|Year : 2016 | Volume
| Issue : 2 | Page : 212-218
Insertion characteristics of three supraglottic airway devices: A randomized comparative trial
Hesham F Soliman MD
Department of Anesthesia, Faculty of Medicine, Ain Shams University, Cairo, Egypt; Department of Anesthesia, Alnoor Specialist Hospital, Makkah, Kingdom of Saudi Arabia
|Date of Submission||10-Feb-2015|
|Date of Acceptance||02-Jul-2015|
|Date of Web Publication||11-May-2016|
Hesham F Soliman
Alnoor Specialist Hospital, PO Box 6251, Makkah 21955
Source of Support: None, Conflict of Interest: None
I-gel is a new single-use supraglottic airway device without an inflatable cuff. The aim of this study was to compare I-gel, a Proseal laryngeal mask airway (PLMA), and a laryngeal tube (LT) for ease of insertion, hemodynamic effects of insertion, and associated airway morbidity.
Patients and methods
Seventy-five adult patients, both sexes, were assigned randomly to I-gel (I), PLMA (P), and LT (L) groups according to the supraglottic device applied. Insertion time, airway sealing pressure, insertion success rate, insertion-associated hemodynamic effects, ease of gastric tube insertion, and associated airway morbidities were assessed.
Demographic data and duration of both surgery and anesthesia in the three groups were comparable. Insertion time (s) was significantly shorter in group I (18.9 ± 0.9) compared with group P (26.2 ± 1.1) and group L (26.2 ± 1.0). Airway sealing pressure (cm H 2 O) was higher in group P (29.6 ± 1.2) compared with group I (26.0 ± 1.0) and group L (22.9 ± 0.9). The success rate at the first insertion attempt was higher in group I (96.0%) compared with group P (84.0%) and group L (88%). Blood-stained devices and occurrence of postoperative sore throat were lower in group I than the P and L group, with no significant differences. Heart rate, mean arterial pressure, and cardiac index were significantly increased in the postinsertion period in the P and L group compared with group I.
In the I-gel group, higher insertion success rate, and lower both hemodynamic changes and airway morbidities were noted compared with PLMA and LT. However, airway sealing ability was better with PLMA.
Keywords: airway sealing pressure, hemodynamic changes, I-gel, laryngeal tube, Proseal laryngeal mask
|How to cite this article:|
Soliman HF. Insertion characteristics of three supraglottic airway devices: A randomized comparative trial. Ain-Shams J Anaesthesiol 2016;9:212-8
|How to cite this URL:|
Soliman HF. Insertion characteristics of three supraglottic airway devices: A randomized comparative trial. Ain-Shams J Anaesthesiol [serial online] 2016 [cited 2021 Apr 19];9:212-8. Available from: http://www.asja.eg.net/text.asp?2016/9/2/212/182260
| Introduction|| |
Supraglottic airway devices (SADs) are now used widely for surgeries requiring general anesthesia. It is an alternative to tracheal intubation as it secures and maintains patients' airway during spontaneous or controlled ventilation in fasting patients by providing a perilaryngeal seal with a cuff [1,2].
Current guidelines recommend supralaryngeal airway devices as an alternative to tracheal intubation during cardiopulmonary resuscitation. Currently, the classical supralaryngeal airway devices have been refined and various alternatives have been introduced into clinical practice .
The I-gel airway is a novel SAD designed to fit the perilaryngeal and hypopharyngeal structures without the use of an inflatable cuff. It is made of both a thermoplastic elastomer (SEBS, styrene ethylene butadiene styrene) and a soft durometer, yielding a gel-like feel that provides a glottic seal in patients with a wide range of anatomical variations. Like the Proseal laryngeal mask airway (PLMA) and laryngeal tube (LT), I-gel has a gastric drainage tube integrated into the upper tube for gastric decompression, which significantly reduces the risk of acid reflux and pulmonary aspiration .
Preliminary studies for I-gel have shown its easy reliable insertion, providing an adequate seal with a low morbidity rate .
