Cuff filling volumes for pediatric classic laryngeal mask airways: comparison of clinical end points versus adjusted cuff pressure

Efficacy and safety of three inflation methods of the laryngeal mask airway Ambu® Auraonce™: a randomized controlled study

The laryngeal mask airway (LMA) is commonly used for airway management. Cuff hyperinflation has been associated with complications, poor ventilation and increased risk of gastric insufflation. This study was designed to determine the best cuff inflation method of AuraOnce™ LMA during bronchoscopy and EBUS (Endobronquial Ultrasound Bronchoscopy) procedure. We designed a Randomized controlled, doble-blind, clinical trial to compare the efficacy and safety of three cuff inflation methods of AuraOnce™ LMA. 210 consenting patients scheduled for EBUS procedure under general anesthesia, using AuraOnce™ LMA were randomized into three groups depending on cuff insufflation: residual volume (RV), half of the maximum volume (MV), unchanged volume (NV). Parameters regarding intracuff pressure (IP), airway leak pressure (OLP), leakage volume (LV) were assessed, as well as postoperative complications (PC). 201 (95.7%) patients completed the study. Mean IP differed between groups (MV: 59.4 ± 32.4 cm H2O; RV: 75.1 ± 21.1 cm H2O; NV: 83.1 ± 25.5 cmH20; P < 0.01). The incidence of IP > 60 cmH2O was lower in the MV group compared to the other two (MV: 20/65(30.8%); RV:47/69 (68.1%); NV 48/67 (71.6%); p < 0.01). The insertion success rate was 89,6% (180/201) at first attempt, with no difference between groups (p = 0.38). No difference between groups was found either for OLP (p = 0.53), LV (p = 0.26) and PC (p = 0.16). When a cuff manometer is not available, a partial inflation of AuraOnce™ LMA cuff using MV method allows to control intracuff pressure, with no significant changes of OLP and LV compared to RV and NV insufflation method.Registration clinical trial: NCT04769791.

Correlation and variation of cuff inflating volumes and pressures in different adult models of laryngeal mask: a prospective randomized trial

BACKGROUND

Hyperinflation of laryngeal mask cuffs may carry the risk of airway complications. The manufacturer recommends inflating cuff until the intracuff pressure reaches 60 cmH2O, or inflate with the volume of air to not exceed the maximum recommended volume. We prospectively assessed the correlation of cuff inflating volumes and pressures, and the appropriated the cuff inflating volumes to generate an intracuff pressure of 60 cmH2O in the adult laryngeal masks from different manufacturers.

METHODS

Two groups of 80 patients requiring laryngeal mask size 3 and 4 during general anesthesia were randomized into 4 subgroups for each size of the laryngeal mask: Soft Seal® (Portex®), AuraOnce™ (Ambu®), LMA-Classic™ (Teleflex®) and LMA-ProSeal™ (Teleflex®). After insertion, the cuff was inflated with 5-ml increments of air up to the maximum recommended volume. After each 5-ml intracuff pressure was measured, the volume of air that generated the intracuff pressure of 60 cmH2O was recorded.

RESULTS

Mean (SD) volume of air required to achieve the intracuff pressure of 60 cmH2O in Soft Seal®, AuraOnce™, LMA-Classic™, LMA-ProSeal™ laryngeal mask size 3 were 11.80(1.88), 9.20(1.88), 8.95(1.50) and 13.50(2.48) ml, respectively, and these volumes in laryngeal mask size 4 were 14.45(4.12), 12.55(1.85), 11.30(1.95) and 18.20(3.47) ml, respectively. The maximum recommended volume resulted in high intracuff pressures (> 60 cmH2O) in all laryngeal mask types and sizes studied.

CONCLUSION

Pressure-volume curves of adult laryngeal masks are all in sigmoidal shape. Cuff designs and materials can effect pressure and volume correlation. Approximately half of the maximum recommended volume is required to achieve the intracuff pressure of 60 cmH2O except LMA-ProSeal™ which required two-thirds of the maximum recommended volume.

TRIAL REGISTRATION

Thai Clinical Trials Registry, TCTR20150602001, May 28, 2015.

Application of Minimum Effective Cuff Inflating Volume for Laryngeal Mask Airway and its Impact on Postoperative Pharyngeal Complications

BACKGROUND

High intracuff pressure can cause severe pharyngeal complications including sore throat or hoarseness after laryngeal mask airway (LMA) removal postoperatively. Though the application of minimum effective cuff inflating volume is suggested to maintain airway sealing and adequacy of ventilation for patients receiving general anesthesia with LMA at lower level of the intracuff pressure, it is currently not a standard care in most of the anesthetic departments. In this study, the minimum effective cuff inflating volume was determined for classic LMA Well Lead™ (Well Lead Medical Co., Ltd., China) and its impact on postoperative pharyngeal complications was also explored.

METHODS

Patients with American Society of Anesthesiologists physical status (I-III) undergoing the short-duration urological surgery were recruited in this trial. First, the minimum effective cuff inflating volume was determined for size 4 or 5 LMA Well Lead in the study 1. Immediately following placement and confirmation of ideal LMA position, the cuff was inflated with 5, 7, 10 ml of air and up to 30 ml at 5 ml increment. The intracuff pressure, oropharyngeal leak pressure (OLP), and inspiratory peak airway pressure under positive pressure ventilation at the corresponding cuff volume as indicated above were recorded. Second, the enrolled patients were randomly allocated into minimum effective cuff inflating volume group (MC) and routine care (RC) group in the study 2. The minimum effective cuff inflating volume was applied and maintained in MC group, whereas the cuff volume was inflated with half of the maximum cuff inflating volume recommended by manufacturer in RC group throughout the surgical procedure and stay in postanesthesia care unit prior to LMA removal. The incidence of pharyngeal complications at 0, 2, 24, and 48 h after removal of LMA and other intra-operative adverse events were also documented.

