This observational study is the first trial to report the airway management in patients with unusual localization of LTS caused by long term intubation for COVID-19 pneumonia. Our study shows that using Tritube and FCV is feasible and safe and creates a good surgical exposure.
The COVID-19 pandemic is expected to trigger a significant increase in laryngeal complications, related to the prolonged intubation [12–14] While actual figures as still unclear, emergent data support this [4, 5, 13, 15, 16]. Our study does not provide data on the incidence of LTS after prolonged intubation during COVID-19, as COVID-19 related LTS was an inclusion criterium. In our study population, consisting of both intubated and tracheostomized patients, we observed that the median of mechanical ventilation was 17 days (range, 7–27 days).
Median intubation duration was 12 days (7–22 days) in line with earlier as reports on LTS in COVID-19 patients [17–19]. Common risk factors for developing LTS [20, 21], Diabetes Mellitus (8 patients) and BMI > 30 kg. m-2 (5 patients), were present in our study population. As aimed for, all patients had been ventilated in prone position, being a key factor for the unusual localization of the stenosis [4].
In 90% of the cases pre_operative radiological images provided correct localization of the stenosis. In two patients (10%; both with tracheostomy status) the stenosis appeared to be unilaterally in the glottis instead of posterior subglottic. This underlines the need for endoscopic assessment to determine appropriate anesthetic and surgical strategies [22], especially in patients that had a tracheostomy. Importantly, we observed that the posterior subglottic stenosis is located distal from the common stenotic site. Moreover, the stenosis is limited to only one subsite depending on the localization of the tracheal tube, which also presents unique challenges for airway management and also surgical procedure.
Surgical treatments including endoscopic dilatation and laser or open surgery are often essential to improve the airway patency [23] In 90% of our cases, endoscopic treatments such as dilatation with intralesional corticosteroid injection were performed due to the low-grade and one-sided stenosis, similarly as earlier described [22, 24, 25] But due to the repeated dilatational procedures by balloon, bougies or rigid endoscopic instrumentations, anesthetic armamentarium is much more challenging in these patients. Therefore, although the anesthetic management in stenosis is well known, post-Covid LTS requires novel approaches. Previously reported airway management strategies in patients with LTS consist of ventilation via a small sized endotracheal tube beyond the stenotic region, HFJV technique or intermittent apneic ventilation [26–28]. In the current study we used in our cases was Tritube in combination with FCV ventilation. The benefits of Tritube in upper airway surgery, a.o. improving surgical exposure and working conditions, have been described [7–9, 29–35]. We confirm the great surgical exposure as the VAS was ranked 9 out of 10 (7–10). Concealment of laryngeal structures was hardly observed, facilitating a relatively easy dilatational process. Note that, in our study, three patients were excluded because it was decided to perform tracheal resection-anastomosis. Recently, Kuut and colleagues [34] described the value of using Tritube in that procedure.
Stenotic patients with hypoxemic respiratory failure have also limited pulmonary function [36] as also observed in our cohort. In cases of severe adhesions of the stenosis to the surrounding connective tissue, a prolonged dilatational process may be demanded. In our study, 19 patients required prolonged apneic ventilation of approximately 10 minutes. In case traditional small sized tubes would have been used, the tube may well have been too short to pass the stenotic lesion site and even if it had been long enough, the dilatational process ordinarily involves repetitive extubating and apneic intervals, likely would have led to hypoxia and hypercarbia [37]. Alternatively, HFJV could have been used in the narrowed airway providing maximal exposure of the surgical field [38]. But, the respiratory impairment in our patient group adds a significant risk on hypercapnia, rapid desaturation and hypoxia to be established HFJV risks, being aspiration (uncuffed catheter) and barotrauma (stenotic airway).
We show that FCV ventilation via cuffed Tritube ensures an efficient ventilation in the narrowed airway. Moreover, the highly efficient ventilation, as described before in various patients, allowed an extended apneic period for the surgical procedure [35, 39–42]. Our respiratory and hemodynamic data show that FCV was able to maintain stable respiratory and hemodynamic levels for almost 80 minutes, without having to accept periods of hypercapnia. Another benefit of using Tritube with FCV is the continuous PetCO2 monitoring, while only intermittent capnometry is possible with HFJV.
We observed that oxygenation (PO2 and SpO2) and respiratory system compliance gradually improved throughout the procedure without an increase in inspiratory plateau pressure. Also, we experienced that, leaving narrowed tube with deflated cuff in situ facilitated the extubation of high-risk patients while avoiding the need for reintubation or tracheostomy in Tritube with FCV.
In one patient with a history of mild chronic obstructive pulmonary disease, reflected by the low lung compliance as measured by Evone, a brief period of desaturation occurred. We defined a SpO2 < 90 as desaturation. Upon induction this patient had a SpO2 declined to 89%. We paused surgical manipulation, adjusted ventilator settings and SpO2 increased.
However, this technique has some drawbacks (1) stenosis with a lumen diameter of less than < 4 mm will not allow the pass the Tritube, (2) the patient needs to be anesthetized using TIVA and (3) spontaneous breathing is not possible.
Also, Tritube is not laser certified. After discussing this within the surgical team we were comfortable to use the tube during CO2 laser procedures while applying general laser-safety protocols as described above. We never experienced any safety issues to laser use in combination with the Tritube when these strict safety measures are taken.
Further, it should be emphasized that this was an observational study without a control group. Further randomized studies with a larger number of patients are needed to evaluate any possible risks or benefits of a Tritube with FCV over a conventional or jet ventilation technique in a narrowed airway in patients with a compromised respiratory function.