EFFECT OF LUNG LIQUID VOLUME ON RESPIRATORY PERFORMANCE AFTER CESAREAN DELIVERY IN THE LAMB

1 The volume of liquid in the lungs of the fetal lamb is reported to f all in the final days of gestation and during labour itself. We aimed to test the hypothesis that this fall in liquid volume adapts the lung s for air breathing and pulmonary gas exchange. 2. In twelve chronical ly catheterized fetal lambs we measured lung liquid volume at 140 days gestation (term is 147 days) and then delivered the fetuses by Caesar ean section under maternal spinal anaesthesia. In five fetuses we remo ved approximately half the liquid contained in the lungs just before d elivery (experimental group) while the remaining seven fetuses were de livered without change to their lung liquid (control group). 3. Lambs born with reduced lung liquid volume improved their arterial blood gas and acid-base status more quickly than lambs born without alteration to lung liquid. 4. Carotid arterial blood gas values in the first 60 m in of postnatal life were significantly related to the volume of liqui d present in the lungs at birth, with higher arterial partial pressure of oxygen (P-a,P-O2) and arterial oxygen saturation (S-a,S-O2) and lo wer arterial partial pressure of carbon dioxide (P-a,P-CO2) levels bei ng associated with lower lung liquid volumes. 5. We conclude that post natal gas exchange is enhanced by a reduction in the volume of liquid remaining in the lungs when breathing starts.