|Year : 2019 | Volume
| Issue : 2 | Page : 81-88
Comparative performance of I-gel and laryngeal mask airway supreme: A randomised, controlled study
B Uma1, Uttam Chand Verma2, Rajesh Singh Rautela3, Anjali Kochhar4
1 Department of Cardiac Anaesthesia, Max Smart Superspeciality Hospital, Delhi, India
2 Department of Anaesthesia and Critical Care, Maulana Azad Medical College, Delhi, India
3 Department of Anaesthesia and Critical Care, University College of Medical Sciences, Delhi, India
4 Department of Anaesthesia and Critical Care, VMMC and Safdarjung Hospital, Delhi, India
|Date of Web Publication||28-Aug-2019|
Dr. B Uma
Max Smart Superspeciality Hospital, Press Enclave, Mandir Marg, Saket, Delhi - 110 017
Source of Support: None, Conflict of Interest: None
Patients and Methods: In a randomised, controlled study, we compared the performance of i-gel against the laryngeal mask airway (LMA) Supreme in 60 anaesthetised and paralysed patients for non-laparoscopic surgical procedures. Results: The primary outcome measure, the oropharyngeal leak pressure (OLP), was significantly higher for i-gel as compared to LMA Supreme (mean [standard deviation] 26.23 [4.09] vs 21.73 [3.19] cm H2O, respectively; P < 0.0001). Twenty-four (80%) of LMA Supreme and 22 (73.3%) of i-gels were successfully placed with similar ease on the first attempt to achieve an effective airway. The time taken for inserting the LMA Supreme was significantly less than that required for i-gel (mean [SD] 7.89 [1.6] s vs 11.48 [4.86] s, respectively; P < 0.0001). Gastric tube insertion was easier in the LMA Supreme as compared to i-gel (96.7% vs 63.3% respectively; P < 0.0001). There were no differences in the positioning of the supraglottic airway devices as evaluated fibreoptically. Postoperative sore throat was comparable with both devices. Conclusion: We conclude that while both these devices are suitable for routine use during maintenance of anaesthesia, a significantly higher OLP might provide the i-gel an advantage in this respect.
Keywords: I-gel, laryngeal mask airway Supreme, oropharyngeal leak pressure, supraglottic airway device
|How to cite this article:|
Uma B, Verma UC, Rautela RS, Kochhar A. Comparative performance of I-gel and laryngeal mask airway supreme: A randomised, controlled study. Airway 2019;2:81-8
|How to cite this URL:|
Uma B, Verma UC, Rautela RS, Kochhar A. Comparative performance of I-gel and laryngeal mask airway supreme: A randomised, controlled study. Airway [serial online] 2019 [cited 2019 Oct 20];2:81-8. Available from: http://www.arwy.org/text.asp?2019/2/2/81/265614
| Introduction|| |
The practice of airway management has become more advanced and refined with the introduction of supraglottic airway devices (SADs). The advantages of SADs include avoidance of laryngoscopy for placement, less invasiveness of the respiratory tract, better patient tolerance, increased ease of placement, improved haemodynamic stability during emergence, less coughing, less sore throat, hands-free airway maintenance and easier placement by less experienced personnel. The American Society of Anesthesiologists' Task Force on Management of the Difficult Airway suggests considering the use of SADs when intubation problems occur in patients with a previously unrecognised difficult airway, especially in a “cannot ventilate, cannot intubate” situation.
Design developments, research findings and clinical experience have resulted in expansion of the use of SADs beyond their original indication in low-risk patients. The i-gel and laryngeal mask airway (LMA) Supreme are two second generation SADs introduced more than a decade ago.
The i-gel (Intersurgical Ltd, Wokingham, Berkshire, UK) is equipped with a cuff that is filled with a medical grade thermoplastic elastomer gel (styrene ethylene butadiene styrene) that does not require inflation. The tube section is rigid proximally and acts as an integral bite block. The tube is elliptical in cross section and is curved longitudinally. A drain tube runs within the device and exits next to the 15 mm airway connector.
The LMA Supreme (LMA-S, Intavent Orthofix, Maidenhead, UK) combines the features of LMA Fastrach (curved shaft), the LMA Proseal (gastric access tube) and LMA Unique (single use device). The oesophageal drain tube with a moulded cuff tip avoids folding over during device placement. A larger, precurved cuff contributes to optimal laryngeal positioning and improved seal. The design of the cuff bowl includes patented 'fins' that are designed to prevent occlusion of the airway by the epiglottis.
