• Users Online: 751
  • Print this page
  • Email this page

 Table of Contents  
Year : 2022  |  Volume : 9  |  Issue : 3  |  Page : 95-99

A randomized trial to compare thenar eminence dimensions-based method with body weight method to determine I-gel size in pediatric patients

Department of Anaesthesiology, B.J. Medical College, Ahmedabad, Gujarat, India

Date of Submission08-Dec-2021
Date of Decision08-Apr-2022
Date of Acceptance09-Apr-2022
Date of Web Publication12-May-2022

Correspondence Address:
Dr. B Sivashankari
No. 31, B.V.M. Nagar, Mooligai Pannai Opp., Thanjavur Medical College Road, Thanjavur - 613 004, Tamil Nadu
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jpcc.jpcc_99_21

Rights and Permissions

Background: In pediatric daycare surgery, I gel has been used safely and effectively in anesthetized children. I-gel size is determined routinely by the manufacture's recommended weight-based method. The dimension of thenar eminence can help in determining I-gel size. The aim of this study was to compare the weight-based method and thenar eminence dimension method in the selection of I gel.
Subjects and Methods: The prospective, randomized, single-blind study included 80 patients of the age group 6 months to 12 years, the American Society of Anesthesiologists class I, II, and III of either gender who were undergoing surgery under general anesthesia. Group 1– (n = 40) recommended weight-based method and group 2 – (n = 40) thenar eminence-based method. Parameters observed were proper placement, adequate ventilation, leak fraction (LF), and number of attempts.
Results: Proper placement and adequate ventilation were comparable between two groups. LF is statistically higher in group 1 compared to group 2 (P = 0.003). The mean insertion time was 17 s in each group. The number of attempts, hemodynamic parameters, and ease of insertion were all comparable between two groups.
Conclusions: Thenar eminence dimension can be the better method for the recommended weight-based method, especially in the emergency situations when the weight cannot be determined.

Keywords: I gel, leak fraction, pediatric patients, thenar eminence

How to cite this article:
Engineer SR, Sivashankari B, Balagopal K T. A randomized trial to compare thenar eminence dimensions-based method with body weight method to determine I-gel size in pediatric patients. J Pediatr Crit Care 2022;9:95-9

How to cite this URL:
Engineer SR, Sivashankari B, Balagopal K T. A randomized trial to compare thenar eminence dimensions-based method with body weight method to determine I-gel size in pediatric patients. J Pediatr Crit Care [serial online] 2022 [cited 2023 Jun 2];9:95-9. Available from: http://www.jpcc.org.in/text.asp?2022/9/3/95/345098

  Introduction Top

I gel is most widely used second-generation supraglottic device, made up of thermoplastic elastomers, which is gel-like and transparent.[1] The potential advantages are safety, ease of insertion, minimal tissue compression, and stability after insertion with low pharyngolaryngeal morbidity.[2] I gel has been used as a rescue device in difficult, failed intubation situation, and resuscitation.[3],[4],[5] Four sizes (1, 1.5, 2, and 2.5) of pediatric I gel are available. The choice of size based on actual body weight (ABW) is recommended by the manufacturer; however, this has several limitations in emergencies where predicting the weight of the patient is difficult. Another important limitation is that the size of oropharyngeal cavity is related to height and age rather than the weight of the child.[6] Using the manufacture's recommended weight-based method might lead to selecting larger-sized I gel, which can cause trauma to the airway or insufficient ventilation. In an interesting study, it was stated that there is an association between the I-gel size and thenar eminence dimension in pediatric patients.[7] In that study, I gel was selected based on the weight-based method and later correlated with thenar eminence in the same participants. The aim of the study was to compare two methods (manufacture recommended weight-based method and thenar eminence dimension) for the selection of I-gel size in the pediatric patients undergoing elective surgeries under general anesthesia.

  Subjects and Methods Top

This prospective, randomized, single-blind, controlled study was conducted after getting the institutional ethics committee approval (65/2020 on 28/02/2020) and registration in the clinical trial registry (CTRI/2020/11/029110). Computer-generated randomization was done using Microsoft Excel 2016 using randomization function, and after that, every alternative patient was allotted in different groups. Eighty patients of age between 6 months–12 years, weight 5–30 kg, the American Society of Anesthesiologists (ASA) class I, II, and III, and either gender were recruited. Patients undergoing surgery of <2 h duration, in the supine position, and not requiring tracheal intubation were selected. Surgical procedures underwent were circumcision for phimosis, hypospadiasis repair, congenital hernia–hydrocele repair, surgery for congenital cataract, squint surgery, fracture humerus, fracture radius, and debridement for fracture femur and tibia. Children having any morphological abnormality of the hand, any previous surgeries of the hand, history of upper respiratory tract infection, anticipated difficult airway, inadequate starvation and with oropharyngeal lesion were excluded from the study. Proper preoperative assessment was done, and the written informed parental consent and assent consent for children between 7 and 12 years of age was taken.

