Respiratory Mechanics Assessment at Different Head of the Bed Elevations in Mechanically Ventilated Patients

Respiratory Mechanics Assessment at Different Head of the Bed Elevations in Mechanically Ventilated Patients

The effects of different degrees of head-of-bed elevation on respiratory mechanics are poorly explored in the literature, and no study has investigated such effects using electrical impedance tomography, esophageal and gastric balloons to identify the ideal angle for optimizing respiratory mechanics. The hypothesis is that there is a optimal degree for the respiratory mechanics.

Respiratory mechanics and regional ventilation will be monitored using electrical impedance tomography (Enlight 2100, Timpel Medical®, Brazil) . Esophageal and gastric pressures will be obtained through esophageal and gastric balloon catheters (Nutrivent®) (validation concerning to modified Baydur maneuver - slope delta esophageal pressure/delta airway pressure (0,8-1,2). We are using the hardware Pneumodrive (Biônica, Recife, Brazil) to record and store the esophageal, gastric and airway pressures, these data will be analyzed using LabVIEW 7.1 (Pneumobench).

Initially, patients will be positioned at 0 degrees of head-of-bed elevation, and after stabilization of the plethysmogram, data from electrical impedance tomography, hemodynamics, and arterial blood gas will be collected (arterial blood will be drawn by a nurse or physician). Sequentially and in the same manner, the bed will be adjusted to 10, 20, 30, and 40 degrees (the same data will be collected, except for the arterial blood sample, which will only be collected at the 40-degree elevation). Then, an alveolar recruitment maneuver will be performed, followed by a PEEP titration with 10-degree of head-of-bed elevation.

Inclusion Criteria:

• Patients under invasive mechanical ventilation, intubated due to respiratory failure

Exclusion Criteria:

• Hemodynamics instability, contraindication for monitoring with esophageal and gastric catheters, and Electrical impedance tomography, no authorization of medical team of the intensive care unit, and contraindication for lung recruitment maneuver