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Year : 2020  |  Volume : 3  |  Issue : 3  |  Page : 135-139

Evaluation of successful insertion of cobra-perilaryngeal airway and laryngeal mask airway supreme by novice anaesthesiologists: Experience from a teaching institute

Department of Anesthesiology, Critical Care and Pain, Tata Memorial Hospital, Mumbai, Maharashtra, India

Date of Submission09-Sep-2020
Date of Acceptance27-Nov-2020
Date of Web Publication25-Dec-2020

Correspondence Address:
Dr. Tushar Mantri
Department of Anaesthesia, Homi Bhabha National Institute, Tata Memorial Hospital, Parel, Mumbai - 400 012, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/arwy.arwy_37_20

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Background and Aim: Because of its simplicity of insertion, supraglottic airway (SGA) plays an important role in airway management. This study was planned to compare success rate within two attempts at correct placement of Cobra perilaryngeal airway (C-PLA) with laryngeal mask airway Supreme (S-LMA) by novice anaesthesiologists. Secondary objectives included the comparison of time to insertion, ease of insertion and incidence of complications with the device. Methods: The trial was approved by the Institutional Review Board and registered with the Clinical Trials Registry-India (CTRI/2014/08/004913). Fourteen eligible and consenting novice anaesthesiologists were included. Each trainee had to insert each SGA for 5 successful times on the Laerdal airway trainer. After obtaining informed consent, 112 adult patients undergoing elective surgery were randomised to the anaesthesiologists and the SGA device. Induction of general anaesthesia was standardised. Only 2 attempts at insertion of SGA were allowed. Ease of insertion by novices was recorded using a numerical rating scale (NRS) 1 to 10 (10 = easiest). Data were entered into IBM SPSS software version 21.0 (IBM, NY, USA). Categorical data were compared using Chi-square test, while scores were analysed using Mann-Whitney test. Results: There was no difference in success rate between S-LMA (91%) and C-PLA (89%) (P = 0.75). Median time (interquartile range) of insertion for S-LMA was 30 (25–34) seconds and C-PLA was 29 (25–32) seconds (P = 0.53). The incidence of complications was similar for both devices. Novices rated insertion of C-PLA NRS score of 8 (7–9) significantly easier than S-LMA NRS score 7 (5–9) (P = 0.0005). Conclusion: Although the success rate of insertion and time to insertion of C-PLA is similar to S-LMA, novices found C-PLA easier to insert.

Keywords: Cobra perilaryngeal airway, ease of insertion, laryngeal mask airway Supreme

How to cite this article:
Mantri T, Bakshi SG, Sharma KS. Evaluation of successful insertion of cobra-perilaryngeal airway and laryngeal mask airway supreme by novice anaesthesiologists: Experience from a teaching institute. Airway 2020;3:135-9

How to cite this URL:
Mantri T, Bakshi SG, Sharma KS. Evaluation of successful insertion of cobra-perilaryngeal airway and laryngeal mask airway supreme by novice anaesthesiologists: Experience from a teaching institute. Airway [serial online] 2020 [cited 2023 Jun 7];3:135-9. Available from: https://www.arwy.org/text.asp?2020/3/3/135/304846

  Introduction Top

Successful airway management and oxygenation are of utmost importance in anaesthetised patients, emergency services and the pre-hospital scenario.[1],[2] In these situations, inexperienced medical personnel may often be required to manage the airway.[3] Supraglottic airway (SGA) devices are relatively safe and easy to use by operators with limited airway management skills.[4]

Various SGA devices have been developed in the past two decades.[5] This study compares two such devices; the laryngeal mask airway Supreme (S-LMA) (The Laryngeal Mask Co Ltd., Jersey, UK) and Cobra-perilaryngeal airway (C-PLA®; Engineered Medical Systems Inc., Indianapolis, USA). S-LMA, a single-use device with a periglottic alignment, is commonly used in our hospital. Previous studies have shown a first-attempt success rate of 86% with the S-LMA in the hands of novice anaesthesiologists.[3] C-PLA is another SGA with a 90% success rate at insertion.[2] However, insertion of C-PLA by novices has not been studied. We hypothesised that the difference in design can affect the success rate and complications during airway management. Hence, this single-centre, randomised controlled trial was planned to confirm whether there was an advantage at insertion of these 2 types of SGAs, especially when used by novices.

The primary objective of this trial was to compare the success rate of S-LMA and C-PLA by novice anaesthesiologists. Success was defined as correct placement of the device with a maximum of two attempts at insertion. Secondary objectives included the comparison of time to insertion (TTI), ease of insertion and incidence of sore throat with each device.

  Patients and Methods Top

Following approval by the Institutional Review Board, the study was registered with Clinical Trials Registry-India (CTRI/2014/08/004913). The criterion for operator participation was no prior experience with the insertion of either SGA. Out of the 20 new entrants to the department, 14 were found to be eligible for the study. After informed consent for participation was obtained, these 14 anaesthesiologists were enrolled in the trial. All participants underwent training which included a brief presentation about SGAs followed by a demonstration on airway training mannequin. Every trainee had to insert each SGA (S-LMA and C-PLA) under experienced guidance for 5 successful times on the standard airway trainer (Laerdal Medical AS, Stavanger, Norway). The participants were asked not to insert any SGA outside the trial till the study was over. Blinding for the device was not possible. The study was done over 3 months between August and October 2014.

