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 eighty 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®), AuraOnceTM (Ambu®), LMA-ClassicTM (Teleflex®) and LMA-ProSealTM (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®, AuraOnceTM, LMA-ClassicTM, LMA-ProSealTM 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-ProSealTM which required two-thirds of the maximum recommended volume. Trial registration: Thai Clinical Trials Registry, TCTR20150602001, May 28, 2015

Correlation and variation of cuff inflating volumes and pressures in different adult models of laryngeal mask airway: 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 cmH 2 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 cmH 2 O in the adult laryngeal masks from different manufacturers. Methods : Two groups of eighty 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 TM (Ambu ® ), LMA-Classic TM (Teleflex ® ) and LMA-ProSeal TM (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 cmH 2 O was recorded . Results : Mean(SD) volume of air required to achieve the intracuff pressure of 60 cmH 2 O in Soft Seal ® , AuraOnce TM , LMA-Classic TM , LMA-ProSeal TM 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 cmH 2 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 cmH 2 O except LMA-ProSeal TM which required two-thirds of the maximum recommended volume. Trial registration: Thai Clinical Trials Registry, TCTR20150602001, May 28, 2015

Correlation and variation of cuff inflating volumes and pressures in the adult laryngeal masks: 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 eighty 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®), AuraOnceTM (Ambu®), LMA-ClassicTM (Teleflex®) and LMA-ProSealTM (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®, AuraOnceTM, LMA-ClassicTM, LMA-ProSealTM 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: Approximately half of the maximum recommended volume is required to achieve the intracuff pressure of 60 cmH2O except LMA-ProSealTM which required two-thirds of the maximum recommended volume. Trial Registration: Thai Clinical Trials Registry, TCTR20150602001, May 28, 2015. Keywords: Laryngeal mask, cuff inflating volume, intracuff pressure.

Structural Design for Oil Well Pump with Soft Sealing and Small Diameter Piston

For the low pumping demand of daily production per well of low permeability oilfield, a diameter of 25mm soft sealing small diameter piston-type subsurface pump is designed, and an external traveling valve to ensure that the valve still application of standard parts is adopted, while reducing the pump barrel diameter. In order to solve the problems of pump leakage increasing with wear, automatically compensate for soft seal ring is adopted in piston design. The liquid pressure of the pump barrel is changed in the pump working process, so that the sealing ring is deformed outwardly. When the pump reaches the upper stroke, the gap between the pump barrel and the piston reduced, and further improve the sealing effect. The innovation of structure and the selection of new materials can reduce the difficulty of pump processing, as well as can extend the maintenance cycle. This paper introduces the overall structure and sealing characteristics of soft sealing small diameter piston-type subsurface pump. If the soft sealing small diameter piston-type subsurface pump and real-time variable frequence control technique of pumping unit combined, a more reasonable machine rod pump combination can be provided to achieve ultra-low permeability oilfield stripped well efficiently pumping.