Comparison of Two Supraglottic Airway Devices: I-gel Airway and ProSeal Laryngeal Mask Airway Following Digital Insertion in Nonparalyzed Anesthetized Patients.

AIMS: The study is aimed to compare the efficacy of I-gel and ProSeal laryngeal mask airway (PLMA) in nonparalysed anesthetized individuals following manufacturer-recommended digital insertion.
MATERIALS AND METHODS: In this prospective randomized observational study, 40 American Society of Anesthesiologists I and II patients, aged 18-65 years scheduled for elective surgical procedures were allocated either to PLMA group (Group P, n = 20) or the I-gel group (Group I, n = 20). Following digital insertion of PLMA or I-gel, the following parameters were compared: insertion time, ease of insertion, number of attempts, failed insertion, airway reaction during insertion, oropharyngeal leak (OPL) pressure, and gastric insufflation on auscultation. Fiberoptic view of both the channels of the airway devices and ease of insertion of 12 F Ryle's tube through gastric drain channel were graded. Postoperative complications were also noted.
RESULTS: First attempt and overall insertion success were similar (PLMA, 85% and 100%; I-gel 80% and 100%, respectively). Mean (standard deviation) insertion times were similar (PLMA, 27.40 [11.51] s; I-gel 25.45 [9.03] s). Mean OPL pressure was 3.5 cm H2O higher with PLMA (P < 0.012). The passage of Ryle's tube was easier through I-gel than PLMA. Grade I glottic view (full view of the vocal cords) was visible in 17 (85%) patients who were managed with I-gel whereas only 9 (45%) patients had Grade I view in the PLMA group.
CONCLUSION: The time required for digital insertion of PLMA and I-gel in nonparalyzed anesthetized patients is similar but PLMA forms a better oropharyngeal seal. I-gel is better positioned over the laryngeal framework and esophagus. I-gel allows easier passage of Ryle's tube through its drain channel than PLMA. The incidence and severity of postoperative sore throat and hoarseness was higher with PLMA. Copyright:

INTRODUCTION

The ProSeal™ laryngeal mask airway (PLMA; Laryngeal Mask Company North America, San Diego, CA, USA) is a laryngeal mask device with a modified cuff and a drain tube.[1] The manufacturer recommends inserting the PLMA using digital manipulation, like the LMA-Classic™, or with an introducer tool, like the Intubating™ LMA (Laryngeal Mask Company North America).[2] When inflated, its modified cuff presses the bowl of the device forwards and improves the seal with the larynx. However, PLMA still possesses few disadvantages of inflatable cuff, which can negatively impact its insertion, positioning and performance.[3] Gum-elastic bougie-guided insertion of PLMA is recommended by a few researchers to overcome these problems.[4]

I-gel is the single use supraglottic airway from Intersurgical, UK (Intersurgical Ltd., Wokingham, Berkshire, UK) with overall insertion success rate is as high as 100%.[5] It possesses an anatomically designed, noninflatable mask made of a gel-like thermoplastic elastomer. It has a widened, flattened stem with a rigid bite block that acts as a buccal stabilizer to reduce axial rotation and malpositioning, and a port for gastric tube insertion.[5] The manufacturer recommends digital insertion technique for I-gel. However, gum-elastic bouige-guided insertion has also been described.[6]

Several studies have compared the safety and efficacy of the I-gel and the PLMA. However, most studies used neuromuscular blocking drugs and insertion was performed using either introducer tool or gum-elastic bougie for PLMA and digital technique or gum-elastic bougie-guided insertion for I-gel.[678]

In the current study, we test the hypothesis that the ease of insertion using manufacturer recommended digital technique and efficacy of seal as measured by oropharyngeal leak (OPL) pressure differ between I-gel and PLMA in nonparalyzed anesthetized patients. The intraoperative orogastric tube insertion success rate, view of the glottis using fiberoptic laryngoscopy, airway reactions during insertion, and postoperative complications associated with the two devices were also compared.

