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