Variations in central venous pressure during spontaneous breathing well correlate with changes in esophageal pressure

Introduction: Spontaneously breathing critically ill patients often make strong inspiratory efforts. These respiratory activity can damage lungs, require supranormal work of breathing and produce alterations in venous return. Clinical exam is not sufficient to determine when the effort is excessive. Strong inspiratory efforts generate falls in pleural pressure, which is difficult to measure directly but is well estimated by variations in esophageal pressure.1 Unfortunately intraesophageal balloon isn’t available in lots of intensive care units. Aim of this study was to investigate whether variations in central venous pressure (ΔCVP) adequately reflect respiratory changes in pleural pressure as assessed by changes in esophageal pressure (ΔPES). Materials and Methods: We studied spontaneous breathing patients, admitted to our intensive care unit to acute respiratory failure who had a central venous catheter and esophageal balloon. We compared ΔCVP to ΔPES during zero end expiratory pressure (ZEEP) and during continuous positive airway pressure (CPAP) by Bland–Altman and regression analysis. Results: We enrolled 5 patients from whom we obtained 5 contemporary measurement of ΔCVP and ΔPES during ZEEP and 5 during CPAP. The average inspiratory ΔPES was 21,08 ± 9,38 cmH2O, and average ΔCVP was 20,90 ± 9,32 cmH2O. In both conditions ΔCVP gave a good estimate of ΔPES (bias = 0.18 cmH2O, limits of agreement +2.49 and –2.14 cmH2O; R2 = 0,984). Conclusions: ΔCVP gives a good estimate of changes in PES (a surrogate of pleural pressure) during spontaneous inspiratory efforts.