Investigating the Fluid Seal of Supraglottic Airway Devices in Humans Using Indicator Dye via the Drainage Tube: A Potential Roadmap for Future Studies

Abstract

Background: The fluid seal of supraglottic airway devices (SGA) protects the airway from fluid contamination. We evaluated the suitability of indicator dye placement in the upper digestive tract of anesthetized patients combined with fiberoptical tracing to investigate the fluid seal of SGA. Methods: Patients swallowed a capsule of indigo carmine green (ICG) prior to induction of anaesthesia. After induction of anesthesia, one of two different SGA (either an i-Gel™ or an LMA-Supreme™ (LMA-S)) was inserted after randomization. Methylene blue stained normal saline was injected through the proximal opening of drainage tube during mechanical ventilation as well as spontaneous breathing. We monitored regurgitation of ICG with a flexible fiberscope (FO) inserted through the drainage tube and checked for the appearance of methylene blue in the mask bowl with the FO inserted through the airway tube. Results: In thirty-six patients with an i-Gel™ and 37 with a LMA-S no regurgitation of ICG was observed at the level of the upper oesophageal sphincter (UES). Methylene blue stained saline was not visible in any patient during pressure-controlled ventilation, but was detected in two of the 36 patients with the i-Gel™ during spontaneous breathing. Conclusion: Instilling dye through the drainage tube of SGA models with a built-in drainage tube represents a useful method to examine and to compare the fluid seal of different SGA. Our protocol presented in this study proved to be an easy and reproducible approach for future studies. Furthermore, the clinical results gained during this evaluation highlight the necessity for further investigations regarding the fluid seal competencies of SGAs in humans under clinical conditions.

Magnetic resonance imaging study of the in vivo position of the extraglottic airway devices i-gel™ and LMA-Supreme™ in anaesthetized human volunteers

“…This is in agreement with results of a study of our group, which evaluated a protocol to investigate the oesophageal seal in humans by instilling dye into the drainage tube of EGA devices. We observed any dye leakage for the i-gel TM or the LMA-S during pressure ventilation but noted dye leaking into the bowl during spontaneous breathing in some patients with the i-gel TM but none with the LMA-S. 17 However, the study of Schmidbauer and colleagues also showed that both the ProSeal TM -LMA and i-gel TM allowed for fast and complete drainage of oesophageal fluids if the drainage tube and oesophageal lumens were open. It remains to be seen whether these results also apply to living humans.…”

Airway Management Evolution – In a Search for an Ideal Extraglottic Airway Device

“…The storage capacity of the LMA Unique is only 3.5 ml which is at least 15 times less than in the SLIPA device (Miller, 2004), and therefore the risks of aspiration with regurgitation are theoretically higher. The use of positive end expiratory pressure or CPAP is likely to provide a measure of protection as it generates a positive pressure gradient (Russo et al, 2012). The posterior force against the pharyngeal wall because of the inadequate natural curvature of the LMA Unique will negate that effect.…”

Efficacy of the LMA-ClassicTM and LMA ProsealTM in Children Undergoing Elective Surgery under General Anaesthesia

“…The modifications in the LMA-Proseal TM are a modified cuff to better seal with both respiratory and gastroesophageal tract; and a drain tube to (a) prevent gastric aspiration; (b) prevent gastric insufflation; (c) facilitate gastric tube insertion; and (d) provide information about position. [7] There was no difference between LMA-Classic TM and LMA-Proseal TM with regard to ease of insertion, number of attempts for insertion, device positional stability, airway trauma and hemodynamic changes. [5] Various randomized controlled trials comparing LMA-Classic TM and LMA-Proseal TM in children have demonstrated no differences in ease of LMA insertion, and number of attempts of LMA insertion.…”