Polygraphic studies of kitten development: respiratory rate and variability during sleep-waking states

The developmental course of respiration rate and variability during sleep states and waking was measured in chronically prepared kittens. Kittens had higher respiration rates during active sleep (AS) as compared to quiet sleep (QS) at all ages, with rates declining developmentally in both sleep states. Compared to waking, respiration rate and variability were decreased during sleep. The decrease was greatest in the youngest animals and during QS. Minute-to-minute respiratory variability declined from 10 to 40 days of age for each state, whereas breath-to-breath variability declined during the same period only during QS. Respiratory variability was higher in AS than QS in older kittens. Heart rate and variability were found to be correlated with respiratory parameters only during QS. These observations support the hypothesis that the control and development of respiration during sleep is achieved by different processes in QS and AS.