Our review of literature revealed limited studies related to these devices. The i-gel and LMA Supreme have been compared with the classic LMA and Proseal LMA (PLMA) previously. Both these devices had favourable outcomes over the classic LMA., The results with the PLMA were comparable., However, we came across limited studies comparing the i-gel with LMA Supreme.,, We, therefore, planned a prospective, randomised controlled study comparing LMA Supreme and i-gel in anaesthetised patients during controlled ventilation.
| Patients and Methods|| |
After approval from the Institutional Review Board and informed written consent, 60 patients aged between 18 and 65 years of either gender belonging to the American Society of Anesthesiologists Physical Status I and II, scheduled for elective surgery (such as open cholecystectomy, upper limb orthopaedic procedures, fibroadenoma breast, gynaecological procedures and urologic procedures) under general anaesthesia were recruited for this study. We excluded anticipated or known difficult airway, pregnant females, patients with BMI >30 kg/m2 or history of gastroesophageal reflux disease.
Routine preanaesthetic examination was performed; modified Mallampati grade and the thyromental distance were noted. Patients were randomly allocated into two groups of 30 patients each (using sealed envelope technique) to receive either the LMA Supreme or the i-gel for airway management during general anaesthesia. The recommended pre-use check for the airway devices was performed before use., Both devices were lubricated using a water-based lubricant over the tip and the posterior surface. The patient's head was supported on a firm headrest and was placed in a neutral position. After preoxygenation with 10 L/min for 3 min, anaesthesia was induced using fentanyl 1 μg/kg intravenously and propofol 1.5-2 mg/kg intravenously. A bolus dose of rocuronium 1 mg/kg was then given to produce muscle relaxation. The lungs were manually ventilated using a facemask with N2O 66% and 1.2% isoflurane in oxygen. After a waiting period of 1 min, the i-gel or LMA Supreme was inserted as per the recommended technique. Size selection of the i-gel depended on the patient's weight: size 3 for patients weighing 30-60 kg, size 4 for those weighing between 50 and 90 kg and size 5 for those weighing over 90 kg. Size selection of LMA Supreme was also based on the patient's weight: size 3 for patients weighing between 30 and 49 kg, size 4 for those weighing between 50 and 69 kg and size 5 for those weighing over 70 kg. Following insertion of the LMA Supreme, air was introduced into the cuff till the intracuff pressure measured using cuff inflation manometer (VBM, Medizintechnik, Sulz, Germany) was 60 cm H2O. All insertions were performed by anaesthesiologists with extensive experience in using these supraglottic devices (≥100 i-gel insertions; ≥100 LMA Supreme insertions).
After insertion of the airway, the breathing system (of Datex Ohmeda Aestiva 5) was connected to the device. Successful placement of the device was confirmed by the presence of smooth chest rise and fall, and a square wave pattern on capnogram during ventilation. If there was any difficulty encountered during device placement, manoeuvres such as extension/flexion of the neck, chin lift, jaw thrust, gentle pulling or pushing of the device, reinsertion or changing to a more appropriate size of the device was performed. The number of manipulations required for successful placement was recorded. A maximum of three attempts were allowed for placement of the SAD. Each 'attempt' was defined as reinsertion of the airway device into the mouth. If successful insertion or ventilation was still not achieved after three attempts, the procedure was abandoned and the patient was intubated.
The time for successful insertion was measured from the time the anaesthesiologist picked up the SAD until the connection to the breathing circuit. Bubble test was performed to confirm position of the device. A gastric tube of appropriate size was inserted through the drain tube; 12 FG gastric tube was planned for use in i-gel sizes 3 and 4, and a 14 FG gastric tube was planned for i-gel size 5. A 14 FG gastric tube was used for all sizes of LMA Supreme as per the manufacturer's guidelines. Correct placement of the gastric tube was assessed by suction of gastric fluid or detection of injected air by auscultation over the epigastrium. Success and number of attempts of insertion were recorded. Insertion difficulty was graded by the anaesthesiologist as 1, 2 or 3 (easy, difficult or impossible, respectively).
