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ORIGINAL ARTICLE
Year : 2022 | Volume
: 23
| Issue : 2 | Page : 118-124
Comparative evaluation of intubating laryngeal mask airway with fiberoptic bronchoscopic intubation in anticipated difficult airway: A randomized controlled study
Neelakshi Koul, Vinod Bala Dhir, Nitin Choudhary, Jyoti Singh, Deepak Kumar Nohwar, Mohandeep Kaur
Department of Anaesthesiology, Atal Bihari Institute of Medical Sciences and Dr. Ram Manohar Lohia Hospital, New Delhi, India
Correspondence Address:
Dr. Jyoti Singh
C-176, Sarita Vihar, New Delhi
India
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/TheIAForum.TheIAForum_37_22
Background: Management of difficult airway remains a cornerstone of anesthesiology requiring constant probe into newer devices challenging set gold standards. Hence, we compared the effectiveness of intubating laryngeal mask airway (ILMA) with flexible fiberoptic bronchoscope (FOB) in anticipated difficult airway.
Aims: The aim of this study was to compare and evaluate ILMA and FOB for tracheal intubation in patients with anticipated difficult airway.
Settings and Design: The study design involves comparative randomized study.
Materials and Methods: Fifty patients undergoing elective surgery under general anesthesia with anticipated difficult airway (Modified Mallampati Class III/Wilson's Score 6-7) were divided into Group I (ILMA) and Group F (FOB). Primary outcomes, i.e., ease of intubation (number and duration of attempts) and success rate; and secondary outcomes, i.e., hemodynamic parameters and adverse events were noted.
Results: Both the groups were comparable in age, gender distribution, body mass index, and type of surgery. The number of attempts required and hemodynamics changes were similar in both groups. ILMA required lesser time, i.e., 59.76 s versus FOB, i.e., 109.88 s in the first attempt (DA1) and 62.67 s for Group I versus 120.86 s for Group F in the second attempt (DA2), being statistically significant. ILMA showed higher adverse event rate versus FOB; however, the difference was statistically insignificant.
Conclusions: ILMA is an effective alternative to FOB in patients with anticipated difficult airway with respect to ease of intubation, with similar hemodynamic stability, success rate, and adverse events.
Anticipated difficult airway, fiberoptic bronchoscope, intubating laryngeal mask airway
Oxygenation and ventilation are the basis of sustaining life; hence, maintaining a patent airway is of utmost importance for an anesthesiologist when general anesthesia is administered. Till date, the cuffed endotracheal tube (ETT) is considered the gold standard for providing a safe glottic seal, and over a period of time, new airway devices have been added to the anesthesiologist's armamentarium.[1]
The incidence of difficult airway in the anesthesia literature ranges from 0.4% to 8.5% of elective intubations.[2]”Cannot intubate, cannot ventilate” is the anesthesiologist's worst nightmare, but fortunately, the incidence is just 1–2 in 10,000 cases.[3] However, anesthesia-related deaths that are due to the inability to mask ventilate or intubate account for 28% of the cases.[4]
The flexible fiberoptic bronchoscope (FOB) introduced in the 1960s has been the preferred instrument in difficult airway management for many years for visualizing airway structures in patients either awake or under general anesthesia for diagnostic and therapeutic purposes. It can be used as both initial management or as a backup technique after direct laryngoscopy has been unsuccessful. The need for fiberoptic intubation may be foreseen based on a history of difficult intubation and various anatomic and anthropometric attributes. It may also be indicated for congenital deformities of the head and neck, cervical spine instability, anatomic malformations of the mandible or larynx, and a history of head, neck, and spine trauma.[5]
The advantages of using FOB are that it is flexible and steerable allowing continuous visualization of the oral or nasal route and visual confirmation of the depth of intubation on withdrawal.[6] It causes minimal trauma and does not need three axes (oral, pharyngeal, and laryngeal) alignment.[7]
Supraglottic airway devices have emerged as a standard fixture in airway management protocol, filling a niche between the facemask and tracheal tube in terms of both anatomical position and degree of invasiveness. A modification of the laryngeal mask airway, the intubating laryngeal mask airway (ILMA), is a device specifically designed to act as a blind intubation guide and an effective ventilatory device in patients with normal as well as abnormal airway. The ILMA facilitates tracheal intubation with a better insertion and intubating characteristics in contrast to the standard LMA.
