PATIENT-TRIGGERED VENTILATION IN NEONATES - COMPARISON OF A FLOW-TRIGGERED AND AN IMPEDANCE-TRIGGERED SYSTEM

We conducted a study with the objective of comparing the performance o f two different systems for patient-triggered ventilation in neonates (impedance versus flow/volume-triggered) by measuring response time, a utotrigger and trigger failure rates, ventilation, and gas exchange. T he two ventilator systems were applied in random order in 10 preterm n eonates (median gestational age: 30.5 wk; range: 27 to 34 wk; body wei ght: 1,266 g; range: 840 to 2,240 g) using identical ventilator settin gs. The median (range) response time was 169 (98 to 305) ms for the im pedance system and 115 (79 to 184) ms for the flow/volume system (p < 0.01). The longer and more variable response time of the impedance sys tem was secondary to a phase lag of the impedance signal caused by che st wall distortion. Although 13.7 (0.2 to 29.4)% of mechanical breaths were autotriggered with the impedance system, there were no autotrigg ered breaths using the flow/volume system (p < 0.01). The rate of trig ger failures was not significantly different with the two systems, at 1.2 (0 to 4.4)% (impedance) versus 3.1 (0 to 6.4)% (flow/volume). Minu te ventilation was smaller with the impedance system (p < 0.001), beca use of the larger number of breaths triggered late in inspiration or d uring expiration. We conclude that the flow/volume-triggered system is less prone to autotriggering and has a shorter and more consistent re sponse time than the impedance-triggered system. The impedance-trigger ed system is more susceptible to artifacts and chest wail distortion.