RESULTS

The intracuff pressure varied with the cuff inflating volume in a positive linear correlation manner (Y = 11.68X - 42.1, r(2) = 0.9191) under the range of 5-30 ml for size 4 LMA. In similar with size 4 LMA, the data were also showed the linear relationship between the intracuff pressure and the cuff inflating volume (Y = 7.39X - 10.9, r(2) = 0.8855) for size 5 LMA. The minimal effective cuff inflating volume for size 4 or 5 LMA was 7-9 ml in combination of considering OLP needed to maintain airway sealing during intermittently positive pressure ventilation. The intracuff pressure in MC group was lower compared with RC group (63.0 ± 3.7 vs. 126.4 ± 24.0 cmH2O for size 4 LMA; 55.6 ± 2.4 vs. 138.5± 26.8 cmH2O for size 5 LMA; P < 0.0001). The incidence of pharyngeal adverse events was lower in MC group versus the RC group at 2, 24 h after LMA removal.

CONCLUSIONS

The relationship between the cuff inflating volume and the intracuff pressure for size 4 or 5 LMA Well Lead(TM) is in a linear correlation manner at the range of 5-30 ml. The minimal cuff inflating volume is adequate for satisfactory airway sealing and consequently associated with lower incidence of postoperative pharyngeal complications for LMA Well Lead.™.

Effect of intranasal dexmedetomidine or oral midazolam premedication on sevoflurane EC50 for successful laryngeal mask airway placement in children: a randomized, double-blind, placebo-controlled trial

INTRODUCTION

This study was conducted to determine the effect of oral midazolam (OM) or intranasal dexmedetomidine (IND) on the EC50 of sevoflurane for successful laryngeal mask airway placement in children. We hypothesize that premedication with either agent might reduce the sevoflurane EC50 for laryngeal mask airway placement in children to a similar extent.

METHODS

Fifty-two American Society of Anesthesiologists (ASA) I children (aged 1-6 years) scheduled for general anesthesia with laryngeal mask airway were randomized to one of the three groups: group M received 0.5 mg · kg(-1) OM with honey and intranasal saline, group D received 2 μg · kg(-1) IND along with oral honey, and group P received oral honey and intranasal saline at least 30 min prior to induction of anesthesia. Anesthesia was induced with incremental sevoflurane up to 8% in 100% O2 . A predetermined target endtidal sevoflurane (ETsevo ) concentration (2% in the first child of all three groups) was sustained for 10 min before the attempt of laryngeal mask airway insertion by adjusting dial concentration. No intravenous anesthetic or neuromuscular blockade was used. ETsevo was increased/decreased (step size 0.2%) using Dixon's and Massey's up and down method in next patient depending upon previous patient's response. Placement of the laryngeal mask airway without movement, coughing, biting, or bucking was considered as successful. EC50 of sevoflurane was calculated as the average of the crossover midpoints in each group, which was further confirmed by probit analysis.

RESULTS

The EC50 of sevoflurane for laryngeal mask airway placement after OM (1.66 ± 0.31) and IND (1.57 ± 0.14) premedications was significantly lower than the placebo group (2.00 ± 0.17, P < 0.0001). The EC95 (95% CI) derived from probit regression analysis was 2.34% (2.22-2.51%) with OM, 1.88% (1.77-2.04%) with IND, and 2.39% (2.25-2.35%) with placebo group.

CONCLUSIONS

Oral midazolam and IND premedications significantly reduce the sevoflurane EC50 for laryngeal mask airway insertion in children by 17% and 21%, respectively.

Randomized evaluation of the size 2 laryngeal tube and classical laryngeal mask airway in different head and neck positions in children under positive pressure ventilation

PURPOSE

The aim of this study was to evaluate the applicability of the laryngeal tube (LT) size 2 and the classical laryngeal mask airway (LMA) size 2 in different head-neck positions under positive pressure ventilation in children by measuring leak pressures, peak pressures and the achievable tidal volumes under positive pressure ventilation.

METHODS

Forty children were randomized to receive airway management by either the LT or LMA as the primary device. Leak pressures, peak pressures and tidal volumes under positive pressure ventilation were measured in the neutral, anteflection, retroversion, left-rotation and right-rotation head-neck positions.

RESULTS

In all head-neck positions, the leak pressures were significantly higher for the LT than for the LMA (neutral 25.9 ± 7.0 vs. 19.1 ± 5.7 cmH2O; anteflection 29.7 ± 7.1 vs. 24.2 ± 8.9 cmH2O; retroversion 24.1 ± 7.6 vs. 17.2 ± 6.9 cmH2O). In both devices, the peak ventilation pressures were higher in the anteflection position (LT 27.1 ± 6.3 cmH2O; LMA 17.8 ± 6.7 cmH2O) than in the retroversion position (LT 13.7 ± 3.9 cmH2O; LMA 12.7 ± 3.6 cmH2O). Compared to the respirator settings, lower tidal volumes were achieved in the anteflection position (LT 65 ± 48 vs. 129 ± 38 ml, LMA 100 ± 21 vs. 125 ± 29 ml) as compared to the other positions.

CONCLUSION

Based on our results, we suggest that in anaesthetized children, the size 2 LT, compared to the size 2 LMA, may be more suitable for positive pressure ventilation due to favorable leak and peak pressures. Both devices can be safely used in head-neck positions other than neutral. Most disadvantageous with regards to the measured parameters was the anteflection position, especially for the LT.