A 70-year-old man was diagnosed with recurrence of right upper lobe lung cancer. Four years ago, he underwent thoracoscopic right upper lobectomy and lymph node dissection for squamous cell carcinoma of the right upper lobe. He visited the hospital with complaints of dyspnea and bloody sputum. Bronchoscopy showed compression of the carina by a hemorrhagic tumor. Tracheal stenting to improve respiratory distress was scheduled under general anesthesia with monitoring of oxygen reserve index (ORi™) (Masimo Corp., Irvine, CA, USA) for indexing respiratory condition and possible hypoxia. ORi™ was measured noninvasively and continuously with a sensor on the left second finger by the pulse oximetry (Radical-7™, Masimo Corp; Irvine, CA, USA). SpO2 was at 96–98% in the room air, but he had stridor on auscultation and orthopnea.
Before induction of general anesthesia, catheters were placed into bilateral femoral veins under local anesthesia in preparation for extracorporeal membrane oxygenation during surgery. An arterial pressure line was inserted into the left radial artery. General anesthesia was induced using 50 μg of fentanyl, 3 μg/ml (TCI) of propofol, and 50 mg rocuronium. Airway was secured by intubating a spiral tube (diameter 9 mm, Parker Medical, USA). Anesthesia was maintained using propofol administration at 2.1–3 μg/ml (TCI) and remifentanil, and the depth of anesthesia was adjusted with reference to the bispectral index (BIS).
First, a flexible bronchoscope was inserted via an adaptor (Bodai Y connector®, Independence Australia Group, Australia) through the tracheal tube to cauterize and reduce the tumor size. As argon plasma coagulation was used, FiO2 was lowered to 0.28 for preventing airway fire. However, due to the large size of the bronchoscope relative to the inner diameter of the tracheal tube, tidal volume was significantly reduced. ORi decreased from 0.3 to 0.2 within few minutes after starting surgery (Fig. 1a). SpO2 started to decrease when ORi was 0.2; however, it was > 90%; even ORi further decreased to 0. SpO2 decreased < 90% approximately 5 min later, when surgery was interrupted. After confirming that SpO2 recovered by raising FiO2 to 1.0, the surgical procedure for tumor resection was resumed. However, due to bleeding from the tumor, there was not enough time for oxygenation to recover SpO2 at 100%. Therefore, when SpO2 recovered slightly, FiO2 was lowered to 0.28 again, and surgery was resumed. After the procedure was completed, FiO2 was raised to 1.0. Then, SpO2 in 5 min recovered to 99–100%, followed by an increase in ORi. About 5 min after SpO2 reached 100%, ORi rose to 0.53 (Fig. 1a).
Next, the flexible scope was extubated and replaced with a rigid scope, and a tracheal stent was placed using the rigid scope. When using a rigid scope, the ventilation volume may decrease, so we used an intrapulmonary percussive ventilator (IPV®, MODEL IPV-1, Percussionaire Corp; Sagle, ID, USA). A breathing circuit was connected directly to the rigid scope, and an IPV was connected to the inspiratory side of the circuit for percussion ventilation. At first, ventilation was performed only pressure-controlled ventilation (PCV:Pi 14 cm H2O, RR15/min, IE = 1:2, PEEP 5 cm H2O), but since the tidal volume decreased to 90 ml, IPV (operating pressure 30 psi, percussion frequency 3 Hz. The optimal drive pressure for IPV is 35–40 psi for adults, but high pressure could interfere with surgical procedure, so we started at 30 psi) was immediately started. FiO2 was managed at 1.0 during rigid bronchoscopic surgery as there is no longer a possibility of airway fire. Applying IPV enabled the maintenance of sufficient oxygenation during rigid bronchoscopy. The level of ORi did not decline, and SpO2 remained above 98% (Fig. 1b). The surgery was completed with a tracheal stent that was placed without complications. Awakening was good, and symptoms of respiratory distress improved immediately after the operation. The patient woke up from general anesthesia without any symptoms of respiratory distress.