After obtaining informed consent, 112 adult patients belonging to the American Society of Anesthesiologists Physical Status I/II scheduled to undergo short duration orthopaedic or breast surgeries were included in the study. Elderly patients (aged > 65 years), body mass index (BMI) > 35 kg/m2, or patients with anticipated difficult airway were excluded from the study. Patients were randomised both for the SGA to be used and the operator in accordance with a computer-generated randomisation sheet. Allotment concealment was maintained by inserting the slip containing details of SGA to be used in sealed opaque brown envelopes.

All patients underwent routine preoperative anaesthetic evaluation. On the operating table, standard monitoring (consisting of 5-electrode electrocardiogram, noninvasive blood pressure, pulse oximetry and capnography) was established and peripheral intravenous (IV) access was secured. Patients were premedicated with IV fentanyl 2 μg/kg and preoxygenated with 100% oxygen at 6–8 L/min for 3 min using semiclosed circuit. General anaesthesia was induced using IV propofol 2-3 mg/kg and IV atracurium 0.5 mg/kg. Face mask ventilation using oxygen and isoflurane/sevoflurane was continued for 3 min. The appropriate SGA (C-PLA or S-LMA as determined by randomisation) was then inserted by the novice.

The size of the SGA selected was in accordance with manufacturers' recommendations.[6] The TTI was noted as the time between the passage of the device beyond the patient's teeth till the appearance of the first capnograph trace. The device was considered optimally positioned if the capnograph tracing was acceptable with no audible leak and no gastric insufflation.[7] As all patients were paralysed, volume control ventilation was continued and a leak in delivered tidal volume of up to 50 mL was considered acceptable. The novice was given two attempts to insert the SGA, each lasting not more than 60 s. The attempt was discontinued if the saturation dropped below 92%. The number of attempts required (1 or 2) to correctly position the device was recorded. The time for insertion was calculated as the total time for both attempts. After two unsuccessful attempts by the novice, a third attempt at SGA placement was made by the senior anaesthesiologist. If this too were to fail, it was labelled as 'failed' SGA placement. For failed SGA placement, the concerned senior anaesthesiologist secured the airway by a technique of their choice. The success rate was calculated on the basis of the first two attempts by the novice.

Once the SGA was optimally inserted, its position was not altered unless clinically indicated and volume controlled ventilation was set at 6–8 mL/kg using oxygen in nitrous oxide or air in the ratio of 40:60 to maintain a minimum alveolar concentration of 1. An audible leak or loss of tidal volume more than 50 mL at any point during the surgery was considered as displacement of the device. If airway manipulation such as neck extension and refixation of the device did not resolve the problem, it was left to the concerned anaesthesiologist to reinsert the SGA or change over to any other suitable SGA/endotracheal tube. The same would be recorded as a 'complication'. Other complications included bronchospasm, trauma due to insertion (as indicated by presence of blood on removal of SGA).

The operators were asked to grade the ease of insertion of the device on a numerical rating scale (NRS) from 1 to 10 (1= most difficult and 10= easiest).[8],[9] In the postoperative period, patients were followed up for any symptoms of sore throat, dysphagia or hoarseness of voice. This was noted on an NRS scale from 0 to 10 (0 = no sore throat and 10 = severe sore throat).[8],[10]

Sample size calculation

The success rate of S-LMA with two attempts is reported as 86% in novices.[3] Taking the maximum permissible difference, i.e., 100% success with C-PLA with two attempts, a sample size of 110 (55 each group) was needed to detect a difference of 14% in the success rate of insertion between C-PLA and S-LMA with Type 1 error of 0.05 and power of 80%. To ensure equal distribution of each device (4 for each) among 14 novices, 112 patients were included in the study.

Parametric data such as age and BMI were compared using an independent sample t-test. Ease of insertion, sore throat and dysphagia score were analysed using nonparametric Mann-Whitney test. Categorical data were compared using Chi-square test. Results were presented as mean ± SD, or actual numbers. For data not normally distributed (TTI), results were expressed using median with interquartile range (IQR) and a nonparametric test was used for comparison. Data were entered and analysed into IBM SPSS software version 21.0 (IBM, NY, USA). A P value < 0.05 was considered to be statistically significant.

