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

BACKGROUND

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 CO clearance.

METHODS

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 cmHO (PEEP 0 cmHO), 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, CO clearance, PEEPtot, and Vt.

RESULTS

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 CO 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.

CONCLUSIONS

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