A novel method to develop an elastic, thin-walled, leak-proof, inflatable tracheal tube cuff

Introduction

Commercially available endotracheal tube (ETT) cuffs are made of PVC polymer that shows little stretch upon inflation, resulting in a need for a cuff diameter larger than the trachea. Such cuffs form folds, which became a ready passageway for bacteria-colonized subglottic secretions. We developed an elastic and smooth balloon with no folds upon inflation.

Methods

In vitro study

Six different ETTs with the newly designed cuff were tested for leakage in a 20 mm internal diameter acrylic tube at 20 cmH₂O (1.96 kPa) inflation pressure, pouring 20 ml methylene-blue colored water into the acrylic tracheal tube above the cuff to visualize any leak. We observed the ETT cuff for 24 hours for possible leakage.

In vivo study

Four Yukatan minipigs were intubated with the new ETT cuff and mechanically ventilated for ~40 hours. Methylene-blue colored water was poured into the subglottic space through a line attached to the ETT. We looked for blue discoloration of mucus retrieved during the tracheal suction at 5, 10 and 30 minutes following instillation. At autopsy, tracheal mucosa was examined for possible cuff-related damage.

Results

The Lycra cuff was devoid of folds upon inflation, and touched the wall of the mock trachea. There was no leakage of methylene-blue colored water. Instead, the average leakage across the Mallinkrodt Hi-Lo cuff was 1,182.2 ± 1,321.0 ml/hour (P < 0.0001 vs. the Lycra prototype); the average leakage across the Microcuff was 12.2 ± 3.6 ml/hour (P < 0.0001 vs. the Lycra prototype, and P < 0.01 vs. the Microcuff).

We observed no methylene-blue in tracheal secretions. The pig trachea appeared normal at autopsy, with no signs of erosion.

Conclusion

We showed that a new concept, a smooth ultrathin elastic tracheal tube cuff, can perform better than present commercially available tracheal tubes.