Compliance characteristics of the Portex Soft Seal Cuff improves seal against leakage of fluid in a pig trachea model

Abstract

The Portex Soft Seal high-volume, low-pressure cuffed tracheal tube was compared with the Mallinckrodt HiLo, Sheridan Preformed and Portex Profile tracheal tubes for leakage of dye placed in the subglottic space of a pig's trachea which was used in a benchtop mechanical ventilation model and in six isolated pig tracheas. There was no leakage, either in the ventilation model or in the isolated tracheas in the Portex Soft Seal group. There was rapid leakage in the ventilation model and in all the isolated tracheas for the Mallinckrodt HiLo, and five out of six isolated tracheas for the Sheridan Preformed and the Portex Profile group. This benchtop study suggests that the improved compliance characteristics of the Portex Soft Seal cuff are beneficial in preventing leakage of fluid in these models.

Background:

The Portex Soft Seal high-volume, low-pressure cuffed tracheal tube was compared with the Mallinckrodt HiLo, Sheridan Preformed and Portex Profile tracheal tubes for leakage of dye placed in the subglottic space of a pig's trachea which was used in a benchtop mechanical ventilation model and in six isolated pig tracheas.

Results:

There was no leakage, either in the ventilation model or in the isolated tracheas in the Portex Soft Seal group. There was rapid leakage in the ventilation model and in all the isolated tracheas for the Mallinckrodt HiLo, and five out of six isolated tracheas for the Sheridan Preformed and the Portex Profile group.

Conclusions:

This benchtop study suggests that the improved compliance characteristics of the Portex Soft Seal cuff are beneficial in preventing leakage of fluid in these models.

Introduction

].

]. These folds always occur in a HVLP cuff inflated within a trachea, because the diameter of the cuff must be greater than that of the trachea for the intracuff pressure to be equal to the tracheal wall pressure. The Portex Soft Seal cuff (Portex Ltd, Hythe, UK) is made of a more compliant material than are traditional HVLP cuffs. Once inflated within the trachea the improved compliance might lead to the elimination of the folds in the cuff wall for a full circumference, thereby protecting against aspiration.

This study compares the Portex Soft Seal with three standard HVLP cuffed tracheal tubes for leakage of dye past the cuff in a benchtop model of mechanical ventilation, in a rigid cylinder and in isolated pig tracheas with dimensions across the human tracheal diameter range.

Static pig trachea model

] was 1.4-2.7 cm, and the mean diameter of a female trachea was 1.84 cm. We felt that it would be reasonable to take 1.4-2.5 cm as an estimate for tracheal size appropriate for a size 8 mm internal diameter tube (ie smaller adults are often intubated with 8 mm internal diameter tube and large adults with a size 9mm internal diameter tube). A 2 cm diameter rigid cylinder (20 ml syringe barrel, Plastipak; Becton Dickinson, Drogheda, Ireland) was also used.

O with a commercial cuff inflator (Portex). The cuff inflator had been checked against a mercury column to confirm accuracy. The tube was hidden so that the observer was blinded to the tube type used. A stopwatch was started once 3.5 ml blue dyed water had been placed above the cuff. The observer stopped the watch when dye was first observed to drip from the trachea below. If no dye had leaked after 15 min, then this was recorded as no leak.

Dynamic lung/trachea model

], but modified so that instead of a silicone trachea a 9-cm section of pig trachea (anteroposterior diameter 1.6 cm, lateral diameter 1.9 cm, measured using a Vernier caliper) was used. The pig trachea was secured by inserting the tubing 1.5 cm into the lower end of the tracheal lumen and binding it tightly with circumferential elastic bands. The trachea lay at 60° to the horizontal.

O.

Blue dyed water (3.5 ml) was instilled above the cuff by one investigator, and an observer blinded to the tube type observed the lower trachea for leakage for 15 min. If no leakage had occurred after 15 min then the cuff was tested by suctioning the trachea for 30s through a 14 CH tracheal suction catheter placed just distal to the tracheal tube tip. The cuffs were also tested for leakage associated with movement of the cuff within the trachea through standardized 2 cm proximal to distal and 45° rotation manoeuvres.

Tubes evaluated

Size 8 mm internal diameter Portex Soft Seal, Portex Profile, Mallinckrodt HiLo (Mallinckrodt Medical GmbH, Hennef/Sieg, Germany) and Sheridan Preformed tubes (Kendall Sheridan, Argyle, New York, USA) were tested.

Results

< 0.05, Fisher's exact test).

The six tracheas in the static model had a mean lateral diameter of 1.76 cm (range 1.4-2.45 cm) and a mean anteroposterior diameter of 1.8 cm (range 1.5-2.5 cm).

Discussion

]. A tube that eliminates leakage from the pharynx to the lungs could have an important role in improving the safety of mechanical ventilation. Leakage past an adequately inflated HVLP tracheal tube cuff occurs exclusively along the folds within the cuff wall.

One of the six tracheas did not permit leakage with the Portex Profile and the Sheridan Preformed tube in the static model. This trachea was at the upper end of the tracheal diameter range for a size 8 mm internal diameter cuffed tube (2.5 cm anteroposterior diameter and 2.4 cm lateral diameter). After cuff inflation, if a trachea happens to have a diameter that closely matches that of the cuff then folding of the cuff material may not occur, eliminating the formation of channels, and leakage is prevented. If this occurs in the clinical situation then a higher cuff pressure is likely to be necessary to prevent an air leak.

. The mechanism by which the more compliant Portex Soft Seal cuff protects against leakage is the elimination of the folds in the cuff wall for a full circumference of the trachea/cuff contact zone, effectively damming the channels. This does not happen with traditional HVLP cuffs, because they are made of poorly compliant material.

] and more recently the Tracoe cuff inflation unit (Tracoe Gesellschaft für medizinische Bedarfsgegenstände mbH, Neu-Isenburg, Germany) have been designed to maintain intracuff pressure. A cuff that prevents aspiration should perhaps always be used with a constant pressure inflation device to prevent aspiration continuously.

].

In conclusion, the present study shows that the Portex Soft Seal tracheal tube cuff effectively prevents leakage of subglottic fluid to the lungs in the isolated pig trachea static and dynamic models. The outcome of a clinical randomized controlled trial is required before recommendations can be made.

Figures and Tables

Dynamic lung/trachea model.

O. Increased distension of the Soft Seal due to increased compliance of the cuff material is seen.

The effect of cuff type on leakage past the tracheal tube cuff in a static and a dynamic pig trachea model

Keywords

• aspiration
• cuff
• intratracheal
• intubation
• pneumonia
• ventilator-associated pneumonia