MATERIALS AND METHODS

With institutional ethical committee approval (Reference: 7821/PG-2Trg/2008) and written informed consent, this prospective randomized noncross observational study of two supraglottic airway devices, namely the PLMA and the I-gel airway was performed. Forty patients in the age group 18–65 years of both sexes belonging to American Society of Anesthesiologists (ASA) physical status I and II scheduled for elective surgical procedures of <1 h duration were studied. Computer generated random numbers were used to allocate patients to either of the two study groups: PLMA group (Group P, n = 20) or the I-gel group (Group I, n = 20). Exclusion criteria included pregnant patients, gastro-esophageal reflux disease, morbid obesity (body mass index >35 kg/m2), coagulation abnormalities, anticipated difficult airway (Mallampati Grade III/IV and mouth opening <3 cm) or oropharyngeal pathology. Size 3 and 4 PLMA used for patients weighing 30–50 kg and 50–70 kg, respectively and size 3 and 4 I-gel for patients weighing 30–60 kg and 60–90 kg, respectively. All patients underwent detailed preanesthetic evaluation, including airway examination. Patients were kept fasted according to the standard nil per oral guidelines. After shifting the patients to the operation theatre, standard 5-lead electrocardiography, noninvasive blood pressure, pulse oximetry and bi-spectral index monitors were attached and baseline parameters were noted. Intravenous access was secured with 18 G cannula and all patients received 2 μg.kg-1 fentanyl. Patients were preoxygenated with 3 min of tidal volume ventilation. Anesthesia was induced with propofol 2 mg.kg-1. Ventilation was assisted using a face mask with 100% oxygen. After the bispectral index (BIS) value of 40 was obtained, the anesthesia provider checked for apnea and the lack of motor response to a jaw thrust.[9]

Additional 0.5 mg.kg-1 propofol was given for ensuring adequate depth if patient was breathing spontaneously, moved or showed motor response to jaw thrust. Either PLMA or I-gel airway was inserted according to the group allocation by the same anesthetist with substantial experience of both devices using manufacturer recommended digital techniques (>75 uses). I-gel was inserted using the rotational technique, whereas PLMA was inserted using the index finger. The cuff was inflated according to the size of PLMA and cuff pressure of PLMA was set at 60 cm H2O using a digital manometer (Mallinckrodt Medical, Athlone, Ireland). The patients' lungs were then ventilated at an inspired tidal volume of 10 ml.kg-1, a respiratory rate of 10 min−1 and an Inspiratory: Expiratory ratio of 1:2. Maintenance anesthesia was given by intravenous propofol in a dose of 75–150 μg.kg-1.min-1 with 33% oxygen in nitrous oxide to maintain BIS value between 40 and 60.

The parameters noted were (1) insertion time (time to successful insertion of the device measured from picking the device to obtaining the first breath). (2) Ease of insertion (easy or no resistance, moderate or minimal resistance, difficult or significant resistance, and impossible). (3) Number of attempts (maximum of three attempts were allowed before considering the device a failure). Failed insertion was defined by any of the following criteria: (1) failed passage of the airway device into the pharynx; (2) malposition (air leaks); (3) ineffective ventilation (maximum expired tidal volume <6 mL.kg-1 or end-expiratory carbon dioxide >6 kPa if correctly positioned), or (4) drainage tube leaks. The etiology of failed insertion was documented. Failed cases were managed with the endotracheal tube. (4) Airway reaction (laryngospasm, bronchospasm, coughing, gagging). (5) OPL pressure (leak detected by audible noise heard on keeping the stethoscope on lateral aspect of thyroid cartilage): With fresh gas flows at 3 L.min-1 and adjustable pressure limit valve set to 40 cm of H2O, ventilation was stopped temporarily and a stethoscope was placed over the neck just lateral to thyroid cartilage to measure the minimal airway pressure at which an audible gas leak occurred.[10] (6) Fiberoptic view of both the channels of the airway devices by a fiberoptic bronchoscope (PENTAX FB 15P) and noted as Grade I – Full view of the vocal cords, Grade II – Posterior cords and arytenoids only, Grade III – Only epiglottis seen, or Grade IV – No laryngeal structures seen. The view via drain tube was scored as: mucosa; closed upper esophagus; open upper esophagus; drain tube occluded; and whether the fiberscope could be/could not be passed.[11] (7) Ability to pass a lubricated 12 F Ryle's tube through gastric drain channel (easy/difficult/impossible); maximum of two attempts were allowed. (8) Any gastric insufflations (by auscultation over the patient's epigastric area).

