Respiratory adaptation to chronic hypercapnia in newborn rats

tory adaptation to chronic hypercapnia in newborn rats. J. Appl. Physiol. 67(l): 311-3X5,1989.-We asked 1) whether newborn rats respond to chronic hypercapnia with a persistent increase in ventilation and 2) whether changes in lung mass were accompanying the respiratory adaptation to chronic hypercap-nia, as previously observed during neonatal chronic hypoxia. Five litters of rats were kept in 7 % COz (with 21 % 02) from day 1 to 7 after birth (CO*exp) and compared with six litters of control rats growing in normocapnia-normoxia (C). Body weight was similar between the two groups. Ventilation, meas-ured by flow plethysmography, increased in CO,exp from day 2 and remained steadily elevated, and at day 7 it almost doubled (174%) the C value because of the large increase in tidal volume and mean inspiratory flow (192 and 189%, respectively) with no changes in respiratory frequency. Two days after return t