title: In vitro evaluation of the method effectiveness to limit inflation pressure cuffs of endotracheal tubes.
abstract: OBJECTIVE
  Cuffs of tracheal tubes protect the lower airway from aspiration of gastric contents and facilitate ventilation, but may cause many complications, especially when the cuff pressure exceeds 30cm H2O. This occurs in over 30% of conventional insufflations, so it is recommended to limit this pressure. In this study we evaluated the in vitro effectiveness of a method of limiting the cuff pressure to a range between 20 and 30cm H2O.
  
  
  METHODS
  Using an adapter to connect the tested tube to the anesthesia machine, the relief valve was regulated to 30cm H2O, inflating the cuff by operating the rapid flow of oxygen button. There were 33 trials for each tube of three manufacturers, of five sizes (6.5-8.5), using three times inflation (10, 15 and 20s), totaling 1485 tests. After inflation, the pressure obtained was measured with a manometer. Pressure >30cm H2O or <20cm H2O were considered failures.
  
  
  RESULTS
  There were eight failures (0.5%, 95% CI: 0.1-0.9%), with all by pressures <20cm H2O and after 10s inflation (1.6%, 95% CI: 0 5-2.7%). One failure occurred with a 6.5 tube (0.3%, 95% CI: -0.3 to 0.9%), six with 7.0 tubes (2%, 95% CI: 0.4-3.6%), and one with a 7.5 tube (0.3%, 95% CI: -0.3 to 0.9%).
  
  
  CONCLUSIONS
  This method was effective for inflating tracheal tube cuffs of different sizes and manufacturers, limiting its pressure to a range between 20 and 30cm H2O, with a success rate of 99.5% (95% CI: 99.1-99.9%).
authors.affiliation: Centro de ensino e Treinamento (CET), Santa Casa de Misericórdia de São Paulo, São Paulo, SP, Brazil. Electronic address: rafaelcoelho.md@gmail.com.
authors.forename: Rafael de Macedo
authors.initials: Rde M
authors.lastname: Coelho
authors.affiliation: Centro de ensino e Treinamento (CET), Santa Casa de Misericórdia de São Paulo, São Paulo, SP, Brazil.
authors.forename: Thiago Trigueiro Morais
authors.initials: TT
authors.lastname: de Paiva
authors.affiliation: Faculdade de Ciências Médicas, Santa Casa de São Paulo, São Paulo, SP, Brazil; Discipline of Anesthesiology and Pain, Santa Casa de Misericórdia de São Paulo, São Paulo, SP, Brazil.
authors.forename: Ligia Andrade
authors.initials: LA
authors.lastname: da Silva Telles Mathias
mesh_terms: D000758:Anesthesia / Q000379:methods*; D004867:Equipment Design; D006801:Humans; D007442:Intubation, Intratracheal / Q000295:instrumentation / Q000379:methods*; D010100:Oxygen / Q000008:administration & dosage; D011312:Pressure
chemical_list: D010100:Oxygen
keywords: Balonetes; Cuffs; Cânulas; Inflation; Insuflação; Method; Método; Pressure; Pressão; Tube