Central airway stenosis is known worldwide as a life-threatening condition with many causes[9–11]. In this study, we retrospectively reviewed 375 cases with CAO undergoing bronchoscopy with general anesthesia. The causes of CAO were primary tracheal tumors or lung cancer, esophageal cancer, scarring after tracheotomy, post-placement of stenting, mediastinal tumor, pulmonary metastatic tumor, and tracheomalacia etc.. As complications of these diseases, tracheal stenosis can be treated in many ways. Surgery may be the preferred approach, but not all patients are appropriate surgical candidates . Therefore, bronchoscopy treatment remains the best tool for the safest management of airway obstructions, and provides prompt and durable palliation to patients ineligible for surgical treatment [3, 7, 12, 13].
Both rigid and flexible bronchoscopes are now available for the interventional pulmonologists to perform this operation for advanced diagnostic and therapeutic purposes. There are some debates as which one is better than the other, and whether the use of muscle relaxants is safe and indispensable in this procedure[14–18]. In some articles, the authors are in favor of the non-use of muscle relaxants in rigid or flexible bronchoscopy for the safe factor, but in some operations, especially in advanced therapeutic and diagnostic procedures, undivided attention of the bronchoscopist and an immobile patient are required[16, 20]. A rigid bronchoscope can be placed in a nonparalyzed patient under deep sedation demanding high doses of analgesic and hypnotic agents, risking cardiovascular instability or residual drug effects harming pulmonary function after the operation. Trauma of the vocal cords and larynx leads to swelling and airway compromise, sometimes even accidental airway perforation could occur if poor insertion of the rigid bronchoscope is attempted even with adequate depth of anesthesia in a nonparalyzed patient, due to the significant response to tracheal manipulation. The use of muscle relaxants can facilitate the placement of rigid bronchoscope, ensure vocal cord adduction, and prevent life-threatening patient moving and coughing during the procedure, thus to provide the best operating conditions. Although SGA(supraglottic airway) insertion itself may not necessitate muscle paralysis, paralyzed vocal cords facilitates bronchoscopy in adduction position. Furthermore, muscle paralysis could attenuate the risk of patient’s coughing and movements during the operation, as well as lower the chest wall resistance and reduce inspiratory pressures needed to achieve satisfactory tidal volumes[21–24]. At the beginning, we also did not dare to use muscle relaxants, but with the improvement of anesthesia equipments, visual technology, and anesthesia skills, we began to experiment with muscle relaxants. Approximately 96.5% patients among the 375 included patients were given skeletal muscle relaxants recorded in the anesthesia notes.
Non-depolarizing muscle relaxants (Cis-atracurium, Atracurium, Rocuronium) instead of depolarizing muscle relaxants are preferred in our department, due to the moderate duration (close to 40 minutes) of the advanced procedure, Hofmann elimination mode and less histamine release, Cis-atracurium (in our department) has been the muscle relaxant of our choice. Short-acting depolarizing neuromuscular blocking drugs (e.g. succinylcholine) are suitable for insertion, but can lead to postoperative myalgia. The typically used non-depolarizing neuromuscular blocking agent of rocuronium has a longer half-life than the others and must be given with caution. The dosages of muscle relaxants and fentanyl used in rigid bronchoscopy are significantly higher than those used in the flexible bronchoscopy due to the higher degree of irritation.
Hypoxemia and hypercapnia may commonly occur during bronchoscopic procedures. No patient was found could not be ventilated in our study under general anesthesia treated with muscle relaxants. We compared ETCO2 ,PaCO2 and PaO2 between the flexible and rigid bronchoscopy group. PaCO2 values were significantly higher than preoperative level in both groups, but there was no significant difference between the two groups. There was no statistical difference in recovery time and lowest pulse oxygen incidence between the two groups. In addition, there was no correlation between the operation time and EtCO2 or PaCO2 after flexible bronchoscopy or rigid bronchoscopy therapy in patients with CAO. During the procedure, we noticed SpO2 decreased in nearly all patients, despite fraction of inspired oxygen (FIO2) being kept at 100%, but no patient suffered severe hypoxemia or hypercapnia. For patients undergoing some transient episodes of SpO2 lowering below 90%, high fresh gas flows are often used to obtain adequate ventilation and compensate for the airway leakage. If it didn’t work, we would remove the placed bronchoscope and then ventilate the patient for several minutes until SpO2 increased to above 95%, then restart the procedure. The results show that the use of skeletal muscular relaxants may be safe in patients with CAO undergoing bronchoscopy therapy. In this study, we assume that the residual normal structure of the tracheal cartilage ring could maintain the airway and the continuously negative suction pressure produced by the operator acts like the way as passive lung ventilation. However, if the airway is highly skeptical of airway collapse, we will pay full attention to the patency of the airway to prevent the patient from being unable to be effectively intubated or ventilated.
In this process, the way of mechanical ventilation is also a key factor affecting gas exchange. A previous study has demonstrated no difference in arterial blood gas analysis values between jet ventilation and conventional ventilation during endobronchial laser surgery, yet jet ventilation may be associated with some complications including hypertension, hypoxemia, hypercapnia, and barotrauma. In this study, the traditional Low-frequency ventilation was used in all patients with CAO. These results indicate that conventional ventilation mode using standard ventilator through the side port of the rigid bronchoscope can supply enough gas exchange at a relatively affordable cost. Since some cases have been excluded in our study for the reason that these cases may have some advantages using HFJV, including bronchopleural, bronchoesophageal and bronchomediastinal fistulae, we still don't recommend the routine use of jet ventilation in the procedures described.
In this study, most of the patients with CAO who underwent bronchoscopy therapy were safely transferred to the ward (86.7%), while the others were sent to ICU postoperatively due to their poor general condition. Three deaths (2 due to hemoptysis and 1 due to acute myocardial infarction) occurred during the procedures or within 48 h postoperatively, with a mortality rate of 0.8%. The causes of these three deaths were not directly related to the procedures even though they occurred in the perioperative period. The rest of the patients (99.2%) recovered without incidents in the recovery room in the immediate postoperative period.
Variables identified as increased complication rate predictors for therapeutic bronchoscopy (including both rigid and flexible) includes: emergent procedures, ASA physical status scores. In this study, we revealed that the grade of ASA and obvious dyspnea or orthopnea were the independent risk factors for postoperative ICU admission. Therefore, ICU admission may be a safe option when an urgent bronchoscopy is carried out in patients with severe dyspnea, or with high ASA scores.
There are still some limitations in our study. Firstly, we did not have a blank control group to compare the procedures performed without muscle relaxants. Secondly, a lot of blood gas data were missing from the data during the operation. And thirdly, there was a lack of studies investigating the optimal dosages of muscle relaxants, we will design some prospective researches in the future.