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 cmH2 O, 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 cmH2 O 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 cmH2 O was recorded.

RESULTS: Mean (SD) volume of air required to achieve the intracuff pressure of 60 cmH2 O 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 cmH2 O) 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 cmH2 O except LMA-ProSeal™ which required two-thirds of the maximum recommended volume.

TRIAL REGISTRATION: Thai Clinical Trials Registry, TCTR20150602001, May 28, 2015.