[The frequency of respiratory variations during daytime and nighttime sleep in 35 normal 2-month-old infants]

Daytime and nighttime polygraphic recordings were made of 35 normal 2-month-old infants. Respiratory rate was calculated every minute in active (AS) and quiet (QS) sleep states. The study indicates a difference in mean rate between the 2 states and also shows that mean respiratory rate was lower at night than during the day (P less than 0.0001 for both states) and that there was a marked increase in rate during the first cycle. Infants with episodes of periodic breathing had a lower mean respiratory rate throughout the recordings. For each QS phase, both day and night, a marked decrease in mean respiratory rate occurred, especially during the first part of the sleep state, which was not found in AS. Intrasleep spontaneous awakening led to a marked increase in respiratory rate after sleep was resumed both in QS and AS. However, differences were only statistically significant when the awakened infant was fed. There was less difference between respiratory rates after spontaneous awakening without feeding since the pre-awakening rate was more elevated than when the infant was subsequently fed.