Impact of Baydur Ratio Correction on the Reliability of Esophageal Pressure Measurement

Tidal changes in esophageal pressure (DPes) are used as a surrogate for pleural pressure changes (DPpl) to assess chest wall mechanics. The Baydur ratio evaluates pressure transmission and guides catheter positioning. The effects of correcting DPes using the Baydur ratio on the accuracy of DPpl estimation and its dependence on ventilation mode, spontaneous inspiratory effort, and body position remain unclear. In 10 pigs, DPpl was measured using intrapleural balloon catheters, whereas Pes was recorded at three esophageal locations in supine and prone positions. Animals underwent controlled and assisted ventilation. Baydur ratios were derived during assisted ventilation and from external chest compressions during controlled ventilation. DPes before and after correction was compared with DPpl using mixed-effects models and Bland–Altman analysis. In addition, we quantified the proportion of values with (DPes ‒ DPpl) ≤ 1 cmH2O. During assisted ventilation, DPes showed good agreement with posterior DPpl. Baydur correction improved scaling and association (slope: 0.76 vs. 0.50; r = 0.81 vs. 0.79, P < 0.01) and increased values within ±1 cmH2O from 29% to 45% when the Baydur ratio fell outside the accepted range. During controlled ventilation, DPes showed weaker association and wider limits of agreement, without improvement after correction. Similar patterns were observed in the prone position. DPes more accurately reflected posterior DPpl during assisted ventilation. Baydur correction improves scaling and association, particularly when the Baydur ratio falls outside the accepted range, but does not improve and may worsen agreement during controlled ventilation.