British Journal of Anaesthesia, 2003, Vol. 91, No. 2 239-248
© 2003 The Board of Management and Trustees of the British Journal of Anaesthesia
Laboratory Investigations |
Good short-term agreement between measured and calculated tracheal pressure
1 Department of Surgical Sciences, Section of Anaesthesiology and Intensive Care Medicine, Uppsala University, Sweden. 2 Department of Anaesthesiology and Surgical Intensive Care Medicine, Klinikum Augsburg, Germany. 3 Department of Medical Sciences, Section of Clinical Physiology, Uppsala University, Sweden. 4 Department of General and Visceral Surgery, Klinikum Augsburg, Germany. 5 Department of Anaesthesiology and Critical Care Medicine, Freiburg University, Germany
Corresponding author. E-mail: m.lichtwarck-aschoff@t-online.de
Background. Tracheal pressure (Ptr) is required to measure the resistance of the tracheal tube and the breathing circuit. Ptr can either be measured with a catheter or, alternatively, calculated from the pressure–flow data available from the ventilator.
Methods. Calculated Ptr was compared with measured Ptr during controlled ventilation and assisted spontaneous breathing in 18 healthy and surfactant-depleted piglets. Their lungs were ventilated using different flow patterns, tidal volumes (VT) 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 Ptr, the difference between calculated and measured Ptr was 0.6 cm H2O (95%CI 0.58–0.65) for volume-controlled ventilation; 0.73 cm H2O (0.72–0.75) for pressure support ventilation; and 0.78 cm H2O (0.75–0.80) for bi-level positive airway pressure ventilation.
Conclusion. The good agreement between calculated and measured Ptr during varying conditions, suggests that calculating Ptr could help setting the ventilator and choosing the appropriate level of support.
Br J Anaesth 2003; 91: 239–48