Search

The phase relationship between ribcage and abdominal movement in 1440 breaths from 12 infants (mean age 3.2 days) showed statistically significant differences between sleep states as judged by physiological criteria. The mean phase difference (+/- 1 SD) was 20 (+/- 16)% in active sleep, 9 (+/- 17)% in indeterminate sleep and 3 (+/- 5)% in quiet sleep (P less than 0.0005). However, the wide scatter within sleep states meant that even the mean value from 50 breaths was not specific enough to delineate sleep state.

To assess whether there is a maturation of the response to tube breathing during the first 10 days of life, we have measured the dynamic ventilatory responses of nine term infants (34 studies) to added tubes equivalent to two anatomical dead spaces. Such a method allows an assessment of the baby's ability to increase dead space ventilation in response to an added stress. There was a significant improvement with age over the first 10 days in the babies' ability to reach "expected" values of minute ventilation when the tubes were added (P = 0.003). The rates at which 63% and maximum adaptation were achieved also increased significantly with age (P less than 0.005). The rate to 63% adaptation appeared to be faster in active compared with quiet sleep (P less than 0.05). The dynamic responses to tube breathing improve over the first 10 days of life. This is likely to be due to a maturation of peripheral chemoreceptor control, although improving lung mechanics may also be important.