Influence of tidal volume on the compliance of the respiratory system in mechanically ventilated newborn infants.

We measured the compliance of the respiratory system (Crs) at 4 different tidal volumes (VT = 2.5, 5.0, 7.5, 10.0 ml/kg) in 29 mechanically ventilated newborn infants and determined the VT associated with the highest Crs ("optimal" VT) and with the lowest Crs ("worst" VT). Crs depended on the VT in all newborn infants investigated. The "optimal" VT most frequently observed was 2.5 and 5.0 ml/kg and the "worst" VT most frequently observed was 2.5 and 10.0 ml/kg. Mean Crs at the "optimal" VT was 62.3% higher than at the "worst" VT. The "optimal" VT was lower (2.5 ml/kg) in newborn infants with controlled ventilation than in newborn infants with intermittent mandatory ventilation (5.0 ml/kg). We conclude that it may be useful to determine the VT associated with the highest Crs in order to avoid unnecessarily high inflation pressures for the mechanical ventilation of newborn infants. Further studies are needed to assess long-term effects of such a Crs guided respirator therapy.