RESPONSE-TIME AND RELIABILITY OF 3 NEONATAL PATIENT-TRIGGERED VENTILATORS

We studied the response time (RT) and reliability of three neonatal patient-triggered ventilator (PTV) systems: the Draeger Babylog(R) 8000, the Bear Cub(R) enhancement module (CEM), and the Infrasonics Star Sync(R). In 10 adult rabbits, airway flow and pressure recordings showed the RT of the Star Sync to be shorter than that of the Bear CEM (53 +/- 13 versus 65 +/- 15 ms, p < 0.05), and both were shorter than that of the Babylog (95 +/- 24 ms, p < 0.01) by ANOVA. The RT of the Bear CEM and the Babylog increased significantly at decreased trigger sensitivity settings. All ventilators triggered successfully on assist-control (A/C). However, the Babylog had a higher rate of asynchrony on SIMV (30 +/- 25%) than the Bear CEM (1.1 +/- 0.3%) and the Star Sync (1.2 +/- 0.4%), p < 0.01. In 10 infants with respiratory failure, recordings of airway flow and pressure were made at ventilator inspiratory time (Tl settings of 0.3, 0.4, and 0.5 s on assist-control and on SIMV at rates of 15,30,45, and 60 breaths/min. The Star Sync and Bear CEM triggered successfully on A/C (100%) and had low rates of asynchrony on SIMV (1 to 3%). The Babylog had a lower success rate on A/C (70 +/- 12%) and a higher rate of asynchrony on SIMV (29 +/- 30%) than the other two ventilators; p < 0.01. The lower reliability of the Babylog was due to its variable refractory period (0.2 to 0.5 s, to equal the set Tl). At Tl greater-than-or-equal-to 0.4 s, this caused missed ventilator triggering on alternate spontaneous breaths, which resulted in phase locking in asynchrony on SIMV at rates of 45 and 60 breaths/min. The Star Sync and Bear CEM had shorter RT than previously reported neonatal PTV systems, and the Babylog had a unique but potentially correctable design feature that adversely affected its reliability.