INCREASED AND MOVE CONSISTENT TIDAL VOLUMES DURING SYNCHRONIZED INTERMITTENT MANDATORY VENTILATION IN NEWBORN-INFANTS

We compared expiratory tidal and minute ventilation during conventiona l and synchronized intermittent mandatory ventilation (IMV and SIMV) i n 30 infants with respiratory failure. Identical ventilator settings w ere used during each mode in each infant. Tidal volumes of ventilator breaths were smaller during IMV than during SIMV (6.2 +/- 1.8 versus 7 .4 +/- 1.9 ml/kg; p < 0.01). The coefficient of variation of tidal vol umes was higher during IMV than SIMV for both ventilator (25 +/- 12% v ersus 15 +/- 8%) and spontaneous breaths (39 +/- 15% versus 24 +/- 10% , p < 0.001). Minute ventilation, however, was the same during both mo des. During IMV, one infant breathed synchronously and two were phase- locked in asynchrony with the ventilator. The infants with a mixed int eraction on IMV (27 of 30) had tidal volumes that depended on the phas e of spontaneous breathing at the time of onset of each ventilator bre ath. Tidal volumes of IMV breaths that began during the first half of spontaneous expiration had the smallest tidal volumes (5.4 +/- 1.8 ml/ kg, p < 0.01), followed by those that began during the last half of in spiration (6.4 +/- 1.8 ml/kg, p < 0.01). Thus, the synchrony produced by SIMV allowed the ventilator to deliver larger and more consistent t idal volumes than during IMV.