Esophageal balloon calibration during Sigh: A physiologic, randomized, cross-over study

Purpose: Optimal esophageal balloon filling volume (V_best) depends on the intrathoracic pressure. During Sigh breath delivered by the ventilator machine, esophageal balloon is surrounded by elevated intrathoracic pressure that might require higher filling volume for accurate measure of tidal changes in esophageal pressure (Pes). The primary aim of our investigation was to evaluate and compare V_best during volume controlled and pressure support breaths vs. Sigh breath. Materials and methods: Twenty adult patients requiring invasive volume-controlled ventilation (VCV) for hypoxemic acute respiratory failure were enrolled. After the insertion of a naso-gastric catheter equipped with 10 ml esophageal balloon, each patient underwent three 30-min trials as follows: VCV, pressure support ventilation (PSV), and PSV + Sigh. Sigh was added to PSV as 35 cmH₂O pressure-controlled breath over 4 s, once per minute. PSV and PSV + Sigh were randomly applied and, at the end of each step, esophageal balloon calibration was performed. Results: V_best was higher for Sigh breath (4.5 [3.0–6.8] ml) compared to VCV (1.5 [1.0–2.9] ml, P = 0.0004) and PSV tidal breath (1.0 [0.5–2.4] ml, P < 0.0001). Conclusions: During Sigh breath, applying a calibrated approach for Pes assessment, a higher V_best was required compared to VCV and PSV tidal breath.