On completion of the procedure, the duration of the surgery and total propofol administered was recorded. The device was removed when the BIS value reached 75–80 and patient became responsive to oral commands. The following parameters were then noted-ease of removal (easy, moderate, difficult), airway reaction (laryngospasm, bronchospasm, coughing and gagging), visible blood on the airway device and evidence of regurgitation of yellowish gastric fluid.

Postoperatively, patients were queried for sore throat, dysphagia, dysphonia, nausea, neck/jaw/ear pain and hoarseness of voice immediately after the procedure (at 0 h) and after 24 h. Soreness was quantified on a 101-point numerical rating score where 0 was no soreness at all and 101 point referred to maximum soreness.[12]

Statistical analysis

The number of individuals was based on preliminary experimental data on I-gel. The mean airway pressure at which gas leaks around the PLMA has been reported to be 29 ± 6[13] and the OPL pressure obtained with I-gel in our pilot study with 10 patients was 25.1 ± 4. To detect a projected difference of 10% (with estimated standard deviation [SD] of 4) between the groups with respect to the primary variable-OPL pressure, a Type I error of 0.05 and a power of 0.8, a total of 18 patients were required in each group, but 20 were included to compensate for possible dropouts.

Parametric data was expressed as mean ± SD and analyzed using the student's t-test. Nonparametric data was expressed as median and interquartile range was analyzed using the Mann–Whitney U-test. Count data was compared using the Chi-square test. P < 0.05 was considered as statistically significant.

RESULTS

The patients' characteristics were similar between the two groups and most of the patients in both the groups were ASA I [P > 0.05, Table 1]. On preoperative airway assessment, the patients in both the groups were not significantly different [Table 2]. The number of patients based on the sizes of I-gel and PLMA used are shown in [Table 3]. There was no significant difference in the dose of propofol used or the duration of surgery between the groups [P > 0.05, Table 3]. Data about intraoperative hemodynamics, arterial saturation, end-tidal CO2 and BIS values were also comparable (P < 0.05).

Table 1

Patient characteristics (n=20)

	Group P (PLMA)	Group I (I-gel)	P
Age (years), mean (SD) (range)	40.75 (13.26) (19-62)	41.90 (10.23) (24-59)	0.761
Height (cm), mean (SD) (range)	161.95 (7.66) (146-179)	162.73 (7.55) (154-178)	0.749
Weight (kg), mean (SD) (range)	62.85 (11.86) (42-90)	67.15 (10.96) (50-90)	0.241
BMI (kg/m2), mean (SD) (range)	23.91 (3.96) (17.15-32.25)	25.23 (2.82) (21.08-32.79)	0.233
ASA I:II	19:1	15:5	0.077
Sex ratio (male:female)	9:11	10:10	0.875

P<0.05 is statistically significant. All values are expressed as mean (SD) (range) except ASA status and male:female ratios. ASA=American society of Anesthesiologists, BMI=Body mass index, SD=Standard deviation, PLMA=Proseal laryngeal mask airway

Table 2

Preoperative airway assessment (n=20)

	Group P (PLMA)	Group I (I-gel)	P
MMP, n (%)
I	3 (15)	5 (25)	0.429
II	17 (85)	15 (75)
MO (cm), mean (SD) (range)	4.17 (0.29) (3.8-4.8)	4.03 (0.27) (3.7-4.6)	0.119
TMD (cm), mean (SD) (range)	6.82 (0.22) (6.4-7.3)	6.82 (0.27) (6.5-7.5)	0.949

P<0.05 is statistically significant. MO and TMD are expressed as mean (SD) (range). MMP=Mallampati grading, MO=Mouth opening, TMD=Thyromental distance, SD=Standard deviation, PLMA=Proseal laryngeal mask airway

Table 3

Laryngeal mask airway size, propofol used and duration of surgery (n=20)

	Group P (PLMA)	Group I (I-gel)	P
LMA size, n (%)
3	4 (20)	0	0.035*
4	16 (80)	20 (100)
Total dose of propofol (mg), mean (SD) (range)	323.75 (104.46) (155-550)	324.25 (125.51) (170-600)	0.989
Total surgical duration (min), mean (SD) (range)	24.65 (12.01) (8-50)	24.90 (12.75) (8-60)	0.949

*P<0.05 is statistically significant. Total dose of propofol and surgical duration are expressed as mean (SD) (range). LMA=Laryngeal mask airway, SD=Standard deviation, PLMA=Proseal LMA

Data related to the ease of insertion, number of insertion attempts and insertion time were also statistically similar [Table 4]. The first attempt success rate was 85% and 80% with PLMA and I-gel, respectively. The second attempt success rate was 100% in both the groups.

