The i-gel® mask is a second generation, single use supraglottic airway device which does not have an inflatable cuff. The cuff consists of a thermoplastic elastomer and its mechanism of sealing still remains unclear. Various theories such as temperature-dependent changes in hardness and volume expansion as well as fluid absorption have been discussed.

The i-gel® mask (Intersurgical, Workingham, UK), is a second generation, single use supraglottic airway device. In contrast to other devices its' cuff consists of a thermoplastic elastomer (styrene-ethylene-butadine-styrene) instead of an inflatable cuff.

Previous studies have shown, that over time the sealing improved compared to the moment of insertion. The sealing process may be based on various mechanisms. It is assumed, that the warming from room to body temperature leads to an improved adaptation to the patient-specific anatomy due to a softening of the elastomer. By definition, an elastomer is softened by the effect of temperature and become harder when reaching the glass transition temperature.

In this context, Dingley et al. described a change in the degree of hardness as a function of temperature. Prewarmed i-gel® masks (42°C, 30min.) seem to have smaller leak volumes compared to masks stored at room temperature postinsertion in paralyzed patients, but was not reproducible in non-paralyzed patients. Looking at the sealing pressure Chauhan et al. reported that i-gel® masks required a lower pressure compared to masks with an inflatable cuff.

At this point it is not yet clear, whether the thermoplastic cuff material only expands due to an increase in temperature. Liquid absorption and a consecutive expansion is also theoretically conceivable.

Therefore, the aim of the present study is to examine the i-gel® mask within the scope of a benchtop study for temperature-dependent volume expansion and liquid absorption.

Inclusion Criteria:

• Elective surgery

Exclusion Criteria:

• Contraindications for the use of i-gel masks.
• Emergency operation
• non fasted patient

Masks used in patients (n=5 per size; #3, #4, #5) requiring general anaesthesia for elective surgery without contraindications for i-gel® were collected postoperatively.