Bench Assessment of Work of Breathing During a Spontaneous Breathing Trial on Zero Pressure Support and Zero PEEP Compared to T-Piece

BACKGROUND: Analysis of observational data suggests that both a T-piece and zero pressure support ventilation (PSV) and zero PEEP impose work of breathing (WOB) during a spontaneous breathing trial (SBT) similar to what a patient experiences after extubation. The aim of our study was to compare the WOB imposed by the T-piece with zero PSV and zero PEEP. We also compared the difference in WOB when using zero PSV and zero PEEP on 3 different ventilators.

METHODS: This study was conducted by using a breathing simulator that simulated 3 lung models (ie, normal, moderate ARDS, and COPD). Three ventilators were used and set to zero PSV and zero PEEP. The outcome variable was WOB expressed as mJ/L of tidal volume.

RESULTS: An analysis of variance showed that WOB was statistically different between the T-piece and zero PSV and zero PEEP on all the ventilators (Servo-i, Servo-u, and Carescape R860). The absolute difference was lowest for the Carescape R860, which increased WOB by 5–6%, whereas the highest for Servo-u, which reduced the WOB by 15–21%.

CONCLUSIONS: Work may be imposed or reduced during spontaneous breathing on zero PSV and zero PEEP when compared to T-piece. The unpredictable nature of how zero PSV and zero PEEP behaves on different ventilators makes it an imprecise SBT modality in the context of assessing extubation readiness.