Secure insertion of the i-gel supraglottic airway device in children

A cohort study

Editor,

The adult i-gel supraglottic airway device (Intersurgical Inc., Berkshire, UK) is marked with a line to show the recommended insertion depth while that for children less than 3 years does not. There is no consensus for the best secure fixation method, and paediatric-size i-gels are prone to sliding out of the mouth, indicating the need for a strategy to secure it in place.^1,2 It is also unclear how the manufacturer determines the insertion depths of larger i-gels for adults. The current study was conducted to determine the best secure position of two different insertion methods for the size #2 i-gel in children by comparing the leak pressure and fibre-optic view of the epiglottis.

The St. Mary's Hospital's Institutional Review Board (no. 16-1009) approved the research, and the protocol was registered before patient enrolment at the UMIN Clinical Trials Registry (number UMIN R000028847). Written informed consent was obtained from the parents. One hundred paediatric surgical patients between ages 1 and 8 years received general anaesthesia using sevoflurane inhalation without a muscle relaxant. The selection of the size #2 device was based on the recommended range of body weight (10 to 25 kg) by the manufacturer. The size #2 i-gel was inserted when the end-tidal concentration of sevoflurane was 4% and was fixed using surgical tape when some resistance was felt (Position A). The leak pressure and tidal volume (V_T, ml kg⁻¹) with manual ventilation at a fresh gas flow of 3 l min⁻¹, the insertion depth defined as the distance between the incisor teeth and the tip of the device, and the fibre-optic glottis view graded (score 1 = full view of vocal cords, score 2 = more than 50% of the visible cords, score 3 = less than 50% of the visible cords and score 4 = only the epiglottis was visible) were all noted. The evaluations were repeated after the breathing system was disconnected. The operator then released the shaft of the i-gel from the hand to allow the device to rise from the oral cavity and it was fixed at this point with surgical tape (Position B). To avoid manipulation bias a single experienced anaesthesiologist performed the fibre-optic bronchoscopy in all cases. Adverse events were also evaluated. A sample size of 27 gave 81% power to a detected leak pressure change of 4.9 cmH₂O at a significance level of 0.05 (SD = 6.2). Overall comparisons of leak pressure within the fibre-optic grades were performed using one-factor ANOVA; post hoc individual comparisons were made using Scheffé's method for multiple comparisons. Differences in fibre-optic grade between the groups were compared using the Wilcoxon–Mann–Whitney test. Data are expressed as mean ± SD except those of the fibre-optic view (median [interquartile range]). P less than 0.05 was considered to indicate a statistically significant difference.

The mean age, height and weight of the enrolled patients were 3.0 [2 to 4] years, 92.8 [85 to 101] cm and 13.7 [12 to 16] kg. The mean insertion depth was deeper at Position A compared with that at Position B by a mean of 2 cm, whereas the leak pressure was higher in Position A than Position B (21.2 ± 5.2 vs. 16.4 ± 6.2 cmH₂O; P < 0.001, Fig. 1a). The median fibre-optic score in Position A (1 [1 to 2]) was better than that of Position B (3 [3 to 4], P < 0.01, n = 100 each, Fig. 1b). There were no differences in the leak pressure among scores 1 to 3, whereas the pressure was least in the score 4 (n = 200, P < 0.05 vs. score 1, 2 or 3, Fig. 1b). The V_T in Position A was larger than that in B (16.6 ± 4.4 vs. 7.45 ± 5.7 ml kg⁻¹, P < 0.01). The higher score for the view related to the lower leak pressure (score 1: 21.1 ± 4.7, score 2: 21.0 ± 5.5, score 3: 18.8 ± 5.3 and score 4: 14.4 ± 6.0 cmH₂O, P < 0.01, Fig. 1b). Bloodstaining at the tip of the i-gel after removal was observed in two cases, whereas postoperative laryngeal discomfort did not occur in any patient. There was no laryngospasm, sore throat, bleeding, bruising or numbness.

Fig. 1: (a) The comparison leak pressure between Position A and Position B. Comparison of the leak pressure between Position A and Position B shown using the box-plot diagram. The leak pressure decreased in Position B compared with Position A (^# P < 0.05). (b) Variation of the fibre-optic score in Position A and Position B. There were no differences in the leak pressure among scores 1 to 3, whereas the pressure was least in the score 4 (n = 200, ^∗ P < 0.05 vs. score 1, 2 or 3).

There are no established criteria for the insertion depth of i-gel in children because of the substantial variation in the oropharyngeal–laryngeal arch in the young. Insertion of the i-gel until some resistance was felt (Position A) resulted in better fibre-optic views along with higher leak pressures. Also, the leak pressure of the i-gel in Position A was comparable with pressure values reported previously.^2–4 These results suggest that the secure fixation at Position A is probably better for insertion of the paediatric #2 i-gel although the difference in insertion depth between Position A and Position B was small (2 cm). One may argue that ventilation from the supraglottic airway device is possible despite the poor fibre-optic view obtained.⁵ The significance of a better fibre-optic view of the larynx, and also higher leak pressure, in terms of the optimum insertion depth for the use of i-gel therefore, is still unclear.

In conclusion, we recommend that clinicians insert the size #2 i-gel until some resistance is felt and secure it in this position. Unlike other supraglottic airway devices the paediatric-size device needs to be actively pushed inward and held in place by tape.