title: PVC tracheal tubes exert forces and pressures seven to ten times higher than silicone or armoured tracheal tubes--an in vitro study.
abstract: OBJECTIVE
  Many types of tracheal tubes (TT) including silicone, polyvinylchloride (PVC) and armoured have been used for blind tracheal intubation (TI) via the intubating laryngeal mask airway (ILMA) and may cause trauma to the airway. We examined the maximal in vitro forces and pressures exerted by the tip of various TT as it exits the ILMA.
  
  
  METHODS
  Silicone, PVC and armoured TT were studied. A #5 ILMA was secured on a wooden platform. With the use of a Harvard pump, force was applied to push the TT through the ILMA at 0.34 cm*sec(-1). Forces exerted to push the TT and forces exerted by the TT tips on distal objects were calculated using proximal and distal pressure manometres. The areas of contact between the distal TT tips and the distal objects were measured by planimetry of an imprint. The final pressures exerted by the TT tips on a fixed distal object were calculated by dividing the forces exerted by the areas of contact.
  
  
  RESULTS
  When compared to silicone and armoured TT, PVC TT exerted seven to ten times higher forces and pressures on distal objects. (P < 0.05). Heating PVC TT and inserting PVC TT with reverse curvature to the ILMA did not decrease the forces and pressures exerted by the distal tip.
  
  
  CONCLUSIONS
  The high forces and pressures exerted by PVC TT may theoretically contribute to increased morbidity to patients' airway and esophagus. Caution should be exercised before attempting blind TI via the ILMA with a PVC TT.
authors.affiliation: Departments of Anaesthesia, St. Michael's Hospital and the University Health Network, University of Toronto, Toronto, Ontario, Canada. hwanjoomd@yahoo.com
authors.forename: Hwan S
authors.initials: HS
authors.lastname: Joo
authors.forename: Mark T
authors.initials: MT
authors.lastname: Kataoka
authors.forename: Robert J B
authors.initials: RJ
authors.lastname: Chen
authors.forename: John
authors.initials: J
authors.lastname: Doyle
authors.forename: C David
authors.initials: CD
authors.lastname: Mazer
mesh_terms: D007442:Intubation, Intratracheal / Q000295:instrumentation*; D017214:Laryngeal Masks; D011143:Polyvinyl Chloride; D011312:Pressure; D012828:Silicones
chemical_list: D012828:Silicones; D011143:Polyvinyl Chloride