The LT and PLMA are SADs with a gastric drain tube that have been used widely in pediatric and adult patients during either spontaneous or controlled ventilation .
Both laryngoscopy and tracheal intubation produce reflex sympathetic stimulation associated with elevated plasma catecholamine levels, leading to hypertension, tachycardia, myocardial ischemia, arrhythmias, and intracranial hypertension .
By avoiding laryngoscopy and tracheal intubation, SAD is assumed to decrease the associated stress response of intubation .
The aim of this study was to compare the I-gel, PLMA, and LT for success of device insertion, associated hemodynamic response, airway leak pressure, and airway morbidities.
| Patients and methods|| |
After approval from the Research and Local Ethics Committee of Alnoor Specialized Hospital in Makkah, 82 patients were screened for eligibility to participate in this prospective randomized double-blinded clinical trial during the period from January 2014 to December 2014. Written informed consent was obtained from 75 patients older than 18 years of age, of both sexes, American Society of Anesthesiologists' physical status I or II, and scheduled for breast surgery, abdominal wall hernia repair, and orthopedic surgery.
Exclusion criteria were patient refusal, emergency, head, neck, and laparoscopic surgeries, patients on adrenoceptor agonists or antagonists, patients with chronic obstructive airway diseases, full stomach, history of regurgitation, BMI more than 30 kg/m 2 , patients known or anticipated to have difficult airway, patients with sore throat, operations that last more than 2 h, and day care patients.
In the preoperative holding area, all patients were premedicated with midazolam 0.03 mg/kg intravenously midazolam (Dormicum, Roche, Basle, Switzerland). In the operating theater, routine anesthesia monitoring was applied for all patients in the form of ECG, noninvasive blood pressure, oxygen hemoglobin saturation, and neuromuscular monitoring using ulnar nerve stimulation (Datex Ohmeda, Avance, model no. USE 1913A; GE Medical Systems, Freiburg, Germany). Following recording of patients' data such as age, sex, weight, and height, a cuff sensor was applied to the patients' index finger, which was connected to a monitor displaying beat-to-beat mean arterial pressure (MAP), heart rate (HR), systemic vascular resistance, stroke volume , cardiac output, and cardiac index (CI) (CNAP Monitor 500 HD; CNSystems Medizintechnik AG, Graz, Austria).
Anesthesia was induced by fentanyl (Janssen Pharmaceutica, Beerse, Belgium) 2 mcg/kg, intravenous, propofol (Recofol N; Primex Pharmaceuticals, Zurich, Switzerland) 2-3 mg/kg, intravenous, over 30 s, whereas neuromuscular blockade was achieved using rocuronium (Esmeron; Organon, the Netherlands) 0.6 mg/kg, intravenous; patients' lungs were ventilated manually for 90 s by sevoflurane in oxygen 6 l/min.
Patients were assigned randomly to three groups, 25 each, using a computer-generated program and the opaque sealed-envelope technique. In group P, patients received laryngeal mask airway (LMA) Proseal (The Laryngeal Mask Company, Saint Helier, Jersey, UK) sizes 3, 4, 5 for patients weighing 30-50, 50-70, and 70-100 kg, respectively, in group I, patients received I-gel airway (I-gel, Intersurgical Ltd, Wokingham, UK) sizes 3, 4, 5 for patients weighing 30-60, 50-90, and more than 90 kg, respectively, and in group L, patients received a LT airway (LTS-D; VBM Medizintechnik GmbH, Einsteinstrasse, Germany) sizes 3, 4, 5 for patients who were less than 155, 155-180, and more than 180 cm in height, respectively.
All devices were inserted by anesthesia consultants after lubrication of the device cuffs by a water-based jelly.
Proper device insertion was confirmed by both adequate chest wall expansion and auscultation on manual bag ventilation with 6 l/min fresh gas flow. If there was improper device insertion or the insertion time exceeded 60 s, the device was removed and counted as an attempt, which was followed by another insertion attempt. Failure was considered after three attempts, followed by insertion of an endotracheal tube.