Oropharyngeal leak pressure (OLP) was measured by manometric stability test as well as auscultatory test. The fresh gas flow was adjusted to 3 L/min and the adjustable pressure limiting valve of the circle system was completely closed. Airway pressure was not allowed to exceed 40 cm H2O and the airway pressure at which the dial of the anaeroid manometer reached stability was noted i.e., airway pressure at which the leak was in equilibrium with the fresh gas flow.
A 3.8 mm flexible fibreoptic bronchoscope (LF-2 Olympus, India) was then passed through the airway tube. With the tip of the bronchoscope positioned at the distal end of the airway tube, the best fibreoptic score was recorded using a standard scoring system as described by Brimacombeand Berry.
- Grade 1: Cords not seen
- Grade 2: Cords plus anterior epiglottis seen
- Grade 3: Cords plus posterior epiglottis seen
- Grade 4: Only cords seen.
Anaesthesia was maintained using 1%-2% isoflurane and nitrous oxide (66%) in oxygen to maintain a MAC of 1-1.2. MAC was maintained with vapour analysis using the infrared analysers of Datex Ohmeda S5. Patients were placed on volume-controlled, time-cycled ventilation after adequate muscle relaxation with a tidal volume of 7 mL/kg and respiratory rate adjusted to maintain normocarbia. End-tidal CO2 as well as spirometric data which included peak airway pressure, mean airway pressure, inspired tidal volume and expired tidal volume were recorded at 15 min intervals throughout the procedure. During the maintenance of anaesthesia, ventilation quality with the LMA in position was scored on a 4-point scale: (1) optimal ventilation defined as normal chest expansion and airway pressure without air leak; (2) air leak or abnormal airway pressure necessitating manoeuvres (adjusting insertion depth, head-neck position, or cuff volume); (3) reinsertion of the LMA required; and (4) failed ventilation after two attempts. Additional analgesics and increments of muscle relaxant were given at the discretion of the attending anaesthesiologist.
Towards the end of the surgery, the OLP and the best fibreoptic score were recorded again maintaining the same depth of anaesthesia. The neuromuscular blockade was reversed with intravenous (IV) neostigmine 0.05 mg/kg and IV glycopyrollate 0.008 mg/kg. With the return of protective airway reflexes and adequate spontaneous breathing, the SAD was removed and inspected for the presence of blood.
Haemodynamic variables including heart rate, systolic blood pressure, diastolic pressure and mean arterial pressure were recorded at baseline, 1 min postinduction and at 1 and 5 min following insertion of the SAD. Complications with each device such as bronchospasm and blood on the device at the time of removal were noted. All patients were followed up at 2 h and 24 h postoperatively for complications such as sore throat, dysphonia, dysphagia, neck, jaw or ear pain. Complications, if present, were graded as mild, moderate or severe. The severity was assessed using a structured interview in the recovery room and recorded by a blinded observer.
The primary outcome of this study was to compare the OLP of LMA Supreme and i-gel. Based on the results of a previous study, the LMA Supreme has an OLP of 25.6 ± 5.1 cm H2O. To detect a difference of 10%, prospective power analysis at 90% power and 0.05 level of significance (two sided), a sample size of 30 patients was required in each group. Therefore, we studied a total of 60 patients. We used SPSS 16.0™ statistical software (SPSS Inc., Chicago, Illinois, USA). Data were tested for normality using the Kolmogorov-Smirnov test. Student's t-test was used to analyse the parametric variables. OLPs at time points was analysed using ANOVA for repeated measurements with post hoc Bonferroni-Holm correction. Changes of parameters within each group over time were analysed using one-way repeated analysis of variance with Tukey's test for multiple comparisons. Results were expressed as mean ± standard deviation. A P < 0.05 was considered statistically significant.
| Results|| |
Sixty patients were recruited and there were no dropouts. Their baseline characteristics and preoperative airway morphology are summarised in [Table 1].
|Table 1: Demographic variables in study groups (mean±standard deviation) or (numbers)|
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About 80% (24/30) LMA Supreme and 73.3% (22/30) i-gels were successfully placed with similar ease on the first attempt to achieve an effective airway. 10% (3/30) of LMA-S and 20% (6/30) of i-gels were inserted successfully in the second attempt [Table 2]. In 8 patients, reinsertion of i-gel was needed. While the same size device was reinserted in 4 of them, 3 required change of device to a larger size and 1 needed a change to a smaller size. Six patients in the LMA Supreme group needed reinsertion with one of them requiring change to a smaller size.
