What question did this study set out to answer?

This study aims to validate the accuracy of the WOB-Bar in estimating respiratory effort during weaning from mechanical ventilation.

May 28, 2026

Proportional Assist Ventilation and Respiratory Effort Monitoring During Transition to Spontaneous Breathing

Key Points

This study aims to validate the accuracy of the WOB-Bar in estimating respiratory effort during weaning from mechanical ventilation.
Physiological randomized crossover study with 35 subjects.
Comparison of WOB-Bar against esophageal pressure-time product and airway pressure metrics across three PAV+ levels.
Effort categorized as low, adequate, or high based on physiological thresholds.
WOB-Bar classified respiratory effort correctly only 44.5% of the time (95% CI 32.9–56.4%), indicating low accuracy.
P occ showed better performance with 66.5% agreement (95% CI 57.9–75%) and a κ of 0.35.
Multivariable model identified WOB pt, P 0.1, and P occ as independent predictors of esophageal pressure-time product.

Abstract

Introduction: Proportional assist ventilation plus (PAV+) uses a work of breathing bar (WOB-Bar) to provide real-time, noninvasive estimates of patient work of breathing (WOB pt ). Although designed to guide titration during the transition to spontaneous ventilation, the clinical accuracy of this tool remains unvalidated against gold-standard measures. Methods: This physiological randomized crossover study included 35 subjects weaning from mechanical ventilation. We compared the WOB-Bar against the esophageal pressure-time product (PTP es-min ), the pressure drop in the airway during the first 100 ms of an inspiratory effort against an occluded airway (P 0.1 ), and the pressure variation during an end-expiratory occlusion (P occ ) across 3 randomized assistance PAV+ levels (20%, 50%, and 70%). Effort was categorized as low, adequate, or high based on suggested physiological thresholds. Results: The WOB-Bar correctly classified effort (relative to PTP es-min ) in only 44.5% of cases (95% CI 32.9–56.4%), with a negligible weighted κ of 0.01. P occ demonstrated the best performance with 66.5% agreement (95% CI 57.9–75%) and a κ of 0.35. A multivariable mixed-effects model ( R 2 = 0.84) showed that WOB pt ( P < .001), P 0.1 ( P = .040), and P occ ( P = .02) were all independent predictors of PTP es-min . However, despite a positive association between WOB pt and PTP es-min , the categorical WOB-Bar showed limited accuracy and tended to underestimate respiratory effort, particularly in high-effort states. Inter-individual variability accounted for 77.5% of the total variance in respiratory effort. Conclusions: The WOB-Bar frequently underestimated effort and was insufficient as a stand-alone tool for PAV+ titration. Airway occlusion maneuvers (P occ and P 0.1 ) were more reliable indicators of PTP es-min . Since current thresholds are extrapolated from healthy individuals and unvalidated during weaning, these findings are hypothesis generating. Future studies should establish context-appropriate thresholds and evaluate their clinical implications.

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