Minute-by-minute means of breathing variables during the spontaneous breathing trial for the groups of subjects with trial success (n = 32) and failure (n = 8). Minute-by-minute means of breathing variables during the spontaneous breathing trial for the groups of subjects with trial success (n = 32) and failure (n = 8). Error bars indicate 1 SD. VT = tidal volume; f = breathing frequency; V̇E = minute ventilation; VT/TI = mean inspiratory flow. Juan B Figueroa-Casas et al. Respir Care 2015;60:155-161 (c) 2012 by Daedalus Enterprises, Inc.