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

摘要

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-GelTM or an LMA-SupremeTM (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-GelTM 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-GelTM 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.