Is Gravity involved in the Postnatal Developments of Heart Rate Variability?
- Paper number
IAC-05-A1.P.10
- Author
Dr. Shunji Nagaoka, Fujita Health University School of Health Sciences, Japan
- Coauthor
Mr. Yoshiaki Shindo, Fujita Health University School of Health Sciences, Japan
- Coauthor
Dr. Yasuhiro Itoh, Fujita Health University School of Health Sciences, Japan
- Coauthor
Dr. Hiroko Nomura, Fujita Health University School of Health Sciences, Japan
- Coauthor
Dr. Tadayoshi Hata, Fujita Health University School of Health Sciences, Japan
- Year
2005
- Abstract
Purpose: The heart rate variability known as a cardiopulmonary reflex is respiratory modulation of the heart rate mostly induced via vagal nerve activities from lung to heart. The origin and the functional development of such reflex is however not well understood. As reported previously, a majority of heart rate variability (HRV) induced by human respiration showed remarkable postnatal development especially in low birth weight neonates. In this report, we analyzed and compared the frequency components of HRV in mammalian neonates (human, pig and rat) and hatched white chicken how the HRV developed with time after the birth, namely exposure to the gravity. Methodology: The animal subjects used were Wister rats, white chicken (Gallus gallus) and pigs in commercial breeder in 0 day-old to postnatal approximately 1 month. For all animals, we measured ECG and respiration simultaneously. Frequency analysis with autocorrelation-FFT method was applied to the heart rate and respiration waves to calculate the respiration-linked component in the power spectra. Results: A comparison of the cardiopulmonary reflex in human and pig neonates resulted in a similar developmental progression. The comparative analysis of the cardiopulmonary reflex using human and rat neonates resulted in a similar developmental status. In case of human immature neonate, as previously reported, respiration-linked frequency component in the heart rate variability was negligible at day-old 0 and significantly increased in the postnatal period. A comparison of the cardiopulmonary reflex in human and pig neonates resulted in a similar developmental progression. In case of normal human neonate, respiration induced HRV was significant within a week after the birth, however it took approximately one month in low birth weight neonate (mean gestational age 33+/-1 weeks). In case of pig neonates, the HRV was significant a few days after the birth and developed in parallel to the body weight. Rat neonates however indicated a significant retardation showing negligible HRV until days 8 and it became significant at postnatal 1 month. The white chicken indicated similar HRV development as that of rat, and became significant after 38days-old (17days post hatching). The results indicated that the development of the respiration linked HRV was triggered by the birth in mammalian neonates and quickly grew in the subsequent period. The results also suggested that the developmental maturity of HRV strongly depend on the gestational period when comparing between rat and the low birth weight human neonates. Conclusion: The trigger for the HRV formation was however still unclear. Considering the previous findings that aquatic reptile and amphibian even fish did not show respiration-linked HRV in entire developmental phases, the respiration-linked HRV seems to be specific in the ground animals, like mammalian or avian. The results strongly imply that the gravity exposure after the birth may play an essential role of the post natal development of the cardiopulmonary reflex.
- Abstract document