Am. J. Respir. Crit. Care Med., Vol 150, No. 5, Nov 1994, 1444-1448.
Increased and more consistent tidal volumes during synchronized intermittent mandatory ventilation in newborn infants
G Bernstein, GP Heldt and FL Mannino
Department of Pediatrics, University of California, San Diego School of Medicine.
We compared expiratory tidal and minute ventilation during conventional and
synchronized intermittent mandatory ventilation (IMV and SIMV) in 30
infants with respiratory failure. Identical ventilator settings were 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 volumes was higher
during IMV than SIMV for both ventilator (25 +/- 12% versus 15 +/- 8%) and
spontaneous breaths (39 +/- 15% versus 24 +/- 10%, p < 0.001). Minute
ventilation, however, was the same during both modes. During IMV, one
infant breathed synchronously and two were phase- locked in asynchrony with
the ventilator. The infants with a mixed interaction on IMV (27 of 30) had
tidal volumes that depended on the phase of spontaneous breathing at the
time of onset of each ventilator breath. 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 inspiration (6.4 +/- 1.8 ml/kg, p < 0.01).
Thus, the synchrony produced by SIMV allowed the ventilator to deliver
larger and more consistent tidal volumes than during IMV.