Table 4

Insertion characteristics and time taken for placement of laryngeal mask airway’s (n=20)

	Group P (PLMA)	Group I (I-gel)	P
Number of insertion attempts, n (%)
1	17 (85)	16 (80)	0.799
2	3 (15)	4 (20)
Fail	0	0
Ease of insertion, n (%)
Easy	9 (45)	8 (40)	0.799
Moderate	10 (50)	11 (55)
Difficult	1 (5)	1 (5)
Impossible	0	0
Time for device placement (s), mean (SD) (range)	27.40 (11.51) (14-54)	25.45 (9.03) (12-44)	0.758

P<0.05 is statistically significant. Time taken for placement of LMA is expressed as mean (SD) (range). LMA=Laryngeal mask airway, SD=Standard deviation, PLMA=Proseal LMA

Mean OPL was 3.5 cm H2O higher with the PLMA [P = 0.012, Table 5]. The incidence of gastric insufflation was more with PLMA (10% as compared to 0% in I-gel group), but the difference was not significant [P = 0.147, Table 5]. Ryle's tube placement was successful and easy in all 20 patients with I-gel. In the PLMA group, the placement was not possible in 3 (15%) patients and was easy only in 60% of the patients. The passage of Ryle's tube was analyzed using Chi-square test and the difference was statistically significant [P = 0.007, Table 5].

Table 5

Oropharyngeal leak pressures, gastric insufflation, passage of ryle’s tube and fibreoptic view through drain tube n (%) (n=20)

	Group P (PLMA)	Group I (I-gel)	P
Oropharyngeal leak pressures	30.55 (4.02)	27.05 (4.40)	0.012*
(cm of H2O), mean (SD) (range)	(24-38)	(18-35)
Gastric insufflation, n (%)	2 (10)	0	0.147
Passage of ryle’s tube, n (%)
Easy	12 (60)	20 (100)	0.007*
Moderate	5 (25)	0
Impossible	3 (15)	0

*P<0.05 is statistically significant. PLMA=Proseal laryngeal mask airway, SD=Standard deviation

The laryngeal views on fiberoptic examination through the shaft of the device were compared in Table 6. Grade I view (full view of the vocal cords) was visible in 17 (85%) patients who were managed with I-gel whereas 9 (45%) patients had Grade I view in the PLMA group. Posterior cords and arytenoids (Grade II) were visible in 10 (50%) Group P patients and 3 (15%) Group I patients and only epiglottis seen (Grade III) in only one patient of the P Group, but none in I Group.

Table 6

Fibreoptic view through airway channel and drain tube (n=20)

	Group P (PLMA), n (%)	Group I (I-gel), n (%)	P
Fiberoptic view (airway channel)
Full view of vocal cords	9 (45)	17 (85)	0.027*
Posterior cords and arytenoids	10 (50)	3 (15)
Only epiglottis seen	1 (5)	0
Fiberoptic view (drain tube)
Mucosa	0	0	NA
Closed upper esophagus	6 (30)	0
Open upper esophagus	13 (65)	0
Drain tube occluded	1 (5)	0
Fiberscope not passed	0	20 (100)

*P<0.05 is statistically significant. NA=Not analyzed, PLMA=Proseal laryngeal mask airway

The fiberoptic view through the drain tube could only be obtained in the PLMA group because only adult fiberscope with external diameter 4.8 mm was available which could not be negotiated through the drain tube of size 4 I-gel. Six (30%) patients in the PLMA group had a Grade II view (closed upper esophagus) while open upper esophagus was seen in 13 (65%) patients of PLMA group [Table 6]. In one patient, drain tube was occluded.

