Tracheal sealing by auto-inflation in tracheal tube cuffs.

BACKGROUND

The purpose of this study was to determine if inspiratory pressure from intermittent positive pressure ventilation may be sufficient to inflate the cuff (thus 'auto-inflation') and thereby seal the trachea.

METHODS

In a laboratory model we investigated the ability of cuffs of seven 5.0 mm internal diameter (ID) tracheal tubes (Sheridan CF, Mallinckrodt Hi-Contour, Mallinckrodt Sealguard, Mallinckrodt Safety-Flex, Portex Soft Seal, Rueschelit Super-Safety Clear and Microcuff PET) to seal the trachea by auto-inflation, i.e. by using the inspiratory pressure to expand and keep open the cuff within the trachea. A mechanical lung connected to a model trachea made from clear, rigid polyvinylchloride (PVC) (12 mm ID) was used to simulate changes in inspiratory pressures. Respirator settings were: fresh gas flow (air) 6 lxmin(-1); positive end-expiratory pressure 5 cmH(2)O; respiratory rate 20 brxmin(-1); I : E ratio = 1 : 2; inspiratory pressure 5, 10, 15, 20, and 25 cmH(2)O. Percentage of expiratory to inspiratory tidal volume (E : I V(t) volume ratio) was calculated.

RESULTS

Using lubricated Mallinckrodt Seal Guard tube cuffs E : I V(t) volume ratio was almost 100% at a peak inspiratory pressure of 10 cmH(2)o whereas in tube cuffs particularly made of PVC an E : I ratio was achieved only at higher inspiratory pressures, if at all.

CONCLUSIONS

Auto-inflation in the Mallinckrodt Seal Guard with high volume-low pressure polyurethane cuff can produce adequate tracheal sealing in the model trachea used. The implication is that such auto-inflation should decrease the risk of tracheal injury from acute or persistent cuff hyperinflation.