Abstract 1793 Poster Session I, Saturday, 5/1 (poster 31)

Volume Guarantee (VG) is a novel mode of assisted ventilation which provides a stable tidal volume (Vt) in the face of changing pulmonary mechanics and variable inspiratory effort by adjusting peak inspiratory pressure (PIP). We compared the short term safety and efficacy of VG versus SIMV in VLBW infants. A prototype Drager Babylog 8000 ventilator provided both ventilation modes. Our hypothesis was that VG would provide ventilation and oxygenation comparable to SIMV but requiring less PIP, mean airway pressure (MAP) and mean driving pressure (MDP = pressure over PEEP × breath duration). Eight clinically stable mechanically ventilated infants [Birth weight (mean ± SD) 853 ± 161g, GA 26.7 ± 1.9wk, age 5 ± 2.3 days] were assigned to consecutive 60-minute epochs of VG (target Vt of 4 to 5 ml/kg), clinical SIMV (ventilator settings chosen by the care team) and match SIMV (PIP adjusted in order to obtain same Vt as in VG mode) in random order. (Table)

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When comparing VG and clinical SIMV, total minute ventilation (V'e tot) was the same, however mechanical minute ventilation (V'e mec) was lower with VG compared to clinical SIMV. Conversely, spontaneous minute ventilation (V'e spt) was higher during VG. MAP and MDP were also significantly lower during VG. Oxygen saturation, TcPO2 and TcPCO2 did not differ significantly. There were no statistically significant differences between VG and match SIMV modes.

These results indicate that VLBW infants frequently require less ventilatory support than that provided in the clinical situation because they are able to increase their inspiratory effort. VG allows them to achieve this while guaranteeing a physiologic Vt, in contrast to SIMV which delivers a constant PIP regardless of tidal volume delivered. Whether VG reduces volutrauma and chronic lung disease if used long term should be the subject of larger randomized clinical trials.