The data related to the postoperative complication are shown in Table 7. There were no airway reactions during placement of the PLMA in any of the patients; whereas 2 patients had bronchospasm during the placement of I-gel LMA. On removal of the airway device, we observed blood on the PLMA in one patient whereas blood was visible on the I-gel in 3 patients. There was significantly higher incidence of sore throat (both at extubation and at 24 h postoperatively) with PLMA (P = 0.005). The sore throat was also more severe in patients in the PLMA group (P = 0.004). Hoarseness was present in 80% and 10% of the patients with PLMA and I-gel, respectively (P < 0.05). No patient had dysphagia, dysphonia, ear, neck, or jaw pain in either groups.

Table 7

Postoperative complications (n=20)

	Group P (PLMA)	Group I (I-gel)	P
Sore throat at 0 h, n (%)	16 (80)	8 (40)	0.005*
Sore throat at 24 h, n (%)	8 (40)	1 (5)	0.004*
NRS at 0 h, mean (SD) (range)	24.75 (20.86) (0-60)	5.50 (8.256) (0-30)	0.002*
NRS at 24 h, mean (SD) (range)	8.00 (11.96) (0-40)	0.50 (2.236) (0-10)	0.007*
Dysphagia at 0 h, n (%)	0	0	NS
Dysphagia at 24 h, n (%)	0	0	NS
Hoarseness of voice at 0 h, n (%)	12 (60)	2 (10)	0.001*
Hoarseness of voice at 24 h, n (%)	4 (20)	0	0.035*
Ear/neck/jaw pain, n (%)	0	0	NS

*P<0.05 is statistically significant. NRS is expressed as mean (SD) (range). NS=Not significant, SD=Standard deviation, NRS=Numerical rating score, PLMA=Proseal laryngeal mask airway

DISCUSSION

The present study compared the efficacy of I-gel with PLMA following their digital insertion in nonparalyzed anaesthetized adult patients. No device is superior to the other in terms of success and ease of insertion. Nonguided digital-aided first attempt insertion of the PLMA was successful in 85% patients. First attempt success rate of insertion with I-gel was 80%. The difference was not significant (P = 0.799). The second attempt success rate was 100% with both the devices. Our findings are consistent with the observations of Bosley et al.,[14] who compared the PLMA and I-gel in nonparalyzed anaesthetized European patients following insertion using manufacturer recommended standard technique. The authors reported 1st time insertion success rate as PLMA 86% and I-gel 78% (P = 0.61). Also, the data from individual studies on PLMA and I-gel are similar to our observations. First attempt and second attempt success rates with the PLMA as observed by Lu et al. were 82.5% and 100%, respectively.[15] Similarly, first attempt success rate in a study where I-gel was inserted by novices in manikins and patients was 82.5%, but reached 100% after three attempts.[16] Gatward et al.[17] evaluated size 4 I-gel and found similar success rates. Jadhav et al.[18] and Das et al.[19] also reported similar first and second attempt success rates with both I-gel and PLMA.

The mean insertion time for PLMA and I-gel in the present study was 27.40 ± 11.51 s (range 14-54 s) as compared to 25.45 s ± 9.03 s (range 12–44 s). The difference was not clinically significant (P = 0.758). Insertion time reported in the present study was higher than that reported in the previous studies;[16172021] however, probably this absolute time difference is of negligible clinical importance in day-to-day anesthetic practice. Bosley et al.[14] reported lesser insertion time for both PLMA and I-gel (mean time LMA ProSeal® 12 s, I-gel® 17 s). However, similar to our study, the difference was not clinically significant (P = 0.06). On the contrary, according to Kini et al.[22] and Hayashi et al.,[23] I-gel provides significantly faster insertion time. Kini et al. found that mean time required for successful insertion of I-gel was 21.98 s and PLMA was 30.60 s (P = 0.001).[22] Hayashi et al. reported insertion time for I-gel 4.4 s as compared to PLMA 16 s, P < 0.01.[23] Jadhav et al.[18] observed even higher mean insertion times with PLMA (41 ± 9.4 s) as compared to I-gel airway (29.5 ± 8 s). However, Singh et al.[24] could achieve faster insertion with both PLMA (23 ± 2.5 s) and I-gel airway (13.5 ± 4.4 s). The definition of “insertion time” varies from studies to studies and that may also explain difference in the result of these studies.

