Oesophageal balloon calibration during pressure support ventilation: a proof of concept study

Oesophageal balloon calibration improves the oesophageal pressure (Pes) assessment during invasive controlled mechanical ventilation. The primary aim of the present investigation was to ascertain the feasibility of oesophageal balloon calibration during pressure support ventilation (PSV). Secondarily, the calibrated Pes (Pes_cal) was compared to uncalibrated one acquired at 4 ml-filling volume (Pes_V4), as per manufacturer recommendation. After a naso-gastric tube equipped with oesophageal balloon was correctly positioned in 21 adult patients undergoing invasive volume-controlled ventilation (VCV) for acute hypoxemic respiratory failure, the balloon was progressively inflated, applying a series of end-inspiratory and end-expiratory holds at each filling volume during VCV and PSV. Upon optimal balloon filling volume (V_best) was identified, Pes_cal was computed by correcting the Pes measured at V_best for the oesophageal wall pressure elicited at same filling volume. Finally, end-expiratory and end-inspiratory Pes_V4 were recorded too. A total of 42 calibrations, 21 per ventilatory mode, were performed. V_best was 1.9 ± 1.6 ml in VCV and 1.7 ± 1.6 ml in PSV (p = 0.5217). Pes_V4 was overestimated compared to Pes_cal at end-expiration and end-inspiration (p <0.0001 for all comparisons) in both VCV (13.4 ± 3.4 cmH₂O and 15.4 ± 3 cmH₂O vs. 8.5 ± 2.9 cmH₂O and 11.4 ± 3 cmH₂O) and PSV (14.7 ± 4.2 cmH₂O and 17 ± 3.9 cmH₂O vs. 8.9 ± 3.4 cmH₂O and 12.4 ± 3.9 cmH₂O). In PSV, oesophageal balloon calibration is feasible and allows to obtain a reliable Pes assessment compared to uncalibrated approach.