There is the dearth of literature comparing ILMA- and FOB-guided intubation in anticipated difficult airway patients. The existing studies show variation in results with regard to the duration of intubation, number of attempts, hemodynamic changes, and adverse events during the procedure. Hence, we conducted this study with an aim of drawing an analogy between both the devices where our primary objective was to compare the ease of intubation (by duration and number of attempts required) and secondary objectives being the success rate, hemodynamic changes, and adverse events noted with both the devices.
Materials and MethodsThis study was conducted in a tertiary care center after approval by the Institutional Review Board and Institutional Ethics Committee (TP [MD/MS] [6/2017]/IEC/PGIMER/RMLH/691/17]). ASA Grade I and II patients of either sex, aged 18 years and above, posted for elective surgery under general anesthesia with an anticipated difficult airway defined by Modified Mallampati (MMP) Class III/Wilson's Score 6–7 patients [Table 1] and [Table 2] with interincisor distance ≥30 mm were included in our study.
Patients whose cervical spine is fixed in flexion, risk of gastric aspiration, morbid obesity (body mass index [BMI] >40), gastroesophageal reflux disease, diabetes mellitus, or history of allergy to drugs used in the study were excluded.
Preanesthetic evaluation was conducted after taking written informed consent from the patient. MMP class and interincisor distance were noted. Patients were premedication with tablet alprazolam 0.25 mg night before the surgery. Standard ASA monitors were attached in the operation theater and baseline vital parameters such as heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) were recorded. Patients received injection glycopyrrolate 0.2 mg, injection midazolam 0.03 mg/kg, and injection fentanyl 2 μg/kg intravenously, followed by preoxygenation with 100% oxygen for 3 min using the appropriate size face mask. Anesthesia was induced with injection propofol 2 mg/kg intravenous (IV), and injection vecuronium bromide 0.1 mg/kg IV was given after facemask ventilation was established. Intubation was carried out after 3 min, with appropriate-sized cuffed ETT using the device undertaken for the study by an experienced anesthesiologist. If airway could not be secured using ILMA or FOB after three attempts, failure of insertion was declared. Each attempt was terminated after 3 minutes or a fall in oxygen saturation up to 90%, whichever was earlier. If three attempts were unsuccessful, either an alternative device was inserted or the procedure was discontinued and the patient was awakened.
Group F
FOB was inserted after an initial equipment check, cleaning, and focusing of the lens. The insertion cord and the outer surface of the ETT were lubricated with lignocaine gel 2%. The ETT was mounted on the flexible bronchoscope, and an oral airway (Ovassapian airway) was used to prevent damage to FOB. The scope was maneuvered in three planes and targets such as the epiglottis, vocal cord, tracheal cartilages, and carina were kept in the center of view. The ETT was advanced into the trachea over the scope once the carina was visible, and FOB was removed gently looking for the position of the ETT.
Group I
With the head in the neutral position, the intubating LMA (LMA FastrachTM) was held by its handle parallel to the patient's chest. After carefully positioning to lie flat against the hard palate, the ILMA was slid backward, following the curve of the rigid airway and the cuff inflated with air. An appropriate-sized ETT was introduced with the longitudinal black line on the tube facing the handle of the ILMA and was just passed beyond 15 cm or the transverse line which corresponds to the point at which the ETT beveled tip is about to enter the mask aperture.
After intubation, placement was confirmed by chest auscultation and capnography.
