oxygen uptake and pulmonary blood flow during resuscitation from asphyxia in foetal and adult sheep

1. The foetuses of twenty-seven Welsh ewes and eight Clun Forest ewes were delivered by Caesarian section at an approximate gestational age of 140 days, maintaining the umbilical circulation. They were asphyxiated by clamping the umbilical cord, and resuscitated with IPPV. Oxygen consumption, heart rate, and blood pressures were recorded, and in one series of eight, blood flow through the left lung was recorded whilst IPPV was applied to this lung only. 2. The hypothesis that oxygen consumption is abnormally low during resuscitation of the new-born from extreme asphyxia because of limited blood flow, was supported. 3. Adult ewes were also asphyxiated and in a series of eight a quite different pattern of behaviour was observed, due to very rapid and complete recovery of the circulation. 4. Observations on the pulmonary vascular resistance suggest that complete vasomotor paralysis occurs during extreme asphyxia, so that resistance falls to a near-minimum level for unexpanded lung. Expansion of the lung produced a large fall in resistance which appeared to be due to the introduction of gas into the alveolar spaces, lessening the resistance to flow of the capillaries.