MINIMUM ARTIFICIAL LUNG EXPANSION NECESSARY FOR RESUSCITATION OF THE NEWBORN LAMB

In a group of seven lambs, pressure-volume relationships wereobtained for the initial artificial expansion of the lungs inthe intact chest and subsequent re-expansion after the lungshad been excised and collapsed. In a second group, of 12 severelyasphyxiated lambs, the lungs were expanded in steps and circulatoryresuscitation was achieved at pressures ranging from 1.75 to3.5 kPa, geometric mean 2.3 kPa, with estimated correspondingvolumes of 3–24 ml kg^–1, geometric mean 5.8 ml kg^–1.In a third group, of 24 severely asphyxiated lambs (mean pH6.84), 22 were successfully resuscitated in the same mannerand nine of these survived in apparent good health for morethan 6 months. Any resuscitation regime for human neonates shouldtake account of the finding that resuscitation occurred at pressuresless than those necessary for full expansion and that, afterthe first sign of an increase in heart rate, there was a delayof 17–45 s before full circulatory improvement and of3 mm before full improvement in Pa_O.