Patients with severe chronic obstructive pulmonary disease (COPD) are highly predisposed to respiratory complications under general anesthesia. Herein, we report the case of a 69-year-old man with severe COPD, forced expiratory volume 1.0 sec rate 37％, underwent surgery for the excision of a large intra-mandibular tumor. Intravenous sedation was chosen over general anesthesia to avoid the acute exacerbation of COPD and the impossibility of postoperative extubation. This intravenous sedation was managed using dexmedetomidine and fentanyl because it is hard to ensure adequate analgesia during surgery with local anesthetics alone. To monitor fentanyl-induced respiratory depression, we used the impedance and thoracic kinematic measurement belts to monitor respiratory movements as well as capnography and intranasal pressure measurements to monitor airway obstruction. Fentanyl administration was discontinued when the amplitude of intranasal pressure waveform decreased to approximately 25％ of the pre-sedation level. Subsequently, a 25 μg dose was administered when the amplitude rose to approximately 75％. We could monitor the relative decrease in respiratory flow continuously via the gradual decrease in the nasal pressure amplitude. However, it was difficult to monitor the decrease in respiratory flow based on the shape of the capnography waveform. The intranasal pressure measurement and waveform of the thoracic kinematics belt could adjust the fentanyl dosage appropriately and perform adequate analgesia for the procedure without any respiratory complications.