Children were randomized into two groups according to I-gel selection, group 1 (n = 40) based on weight-based methods (1/1.5/2/2.5 I Gel for 2–5 kg/5–12 kg/10–25 kg/25–35 kg used, respectively) and group 2 (n = 40) based on thenar eminence-based method. Thenar eminence size was measured using a paper ruler from the hand while fingers were placed in the neutral position and recorded in centimeters by the same investigator throughout the study, as follows:

  • Long axis of thenar eminence measured from junction point of the thumb to wrist curl. (It will be correlated as the length of soft noninflatable cuff of I gel)
  • Short axis measured from the largest portion of the thenar eminence from the lateral end of the thumb to the first-hand line. (It will be correlated as the width of soft noninflatable cuff of I gel) [Figure 1]
  • The width (short axis) and length (long axis) of the I-gel's soft noninflatable cuff were measured [Figure 2].
Figure 1: Measurements of thenar eminence (long and short axis)

Click here to view
Figure 2: Measurements of I gel (long and short axis)

Click here to view

I gel was selected based on both length and width; if there were any discrepancies, length was preferred to width.

In all eligible patients, standard monitors were attached, intravenous (IV) line secured, and premedicated with injection glycopyrrolate (0.04 mg/kg), ondansetron (0.16 mg/kg), and fentanyl (1 μg/kg). Anesthesia was induced with 6% sevoflurane with oxygen 4 L and N2O 4 L with injection succinylcholine 1.5–2 mg/kg using computer-generated randomization well-lubricated I gel as per allotted Group 1 or 2 was introduced into the oral cavity. Manipulations such as jaw thrust and chin lift were performed as required. Proper placement of I gel was assessed by chest expansion on positive pressure ventilation, absence of audible leak, and square wave capnography waveform. Adequacy of ventilation was judged by an oxygen saturation of ≥95% and an end-tidal carbon dioxide (ETCO2) of 35–45 mmHg at a tidal volume (TV) of 6–8 ml/kg. Leak fraction (LF) was determined by comparing the difference between inspired and expired TVs and dividing them by the inspired TV. Data were set as TV of 8–10 ml/kg ABW with an I: E ratio of 1:2 and respiratory rate of 20 breaths/min. In case of failure to achieve adequate ventilation with two attempts, alternative supraglottic airway or endotracheal tube was used and considered the failure of I-gel airway. Anesthesia was maintained with O2 (50%), N2O (50%), sevoflurane (1.5%–3%), and injection of atracurium 0.5 mg/kg. During insertion of I gel, manipulations such as gentle pushing/pulling/chin lift/jaw thrust/head-and-neck extension/flexion, number of attempts, insertion time (time for the pickup of device and the achievement of adequate ventilation), ease of insertion of I gel, and gastric drainage tube were recorded.

Ease of device insertion was recorded as very easy: no resistance to insertion, easy: when insertion into the pharynx required maneuver such as jaw thrust, and difficult: when more than two maneuvers were needed. The ease of placement of gastric drainage tube was recorded as easy: passage without resistance and difficult: resistance felt requires manipulation of I gel for insertion. Complications: incidence of mucosal injury was assessed by trauma or minor injury to the airway seen as blood on the device after removal. Laryngospasm, coughing, and postoperative sore throat were also noted.

Sample size calculation was performed by computer software for two independent study groups. It revealed that at least 35 patients were needed in each group for the detection of at least 8% change in the oropharyngeal sealing pressure, (as our aim is the selection of appropriate size, oropharyngeal sealing pressure is taken as the parameter for sample size selection) assuming its incidence is 26 ± 3 with a power of 0.8 and a significance level at 80% power (α = 0.05, β = 0.2).[8] We decided to include 40 patients in each group for the possibility of dropout. We do not have any dropouts in our study.

Statistical analyses were performed using Microsoft Excel software. Categorical data were analyzed using the Chi-square tests and continuous data variables were analyzed using Student's t-test unpaired as the data were compared across the two groups, while paired t-test when comparing data within the group. Linear regression was used in finding the correlation between length and width of I gel and thenar eminence. P < 0.05 was considered statistically significant.

