• M Lichtwarck-Aschoff, A Helmer, R Kawati, M Lattuada, U H Sjöstrand, N Zügel, J Guttmann, and G Hedenstierna.
• Department of Surgical Sciences, Section of Anaesthesiology and Intensive Care Medicine, Uppsala University, Sweden. m.lichtwarck-aschoff@t-online.de
• Br J Anaesth. 2003 Aug 1; 91 (2): 239-48.

BackgroundTracheal 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.MethodsCalculated 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.ResultsIn 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.ConclusionThe 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.

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