Anesthesia was maintained using oxygen, nitrous oxide (50:50), intermittent vecuronium, and either sevoflurane or isoflurane with a tidal volume of 6–8 ml/kg IBW. The HR, SBP, DBP, MAP, and SpO2 were noted before premedication, preinduction, and thereafter at 1, 3, 5, and 7 min after insertion of ETT. Toward the end of surgery, patients were extubated when all the subjective and objective criteria were fulfilled. Postextubation, any complications such as soft-tissue trauma, sore throat, cough, laryngospasm, and bronchospasm were recorded and treated accordingly.
The primary outcome (ease of insertion) was noted in the form of number of attempts and duration of each attempt (measured from the start of group-specific procedure to the end-tidal CO2 curve reappeared on the monitor). Another parameter noted was the success of insertion, which was confirmed by the detection of end-tidal CO2 on the capnogram.
Secondary outcomes, i.e., HR, SBP, DBP, and MAP were measured at baseline, before induction (before premedication), before intubation, and 1, 3, 5, and 7 minutes after intubation along with adverse events.
The data were entered in the MS EXCEL spreadsheet and analysis was performed using the Statistical Package for the Social Sciences (IBM SPSS, Version 21.0. Armonk, NY, USA).
Statistical analysis
With reference to the previous study by Langeron et al.,[8] it was found that the number of attempts and success rate were comparable in both the groups. Thus, we based our sample size estimation on the duration of attempts. The median duration of attempts was 87 s in the ILMA group and 110 s in the FIB group. The total sample size was set as 25 per group calculated with a power of 90%, an α of 0.05, where the standard deviation of the two groups was assumed 25 s.
Categorical variables were presented in number and percentage (%), and continuous variables were presented as mean ± SD and median. Normality of data was tested by Kolmogorov–Smirnov test. If the normality was rejected, then nonparametric test was used.
Quantitative variables were compared using unpaired t-test/Mann–Whitney test (when the data sets were not normally distributed) between the two groups and paired t-test/Wilcoxon rank-sum test for comparison within the group across follow-up. Qualitative variables were correlated using the Chi-square test/Fisher's exact test. A value of P < 0.05 was considered statistically significant.
ResultsBoth the groups were comparable in age distribution, gender distribution, and BMI with no statistically significant difference between the groups with P = 0.849, 0.569, and 0.385, respectively. Both the groups were comparable in type of surgery with no statistically significant difference with P = 0.675 [Table 3].
Table 3: Comparison of demography, gender, body mass index, and type of surgery in patients of both the groupsThe number of attempts required in patients of both the groups was statistically insignificant on the comparison (P = 0.289) [Figure 1]. A statistically significant difference was found on comparing the time taken for intubation (P < 0.0001) [Figure 2]. Intubation with ILMA required lesser time, i.e., 59.76 s as compared to FOB, i.e., 109.88 s in the first attempt (DA1-duration of 1st attempt). Duration of intubation in the second attempt (DA2) was also statistically significant (P < 0.0001), being 62.67 s for Group I versus 120.86 s for Group F.
Figure 1: Distribution of patients according to number of attempts in both the groups
Figure 2: Comparison of time required for intubation in patients of both the groupsThe success rate of intubation among patients of both the groups was same (100%). The mean baseline HR, i.e., 78.76 bpm in Group F and 79.28 bpm in Group I were comparable. Both the groups showed a similar fall in HR after induction.
At 1 min after intubation, the HR increased by 16.4% and 14.22% above the baseline in Group F and Group I, respectively. The baseline mean SBP was 126.52 mmHg in Group F and 124.2 mmHg in Group F, found to be statistically insignificant. Following induction of anesthesia, there was a fall in SBP by 14.63% in Group F and 11.17% in Group F. At 1 minute after intubation, the percentage increase in SBP in Group F was 4%, whereas in Group I, it was 5% above the baseline value. The baseline mean SBP was 79.56 mmHg in Group F and 80.04 mmHg in Group I. Following induction, there was a decrease of 11% in Group F and 12.4% in Group I. At 1 min after intubation, the percentage increase in DBP in Group F as compared to baseline values was 2.4%, whereas in Group I, it was 3.44%. The baseline mean of MAP was 94.88 mmHg in Group F and 94.36 mmHg in Group I. Following induction of anesthesia, there was a fall of MAP by 12.5% in Group I and 17% in Group F, which was statistically insignificant. At 1 min after intubation, there was a 3.2% increase in MAP in Group F as compared to the baseline value, whereas in Group I, it was 4.7%.
