Airway management is closely related to the safety and quality of anesthesia. In 2015, the Difficult Airway Society suggested that endotracheal intubation should be fiberoptic bronchoscope (FOB)-guided and blind intubation should be avoided. The supraglottic airway device (SAD) BlockBusterTM with matched tracheal tube (BlockBusterTM tracheal tube, BTT; Tuoren Medical Instrument Co., Ltd., Changyuan, Henan, China) is an improved second-generation SAD with intubation function.[1,2] The fiberscope-monitored intubation via SAD BlockBusterTM can make the whole process visible. So, we investigated the feasibility, success rate, and complications of the new intubation technique in a well-positioned SAD BlockBusterTM by sequential case observation.

This study included 106 patients with the American Society of Anesthesiology (ASA) Grades 1 and 2, aged 20–65 years, scheduled for elective surgery at Beijing Friendship Hospital affiliated with Capital Medical University from January to October 2020 (No. ChiCTR2000028719, http://www.chictr.org.cn). The exclusion criteria were as follows: Patient refusal, or combined symptoms of asthma, cervical instability, mouth opening <3 cm, severe obstructive sleep apnea syndrome, or allergy to intravenous anesthetics. The study was approved by the Institutional Ethics Committee of Beijing Friendship Hospital (No. 2019-P2–268-02). The written informed consent forms were obtained from all patients before the initiation of the study.

Upon arrival in the operating room, standard multi-channel monitors including non-invasive blood pressure, electrocardiograph, pulse oxygen saturation, and end tidal carbon dioxide (ETCO2) waveforms were applied throughout the procedure. In the supine position, all patients were pre-oxygenated using a mask with a 100% oxygen for 3 min, followed by an intravenous injection of midazolam 0.03 mg/kg, sufentanil 0.4 μg/kg, and etomidate 0.3 mg/kg for anesthesia induction.

An appropriate size of the SAD BlockBusterTM was selected, with No. 3 and No. 4 for female and male patients, respectively. Neuromuscular block was induced using cisatracurium 0.2 mg/kg, after which, the SAD BlockBusterTM was placed into the upper airway. After the cuffs were filled to achieve an intracuff pressure of 30–40 cm H2O using a pressure gauge, the SAD BlockBusterTM was connected to the breathing circuit, and mechanical ventilation was performed. A flexible fiberscope (4.0 mm external diameter, Karl Storz SE & Co. KG, Tuttlingen, Germany) was passed through the SAD with its tip located at the distal end of the airway channel. The fiberscopic view of the SAD positioning was evaluated and graded as follows: Grade 1, only the glottis seen; Grade 2, vocal cords plus posterior epiglottis seen; Grade 3, vocal cords plus anterior epiglottis seen; Grade 4, vocal cords not seen [Supplementary Figure 1, https://links.lww.com/CM9/B845].[3] Grades 1 and 2 were good fiberscopic views and suitable for fiberscope-monitored tracheal intubation. Grade 3 needed the device position to be adjusted. Tracheal intubation was discontinued in Grade 4 patients owing to its poor location.

The appropriate size of BTTs (inside diameter 6.5 mm and 7.0 mm tubes for No. 3 and No. 4 SADs, respectively) was selected. After completing the SAD BlockBusterTM insertion and checking the fiberscopic view grading, the BTT was inserted into the airway channel of the SAD BlockBusterTM. The fiberscope passed through the BTT with the tip located immediately behind the tube tip. On visualizing the glottis with a fiberscope, the tracheal tube was delivered into the trachea, and the tube cuff was inflated up to 25 cm H2O. The SAD BlockBusterTM was remained in the throat cavity with the cuff deflated until the end of anesthesia and extubated together with the tracheal tube. If the procedure was unsuccessful, patients were intubated using a Macintosh laryngoscope (Rudolf Riester GmbH, Jungingen, Germany). A lubricated gastric tube of 14-French size was inserted via the drainage channel, and the success rate was recorded.

