ABSTRACT
This is derived from the percentage of maximal transdiaphragmatic pressure (Pdi) expended with each breath (Pdi/Pdimax) and the fraction of the breathing cycle time spent in inspiration
(T i/TTOT)
19. Values of Ttdi below 0.15 predict the ability to sustain unassisted respiration for longer than 45 min. Values of Ttdi above 0.15 predict eventual
ventilatory failure, possibly because of limitation of diaphragmatic blood flow (Figure 18.1). Although transdiaphragmatic pressure and inspiratory time are not routinely measured, devices such as the Bicore can provide surrogate measurements that have been advocated by some in enhancing weaning20.