There was no statistically significant difference in HR, SBP, DBP, and MAP between the two groups for the first, 3, 5, and 7 min after intubation, and the difference between the two groups was statistically insignificant. The time taken to reach the maximal stress response was similar in both groups.
Adverse effects noted in the study were laryngospasm/bronchospasm and dental/soft tissue injury. Dental/soft-tissue injury did not occur in Group F versus 12% of patients in Group I. Bronchospasm occurred in 12% of patients in Group F. It was observed that ILMA had a higher rate of adverse events compared to FOB; however, the difference was not statistically significant [Table 4]. The flow of patients enrolled in the study is represented in the CONSORT flow diagram [Figure 3].
Figure 3: CONSORT Flow Diagram showing the division of patients at every stage of the randomized controlled trial Discussion The key findings of our study suggest:
The duration of intubation with ILMA was lesser compared to FOB-guided intubationThe number of attempts required was lesser compared to intubating laryngeal mask airway, but statistically insignificantRate of success and hemodynamic stability were comparable with both the devicesILMA is an effective alternative to FOB-guided intubation in difficult airway patients with respect to ease of intubation, similar hemodynamics, and adverse events.Airway management is a fundamental skill and responsibility of the anesthesiologist. In the past, anticipated difficult airway was presented as a challenging clinical problem with a limited number of suboptimal solutions.
With the introduction of FOB in the 1960s, the scenario revolutionized, and since then, it proved to be an indispensable tool used for the management of difficult airway. Serving both diagnostic and therapeutic purposes, its use in patients with anticipated difficult intubation significantly reduces the number of complicated intubations, trauma, and postoperative upper airway edema.[9],[10]
The next breakthrough in difficult airway management appeared in 1981 when Dr. Archie Brain[11] developed the laryngeal mask airway, a family of supraglottic devices, among which some are still in use while others dwindled into oblivion. However, ILMA manifested to be a very effective means of securing difficult airway with the advantage of blind intubation.
In our study, the two groups were comparable with respect to age, gender, and BMI, and no statistically significant difference was found with respect to the above parameters in both the groups, thus eliminating their confounding effect.
Of 25 patients in Group F, 18 (72%) patients were intubated in the first attempt, 7 (28%) in the second attempt, and none required the third attempt, whereas in Group I, 22 (88%) patients were intubated in the first attempt, 3 (12%) in the second attempt, and none required the third attempt. Hence, it was found that ILMA required a lesser number of attempts than FOB, but the difference was not statistically significant (P < 0.289). The reason behind this could be that ILMA insertion is a blind technique with a short learning curve, acting as an effective ventilating device and an intubation guide for routine and difficult airway patients; whereas fiberoptic intubation requires more technical skill and hand-eye coordination. Thus, ILMA is more appropriate to be used in emergencies, even by paramedic staff than FOB.
Similar findings were observed in a study conducted by Agrò et al.,[12] in which ILMA was successfully inserted at the first attempt in all 110 patients. Another study conducted by Chan et al.[13] on 100 patients concluded that 50% of patients were successfully intubated in the first attempt, 42% in the second, and 5% in the third attempt. In the study conducted by Langeron et al.,[8] the first insertion attempt success was found to be lower in the ILMA group (34 patients) versus FOB group (31 patients), but not statistically significant as in our study.
