title: Good short-term agreement between measured and calculated tracheal pressure.
abstract: BACKGROUND
  Tracheal pressure (P(tr)) is required to measure the resistance of the tracheal tube and the breathing circuit. P(tr) can either be measured with a catheter or, alternatively, calculated from the pressure-flow data available from the ventilator.
  
  
  METHODS
  Calculated P(tr) was compared with measured P(tr) during controlled ventilation and assisted spontaneous breathing in 18 healthy and surfactant-depleted piglets. Their lungs were ventilated using different flow patterns, tidal volumes (V(T)) and levels of positive end-expiratory pressure.
  
  
  RESULTS
  In terms of the root mean square error (RMS), indicating the average deviation of calculated from measured P(tr), the difference between calculated and measured P(tr) was 0.6 cm H(2)O (95%CI 0.58-0.65) for volume-controlled ventilation; 0.73 cm H(2)O (0.72-0.75) for pressure support ventilation; and 0.78 cm H(2)O (0.75-0.80) for bi-level positive airway pressure ventilation.
  
  
  CONCLUSIONS
  The good agreement between calculated and measured P(tr) during varying conditions, suggests that calculating P(tr) could help setting the ventilator and choosing the appropriate level of support.
authors.affiliation: Department of Surgical Sciences, Section of Anaesthesiology and Intensive Care Medicine, Uppsala University, Sweden. m.lichtwarck-aschoff@t-online.de
authors.forename: M
authors.initials: M
authors.lastname: Lichtwarck-Aschoff
authors.forename: A
authors.initials: A
authors.lastname: Helmer
authors.forename: R
authors.initials: R
authors.lastname: Kawati
authors.forename: M
authors.initials: M
authors.lastname: Lattuada
authors.forename: U H
authors.initials: UH
authors.lastname: Sjöstrand
authors.forename: N
authors.initials: N
authors.lastname: Zügel
authors.forename: J
authors.initials: J
authors.lastname: Guttmann
authors.forename: G
authors.initials: G
authors.lastname: Hedenstierna
mesh_terms: D000399:Air Pressure; D000403:Airway Resistance / Q000502:physiology; D000818:Animals; D005260:Female; D007442:Intubation, Intratracheal; D008297:Male; D011175:Positive-Pressure Respiration; D011312:Pressure; D015203:Reproducibility of Results; D012121:Respiration, Artificial / Q000379:methods*; D013552:Swine; D013990:Tidal Volume / Q000502:physiology; D014132:Trachea / Q000502:physiology*