  Results Top

A total of 80 patients, 40 in each group, were enrolled in the study. Demographic data (age, gender, and weight), ASA grading, and type of surgery were comparable in both groups [Table 1]. The mean insertion time, number of attempts, ease of insertion, manipulation required or not, and variables for optimal ventilation were comparable in both groups. LF was <0.05 in 30% (12) of patients in group 1 and 70% (28) of patients in group 2. Only one patient in group 1 and none of the patients in group 2 had LF >0.2. There was significantly higher LF in group 1 compared to group 2 (P = 0.003), LF (mean ± standard deviation [SD]) of group 1 and group 2 was (0.08 ± 0.06) and (0.04 ± 0.04), respectively [Table 2].
Table 1: Demographic data

Click here to view
Table 2: Insertion parameters

Click here to view

In group 2, the mean ± SD values for (I gel-length) and (I gel-width) were 3.93 ± 0.75 and 2.80 ± 0.60), respectively, and the mean ± SD values for (thenar eminence-length) and (thenar eminence-width) were 3.80 ± 0.74 and 2.62 ± 0.60, respectively. There was a statistically significant correlation between thenar eminence-width and I gel-width (r = 0.95, P < 0.001) and between thenar eminence-length and I gel-length (r = 0.96, P < 0.001). According to the simple linear regression analyses, each 1 cm increase in I gel-length measurement resulted 15 in 0.920 cm increase in thenar eminence-length measurement (95% confidence interval, 0.67---1.17; P < 0.001), and each 1 cm increase in I gel-width measurement resulted in 0.914 cm increase in thenar eminence-length measurement (95% confidence interval, 0.724–1.104; P < 0.001).

In group 2, according to thenar eminence dimensions, I-gel size 1.5 was used in the weight range of 8–18 kg; similarly, I-gel size 2 was used in weight range of 9–28 kg and I-gel size 2.5 was used in the weight range of 14–35 kg. This shows a wide weight range for particular I-gel size.

There was no statistically significant difference in intraoperative heart rate and systolic and diastolic blood pressures in both groups. Complications such as sore throat, laryngospasm, aspiration, and hoarseness of voice were not observed in any patients of both groups.

  Discussion Top

I gel has been used most commonly nowadays in pediatric patients. The size selection was always based on the manufacturer recommended weight-based methods.[2],[3],[6],[7],[9] Our aim of the study was to compare recommended weight-based method and thenar eminence dimension-based method to select I-gel size in pediatric patients. In the literature, we were not able to find a comparative study of alternative method for selecting the size of I gel. This study shows that I-gel size selected by thenar eminence dimension method fitted well with lesser LF compared to the weight-based method. The study by Cuvas Apan and Apan mentioned that shape and size of the thenar eminence were similar to that of the I-gel's cuff. Therefore, for selecting the size of I-gel anatomical region – thenar eminence was investigated. Their study shows a statistically significant correlation between the dimension of the thenar eminence and the manufacturer's weight-based recommendation for selecting I gel size in pediatric patients.[7]

The success rate of insertion at the first attempt was 92.5% in group 1 and 97.5% in group 2 in the study was comparable with results in previous studies.[6],[9],[10],[11]

I-gel size selection on a weight-based method had created problem and lower first-attempt success rate due to overlapping of weight which is confusing for the users.[9],[11] Like for size 1.5 (5–12 kg), size 2 (10–25 kg), size 2.5 (25–35 kg), and size 3 (30–60 kg). Janaki Raman's study recommends the manufacturers to review the sizing guidelines to improve the success rate.[11]

The mean insertion time in our study was 17 s in each group which was comparable with previous studies.[9],[12],[13] In other studies, insertion time was ranging between 9.5s and 15s.[6],[10],[12],[14] Longer insertion time in this study can be due to difference in criteria to measure the time for insertion. We calculated the time for insertion as the time from the picking up the device until the achievement of adequate ventilation and I gel was inserted by trainee doctors.

In the present study, ease of insertion of airway devices was difficult in 20% of patients in group 1 compared to 7.5% of patients in group 2. To eliminate observer bias, it was graded subjectively by single anesthesiologist inserting the devices. The first observational study by Beylacq et al. mentioned that I gel is reliable in terms of ease of insertion, adequate seal pressure (mean value of 25 cmH2O), and a low complication rate.[1] This was found to be similar to other studies.[2],[6],[9] Difficulty observed in the present study can be due to the overlapping of weight in the weight-based method.

Airway leak pressure is often used as a marker of the quality of the airway seal. Comparison of leak pressures is complicated by differences in methodology and presentation of results.[6] In this present study, we calculated LF by comparing the difference between inspired and expired TVs and dividing them by the inspired TV. The mean LF was 0.08 ± 0.06 in group 1 and 0.04 ± 0.04 in group 2 (P < 0.05).

