Subglottic airway injury during fiberscope-monitored intubation with a supraglottic airway device: A randomized controlled comparison of three tracheal tubes
Year: 2024
Type: article
Study designs: Randomized Controlled Trial, Clinical Trial
Abstract: Tracheal intubation through a supraglottic airway device (SAD) is recommended for difficult airway management. However, specific tracheal tubes for SAD-guided intubation are not always available in emergencies, necessitating the use of non-specific tubes such as polyvinyl chloride (PVC) and reinforced tracheal tubes. Although successful intubation with these tubes has been reported, clinicians often face difficulties passing them through the SAD, increasing the risk of airway injury even with correct SAD placement. Various strategies, including using different tube types, pretreatment of PVC tubes, SAD position adjustments, reverse loading, and fiberoptic guidance, have been attempted to address this issue. Importantly, few studies to date has assessed the impact of various tracheal tubes on subglottic airway injury during fiberoptic intubation via a SAD. This randomized controlled trial was designed to compare the subglottic airway injury caused by PVC, reinforced, and BlockBusterTM tracheal tubes (Tuo Ren Medical Instrument, Tianjin, China) during fiberoptic-monitored intubation through the SAD BlockBusterTM (Tuo Ren Medical Instrument), a second-generation SAD designed to facilitate blind or fiberoptic-guided intubation. This single-center, prospective, randomized controlled trial was approved by the Beijing Friendship Hospital Ethics Committee (No. 2018-P2-038-01) and registered in the Chinese Clinical Trial Register (ChiCTR1800017598). Adult patients with an American Society of Anesthesiologists physical status of 1 or 2 undergoing elective surgery with general anesthesia and orotracheal intubation were enrolled. Preoperative airway assessment parameters included the interincisor distance, thyromental distance, upper lip bite test result, and modified Mallampati classification. The exclusion criteria were acute respiratory disorders, known or anticipated difficult airways, otorhinolaryngologic surgery, neurosurgery, and surgeries expected to last more than 6 h. The patients were informed about the study details and given the choice to opt out. Written informed consent was obtained from all participants. The PVC tracheal tube (Covidien, Dublin, Ireland) used in this study has an anterior curvature of nearly 130°, resulting in a 35° angle with the horizontal plane after passing through the SAD BlockBusterTM. This is similar to the angle produced by a flexible reinforced tracheal tube (Covidien). By contrast, the BlockBusterTM tracheal tube, specifically designed for use with the SAD BlockBusterTM , creates an angle of 20° [Supplementary Figure 1, https://links.lww.com/CM9/C164]. All three tracheal tubes have high-volume, low-pressure cuffs, and a 7 mm inner diameter was used for patients of both sexes. The patients were randomized with a 1:1:1 allocation ratio using a computer-generated list of random numbers. A research assistant not involved in the study extracted a random code from an opaque envelope before intubation to prepare the corresponding tracheal tube. All patients fasted for 8 h before surgery. In the operating room, an intravenous cannula was placed, and standard monitoring (heart rate, non-invasive blood pressure, and pulse oximetry) was applied. An isotonic crystalloid solution was infused. The size of the SAD BlockBusterTM was selected according to patient weight, following the manufacturer’s recommendations and clinical experience.[1] Size 3, 4, and 5 devices were used for women weighing <70 kg, 70–100 kg, and >100 kg, respectively, and for men weighing <60 kg, 60–90 kg, and >90 kg, respectively. After 3 min of preoxygenation with 100% oxygen, anesthesia was induced using sufentanil (0.3–0.4 μg/kg) and propofol (2 mg/kg) intravenously along with rocuronium (0.6 mg/kg) for neuromuscular blockade. The ease of SAD insertion and the fiberscopic view of SAD positioning were both assessed using a previously described 4-point scale.[2,3] Before tracheal intubation, a flexible fiberscope was inserted into the tracheal tube without advancement beyond its tip.