Anesthesia was maintained by sevoflurane 2 volume% in an oxygen/air mixture (FiO 2 = 0.5) with fresh gas flow of 2 l/min. Neuromuscular blockade was maintained by rocuronium 0.1 mg/kg increments. The lungs were ventilated in the volume-controlled mode with a tidal volume of 6-8 ml/kg and the respiratory rate was adjusted to maintain normocapnia.
Insertion time was recorded by an unblinded observer and was started from the time of passing the incisors by the device cuff completely until the appearance of end-tidal CO 2 .
Ease of device passage was graded as easy if device insertion occurred without resistance in a single maneuver and was graded as difficult if the device was inserted successfully by corrective maneuvers such as adjustments of head position or upward-downward movements of the device.
Airway sealing pressure was determined by gradual closure of the adjustable pressure limiting valve at a fresh gas flow of 3 l/min till hearing of air leak from the patients' mouth, at which point the displayed airway pressure was recorded.
After taping the airway device to the patients' chin, the anesthetist assessed the ease of passage of an appropriate-size gastric tube through the suction channel for each device, which was confirmed to be in place by epigastric auscultation of air injected by a 50 ml syringe. Gastric tube placement was graded as easy or difficult.
Intraoperative airway leak was assessed immediately after commencement of mechanical ventilation using the pressure volume loop closure technique monitor (GE Healthcare Finland Oy, Helsinki, Finland).
Cardiovascular parameters such as MAP, HR, and CI were measured before induction of anesthesia (baseline), immediately before device insertion, immediately after insertion (0 min), and 2, 4, 6, 8, and 10 min thereafter.
At the end of surgery and after establishment of spontaneous breathing, reversal of the neuromuscular blocking effect, and patients were in a fully awake status, the airway device was removed, with recording of blood-stained cuff. Also, airway complications such as sore throat, hoarseness of voice, and dysphagia were recorded 1 and 24 h postoperatively during the pain management round.
The sample size required was calculated using the G*Power Software (version 3.1.7; Moorenstraße 5, 40225 Düsseldorf, Germany). The primary outcome measure was the first-time success rate. The secondary outcome measure was the insertion time. It was estimated that a total sample size of 75 patients equally randomized into the three study groups would have a power of 80% to detect statistical significance for a medium-to-large effect size of w = 0.36 for the first-time success rate using a two-sided c2 -test and assuming a type I error of 0.05. For the insertion time, this sample size was estimated to have a power of 80% to detect statistical significance for a medium-to-large effect size of f = 0.37 using a two-sided F test and assuming a type I error of 0.05.
Data were analyzed using IBM SPSS Statistics (version 22; IBM Corp., Armonk, New York, USA).
Continuous numerical variables were presented as mean (SD) and intergroup differences were compared using one-way analysis of variance (ANOVA). The Student-Newman-Keuls test was used for multiple post-hoc pair-wise comparisons whenever the ANOVA test showed a statistically significant difference among the groups. Repeated-measures ANOVA was used to analyze serial measurements.
Categorical variables were presented as ratio or as n (%) and between-group differences were compared using the Pearson c2 -test, or Fisher's exact test, when appropriate.
A two-sided P-value less than 0.05 was considered statistically significant.
