Physiological comparison of high-flow oxygen via endotracheal tube and T-piece strategies during spontaneous breathing trials: a randomized crossover study

<title>Abstract</title> Background The optimal spontaneous breathing trial (SBT) strategy remains uncertain because commonly used approaches involve distinct physiological trade-offs. Pressure support ventilation (PSV) may underestimate the respiratory load after extubation, whereas T-piece trials better reproduce unsupported breathing but may promote derecruitment and cardiopulmonary stress. High-flow oxygen (HFO) delivered via endotracheal tube has been proposed as an alternative SBT strategy, but the physiological basis for its potential clinical usefulness remains insufficiently defined. Methods In a randomized crossover physiological study, patients receiving mechanical ventilation for at least 24 hours and deemed ready for weaning underwent five SBT conditions: T-piece and four HFO via endotracheal tube settings combining two interfaces with different expiratory port diameters (9.8 and 6.9 mm) and two flow rates (40 and 60 L/min). Airway and esophageal pressures, respiratory variables, and electrical impedance tomography (EIT) parameters were measured during baseline mechanical ventilation and under each SBT condition. Esophageal pressure was also measured after extubation for comparison with post-extubation inspiratory effort. A complementary bench study assessed 24 simulated conditions across four interface diameters and six flow rates. Results Twenty patients were included in the analysis. HFO via endotracheal tube generated a flow- and diameter-dependent increase in airway pressure and end-expiratory lung volume (all <italic>p</italic> &lt; 0.001 vs T-piece). While HFO with both expiratory port diameters elevated airway pressure and lung volume, downstream improvements in ventilation homogeneity and oxygenation, together with reductions in dynamic transpulmonary driving pressure and respiratory rate, occurred primarily with the smaller diameter at higher flows, indicating a pressure threshold effect. Inspiratory effort was similar across SBT conditions and comparable to post-extubation values. Bench simulations closely reproduced these flow- and diameter-dependent physiological relationships. Conclusions HFO via endotracheal tube produced a flow- and expiratory port diameter-dependent physiological response, linking airway pressure generation to lung-volume preservation, improved oxygenation, and lower dynamic transpulmonary driving pressure while maintaining inspiratory effort. Tracheal HFO may therefore represent an alternative SBT strategy that preserves a post-extubation-like inspiratory workload while limiting derecruitment and dynamic lung stress during liberation from invasive ventilation. Trial registration: ClinicalTrials.gov (NCT06816706). Registered on 6 February 2025.