Abstract 1741
Poster Session I, Saturday, 5/1 (poster 33)
Optimal FRC can be defined as the MAP with the best dynamic compliance and maximal alveolar blood flow (best V/Q). We sought to test the hypothesis that bedside on-line pulmonary mechanics using flow synchronized assist-control ventilation (VIP Bird) could achieve this in neonates with HMD (see Ped Res 37:A1382, 1995). We did a prospective, randomized, controlled trial enrolling subjects between 500-2000g, <1 d/o, requiring ventilation with FiO2 > 0.3 after surfactant administration. These infants were followed until extubation or postnatal day 7. Infants with major malformations, sepsis, oscillator use, or <24h of ventilation were excluded. Termination sensitivity was set at 5% with a maximal Ti <0.3 s used with or without online pressure-volume loops. All infants were initially put on a PIP of 20 cmH2O to recruit an FRC, then reduced to 15 & then to 10 × 15 min at each step to achieve targeted blood gases. Infants were managed to achieve clinical endpoints of pH >7.25 & saturations >92% (permissive hypercapnia) with or without use of on-line graphics. PIP, PEEP, MAP, & Ti data were recorded every 30 minutes from the VIP Bird data storage and averaged per day × 7d. FiO2, pH, and saturations were tabulated manually. Subjects in the no-graphics group (n=8, 1238 ± 92g, 28 ± 1 wk; x±sem) were larger (P < 0.02) and more mature (P < 0.006) than the graphics group (n=9, 933 ± 77g, 26 ± 1wk). There were no differences in respiratory status at study entry for Ti, PIP, PEEP, MAP, ABG or FiO2. Over the first week, the graphics analysis group showed a lower average: PIP (9 ± 0.2 vs 13 ± 0.5 cm H2O (P < 0.001), MAP (4.6 ± 0.2 vs 6.2 ± 0.3 cmH2O, P < 0.001), respiratory index (-27%, p < 0.03) and ventilatory index (-38%, p < 0.001). There were no differences noted in Ti, pH, FiO2 or saturations. All babies with pneumothorax (2) or PIE (1) were in the no-graphics group. We conclude that optimizing FRC through use of on-line pulmonary mechanics is useful for reducing MAP and PIP in neonates with HMD. We speculate that an optimal FRC strategy will result in less volutrauma and have a significant impact in reducing chronic lung disease if applied more widely.