Most of the studies measured the oropharyngeal leak pressure by various methods where I gel was selected according to the recommended weight-based method. The oropharyngeal leak pressure varied between 20 cm and 26 cm H2O.[1],[2],[6],[8],[9],[10]

In this study, correct placement of I gel was confirmed by adequate chest rise, square wave capnography, audible leak, Spo2 >95%, and EtCO2 <40. Satisfactory placement can be noted if the expired TV more than 8 ml/kg and no (gastric) drain tube leak.[9]

Other methods such as fiber-optic assessment of the laryngeal view through the I gel[6] and visualization of the glottis by passing a fiber-optic scope through the airway tube to a position 1 cm proximal to the end of the airway tube and scoring view using Brimacombe score.[9]

Studies mentioned minor and infrequent complications[2] to other complications such as laryngospasm, stridor, airway trauma, change of voice, and sore throat,[6],[9] which were neither clinically nor statistically significant. In our study, no complication was observed during insertion or after removal of the I gel in both groups. Hemodynamic parameters were comparable between two groups.

The absence of fiber-optic confirmation of the airway patency, confirmation of correct placement of I gel by only clinical assessment, and inclusion of only low-risk (ASA 1–3) patients with normal airway may be the limitations of our study.

This study would be more helpful in syndromic children, where there is height and weight disproportion.

  Conclusions Top

Thenar eminence dimension method scores well than the weight-based method in terms of lesser LF and lesser incidence of second attempt. A simple method such as thenar eminence dimension may be especially relevant for ambulance staff and emergency physicians is a good proxy for the recommended weight-based method of I-gel size selection.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Beylacq L, Bordes M, Semjen F, Cros AM. The I-gel, a single-use supraglottic airway device with a non-inflatable cuff and an esophageal vent: An observational study in children. Acta Anaesthesiol Scand 2009;53:376-9.  Back to cited text no. 1
Tandale S, Dave N, Garasia M. Evaluation of the I-gel, a supraglottic airway device in children undergoing day care surgery. Med J Dr DY Patil Univ 2015;8:330-3.  Back to cited text no. 2
Wharton NM, Gibbison B, Gabbott DA, Haslam GM, Muchatuta N, Cook TM. I-gel insertion by novices in manikins and patients. Anaesthesia 2008;63:991-5.  Back to cited text no. 3
Soar J. The I-gel supraglottic airway and resuscitation-some initial thoughts. Resuscitation 2007;74:197.  Back to cited text no. 4
Gatward JJ, Thomas MJ, Nolan JP, Cook TM. Effect of chest compressions on the time taken to insert airway devices in a manikin. Br J Anaesth 2008;100:351-6.  Back to cited text no. 5
Beringer RM, Kelly F, Cook TM, Nolan J, Hardy R, Simpson T, et al. A cohort evaluation of the pediatric i-gel(™) airway during anaesthesia in 120 children. Anaesthesia 2011;66:1121-6.  Back to cited text no. 6
Cuvas Apan O, Apan A. The association between thenar eminence and I-gel™ dimensions in pediatric patients. Braz J Anesthesiol 2016;66:171-5.  Back to cited text no. 7
Das B, Mitra S, Samanta A, Vijay BS. Comparison of i-gel™ supraglottic device with classic laryngeal mask airway in anesthetized paralyzed children undergoing elective surgery. Anesth Essays Res 2012;6:180-3.  Back to cited text no. 8
  [Full text]  
Gatward JJ, Cook TM, Seller C, Handel J, Simpson T, Vanek V, et al. Evaluation of the size 4 i-gel airway in one hundred non-paralysed patients. Anaesthesia 2008;63:1124-30.  Back to cited text no. 9
Saran S, Mishra SK, Badhe AS, Vasudevan A, Elakkumanan LB, Mishra G. Comparison of i-gel supraglottic airway and LMA-ProSeal™ in pediatric patients under controlled ventilation. J Anaesthesiol Clin Pharmacol 2014;30:195-8.  Back to cited text no. 10
[PUBMED]  [Full text]  
Janakiraman C, Chethan DB, Wilkes AR, Stacey MR, Goodwin N. A randomised crossover trial comparing the i-gel supraglottic airway and classic laryngeal mask airway. Anaesthesia 2009;64:674-8.  Back to cited text no. 11
Lee JR, Kim MS, Kim JT, Byon HJ, Park YH, Kim HS, et al. A randomised trial comparing the i-gel (TM) with the LMA Classic (TM) in children. Anaesthesia 2012;67:606-11.  Back to cited text no. 12
Francksen H, Renner J, Hanss R, Scholz J, Doerges V, Bein B. A comparison of the i-gel with the LMA-Unique in non-paralysed anaesthetised adult patients. Anaesthesia 2009;64:1118-24.  Back to cited text no. 13
Kannaujia A, Srivastava U, Saraswat N, Mishra A, Kumar A, Saxena S. A preliminary study of I-gel: A new supraglottic airway device. Indian J Anaesth 2009;53:52-6.  Back to cited text no. 14
[PUBMED]  [Full text]  


  [Figure 1], [Figure 2]

  [Table 1], [Table 2]


Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)

  In this article
Subjects and Methods
Article Figures
Article Tables

 Article Access Statistics
    PDF Downloaded63    
    Comments [Add]    

Recommend this journal