oxygen supply is adequate, and then take a slow induction of conscious intubation to establish a guaranteed airway.Saitoh et al. have reported a case of thyroid cancer, as a result of the tumor invasion of tracheal trachea caused by tracheal stenosis, causing difficulties to tracheotomy, and also to the trachea. Saitoh et al. reported a case of thyroid cancer in which tracheal stenosis was caused by tumor invasion of the trachea, which made tracheotomy difficult and challenged airway management. We believe that establishing extracorporeal circulation first is a reasonable choice to guarantee a safe and reliable intubation process. Even if intubation fails or sudden respiratory arrest occurs, the femoral artery-femoral vein diversion established first provides a favorable means for cardiopulmonary and cerebral resuscitation with adequate oxygen supply and oxygenation. The anesthetic dose is smaller than for normal surgery because the patient is hypoxic and hypercapnic for a longer period of time, and the sensitivity to anesthesia increases dramatically once the patient is placed in a normoxic or hyperoxic state. When thyroid cancer invades the trachea, it can be categorized into three types: type A: invades the outer tracheal fascia, type B: invades the cartilaginous rings of the trachea, and type C: invades the mucosa of the trachea and protrudes into the lumen. For patients with type A and stenosis caused by compression of the trachea, the tumor should be completely resected during the operation, and at the same time, the involved epithelium should be enlarged, so as to eliminate the small lesions that are easy to be retained as much as possible. Most patients can be effectively controlled locally with postoperative adjuvant radiotherapy and chemotherapy, and have a better survival outcome. Due to long-term tracheal pressure, the trachea is easy to be softened and collapsed, so it is advisable to perform tracheal suspension, or to make a suitable size of sternocleidomastoid muscle hyoid flap, which can be spanned on the lateral side of the collapsed trachea, so as to suspend the collapsed trachea by suture. Tracheotomy should be routinely performed to prevent postoperative re-infarction of the airway. Recent studies have shown that obstruction, bleeding, and respiratory distress caused by invasive thyroid cancer are the most common causes of death from thyroid cancer; extensive resection of thyroid cancer (including partial resection and reconstruction of the trachea or esophagus) does not increase surgical risk. In the surgical treatment of tracheal luminal invasion, different repair methods can be adopted according to the extent of the tracheal defect to achieve as much as possible preservation of tracheal function while eradicating the tumor. The repair materials for partial tracheal defects may include: application of rotational 180° sternocleidomastoid muscle flap to reconstruct the trachea, combined repair of anterior cervical muscle flap and sternocleidomastoid myofascial flap, repair of pectoralis major muscle flap, or repair of myocutaneous flap with tibial sternocleidomastoid myofascial flap, and so on. If the tumor from the anterior or lateral wall of the trachea invades the lumen of the circumference of the ring is not more than 50%, and the tracheal ring invasion is not more than 4 rings, the tracheal wall window resection can be used, and the defective part of the tracheal wall can be repaired by sternocleidomastoid clavicle periosteal flap. Smaller defects do not need to be repaired, and a postoperative tracheostomy can be performed directly through the tracheal wall defect. If the tracheal invasion of thyroid cancer exceeds 50% of the circumference, tracheal sleeve resection with tracheal end-to-end anastomosis is the ideal procedure. Because the submucosal infiltration of the tumor is more extensive than the tumor protrudes into the luminal surface of the trachea, tracheal sleeve resection must be sufficient to ensure an adequate safety margin. Upon release of the trachea and laryngeal body, segmental resection of the trachea can reach a maximum length of 5 cm to 6 cm (6 to 7 rings). For cervical segmental tracheal defects up to 4 cm~6 cm, it is safer to perform an end-to-end anastomosis, and reconstruction with a substitute is required for lengths longer than this. For longer tracheal lateral or lateral posterior wall defects with cervical tracheal defects of more than 6 cm and better retention of tracheal stents, pectoralis major myocutaneous flap or anterior cervical myocutaneous flap combined with sternocleidomastoid myofascial flap can be used for reconstruction. Due to the lack of scaffolding effect of pectoralis major myocutaneous flap itself, it is only suitable for the repair of longer tracheal lateral wall defects with better retention of tracheal stent, and in order to prevent it from collapsing into the lumen of the trachea, the base of the flap can be appropriately suspended outwardly and fixed to the surrounding tissues during the operation. In this group of patients, tracheal end-to-end anastomosis, anterior cervical musculocutaneous flap was used to repair tracheal defects, and pectoralis major muscle musculocutaneous flap was used to repair tracheal defects, respectively, with good results.