Tidal lung hysteresis to interpret PEEP-induced changes in compliance in ARDS patients

• Published in: Critical care (London, England) Vol. 27; no. 1; p. 233
• Main Authors: Mojoli, Francesco, Pozzi, Marco, Arisi, Eric, Mongodi, Silvia, Orlando, Anita, Maggio, Giuseppe, Capra Marzani, Federico, Brochard, Laurent
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 13.06.2023; BioMed Central; BMC
• Subjects: Body Fluids; Continuous positive airway pressure; COVID-19; Critical care; Decremental PEEP trial; Health aspects; Humans; Hysteresis; Lung; Lung hysteresis; Lung recruitability; Mechanics; Methods; Patient compliance; Patient outcomes; Patients; PEEP setting; Pressure–volume curves; Respiratory Distress Syndrome - therapy; Respiratory system; Tidal recruitment; Variance analysis; Ventilators; United Kingdom; Lung hysteresis; Pressure–volume curves; Lung recruitability; Tidal recruitment; Decremental PEEP trial; PEEP setting
• ISSN: 1364-8535; 1466-609X; 1364-8535; 1366-609X
• DOI: 10.1186/s13054-023-04506-6

In ARDS, the PEEP level associated with the best respiratory system compliance is often selected; however, intra-tidal recruitment can increase compliance, falsely suggesting improvement in baseline mechanics. Tidal lung hysteresis increases with intra-tidal recruitment and can help interpreting changes in compliance. This study aims to assess tidal recruitment in ARDS patients and to test a combined approach, based on tidal hysteresis and compliance, to interpret decremental PEEP trials. A decremental PEEP trial was performed in 38 COVID-19 moderate to severe ARDS patients. At each step, we performed a low-flow inflation-deflation manoeuvre between PEEP and a constant plateau pressure, to measure tidal hysteresis and compliance. According to changes of tidal hysteresis, three typical patterns were observed: 10 (26%) patients showed consistently high tidal-recruitment, 12 (32%) consistently low tidal-recruitment and 16 (42%) displayed a biphasic pattern moving from low to high tidal-recruitment below a certain PEEP. Compliance increased after 82% of PEEP step decreases and this was associated to a large increase of tidal hysteresis in 44% of cases. Agreement between best compliance and combined approaches was accordingly poor (K = 0.024). The combined approach suggested to increase PEEP in high tidal-recruiters, mainly to keep PEEP constant in biphasic pattern and to decrease PEEP in low tidal-recruiters. PEEP based on the combined approach was associated with lower tidal hysteresis (92.7 ± 20.9 vs. 204.7 ± 110.0 mL; p < 0.001) and lower dissipated energy per breath (0.1 ± 0.1 vs. 0.4 ± 0.2 J; p < 0.001) compared to the best compliance approach. Tidal hysteresis ≥ 100 mL was highly predictive of tidal recruitment at next PEEP step reduction (AUC 0.97; p < 0.001). Assessment of tidal hysteresis improves the interpretation of decremental PEEP trials and may help limiting tidal recruitment and energy dissipated into the respiratory system during mechanical ventilation of ARDS patients.