| Results|| |
There was no difference between groups with respect to demographic data and surgical details [Table 1]. Duration of devices insertion was significantly shorter in group I (18.9 ± 0.9 s) compared with both group P (26.2 ± 1.1 s) and group L (26.2 ± 1.0 s) (P < 0.001) [Table 2]. The airway sealing pressure was significantly higher in group P (29.6 ± 1.2 cm H 2 O) than both group I (26.0 ± 1.0 cm H 2 O) and group L (22.9 ± 0.9 cm H 2 O), whereas it was significantly higher in group I than group L (P < 0.001) [Table 2] The success rate at the first attempt of device insertion in group I was 24/25 (96.0%), that in group P was 21/25(84.0%), and that in group L was 22/25(88.0%), without a significant difference between groups [Table 2]. The ease of device insertion was greater in group I (24/25) than both group P (21/25) and group L (22/25) [Table 2]. In group P, intraoperative air leak was detected in two patients, whereas air leak was detected in five and seven patients in groups I and L, respectively, without a significant difference between groups [Table 2]. Blood-stained devices were recorded in one, five, and six patients in groups I, L, and P, respectively, without significant differences; also, two, four, and six patients experienced sore throat at 1 and 24 h postoperatively in groups I, L, and P, respectively, but the difference was statistically nonsignificant [Table 3]. No patients in group I experienced dysphagia, whereas two and four patients in group P and L, respectively, developed dysphagia, without significant differences [Table 3]. Three patients in group P and one patient in groups I and L experienced hoarseness of voice, with no statistically significant difference between groups [Table 3].
|Table 2 Details of the device insertion procedure in the three study groups|
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|Table 3 Incidence of procedure-related unwanted outcomes in the three study groups|
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HR was significantly increased immediately, 2, and 6 min after device insertion in the patients groups P and L compared with group I (P < 0.001) [Table 4]. MAP was significantly increased in groups L and P compared with group I immediately after device insertion and 2, 4, 6, and 10 min thereafter (P < 0.001)[Table 5]. Also, CI increased significantly in groups P and L compared with group I at the postinsertion interval and 2, 4, and 6 min after device insertion (P < 0.001) [Table 6].
|Table 4 Changes in the heart rate associated with device insertion in the three study groups|
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|Table 5 Changes in the mean arterial pressure associated with device insertion in the three study groups|
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|Table 6 Changes in the cardiac index associated with device insertion in the three study groups|
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| Discussion|| |
This prospective randomized clinical trial showed that the I-gel group had shorter device insertion time, lower hemodynamic changes, higher success rate at the first insertion attempt, and lower incidence of air way morbidities compared with PLMA and LT groups.
To overcome the limitations of currently available SAD such as PLMA and LT (e.g. high cost, demand for careful handling to prevent cuff damage, and relatively difficult insertion), a new and cheaper SAD 'I-gel' has been developed. Various methods were used to detect air leak during the use of SAD such as detection of expired CO 2 by placing a capnogram sampling line in the oropharynx, detection of air leak by a stethoscope placed over the thyroid cartilage, and detection of audible leak from the mouth during partial closure of the expiratory valve . The latter method was used in the present study. Several studies have reported a higher leak pressure in I-gel and LMA supreme airway devices compared with LT [4,10-13].
The present study showed a higher leak pressure in PLMA compared with I-gel, but lowest in LT. This sealing pressure was measured by closing the expiratory valve of the circle system at a fixed fresh gas flow of 3 l/min until airway pressure reached a steady value [14,15]. A study carried out by Sebastian et al. , showed that fiberoptic assessment of the LT position showed improper fitting of the LT aperture to the glottic opening, which explains the lower sealing airway pressure in the current study.
Gaitini et al. , reported that dynamic compliance was superior in I-gel, which might be because of proper fitting of the device to the laryngeal inlet compared with LT. Levitan and Kinkle  assessed the I-gel position in cadavers using fiberoptic examination and neck dissection and found that I-gel conformed to the perilaryngeal anatomy despite the lack of an inflatable cuff.
The present study showed that the airway sealing pressure was the highest in the PLMA group, followed by the I-gel group, and it was the lowest in the LT group. Similar to the present study, Gasteiger et al.  reported a higher sealing pressure in PLMA than that of I-gel by a mean pressure of 7 cm H 2 O. Similar to the current study, they measured the sealing pressure at a flow rate of 3 l/min, but in spontaneously breathing nonparalyzed patients, which might have led to the difference in sealing pressures between the two trials.
