Developmental changes in heart rate variability during exposure to prolonged hypercapnia in piglets.
The hypothesis that hypercapnia-induced differences in heart rate variability (HRV) would emerge during early maturation was tested using a developing porcine model. Piglets were randomly assigned to either exposed (10% CO2 for 1 h) or control (100% O2) conditions, and then to one of three study groups: (a) 5-8 days old, (b) 13-15 days old, (c) 26-34 days old. Experiments were performed on pairs of age-and litter-matched animals that were anesthetized, paralyzed, and artificially ventilated. HRV was evaluated using power spectral analysis, SD of differences between successive RR intervals, and cardiac interval analysis. Statistical comparisons of simultaneously studied animals were made at baseline, 15 and 55 min after onset of hypercapnia, and 2 h after offset of hypercapnia. Our analyses revealed that only HRV of 26-34-day-old animals differed significantly from values of control animals. Cardiac intervals of those animals were distributed in such a manner that hypercapnia likely elicited coactivation of sympathetic and parasympathetic systems. Comparison of the distribution of cardiac intervals for other animals showed that 5-8-day-old animals had high frequency of balanced intervals at baseline that remained so during hypercapnia. Given that such coactivation may be neuroprotective, the paucity of balanced intervals in 13-15-day-old animals could mean that the end of the second postnatal week is associated with increased vulnerability.
Sica
Anthony L
AL
Department of Physiology and Pharmacology, State University of New York, Downstate Medical Center, Brooklyn 11203, USA. asica@netmail.hscbklyn.edu
Ruggiero
David A
DA
Zhao
Ning
N
Gootman
Phyllis M
PM
D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001341:Autonomic Nervous System / Q000502:physiology; D004569:Electroencephalography / Q000379:methods; D006321:Heart / Q000254:growth & development / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006935:Hypercapnia / Q000503:physiopathology*; D011897:Random Allocation; D013552:Swine; D013997:Time Factors