|Table 2: Clinical performance of supraglottic airway devices (mean±standard deviation) or (numbers)|
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The time taken for device insertion in the LMA Supreme group (7.89 ± 1.6 s) was significantly less than that required in the i-gel group (11.48 ± 4.86 s) (P < 0.0001) [Table 2]. Appropriate size gastric tube was inserted in the LMA Supreme as recommended by the manufacturer and it was easy to insert the same in 96.7% of cases (29/30) except for one where difficulty was encountered. In the i-gel group, insertion was easy in 63.3% (19/30) and difficult in 36.6% (11/30) of cases. The gastric tube insertion was much easier through the LMA Supreme (P < 0.0001). The intracuff pressure, which was set at 60 cm H2O for the LMA Supreme group at the start of surgery, increased to 84.07 cm H2O by the end of surgery (P < 0.0001).
The mean OLP in the LMA Supreme group (21.73 cm H2O and 23.17 cm H2O at the beginning and end of surgery, respectively) was significantly lower than in the i-gel group (26.23 cm H2O and 27.2 cm H2O at the beginning and end of surgery respectively) (P < 0.0001) [Table 3].
|Table 3: Oropharyngeal leak pressures of the i-gel and laryngeal mask airway Supreme at the beginning and end of surgery (mean±standard deviation)|
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With regard to fibreoptic view of laryngeal structures, 22 patients in the i-gel group had grade 4 view, 7 had grade 3 view and 1 had grade 2 fibreoptic view in the beginning. In the LMA Supreme group, 28 patients had grade 4 view and 2 had grade 3 view which did not change by the end of surgery. At the end of surgery, 25 patients in i-gel group had grade 4 view and 5 had grade 3 view [Table 4].
|Table 4: View of glottic structures as obtained by fibreoptic evaluation at the beginning and end of surgery|
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The haemodynamic consequences of airway placement between the two groups were similar [Figure 1], [Figure 2], [Figure 3], [Figure 4]. There was no difference between the two groups in ETCO2, peak airway pressure, mean airway pressure, inspired tidal volume and expired tidal volume as measured by the ventilator.
|Figure 1: Mean (standard deviation) of heart rate measured at varying time intervals with laryngeal mask airway Supreme and i-gel|
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|Figure 2: Mean (standard deviation) of systolic blood pressure measured at varying time intervals with laryngeal mask airway Supreme and i-gel|
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|Figure 3: Mean (standard deviation) of diastolic blood pressure measured at varying time intervals with laryngeal mask airway Supreme and i-gel|
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|Figure 4: Mean (standard deviation) of mean arterial pressure measured at varying time intervals with laryngeal mask airway Supreme and i-gel|
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One patient in each group developed intraoperative bronchospasm which was managed effectively. The device was blood stained in one patient in the i-gel group and in three patients in the LMA Supreme group (P = 0.612). Postoperative complication rates were low and comparable between the groups.
| Discussion|| |
Under the conditions of our study, the mean time for i-gel insertion was 11.48 s and it was 7.89 s for the LMA Supreme. The preformed shape and the thin wedge shaped leading edge of the LMA Supreme could have aided in easier and faster placement as well as higher success rate of insertion at first attempt as compared to the i-gel. Compared to the PLMA, LMA Supreme does not require the metal introducer. Torque applied to the airway connector translates to the mask and allows it to rotate easily. The bulky design of the i-gel not only made insertion time longer but also resulted in a broader variance (range 5.8 to 20.6 s) that reinforces our observation that the insertion of i-gel was less predictable compared to the LMA Supreme (range 5.1-10.8 s).
We encountered difficulty in inserting a gastric tube through the i-gel based on the manufacturer's guidelines i.e., 12 FG gastric tube for i-gel size 3 and 4. We inserted size 10 FG gastric tube in i-gel size 3 and 12 FG in i-gel size 4. It was inserted with ease in 19 patients and with difficulty in 11 patients. Our findings are consistent with those of Teoh et al. who also reported difficulty in insertion of 12 FG gastric tube through the i-gel size 3 due to the smaller aperture of the gastric access port. The drainage tube in the LMA Supreme has a larger orifice than that in the i-gel. It is not yet known whether this is significant, but cases have been reported of the failure of the i-gel to protect against aspiration. Of note, even if protection is incomplete, the presence of a drain tube allows early identification of regurgitation and prompts initiation of steps to prevent or minimise aspiration. We had no episodes of regurgitation or aspiration in any of our cases in both the groups.