  Results Top

Data from all 112 patients were analysed. The two groups (C-PLA and S-LMA) were comparable [Table 1]. The overall success rate of S-LMA and C-PLA for novices was 91% and 89% respectively (P = 0.75). The first attempt success rate for S-LMA and C-PLA was 73% and 78% respectively [Table 2]. The median value (IQR) for time to insert for S-LMA was 30 (25-34) seconds and C-PLA was 29 (25-32) seconds (P = 0.53) which was not statistically significant. Novices rated C-PLA (NRS 8 with IQR 7-9) as easier to insert as compared to S-LMA (NRS 7 with IQR 5-9) (P = 0.0005). There was no difference in the incidence of complications in the intraoperative period between the two devices [Table 2]. All instances of intraoperative displacement of devices were managed with neck extension and refixation of the device. Reinsertion or change of device was not required in any patient. We found that 6/56 S-LMA group had blood on the device suggestive of trauma. Out of these 6 cases, 5 were inserted successfully on the second attempt. For C-PLA, 8/56 were traumatic insertions. In these 8 cases, 6 were inserted on the second attempt. Mild sore throat was present in 20 patients. No incidence of dysphagia and hoarseness of voice was observed.
Table 1: Demographic data of study groups

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Table 2: Summary of parameters studied

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  Discussion Top

In our study, both devices S-LMA and C-PLA had similar success rates. The incidence of complications was similar. Ease of insertion as rated by novices was significantly better with C-PLA.

S-LMA has been evaluated in several previous studies. The preformed curved tube appears to facilitate insertion and does not require the metal introducer that is recommended for insertion of the ProSeal LMA.[3] Results of other studies suggest that it is readily inserted (90% first attempt; 100% after three attempts) and almost invariably provides a clear airway.[11],[12] We had an overall success rate of 91% in novices with S-LMA in our study. This difference in overall success rate could be influenced by our study design that allowed only 2 attempts while other trials allowed more than 2 attempts. The median (IQR) TTI for S-LMA was 30 (25–34) seconds. This finding was comparable with a previous study where they found time to establish an airway was in the range of 26-40 s.[3]

The C-PLA is a breathing tube with a cuff at the distal end.[2] The inflated cuff helps in sealing off the distal end from the upper airway. In our study, novices found the C-PLA easier to insert in comparison to S-LMA. Reasons for better ease of insertion for the C-PLA could be explained by its smaller anterior-posterior diameter, smaller and stiffer triangular tip, and the fact that the device need not be glided over the hard palate while inserting the device.[13] Previous studies have shown that the learning curve for the C-PLA was shorter than the Classic and Unique LMA.[14]

Trauma during insertion can lead to sore throat postoperatively.[15] The presence of blood on the device upon removal is suggestive of minor trauma associated with device insertion.[16] The incidence of trauma in our study was similar for both SGAs. Although the incidence of sore throat was higher with C-PLA, this was not significant. One of the reasons for a higher incidence of sore throat with C-PLA is that the cobra head of the C-PLA is stiffer than the S-LMA cuff which may abut against periglottic structures if it is pushed inadvertently.[17]

Our study is not without its limitations. Patients included in the trial were planned for elective surgeries and had normal airways. All of them received muscle relaxants before insertion of the SGA. The results of our study may not be applicable to patients with difficult airways or in an emergency surgery, and with spontaneously breathing patients.

In our study, clinical parameters were used for confirmation of the SGA. One can debate that anatomical placement of the SGA was not confirmed using fibreoptic or ultrasound assessment.[18] However, it has been shown that SGA placement can be clinically acceptable though the anatomic placement may be less than perfect.[19] Hence, using a pragmatic model, anatomical confirmation was not included in our study design. Finally, the cuffs of both SGA were filled to the maximum allowable volume. In ideal circumstances, this should have been done using cuff pressure monitoring. For standardising the study design and also as all surgeries were for a short duration, cuff pressure monitoring was not included. Literature suggests that cuff pressure monitoring may not be needed in brief anaesthetics.[20]

  Conclusion Top

We conclude that despite differences in the design of SGAs, S-LMA and C-PLA took the same time and had a similar success rate for insertion. The complication rate was similar for both devices. The C-PLA has the advantage of easy insertion in the hands of novices and hence could be preferred over S-LMA in this operator group.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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Ratajczyk P, Malachowska B, Gaszynska E, Gaszynski T. A randomised comparison between Cobra PLA and classic laryngeal mask airway and laryngeal tube during mechanical ventilation for general anaesthesia. Anaesthesiol Intensive Ther 2013;45:20-4.  Back to cited text no. 2
Howes BW, Wharton NM, Gibbison B, Cook TM. LMA Supreme insertion by novices in manikins and patients. Anaesthesia 2010;65:343-7.  Back to cited text no. 3
Bosch J, de Nooij J, de Visser M, Cannegieter SC, Terpstra NJ, Heringhaus C, et al. Prehospital use in emergency patients of a laryngeal mask airway by ambulance paramedics is a safe and effective alternative for endotracheal intubation. Emerg Med J 2014;31:750-3.  Back to cited text no. 4
Hernandez MR, Klock PA Jr., Ovassapian A. Evolution of the extraglottic airway: A review of its history, applications, and practical tips for success. Anesth Analg 2012;114:349-68.  Back to cited text no. 5
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Gill RK, Tarat A, Pathak D, Dutta S. Comparative study of two laryngeal mask airways: Proseal laryngeal mask airway and Supreme laryngeal mask airway in anesthetized paralyzed adults undergoing elective surgery. Anesth Essays Res 2017;11:23-7.  Back to cited text no. 7
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  [Table 1], [Table 2]


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