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

Source abstract

Background: Esophageal pressure (P es ) 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. The authors aimed to determine whether endotracheal tube cuff pressure (P CUFF ) could serve as a more accessible surrogate. Methods: In this prospective study, P es and P CUFF were simultaneously recorded in 30 orally intubated adult patients undergoing pressure support ventilation. A downward pressure support titration (15 to 5 cm H 2 O) was performed. P CUFF was calibrated using occlusion-induced changes in airway pressure. The correlation between tidal swings of P CUFF and P es 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 P CUFF to detect extremes of inspiratory effort, using inspiratory muscle pressure (P mus ) and P mus -time product (PTP mus ) per minute as references, alongside high transpulmonary driving pressure (greater than 20 cm H 2 O) and high transpulmonary mechanical power (greater than 12 J/min). Results: Across 840 analyzed breaths, P CUFF correlated with P es (marginal R 2 = 0.772; conditional R 2 = 0.949) with a mean bias (limits of agreement) of 0.25 (−5.42 to 5.92) cm H 2 O. For detecting low effort (P mus less than 5 cm H 2 O or PTP mus /min less than 50 cm H 2 O · s/min), P CUFF yielded areas under the receiver operating characteristics curve (AUCs) of 0.95 (95% CI, 0.91 to 0.99) and 0.94 (95% CI, 0.86 to 1.00), respectively. For identifying high effort (P mus greater than 10 cm H 2 O or PTP mus /min greater than 150 cm H 2 O · s/min), the respective AUCs were 0.93 (95% CI, 0.89 to 0.97) and 0.82 (95% CI, 0.76 to 0.88). Utilizing a leave-one-out cross-validation framework to prevent overfitting, P CUFF successfully discriminated high transpulmonary driving pressure and transpulmonary mechanical power with AUCs of 0.89 (95% CI, 0.83 to 0.95) and 0.88 (95% CI, 0.82 to 0.93), respectively. Conclusions: Although P CUFF cannot entirely replace P es for precise quantification due to relatively wide limits of agreement, it exhibits excellent diagnostic discrimination. P CUFF holds promise as an accessible, continuous bedside monitor for identifying patients with potentially injurious levels of effort, stress, and energy intensity.