The following data were recorded: (1) Attempts and duration needed to insert the SAD BlockBusterTM; (2) Fiberscopic check of the SAD position by Brimacombe J scoring system[3]; (3) The success rate of fiberscope-monitored intubation via the SAD BlockBusterTM; (4) Attempts and duration needed to intubate the BTT; and (5) Airway trauma and complications were recorded post-operatively.

Statistical analyses were performed using the SPSS software version 13.0 (SPSS Inc., Chicago, IL, USA). All data were expressed as the mean ± standard deviation for continuous variables or n (%) for categorical variables. Continuous variables such as intubating time between groups were compared using a Student’s t-test. Categorical variables were compared using Chi-squared or Fisher’s exact tests. P value <0.05 was considered statistically significant.

A total of 106 patients enrolled in this study were successfully inserted with SAD BlockBusterTM at the first attempt and the ventilation function was normal. Among the 106 patients, 4 patients with blood staining on the device, and 6 patients reported sore throats. No complaints were reported 3 h post-operation. The sex ratio (female/male) was 70/36, the time of SAD BlockBusterTM insertion was 17.0 ± 2.9 s, and the success rate of gastric tube insertion was 99.1% (105/106) [Supplementary Table 1, https://links.lww.com/CM9/B845]. While 5 patients abandoned tracheal intubation owing to the poor position of the SAD, 101 patients were successfully intubated. The intubation attempts, success rates, and time required for each fiberscopic view grade for the 101 patients were shown in Table 1.

Table 1 - Intubation attempts, success rates, and time required for each fiberscopic view grade (n = 101). Variables Success rates Grade 1 ( n = 57) Grade 2 ( n = 22) Grade 3 ( n = 22) Total ( n = 101) Attempts First 57 (100) 22 (100) 18 (81.8) 97 (96.0) Second 0 0 3 (13.6) 3 (3.0) Third 0 0 1 (4.6) 1 (1.0) Intubation time (s) 14.2 ± 3.3 16.6 ± 2.5 30.9 ± 8.9* 18.3 ± 8.3

Data are expressed as mean ± standard deviation or n (%). *Compared with the intubation time in fiberscopic view Grade 1, P <0.05.

In a prospective randomized study, Sood et al[4] compared fiberoptic-guided endotracheal intubation through the i-gel and LMA FastrachTM, the success rate of the first intubation was 96.7% (29/30) and 93.3% (28/30) in the i-gel and LMA FastrachTM groups, respectively. The time taken for fast tracheal intubation was 69.5 ± 5.1 s and 72.3 ± 6.7 s in the LMA FastrachTM and i-gel groups, respectively. In this study, the first fiberscope-monitored intubation success rate was 96.0% (97/101), and the intubation time using the SAD BlockBusterTM was roughly one-third of the results of Sood et al[4]. The higher success rate of intubation and less intubation time via SAD BlockBusterTM may be due to its unique design, such as a short one curve airway channel with large oval cavity and a circular exit with ramp, a modified inflatable cuff [Supplementary Figure 2, https://links.lww.com/CM9/B845]. The dedicated BTT is a new reinforced tube and is recommended to use when intubating through SAD BlockBusterTM [Supplementary Figure 3, https://links.lww.com/CM9/B845]. The advantage of monitored intubation over guided intubation is that the entire process of the tube entering the glottis and trachea can be observed, and problems can be detected in time. Furthermore, this “monitored intubation” manipulation is easier and quicker than “guided intubation” because it is simple to operate and does not require complex training.

