Fig. 3
Closed catheter suctioning. Model airway pressures (PPEAK MA and PEEP MA, panel a) and inspiratory/expiratory tidal volumes (panel b) detected by the ventilator (Vti / Vte) are shown during suctioning with closed catheters (14 Fr in 8 and 9 mm ID ETT and 12 Fr in 7 mm ID ETT). Data are from experiments in PCV (left) and VCV (right) with I:E ratio 1:2 and flowtrigger. Measurements with trigger settings P0, P-5, P-10, P-15 and P-20 cm H2O are shown as ranges. The choice of trigger setting and suction level (12 combinations used in this experiment) did not affect measurements prior to suctioning; significant changes from catheter insertion are therefore shown accordingly. During suctioning, however, pressures and volumes were strongly influenced by high frequency ventilator trigging. The dynamics of such trigging depends on the choice of suction pressure and ventilator trigger sensitivity. Pressures and volumes measured during suction were therefore unique for each of the 12 permutations (thus not subject to statistical analysis)