Abrupt EtCO2 elevation during a digestive endoscopy in a patient of a malignant tracheoesophageal fistula

Dear Editor:

Malignant tracheoesophageal fistula develops in 5%–15% of patients with oesophageal cancer, and its presence generally indicates unresectability.¹ The treatment of choice in these cases is the placement of a self-expanding prosthesis in the oesophagus, trachea, or both.² The management of these patients during the technique is complex, especially due to the difficulty of ventilation and oxygenation after anaesthetic induction and the high risk of aspiration.³

The following is a case study that illustrates the usefulness of capnography during mechanical ventilation to support the diagnosis of a malignant tracheoesophageal fistula in a stage IV oesophageal cancer setting.

We report the case of a 70-year-old man, former smoker of 25 cigarettes/day who gave up smoking 2 years before, diagnosed with squamous cell carcinoma of the mid-oesophagus with single rib metastasis under treatment with palliative radiotherapy (20 Gy), palliative chemotherapy (cisplatin and 5 FU) and oesophageal stenting. He presented with a few-days history of hypersalivation, fluid dysphagia, dyspnoea on moderate efforts and productive cough. The examination showed the presence of scattered bilateral rhonchi on pulmonary auscultation. A gastroduodenal study was performed with Gastrografin®, showing an irregular 3−4 cm long oesophageal lumen stenosis in the proximal third of the stenting with contrast leakage and filling of the lobar bronchi of both upper lobes, suggesting tracheal fistulisation, cranial to the carina. Subsequently, a fibreoptic bronchoscopy was performed where a slight bulging is observed in the membranous part of the distal third of the trachea and stenosis of the proximal third of the left main bronchus that prevents the passage of the bronchoscope, without clearly observing a solution of continuity that confirms a tracheoesophageal fistula. The study was completed with a chest CT that showed extraluminal air cranial to the oesophageal stent and stenosis of the left main bronchus; all suggestive of tracheoesophageal fistula in this area, which could not be visualised. Given the suspected diagnosis, it was decided to perform a new digestive endoscopy under general anaesthesia with orotracheal intubation for proximal stent placement. After establishing mechanical ventilation and checking the correct location of the ETT and the endotracheal tube cuff, the exhaled tidal volume was less than the inspired tidal volume, suggesting an air leak somewhere in the tracheobronchial tree. After inserting the endoscope, the capnograph showed an abrupt increase in exhaled carbon dioxide (EtCO₂) up to 70 mmHg, which decreased rapidly after removing the endoscope. This was repeated on 3 occasions, coinciding with the introduction of the endoscope, suggesting passage of CO₂ from the oesophagus to the trachea. After the placement of the new oesophageal stent, cranial to the previous one, the sudden EtCO₂ increase did not recur, remaining constant between 35−40 mmHg until the end of the examination. The patient progressed favourably after performing the technique. At the time of discharge the patient was tolerating a liquid diet with thickening agents and the dyspnoea and productive cough had disappeared.

The occurrence of tracheoesophageal fistulas is related to the progression or recurrence of the disease.^1,2 The most effective treatment to avoid stenosis compared to other alternatives is the placement of self-expanding stents,¹ which is the treatment of choice in patients with unresectable tumours. Tumor growth is one of the most common causes of restenosis in patients with oesophageal stents.^2,4,5 In the case reported, given that the patient had oesophageal restenosis and a tracheoesophageal fistula that was difficult to treat from the tracheal lumen, we opted for a new oesophageal stent placement. Capnography is a monitoring standard during general anaesthesia procedures³ and usually, the increase in EtCO₂ occurs progressively.^3,4 The abrupt EtCO₂ elevation after inserting the endoscope and its return to normal values after its removal allows to demonstrate the passage of the insufflated gas (CO₂) to the bronchial tree, and the clinical confirmation of the existence of a tracheoesophageal fistula. Restoring the parameter to normal values after stenting suggests the success of the treatment.