title: Tracheal sealing by auto-inflation in tracheal tube cuffs.
abstract: 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.
authors.affiliation: Department of Anaesthesia, University Children's Hospital, Zurich, Switzerland. markus.weiss@kispi.unizh.ch
authors.forename: Markus
authors.initials: M
authors.lastname: Weiss
authors.forename: George
authors.initials: G
authors.lastname: Shorten
authors.forename: Katharina
authors.initials: K
authors.lastname: Stutz
authors.forename: Vera
authors.initials: V
authors.lastname: Bernet
mesh_terms: D004867:Equipment Design; D007385:Intermittent Positive-Pressure Ventilation / Q000379:methods; D007442:Intubation, Intratracheal / Q000009:adverse effects / Q000295:instrumentation*; D013990:Tidal Volume / Q000502:physiology