In a pilot study (5 patients in each group intubated by a trained anaesthesiologist who was familiar with both techniques) prior to this research, the NTI time, which was deﬁned as the time from when the fibreoptic bronchoscope or aseptic suction catheter was inserted into the nasal cavity to the time at which the tracheal tube was correctly inserted through the glottis, was significantly longer in the fibreoptic group than in the Disposcope group (43.0 ± 13.4 sec vs 24.0 ± 3.2 sec). For this study, the total sample size to achieve 95% power and an α-error of 5% was 8 patients per group according to G*Power 18.104.22.168 software. Sixty adult patients rated American Society of Anaesthesiologists (ASA) I and II who were scheduled to undergo elective oral and maxillofacial surgery requiring NTI under general anaesthesia were selected. We excluded patients from our study if they fell into any of the following categories: (1) age younger than 18 years or older than 80 years; (2) a body mass index (BMI) ≥ 30 kg/m2; (3) a preoperative Mallampati score of III or higher; (4) a history of nasal abnormality (e.g., nasal trauma, surgery, obstruction, and polyps); (5) current anticoagulation therapy; (6) the presence of an oral malignant tumour or difficulty anticipated in airway management; (7) a mental disorder diagnosis; and (8) cervical vertebra instability, trauma or rheumatoid arthritis. None of the patients were premedicated, and standard monitoring equipment was used in the operating room. All study subjects were randomized by a researcher blinded to the study, and envelopes containing randomization numbers were used to allocate the patients to the following two groups (n = 30 per group) according to the airway device that would be used to guide NTI: the fibreoptic bronchoscopy-guided group (fibreoptic group) and the Disposcope endoscope-guided group (Disposcope group).
General anaesthesia was induced with 1.5-2 mg/kg intravenous propofol and 0.3 μg/kg sufentanil, and muscle relaxation was achieved by intravenous administration of 0.15 mg/kg cisatracurium. Airway size and patency were estimated by fibreoptic bronchoscopy (Pentax FI-10BS, Pentax Corporation, Tokyo, Japan) in each nostril. Before intubation, manual ventilation was performed with 100% oxygen through a facemask for 3 minutes. Five drops of 1% ephedrine solution were instilled into larger nasal cavities to prevent bleeding. Males and females were intubated with 6.5-mm and 6.0-mm wire-reinforced tracheal tubes, respectively (TUORen Medical Equipment Co., Henan, China) with high-volume, low-pressure cuffs. Anaesthesia was maintained with propofol and remifentanil at rates of 0.1-0.15 mg/kg/min and 0.1-0.2 μg/kg/min, respectively.
In the fibreoptic group, intubation was performed with the one-hand manoeuvre by putting the little finger below the mandible angle, the ring finger below the mandible body, and the middle finger under the mental region; this gesture mimics the one-handed facemask ventilation technique. By applying this manoeuvre, the operator can simultaneously insert the fibreoptic bronchoscope and lift the chin . In the Disposcope group, the depth of the wire body that was lubricated with aseptic liquid paraffin for insertion was pre-measured to ensure that the wire tip did not protrude from the tube before NTI, and the shape of the wire transfer was curved by the operator before NTI. An aseptic suction catheter (OD, 5.33 mm, TUORen Medical Equipment Co., Henan, China) lubricated with aseptic liquid paraffin was then inserted through the tracheal tube (Fig. 1, C and D). The tip of the catheter was directed ventrally with the tip of the catheter protruding from the distal end of the tube by approximately 10 cm , and the tracheal tube was then advanced through the nasopharynx. The suction catheter was withdrawn after the above steps were completed. The operator then used the thumb and index finger of one hand to lift the mandible during intubation . The entire intubation process is shown in Fig. 2 (A-F). All intubations were performed by an anaesthesiologist who was familiar with both techniques and had 15 years of experience and a trained assistant. Minute adjustments to ventilation were performed to maintain end-tidal CO2 pressures at 35 - 45 mmHg after intubation.
The NTI time was recorded. Epistaxis was assessed by an investigator blinded to the group assignments using direct laryngoscopy at ﬁve minutes after completing NTI and was scored as one of four grades according to the following modiﬁed criteria: no epistaxis (no blood observed on either the surface of the tube or the posterior pharyngeal wall); mild epistaxis (blood apparent on the surface of the tube or posterior pharyngeal wall); moderate epistaxis (pooling of blood on the posterior pharyngeal wall); and severe epistaxis (a large amount of blood in the pharynx impeding NTI and necessitating urgent orotracheal intubation) .
Each patient received 0.1 μg/kg sufentanil intravenously for postoperative analgaesia upon completion of the operation. Neuromuscular blockade was reversed using neostigmine (1 mg) and atropine (0.5 mg), and the trachea was extubated when the patient was awake. At 15 minutes, 1 h and 24 h after extubation, the patients were asked to rate their nasal pain on a visual analogue scale (VAS) according to a 10-cm vertical score ranging from 0 = no pain to 10 = worst pain imaginable by an independent anaesthetist who was unaware of which method had been used for NTI.
The study protocol was reviewed and approved by the Institutional Research Ethics Committee of The First People’s Hospital of Hefei (No. 2016-6) on 3 March 2016. The study was also registered in the Chinese Clinical Trial Registry (www.chictr.org.cn, ChiCTR-IPR-17011462). Informed written consent was obtained from all patients in this study, and the study was conducted in accordance with the Declaration of Helsinki.
Data are expressed as the mean (SD). Parametric data were compared between the groups by analysis of variance and post hoc testing. The mean difference and the 95% confidence interval (CI) of the mean difference were calculated. Categorical data were analysed using Fisher’s exact test. The relative risks of the proportion of categorical data and 95% CIs were calculated. Statistical signiﬁcance was considered at P values < 0.05. All statistical analyses were performed with Statistical Package for Social Sciences (SPSS) software 13.0.