Non-invasive estimation of inspiratory muscle pressure and work of breathing by airway pressure extrapolation from the P0.1 maneuver during assisted ventilation

Abstract

Abstract Monitoring inspiratory effort during assisted mechanical ventilation is essential to balance lung protection and respiratory muscle loading. Esophageal pressure monitoring remains the reference standard for estimating inspiratory muscle pressure and work of breathing but is invasive and rarely used in routine clinical practice. Non-invasive alternatives based on routinely available ventilator signals are therefore needed. This monocentric physiological substudy of the ICEBERG observational trial included adult patients with acute hypoxemic respiratory failure undergoing assisted mechanical ventilation. Inspiratory muscle pressure (P mus ) was first estimated non-invasively by linear extrapolation of the airway pressure drop recorded during a standardized end-expiratory occlusion (P0.1 maneuver) into early inspiration (up to 500 ms after occlusion). Using the extrapolated P mus together with airway pressure, airway resistance was calculated during early inspiration, both with and without correction for respiratory system elastance determined by occlusion maneuvers. The resulting resistance and elastance were then used to parameterize the equation of motion of the respiratory system, allowing subsequent reconstruction of the inspiratory P mus waveform over the entire breath. From the reconstructed pressure signal, peak inspiratory P mus , work of breathing, and pressure–time product were calculated. Esophageal pressure–derived measurements served as the reference standard, and agreement was assessed using linear regression and Bland–Altman analysis. Eighteen patients (age 67 ± 12 years, PaO₂/FiO₂ 198 ± 44 mmHg) contributed 33 valid measurements. Based on a patient-average analysis, non-invasively estimated P mus during early inspiration showed statistically significant correlations with esophageal pressure–derived values across all analyzed time points (all p < 0.01), with the highest agreement and lowest bias observed at 100 ms extrapolation time after the end of the P0.1 maneuver. Elastance-corrected airway resistance demonstrated slightly improved agreement compared with uncorrected resistance estimates. Work of breathing derived from non-invasive inspiratory P mus showed good agreement with reference measurements (R 2  = 0.70; bias =  − 0.05 J), whereas pressure–time product exhibited greater bias and wider limits of agreement. A P0.1-guided, non-invasive method based on airway pressure extrapolation allows feasible and physiologically meaningful estimation of inspiratory P mus during assisted ventilation. Derived work of breathing shows good agreement with esophageal pressure-based measurements, supporting the potential of this approach for non-invasive monitoring of inspiratory effort in patients with acute hypoxemic respiratory failure.