Comparison of ventilatory responses of different respiratory profiles between humidified high-flow, pressure support and T-piece spontaneous breathing trials: A bench study.

No spontaneous breathing trial (SBT) procedure has stood out compared to others. A clinical study observed that conducting SBT via humidified high-flow device (HHF-SBT) compared to T-piece (TP-SBT) in patients at risk of weaning failure was associated with a reduction in reintubation rate. No study has been conducted to understand or compare HHF-SBT mechanisms with other SBTs. The objective of our bench study is to evaluate the effects of HHF-SBT compared to standard SBT procedures. We tested 5 differents SBT modalities, T-piece with and without O2 adjunction, pressure support (PS-SBT) with no positive end expiratory pressure (PEEP) and HHF at 50 and 60 L/min. We used an ASL 5000 mechanical lung (IngMar Medical) on which we simulated 3 pulmonary models (normal, obstructive, restrictive) paired with 3 levels of inspiratory efforts (low, normal, intense). The lung was connected to a mannequin head with realistic upper airways (George, Kernelbiomedical) intubated using a 7mm endotracheal tube. A protective balloon was inserted into the circuit, and CO2 was added at a continuous flow rate of 0.2 L/min. Under each SBT modality, we measured PEEP effect, tidal volume, work of breathing (WOB) and dead space washout rate (CO2 washout). In each condition, we observed an increase in PEEP effect, a significant 5% reduction in WOB and an increase CO2 washout in favor of PS-SBT. HHF-SBT appears to be less effective than PS-SBT at relieving breathing mechanics. HHF-SBT appears to be similar to SBT-TP, but with a better PEEP effect. Clinical studies with physiological measurements are needed to fully understand HHF-SBT.