One of the statistically significant differences between performances of the two devices was that the PLMA achieved a significantly higher airway leak pressure than the I-gel®. Mean OLP of PLMA was 30.55 cm H2O and was 3.5 cm H2O higher than that with I-gel. This small difference may be important in obese patients, patients with poor lung compliance, or during laparoscopy surgeries. Cook et al.[21] and Lu et al.[15] observed mean OPL pressure of 29 cm of H2O for PLMA. Bosely et al.[14] compared PLMA and I-gel in 100 European patients using standard insertion techniques. Airway leak pressure was higher in the PLMA group (LMA ProSeal® 28 cm. H2O, I-gel® 22 cm. H2O, difference 6.0 cm. H2O, 95% confidence interval 3.0-9.0 cmH2O, P = 0.002). Curpod and Basavalingaiah[25] also observed higher OPL with PLMA (29 ± 0.75) as compared to I-gel airway (23.9 ± 0.7), findings quite comparable to our study. On the contrary, but similar to the findings of Uppal et al.[26] (mean seal pressure of 28 cm H2O for I-gel), we observed mean OLP of 27.05 ± 4.4 s in patients with I-gel. Whether different outcomes in OPL pressure with the use of I-gel in these studies was due to digital insertion over guided-insertion or due to difference in patient characteristics is uncertain. In either case, the inflatable cuff of PLMA with a ventral and dorsal cuff could have resulted in better seal than I-gel with a noninflatable cuff.

In the present study, all the patients in the two groups had adequate ventilation without any sign of obstruction. However, on fiberoptic examination of upper airway, only 45% patients in the PLMA group had Grade I laryngeal view (full view of vocal cords). Poor laryngeal visualization with PLMA was also seen in previous investigations. Only 54% patients had optimum positioning of PLMA in a study by Brain et al.[1] One plausible reason for these observations was the broader proximal cuff of PLMA catching the epiglottis during insertion, resulting in greater epiglottic downfolding. It seems that down folded epiglottis does not significantly impede air flow with PLMA, perhaps, because of accessory vent. Possibly that is why, the respiratory variables of PLMA were similar to the LMA even though the full view of the vocal cords was seen only in 13% patients by Brimacombe et al.[20]

In contrast, we observed Grade I view (full view of vocal cords) in 85% patients in I-gel group. Similarly, full view of the vocal cords was seen in 91% of the patients with I-gel in a study by Gatward et al.[17] and Janakiraman et al.[27] could see vocal cords plus other parts of larynx in all 42 patients (100%) with I-gel. The I-gel group provided a better fiberoptic view of glottis than PLMA in another study by Curpod and Basavalingaiah[25] similar to our study. They observed that 37 (92.5%) and 3 (7.5%) patients in I-gel group and 30 (75%) and 10 (25%) patients in the ProSeal group had fiberoptic score of 1 and 2 respectively (P = 0.034). These findings were consistent with our study.

Thus, in our study, I-gel was better positioned over laryngeal framework. However, PLMA group had higher leak pressure of 30.55 cm of H2O as compared to 27.05 cm of H2O for I-gel. The data show that there is no relation between fiberoptic view and the seal provided by supraglottic airway device. Earlier studies also demonstrated lack of correlation between fiberoptic views and clinical consequences.[2829]

The drainage tube aligns the orogastric tube with the upper esophageal sphincter and is designed to reduce gastric inflation and risk of regurgitation. This has been widely investigated in PLMA; however, efficacy of drain tube in I-gel is still doubtful. A recent study by Singh et al.[24] observed prolonged insertion times for orogastric tube in the I-gel group (12.21 ± 3.82 s) and attributed it to the smaller aperture of the gastric port in the device which may increase the time to insert the leading edge of the tube into the gastric port aperture. Interestingly, in the present study, placement of 12 F orogastric tube was successful and easy in all patients with I-gel, but only in 85% in PLMA group (P = 0.007).

Incidence of postoperative sore throat and hoarseness of voice was significantly higher in PLMA group as compared to the I-gel (P < 0.05). Our findings were similar to those observed by Jadhav et al.[18] They demonstrated 16.7% patients in the PLMA group to have sore throat as compared to only 3.3% in the I-gel airway group. Postoperative sore throat is probably caused by a combination of trauma on insertion, intracuff pressure being maintained at 60 cm H2O, and a large cuff of PLMA exerting pressure against the pharyngeal mucosa. There was no evidence of any aspiration or regurgitation in either of the groups.