The overall success rate for intubation was 100% with both devices. Similar high success rates for ILMA were found in studies conducted by Agrò et al.,[12] and also for awake ILMA- versus FOB-guided intubation in studies done by Dhar et al.[14] and Langeron et al.[8] Success was improved by pulling the metal handle of the ILMA toward the intubator in an extension maneuver if intubation failed in the first attempt which correlated with the study done by Chan et al.[13] Maintaining the head of the patient in the neutral position increased the success rate in the study done by Caponas.[15]
The mean time required for tracheal intubation with ILMA (Group I) in the first attempt was 59.76 s and 62.67 s in the second attempt, which was lesser compared to FOB-guided tracheal intubation (Group F), in which the first attempt required 109.88 s, the second attempt 120.86 s, and this difference was statistically significant (P < 0.0001), which was similar to results found in the study conducted by Langeron et al.[8] among patients with anticipated difficult airway. The mean duration of intubation with FOB was found 110 s that was longer than that by intubating LMA which was 87 s. Furthermore, in the study conducted by Choyce et al.[16] and Dhar et al.,[14] they found that tracheal intubation using ILMA required lesser time compared to using an LMA and FOB, respectively. Significantly longer intubation time in the FOB group could be explained by the loss of pharyngeal muscle tone after muscle relaxation where the tongue and epiglottis tend to fall toward the posterior pharyngeal wall, decreasing the pharyngeal space, thus making visualization difficult. On the other hand, ILMA allows the ETT to lift the epiglottis with the help of the epiglottis elevating bar making intubation easier.
A study done by Chalam and Gupta[17] showed contrasting results to our study where the mean time duration for intubation in the ILMA group was 38.1 s versus 29.8 s in the FOB group. These differences in studies may be attributed to the technical expertise of a particular anesthesiologist with one device over the other.
The mean baseline parameters, the trend of mean HR, mean SBP, mean DBP, and mean MBP within patients of each group were found to be statistically insignificant at different time intervals when compared to baseline. There was a drop in all the parameters at preinsertion, which could be attributed to the use of premedication and induction agents. Studies conducted by Dhar et al.[14] and Chalam and Gupta[17] also concluded hemodynamic changes to be comparable in each group.
Adverse events in total were witnessed less, i.e., 8% of patients in Group F against 16% of patients in Group I, being statistically insignificant. In Group I, 4% and 12% of patients had dental/soft-tissue trauma and laryngospasm/bronchospasm, respectively, as compared to Group F, where in 12% had dental/soft-tissue trauma, but none had laryngospasm. In a similar study by Chalam and Gupta,[17] they recorded more adverse effects with ILMA than FOB, but none were statistically significant. However, in a study conducted by Langeron et al.,[8] statistically significant adverse effects (oxygen desaturation <90% and bleeding) occurred in the FOB group than ILMA group (18% vs. 0%), which might be due to awake intubation with induction agents and local anesthetics without muscle relaxation.
Limitations of this study include the small sample size and the fact that the results of this study cannot be extrapolated to patients with an unanticipated difficult airway or to anesthesiologists with differing levels of training in ILMA and FOB techniques. Thus, the level of investigator experience should also be taken into account.
Since its first use in the 1960s in the OT setting, FOB-guided intubation has been considered a gold standard in difficult airway. Newer equipment like the ILMA (1980s) needs to be evaluated and compared to FOB, so that they can be used interchangeably while handling an anticipated difficult airway situation.
Intubation skills with the ILMA are easier to acquire when compared to FOB, which has a steep learning curve. Furthermore, ILMA is a more feasible option to secure the airway during an emergency situation compared to FOB, which becomes difficult to navigate in the event of trauma hampering adequate visibility.
ConclusionsILMA-guided tracheal intubation is an effective alternative to FOB-guided tracheal intubation in patients with anticipated difficult airway during general anesthesia with respect to ease of insertion (number of attempts required and duration of attempt); however, with respect to hemodynamic stability, the success rate of intubation, and adverse events, both the devices were similar.
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Conflicts of interest
There are no conflicts of interest.
References
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