All patients were successfully inserted with SAD BlockBusterTM and the ventilation function was normal, which was similar to the results of Wan et al[5]. The insertion time was 17.0 ± 2.9 s, which was similar to the result (17.2 ± 2.5 s) obtained by Zhou[6]. Gao et al[7] found that the rate of good view and satisfactory positioning of SAD was significantly increased in the SAD BlockBusterTM than LMA Supreme. In this study, all fiberscope-monitored endotracheal intubation through SAD BlockBusterTM with the good fiberscopic view was successful by the first attempt, suggesting that glottic fiberscopic view quality affects the intubation effect. While three patients with fiberscopic view Grade 3 needed to rotate the BTT under fiberscope monitoring were successfully intubated by the second attempt. In one case, the fiberscopic view grade was improved to Grade 2 by jaw-lift maneuver, then the third intubation was successful under fiberscope monitoring. So, the intubation time of these patients with fiberscopic view Grade 3 was significantly prolonged than Grades 1 and 2. These results indicated that endotracheal intubation via SAD BlockBusterTM could be achieved under fiberscope monitoring when the fiberscopic view grade was 1–3.

Endigeri et al[2] found that complications such as sore throat were obviously decreased with the SAD BlockBusterTM, because the device fits closely with the oropharyngeal curve. Furthermore, the BTT tip is centered and bendable which is easy to pass into the glottis and tracheal, thus reducing subglottic mucosal damage. In this study, four patients were found with blood staining on the SAD and six patients complained of sore throat after the removal of the SAD. Otherwise, these observed cases were all with normal airways. Furthermore, females accounted for about 66.0% of all study populations, the results are for clinical reference.

Overall, with the fiberscope-monitored intubation via SAD BlockBusterTM by the BTT, the tracheal intubation is satisfactory and assured when the fiberscopic glottis view of the device position is good. The entire process of intubation is visible, easy, and quick. Airway irritation and damage is minor.

Acknowledgments

The authors thank Ms. Na Zeng, Master of Public Health at Clinical Statistical Centre, Beijing Friendship hospital for her kind help with statistics.

Funding

This work was supported by a grant from the Capital’s Funds for Health Improvement and Research (No. 2018-4-1116).

Conflicts of interest

None.

References 1. Zhang S, Zhou J, Zhang Y, Hao XF, Tian M. Application of blind orotracheal intubation via BlockBuster laryngeal mask in patients undergoing general anesthesia. Int J Anesth Resus 2016;37:917–920,924. doi: 10.3760/cma.j.issn.1673-4378.2016.10.012. 2. Endigeri A, Ganeshnavar A, Varaprasad B, Shivanand YH, Ayyangouda B. Comparison of success rate of BlockBuster® versus Fastrach® LMA as conduit for blind endotracheal intubation: A prospective randomised trial. Indian J Anaesth 2019;63:988–994. doi: 10.4103/ija.IJA_396_19. 3. Brimacombe J, Berry A. A proposed fiber-optic scoring system to standardize the assessment of laryngeal mask airway position. Anesth Analg 1993;76:457. 4. Sood S, Saxena A, Thakur A, Chahar S. Comparative study of fiber-optic guided tracheal intubation through intubating laryngeal mask airway LMA FastrachTM and i-gel in adult paralyzed patients. Saudi J Anaesth 2019;13:290–294. doi: 10.4103/sja.SJA_707_18. 5. Wan L, Shao LJ, Liu Y, Wang HX, Xue FS, Tian M. A feasibility study of jaw thrust as an indicator assessing adequate depth of anesthesia for insertion of supraglottic airway device in morbidly obese patients. Chin Med J 2019;132:2185–2191. doi: 10.1097/CM9.0000000000000403. 6. Zhou J. The Comparison of two kinds of Fiberoptic Guided Tracheal Intubation via BlockBuster laryngeal mask airway[D]. Capital Medical University, 2014. 7. Gao X, Liu JH, Chen CM, Wang Y, Wang ZY, Yan CL, et al. Comparison of the supraglottic airway device BlockBusterTM and laryngeal mask airway supreme in anaesthetised, paralyzed adult patients: A multicenter randomized controlled trial. Expert Rev Med Devices 2022;19:649–656. doi: 10.1080/17434440.2022.2130048.