Oxygen transport and utilization during feeding in the young lamb.

1. Five lambs (19-27 days old) were studied to determine the effects of feeding on cardiorespiratory function. 2. Each lamb was instrumented to record cardiac output, aortic and pulmonary artery pressure and arterial and mixed venous oxyhaemoglobin saturations (Sa,O2 and Sv,O2). 3. During feeding, arterial haemoglobin desaturated and resaturated sequentially during the periods of sucking and non-sucking. The nadir of these Sa,O2 desaturations (83 +/- 2%, mean +/- S.E.M.) was significantly lower than the baseline value (92 +/- 2%, P < or = 0.05, ANOVA). Sa,O2 returned to the baseline level between periods of sucking. Sv,O2 also decreased (55 +/- 3% baseline, 46 +/- 3% sucking, P < or = 0.05) but, in contrast to Sa,O2, it remained significantly lower than baseline levels in the pauses between periods of sucking. 4. Arterial pressure increased during feeding (94 +/- 4 mmHg baseline, 113 +/- 6 mmHg feeding, P < or = 0.05), while heart rate and cardiac index did not change. 5. Total body oxygen consumption rose during the pauses between sucking periods (10.9 +/- 1.1 ml O2 min-1 kg-1 baseline, 13.9 +/- 1.2 ml O2 min-1 kg-1 non-sucking, P < or = 0.05) and was provided for by a significant increase in total body oxygen extraction as systemic oxygen transport was unchanged. 6. Our results reveal that during feeding in young lambs oxygen consumption increases and body stores of oxygen (e.g. Sv,O2) become depleted; this combination may promote rapid arterial desaturation and cyanosis during feeding.