Tidal swing of endotracheal tube cuff pressure as a measurement of inspiratory effort and lung stress during pressure support ventilation: a proof-of-concept study

BACKGROUND: Esophageal pressure (Pes) is the reference standard for monitoring inspiratory effort and lung stress during assisted ventilation, but its routine application is hindered by the lack of specialized equipment and specific training. We aimed to determine whether endotracheal tube cuff pressure (PCUFF) could serve as a more accessible surrogate. METHODS: In this prospective study, Pes and PCUFF were simultaneously recorded in 30 orally intubated adult patients undergoing pressure support ventilation. A downward pressure support titration (15 to 5 cmH2O) was performed. PCUFF was calibrated using occlusion-induced changes in airway pressure. The correlation between tidal swings of PCUFF and Pes was analyzed using a linear mixed-effects model. Agreement between the two parameters was evaluated by Bland-Altman analysis (for repeated measures). Diagnostic performance was analyzed for PCUFF to detect extremes of inspiratory effort, using inspiratory muscle pressure (Pmus) and Pmus-time product per minute (PTPmus/min) as references, alongside high transpulmonary driving pressure (∆PL>20 cmH2O) and high transpulmonary mechanical power (MPL>12 J/min). RESULTS: Across 840 analyzed breaths, PCUFF correlated with Pes (marginal R²=0.772; conditional R²=0.949) with a mean bias (limits-of-agreement) of 0.25 (-5.42-5.92) cmH₂O. For detecting low effort (Pmus<5 cmH2O or PTPmus/min<50 cmH2O·s/min), PCUFF yielded areas under the curves (AUCs) of 0.95 (95% confidence interval: 0.91-0.99) and 0.94 (0.86-1.00), respectively. For identifying high effort (Pmus>10 cmH2O or PTPmus/min>150 cmH2O·s/min), the respective AUCs were 0.93 (0.89-0.97) and 0.82 (0.76-0.88). Utilizing a leave-one-out cross-validation framework to prevent overfitting, PCUFF successfully discriminated high ∆PL and MPL with AUCs of 0.89 (0.83-0.95) and 0.88 (0.82-0.93), respectively. CONCLUSIONS: Although PCUFF cannot entirely replace Pes for precise quantification due to relatively wide limits of agreement, it exhibits excellent diagnostic discrimination. PCUFF holds promise as an accessible, continuous bedside monitor for identifying patients with potentially injurious levels of effort, stress and energy intensity.