Arterial blood gas tensions during exercise in neonatal lambs

At the onset of exercise. adult animals increase ventilation to match or ex ceed the metabolic requirement. This error-free regulation of arterial bloo d gas tensions may be attributable to adaptive feed-forward control'-respir atory control based on experience gained in infancy. This hypothesis predic ts that neonates exhibit hypercapnia at the onset of exercise. To test this prediction, seven lambs were exercised on a treadmill at 0.8 m/sec at the ages of 2-5 days. and again at 9-12 days. Arterial blood samples were drawn pre-exercise and at 0.5, 1, 2, 5, 7 and 10 min of exercise. Seven adult sh eep were similarly rested for comparison. The lambs had significantly highe r arterial CO2 tensions (Pa-CO2) and lower arterial O-2 tensions (Pa-O2) th an adult sheep both at rest and during exercise. Nonetheless, the lambs mai ntained Pa-CO2 at or below the resting level throughout exercise. Pa-O2 ros e significantly during exercise ill the sheep and lambs. The results do not support the hypothesis since hypercapnia was not observed in the exercisin g neonatal lambs. (C) 1999 Elsevier Science B.V. All rights reserved.