AJP - Heart and Circulatory Physiology, Vol 247, Issue 1 67-H73, Copyright © 1984 by American Physiological Society
Rhythmic variations in R-R interval during sleep and wakefulness in puppies and dogs
G. G. Haddad, H. J. Jeng, S. H. Lee and T. L. Lai
We studied the short-term oscillations in the R-R interval in five puppies
at 4 wk of age and five adult dogs during sleep and wakefulness. The R-R
interval was measured using an R-R preprocessor, and respiration was
recorded using barometric plethysmography. Puppies showed much smaller
fluctuations in the R-R interval (SD between 6 and 40 ms) than adult dogs
(SD between 124 and 367 ms) in both rapid eye movement (REM) and quiet
sleep. Spectral analysis demonstrated that these oscillations were
primarily of low frequencies, and the contribution of respiratory sinus
arrythmia (RSA) to total power was low. In contrast, in adult dogs during
sleep, the spectral distributions were peaked in frequency bands
corresponding to mean respiratory rate, and the percent contribution of low
frequencies to power was small. Furthermore, the mean R-R interval was
considerably larger during expiration than during inspiration in adult dogs
(showing 20-140% increase), but not in puppies (showing only -0.4 to 4.4%
increase). We conclude that 1) the mechanisms responsible for RSA mature
postnatally in the dog; 2) the magnitude of RSA depends on the state of
consciousness in the adult dog, being greater in sleep than during
wakefulness; and 3) low-frequency oscillations, not related to breathing
and independent of sleep state, characterize the variations in the R-R
interval in early life but are insignificant in the adult dog.
