Developmental changes in heart rate variability during exposure to prolonged hypercapnia in piglets
Anthony L Sica1, David A Ruggiero, Ning Zhao
1Department of Physiology and Pharmacology, State University of New York, Downstate Medical Center, Brooklyn 11203, USA. asica@netmail.hscbklyn.edu
Insights
Heart rate variability (HRV) differences emerged in older piglets during hypercapnia, suggesting sympathetic and parasympathetic coactivation. Younger piglets showed stable HRV, indicating potential vulnerability during early maturation.
Area of Science:
- Physiology
- Developmental Biology
- Cardiovascular Research
Background:
- Heart rate variability (HRV) changes during maturation are not fully understood.
- Hypercapnia (elevated CO2) can impact autonomic nervous system function.
- Early life autonomic responses may influence long-term health outcomes.
Purpose of the Study:
- To investigate age-dependent effects of hypercapnia on heart rate variability (HRV) in developing piglets.
- To determine if hypercapnia induces changes in autonomic nervous system activity during early maturation.
- To identify potential windows of vulnerability in early postnatal development.
Main Methods:
- Developing porcine model with three age groups (5-8, 13-15, 26-34 days old).
- Animals were exposed to hypercapnia (10% CO2) or control (100% O2) conditions.
- HRV assessed using power spectral analysis, SD of RR intervals, and cardiac interval analysis.
Main Results:
- Significant HRV differences were observed only in the oldest group (26-34 days old) during hypercapnia.
- Older piglets exhibited cardiac interval distributions suggesting coactivation of sympathetic and parasympathetic systems.
- Younger piglets (5-8 days old) maintained balanced cardiac intervals, while 13-15 day olds showed a paucity of balanced intervals.
Conclusions:
- Autonomic nervous system responses to hypercapnia mature significantly by the fourth postnatal week in piglets.
- The period around the second postnatal week may represent a vulnerable stage with altered autonomic regulation.
- Understanding these developmental changes in autonomic control is crucial for assessing neuroprotection and health risks.
Abstract:
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.
