Comparative evaluation of spontaneous breathing trial techniques for ventilator weaning: a bench study

Spontaneous breathing trials (SBT) are crucial for determining when mechanically ventilated patients are ready for extubation. While pressure support (PS) and T-piece trials are commonly used, humidified high-flow (HHF) is increasingly considered, but its physiological effects remain unclear. This bench study compares T-piece, PS, and HHF modalities, evaluating their impact on work of breathing (WOB), tidal volume (Vt), total positive end-expiratory pressure (PEEPtot) and CO₂ clearance.

A 3D-printed manikin head connected to an artificial lung was used. Four SBT modalities were tested: T-piece with and without supplemental oxygen, PS at 7 cmH₂O (PEEP 0 cmH₂O), and HHF at 50 L/min. The tests were performed under three lung conditions (normal, obstructive, restrictive) and two respiratory drive and effort settings (normal and intense), resulting in 24 scenarios. Measurements included WOB, CO₂ clearance, PEEPtot, and Vt.

T-piece and HHF50 SBTs exhibited similar effects on WOB, irrespective of the effort pattern associated with the underlying respiratory mechanics. For intense effort patterns, the CO₂ concentration was lower with HHF than with PS, regardless of respiratory mechanics. The HHF50 SBT increased PEEPtot more than T-piece SBTs, but less than PS SBT, for all scenarios. HHF50 SBT generated lower tidal volume than T-piece and PS SBTs.

Humidified high-flow at 50 L/min, while preserving WOB and not increasing tidal volume, may offer specific advantages, such as improved CO₂ clearance and PEEP effect, and could be considered as a trade-off for T-piece or PS SBTs.