[4] The tracheal tube with the fiberscope was then inserted into the SAD, with the tube’s curvature facing upward, and advanced until the glottis was visible. During fiberscope-monitored intubation, the alignment of the tracheal tube tip with the glottis was continuously observed. Maneuvers to align the tube within the glottis were classified on a 4-point scale: 0, no maneuver; 1, slight withdrawal of SAD; 2, slight withdrawal of SAD combined with tracheal tube rotation (direction depending on the position of the tube tip relative to the glottis or other obstacles); and 3, fiberscope-guided intubation with the fiberscope inserted into the trachea. During advancement of the tracheal tube through the glottis, resistance was evaluated on a 4-point scale.[5] Before recovery from anesthesia, the tube cuff was deflated and the tracheal tube was gently removed through the SAD BlockBusterTM, which remained in place for lung ventilation. A flexible fiberscope was used to check for subglottic airway injury from the glottis to the carina. Two independent, blinded investigators evaluated the fiberscopic video data. The extent of subglottic airway injury was assessed based on previous research.[5] The sample size for this study was calculated based on a pilot study of 30 patients undergoing fiberscope-monitored intubation through the SAD BlockBusterTM with three different tracheal tubes. The mean subglottic airway injury scores were 4.2, 1.3, and 2.6 for the PVC, reinforced, and BlockBusterTM tubes, respectively, with standard deviations of 3.2, 1.5, and 3.6. Using a mean standard deviation of 2.8, we determined that a sample size of at least 55 patients per group was needed to detect a 30% between-group difference in the primary outcome with a type I error rate of 0.05 and power of 0.8. To account for potential dropouts, 60 patients per group were recruited. Statistical analysis was conducted using SPSS 26.0 for Windows (IBM Corp., Armonk, NY, USA). Normally distributed data with homogeneous variance are presented as mean ± standard deviation and were compared using one-way analysis of variance with corrections for multiple comparisons. Non-normally distributed data or those with inhomogeneous variance were compared using the Mann–Whitney U-test with corrections for multiple comparisons. Categorical variables were compared using either the chi-squared test or Fisher’s exact test, as appropriate. A P value of <0.05 was considered statistically significant. Two hundred patients were initially enrolled, but three were excluded because they did not meet the inclusion criteria (n = 1) or declined to participate (n = 2). Additionally, the intervention was discontinued in four patients because of upper airway lesions revealed by fiberscopy during device positioning assessment (n = 3) and major bleeding during surgery (n = 1). Ultimately, data from 193 patients were included in the statistical analysis [Supplementary Figure 2, https://links.lww.com/CM9/C164]. The three groups showed comparable patient characteristics, airway features, and data regarding SAD BlockBusterTM insertion [Supplementary Tables 1 and 2, https://links.lww.com/CM9/C164]. The median (Q1–Q3) subglottic airway injury scores were significantly higher with the PVC tracheal tubes 4.0 (2.0–7.3) than with the BlockBusterTM 1.0 (0–2.0) and reinforced tracheal tubes 1.0 (0–3.3), with no statistically significant difference between the reinforced and BlockBusterTM tracheal tubes. All fiberscope-monitored intubations via the SAD BlockBusterTM were successful within one or two attempts. Significantly fewer maneuvers were required for tracheal tube alignment and resistance to passage with the BlockBusterTM tracheal tube than with the PVC and reinforced tracheal tubes. The intubation time was significantly shorter with the BlockBusterTM tracheal tube than with the PVC and reinforced tracheal tubes [Table 1]. Table 1 - Data of tracheal intubation via the SAD BlockBusterTM in 193 patients intubated with the PVC, reinforced, and BlockBusterTM tracheal tube. Variables Tube type PVC tube vs.reinforced tube PVC tube vs.BlockBusterTM tube Reinforced tube vs.BlockBusterTM tube PVC tube (n = 66) Reinforced tube (n = 62) BlockBusterTM tube (n = 65) Statistics P value Statistics P value Statistics P value 1st intubation attempt success 63 (95.5) 61 (98.4) 65 (100) 0.908* 0.620 3.024* 0.244 1.057* 0.488 2nd intubation