Esophageal Balloon Calibration in Assisted Ventilation Mode (EBC-PSV+Sigh)

Esophageal balloon calibration (EBC) has been proposed during controlled mechanical ventilation in intubated patients in order to optimize esophageal pressure (Pes) signal. Actually, at our knowledge, no data exist about EBC during assisted ventilatory modes such as Pressure Support Ventilation (PSV). The primary endpoint of the present investigation is to assess the feasibility of EBC during PSV and PSV plus Sigh.

Assisted ventilatory modes, nowadays, have been proved to reduce complications related to controlled mechanical ventilation. With these modes, ventilatory cycling is under the patient's control to an extent depending on the type of ventilatory modality. Sigh improves oxygenation and lung mechanics during pressure control ventilation and pressure support ventilation (PSV) in patients with acute respiratory distress syndrome. In order to better quantify the effects of both PSV and PSV plus Sigh on respiratory mechanics, the esophageal pressure monitoring could be helpful. However, esophageal pressure (Pes) assessment requires esophageal ballon calibration (EBC) as demonstrated in intubated patients under controlled mechanical ventilation. At our knowledge, no data exist about EBC during assisted ventilatory modes. The primary aim of the present study is to evaluate the effects of PSV and PSV plus Sigh ventilation on esophageal balloon best volume in patients admitted to the intensive care unit for acute respiratory failure. .

A nasogastric tube, equipped with esophageal and gastric balloons, will be inserted in each patient enrolled in the study. After definitive catheter positioning has been obtained, Esophageal ballon calibration will be run in volume-controlled ventilation, pressure support ventilation and sigh + pressure support ventilation.

After definitive catheter positioning, esophageal balloon calibration will be performed in: volume-controlled mode with tidal volume set to obtain 6-8 lm/kg of ideal body weight (reference), pressure support ventilation (PSV) with support set to obtain a tidal volume ranging between 6-8 ml/kg of ideal body weight at equal PEEP of volume control mode (PSV baseline); PSV + sigh ventilation (sigh setting: total inspiratory pressure equal to 35 cmH2O at a rate of 1/ minute; inspiratory time equal to 4 seconds).

Number of patients in who esophageal balloon calibration is performed (feasibility) during PSV + Sigh

Evaluate the feasibility of esophageal catheter calibration during assisted ventilation modes during PSV + Sigh

Inclusion Criteria: patients older than 18 years; undergoing mechanical ventilation for more than 24 hours (in volume-controlled mode) and with readiness to run assisted ventilation; Exclusion Criteria: severe COPD with air trapping clinical suspicion; hemodynamic instability requiring inotropic or vasopressor support; any contraindications to esophageal catheter positioning

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