There has been ample literature on supraglottic airway devices and many of the studies have compared PLMA and I-gel, in adult patients undergoing general anesthesia with neuromuscular blocking drugs.[71319242530313233343536] The parameters like time to insertion, ease of insertion, overall success rate, OLP and complications such as hoarseness and sore-throat may be affected by the use of muscle relaxants.

Few studies have directly compared PLMA and I-gel in nonparalyzed anaesthetized patients; two of these used gum-elastic bougie-guided insertion technique. Gasteiger et al. studied 151 patients in a combination of European and Australian settings and compared insertion characteristics when LMA ProSeal® and I-gel® were inserted using a laryngoscope and gastric tube guided technique.[6] They reported very high first attempt insertion success rates (LMA ProSeal® 99%, I-gel® 97%) and observed a mean OLP of 30 ± 7 s with PLMA. However, the mean OLP with I-gel was 23 ± 7 s only. Van Zundert et al., studied 150 patients in a European setting (50 each LMA ProSeal®, I-gel® and Supreme LMA) using the same insertion technique.[37] LMA ProSeal® and I-gel® performance were entirely equivalent during insertion and spontaneous breathing anaesthesia.

Few studies utilized manufacturer recommended standard insertion techniques for PLMA and I-gel in nonparalyzed anaesthetized patients.[141822232538]

But, three of these RCTs did not specify whether the index finger or the thumb-insertion technique was used for PLMA.[142223] Hence, the result of these studies could not be compared to the present study where both the devices were introduced by the nonguided digital techniques, specifically index finger technique for PLMA and rotational technique for I-gel. Moreover, one of these studies was performed on Japanese population and one on European population.

The studies that used the similar insertion technique in nonparalyzed anaesthetized patients was by Liew et al.,[38] and Jadhav et al.[18] Liew et al. studied 150 patients in an Asian setting (50 each LMA ProSeal®, I-gel® and Supreme LMA). In similarity to our findings, the mean insertion time and first attempt success rate was not significantly different between PLMA and I-gel. However, contrary to our study, airway leak pressure was found to be higher for the I-gel than the PLMA (mean ± standard error of the mean: 27.31 ± 0.92 cm H2O and 24.44 ± 0.70 cm H2O, respectively; P = 0.003). According to the authors, one possible reason for the I-gel's higher leak pressure was the modification applied to its weight-based size selection criteria to account for the 10-kg overlap between sizes 3 and 4. Nevertheless, there was a higher incidence of significant air leakage in the I-gel group, with three cases of the size 3 I-gel as opposed to none in the other devices (0.047); two patients had tracheal intubations, and another patient was changed to ProSeal.

The present study has few limitations. First, the investigators had more experience with PLMA than I-gel LMA. However, there is evidence showing similar success rates of the I-gel insertion by novices and more experienced individuals.[16] Secondly, our data only applied to use of the size 4 I-gel device as none of the patient in the I-gel Group weighed <50 kg or more than 90 kg; hence, size 3 I-gel or size 5 I-gel was not used in any patient, according to manufacturer's recommendation. Thirdly, the study was unblinded, which can be a possible source of bias. The devices were used in nonobese patients with normal airways and no underlying respiratory disorder; hence, the results cannot be extrapolated to other groups of patients. Lastly, due to nonavailability of the pediatric fiberscope, we could not grade the drain tube fiberoptic view as the adult fiberscope could not be negotiated through the narrow drain tube of the size 4 I-gel airway.

CONCLUSION

Both PLMA and I-gel can be inserted easily and rapidly using nonguided digital technique: index finger method for PLMA and rotational technique for I-gel. The time required for insertion is similar but the PLMA forms a better oropharyngeal seal. However, I-gel is better positioned over the laryngeal framework and the esophagus and it allows easier passage of orogastric tube through its drain channel than the PLMA. The incidence of intraoperative complications is similar, however, incidence and severity of postoperative sore throat and hoarseness of voice is higher with the PLMA.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.