The OLP is commonly performed to quantify the quality of seal of a supraglottic airway. This has been commonly used as a model in LMA studies to denote the successful placement of the airway. The mean OLP achieved with the i-gel was more than that with the LMA Supreme. The i-gel is made of thermoplastic elastomer which is designed to anatomically fit the perilaryngeal and hypopharyngeal structures without the use of an inflatable cuff. This may explain the reason for the improved seal with the i-gel. The lower OLP of the LMA Supreme is probably related to the less elastic and less mouldable property of the polyvinyl chloride single cuff.
Literature review of the OLP of the LMA Supreme as compared to the i-gel reveals conflicting results. A randomised comparison of the LMA Supreme and the i-gel in 90 patients showed that the mean OLP with the LMA Supreme (25.6 cm H2O) was higher than the i-gel (20.7 cm H2O). This study evaluated spontaneously breathing patients which may have acted as a confounding factor. In another study by Theiler et al., the OLP between the i-gel and the LMA Supreme was found to be comparable (27 ± 9 cm H2O vs 26 ± 8 cm H2O). These authors, however, compared the use of these devices in simulated difficult airway. Teoh et al. found no difference in the OLP between the LMA Supreme (26.4 cm H2O) and the i-gel (25 cm H2O) when comparing these devices during laparoscopic surgeries. Cook et al. evaluated the LMA Supreme and found the median OLP to be 24 cm H2O. The median seal pressure with the i-gel in a study by Francksen et al. was 24 cm H2O.
Anatomical positioning of the i-gel and the LMA Supreme appears to compare well with other SADs. Filling of the anterior neck occurred with all insertions and the device stayed in the midline. The fibreoptic view depends on the hypopharyngeal position of the SAD and whether the epiglottis is folded down during insertion or not. On fibreoptic examination, a grade 4 view was obtained in 73.3% of cases of i-gel. The LMA Supreme had a better fibreoptic view with 93.3% of cases having a grade 4 view. In addition, the fibreoptic view at the end of the surgery did not change, indicating that the LMA Supreme remains in its initial position with the help of its distinct fixation system. It is important to note, however, that the better fibreoptic view with the LMA Supreme does not equate to it being well adapted for use as a conduit in difficult airway management or failed intubation, as the drain tube of the LMA Supreme lies within the airway tube and divides it into two lateral channels of small diameter. The combination of these narrow channels and the curvature of the stem of the LMA Supreme mean that passage of even a 4.5 mm fibreoptic bronchoscope is awkward, and the use of an Aintree intubation catheter may fail. On the other hand, the i-gel has been successfully used as a conduit in difficult airway management and failed intubation.,
In our study, we chose the size of the i-gel airway according to the manufacturer's recommendations for weight criteria: size 3 for 30-60 kg, size 4 for 50-90 kg and size 5 for 90 kg and more, but some degree of overlap existed. We inserted a smaller size i-gel (size 3) in two of our patients who weighed more than 50 kg. In four patients weighing <50 kg we inserted a size larger i-gel. Both these patients were females with a thyromental distance of <6.5 cm. There was no difficulty in ventilating these patients throughout the duration of surgery. The device selection depends on the patient's mouth opening, thyromental distance and neck width. Gatward et al. have previously demonstrated the suitability of i-gel size 4 in 100 non-paralysed patients weighing 42-113 kg. Based on the discretion of the anaesthesiologist, patient's mouth opening, neck width and thyromental distance, we have observed that size 3 i-gel is most suitable for Indian females and size 4 is appropriate for Indian males. No such discrepancy was observed with the LMA Supreme and hence we recommend size selection according to the manufacturer's guidelines in the Indian population as well. The incidence of complications was low with both these devices.
Our study has a few limitations. It was limited to evaluating the LMA Supreme and i-gel only under 'ideal conditions' as it excluded obese patients and those at risk of regurgitation or aspiration. Second, as our data were collected in an unblinded manner, some observer bias could have been possible.
| Conclusion|| |
We have demonstrated that both the devices provide safe and effective airway control. LMA Supreme had better performance characteristics in terms of ease of insertion, success rates on the first attempt, time to insertion and OLP. We found longer time to insert the gastric tube in the i-gel even though the clinical relevance is questionable. The higher OLP of i-gel may provide additional advantage over the LMA Supreme.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4]