attempt success 3 (4.5) 1 (1.6) 0 Maneuvers to align tube with glottis 0.244* 0.965 30.974* <0.001 28.964* <0.001 No 30 (45.5) 29 (46.8) 59 (90.8) Withdrawal of device 28 (42.4) 27 (43.5) 5 (7.7) Withdrawal of device + tube rotation 7 (10.6) 5 (8.1) 1 (1.5) FOB guidance 1 (1.5) 1 (1.6) 0 Resistance of tube passage into trachea 6.328* 0.082 78.380* <0.001 46.960* <0.001 0: no resistance 10 (15.2) 21 (33.9) 60 (92.3) 1: mild resistance 23 (34.8) 15 (24.2) 2 (3.1) 2: moderate resistance 32 (48.5) 25 (40.3) 3 (4.6) 3: sever resistance 1 (1.5) 1 (1.6) 0 Intubation time (s) 48.8 ± 21.9 41.9 ± 19.0 30.2 ± 11.9 NA† 0.110 NA† <0.001 NA† 0.001 Subglottic airway injury score 4.0 (2.0–7.3) 1.0 (0–3.3) 1.0 (0–2.0) –5.231‡ <0.001 –6.625‡ <0.001 1.467‡ 0.143 Data are shown as n (%), mean ± standard deviation, or median (Q1–Q3). PVC: Polyvinyl chloride; SAD: Supraglottic airway device.*Chi-suqared value;†F value; ‡Z value. This study highlights how the type of tracheal tube impacts the severity of subglottic airway injury during fiberscope-monitored intubation through the SAD BlockBusterTM. The BlockBusterTM and reinforced tracheal tubes were associated with significantly less severe subglottic airway injury than was the PVC tracheal tube. Variations in anterior curvatures, material hardness, bevel orientations, and exit angles from the distal aperture of the SAD BlockBusterTM may have contributed to this difference. The PVC tracheal tube is stiff with a right bevel, whereas the reinforced and BlockBusterTM tubes are flexible. The reinforced tube has a milder curvature, while the BlockBusterTM tube is straight with an anterior bevel. Despite having the same exit angle from the SAD BlockBusterTM for both the PVC and reinforced tubes, the stiffer PVC tip is more likely to press against the anterior tracheal wall, increasing the risk of subglottic airway injury. In contrast, the straight BlockBusterTM tube, with its soft half-bullet-like tip, slides more easily into the trachea. Aligning the tracheal tube into the glottis required significantly more maneuvers for the PVC tubes (54.5%) and reinforced tubes (53.2%) than for the BlockBusterTM tubes (9.2%). Fiberscopic observation revealed that the right bevels of the PVC and reinforced tubes frequently became stuck on periglottic structures. To address this, maneuvers such as withdrawing the device, rotating the tube, and using fiberscope guidance were employed, which helped to avoid additional airway injury. Consequently, patients with PVC and reinforced tubes experienced longer intubation times because of the increased need for these maneuvers [Table 1]. This study has several limitations. First, the intubators were not blinded to the tracheal tubes used. Second, patients with anticipated difficult airways were excluded, limiting applicability to such cases. Third, we used the SAD BlockBusterTM, the results of which may differ from those of other second-generation SADs. Fourth, continuous optical observation was used, which might not reflect the outcomes of blind intubation. Finally, as a single-center study, the generalizability of the findings is limited. In conclusion, this study demonstrates that the BlockBusterTM tracheal tube facilitates easier fiberscope-monitored intubation through the SAD BlockBusterTM. If this tube is unavailable, the reinforced tube is a preferable alternative due to its relatively low risk of subglottic airway injury. In contrast, the PVC tube results in the most severe subglottic injury. Acknowledgements The authors gratefully acknowledge Dr. Xue Gao (Beijing Friendship Hospital, Capital Medical University) for his help in the implication of study and all the patients who participated in this trial, and the staff members at participating sites who were not listed as authors but made contributions to this study. Funding This research was supported by grants from the Capital Health Improvement and Research (No. 2018-4-1116) and Beijing Municipal Natural Science Foundation (No. 7214221). Conflicts of interest None.
Source: Chinese Medical Journal
Authors: Kai Su, Shangjun Xu, Haixia Wang, Xintao Li, Fushan Xue, Ming Tian
Institutions: Capital Medical University, Beijing Friendship Hospital
Language: English
Subfield: Anesthesiology and Pain Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $2,000
OpenAlex ID: W4403764529