Calibration of Esophageal Balloon catheter in spontaneous and mandatory mechanical ventilation.

Calibration of the esophageal balloon catheter (Pes) is important for the right
interpretation of the derived transpulmonary pressures during mechanical
ventilation. Calibration of the Pes catheter has only been validated in
mandatory ventilation but not in support modes in which the patient triggers
the ventilator and exhibits spontaneous breathing activity. Because the forces
in the thoracic cage are very different between the two modes it is to be
expected that the calibration process yields different filling volumes and
therefore to a different calibration approach. This would lead to a more
reliable filling volume in spontaneous mechanical ventilation and mor reliable
derivation of transpulmonary pressure and therefore to a better treatment of
patients.

To obtain the best filling pressure of the Pes catheter in spontaneous
mechanical ventilation, to obtain the esophagus elastance in spontaneous
mechanical ventilation, and to compare the best filling pressures between the
two modes (spontaneous and mandatory ventilation).

Use a standardized calibration protocol to obtain the best filling pressure in
both ventilator modes. The first calibration measurement will be in spontaneous
mechanical ventilation, the second calibration measurement after a swich to a
mandatory mode. Two Pes catheters will be tested

Risk is nihil. Patients are sedated and the burden is also nihil. The increase
in sedation and possible use of neuromuscular blockade could possibly extend
the length of ICU stay. However this is estimated as without clinical
consequences.