It is logical that PLMA had a higher sealing pressure than I-gel as the latter has a noninflatable cuff that would not conform to the pharyngeal structures to the same degree as that of PLMA, which was recommended to be used in patients who need higher tidal volumes such as obese patients, laparoscopy, and the head-down position .
Many studies have reported that sealing airway pressure is lower in I-gel than LMA supreme [21-23], but others have reported that the sealing pressure in I-gel equals that of LMA supreme but is higher than that of LMA classic and LMA unique [10, 24, 25].
Previous studies have reported that I-gel is more prone to sliding out after insertion. However, the present study did not report any case of sliding out in the I-gel group. This may be attributed to the smaller age group used in this study compared with the present study .
Incidences of airway morbidities such as blood-stained device, sore throat, and dysphagia were lower in I-gel compared with PLMA and LT. This was similar to a study carried out by Sebastian et al. , who inflated the LT cuff to a pressure of 60 cm H 2 O without measuring the amount of air injected into the cuff, which might have influenced the airway morbidity. In the present study, the LT cuff was inflated by a predetermined volume of air according to the manufacturer's recommendations, but the cuff pressure was not measured. The cuff-induced pressure is dependent on the elasticity of the cuff material, dimensions of the cuff, and compliance of the mucus membrane ; if the cuff pressure exceeds the mucus membrane perfusion pressure, it will lead to mucosal ischemia, with subsequent airway morbidity.
The present study reported lower complications associated with I-gel insertion, which might have been because of ease of insertion, fewer insertion attempts, and the relatively soft, smaller noninflatable cuff. Similarly, other studies have reported lower morbidity with I-gel .
The present study reported greater complications in the PLMA group than the I-gel group, which is in agreement with the study carried out by Levitan and Kinkle , who attributed these complications to PLMA cuff-induced compression of the microvascular structures and terminal nerve endings.
The success rate of the first attempt at insertion for I-gel insertion was higher than that of PLMA and LT (96, 84, and 88%, respectively), which is in agreement with the Richez et al.'s  study, in which the success rate of I-gel insertion was 97%, whereas another study showed that the success rate of I-gel insertion was 86% at the first attempt, 11% at the second attempt, and 3% at the third attempt. This discrepancy in results might be because of I-gel insertion in nonparalyzed patients without assessment of anesthetic depth .
It was obvious that I-gel insertion was easy compared with the other devices in the present study. Similarly, previous studies have reported that the insertion rate for I-gel in novices equals that of experienced anesthetists [25,30], whereas another study reported that I-gel was inserted by nonanesthetists in more than two attempts using simple maneuvers .
In terms of the hemodynamic effect of insertion of I-gel, it was clear that it had the least effect on HR, MAP, and CI compared with PLMA and LT, which may be attributed to the absence of an inflatable cuff in I-gel, which enables easy, atraumatic, and rapid insertion. This is in agreement with the study of Jindal et al. , in which I-gel insertion caused less hemodynamic changes than PLMA. In contrast to the present study, another study carried out by Helmy et al.  reported no hemodynamic differences between I-gel versus classic LMA.
Also, another study reported that PLMA insertion induced an increase in the MAP than I-gel after 5, 10, and 15 min intraoperatively and they recommended that the I-gel be used instead of PLMA in patients with difficult airway because of easy rapid insertion and for high-risk patients because of insertion-associated hemodynamic stability, but they did not administer intraoperative analgesics, except nitrous oxide; thus, this increased MAP might be because of surgical response rather than device insertion .
First, this study was carried out on American Society of Anesthesiologists I and II, nonobese patients with suspected normal airways; thus, further trials are recommended to include both high-risk patients and those with anticipated difficult airways. Second, fiberoptic assessment of studied airway tools position was not performed. The aim was to avoid time consumption. Third, this study was not powered to detect small differences between groups in airway morbidity.
In conclusion, the present study showed that insertion success rate, hemodynamic stability, and airway morbidities of I-gel are better than that of PLMA and LT. However, airway sealing ability is better with PLMA.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]