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Cardiorespiratory responses to bidirectional tilts in infants
W P Fifer1, M Greene, A Hurtado
1New York State Psychiatric Institute and Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York 10032, USA. wpfl@columbia.edu
Insights
Newborns show distinct heart rate changes with head-up and head-down tilting. By 2-4 months, infants lose the sustained heart rate increase to head-up tilts, potentially impacting blood pressure regulation during sudden infant death syndrome (SIDS) risk periods.
Area of Science:
- Neonatal physiology
- Infant autonomic nervous system function
- Sudden Infant Death Syndrome (SIDS) research
Background:
- Newborns exhibit altered heart rate (HR) responses to head-up and head-down tilting.
- Previous studies suggest varying HR responses to head-up tilting in infants at risk for SIDS.
- Autonomic nervous system (ANS) regulation is critical in infant development and SIDS risk.
Purpose of the Study:
- To investigate changes in heart and respiratory rates in infants during bidirectional tilting.
- To compare these responses in newborns versus infants during the peak SIDS risk period (2-4 months).
- To test the hypothesis of reduced compensatory ability in infants at higher SIDS risk.
Main Methods:
- Recording of heart rate and respiratory rate in sleeping infants.
- Utilizing bidirectional tilting (head-up and head-down) at 30 degrees.
- Data collected on Day 1-2 of life and at 2 and 4 months of age.
Main Results:
- Newborns increased HR with head-up tilt and decreased HR with head-down tilt.
- Respiratory rate decreased with head-up tilt; no significant change with head-down tilt.
- At 2-4 months, HR elevations to head-up tilt diminished, while head-down tilt responses and respiratory changes remained comparable to newborns.
Conclusions:
- Infants' ability to sustain heart rate elevations during head-up tilting decreases between the newborn period and 2-4 months.
- This age-related change may indicate a reduced capacity to manage blood pressure challenges during the peak SIDS risk window.
- Findings support the hypothesis of altered autonomic compensation in infants at heightened risk for SIDS.
Abstract:
Prior research in newborns has shown that head-up and head-down tilting elicits sustained increases and decreases in heart rate, respectively. Other studies in older infants have suggested that the pattern of heart rate responses to head-up tilting varies with risk for sudden infant death syndrome (SIDS). In this study, heart and respiratory rate changes following bidirectional tilting were recorded in sleeping infants on Day 1 or 2 of life, and during the period of maximum risk for SIDS, at 2 and 4 months of age. Newborns show increases in heart rate following 30 degrees head-up tilts and decreases in heart rate to 300 head-down tilting. Respiratory rates decreased to head-up tilting but did not change significantly to head-down tilting. While respiratory rate changes at 2 and 4 months of age are comparable to those of newborns, and decreases in heart rate to head-down tilting are similar across ages, sustained elevations in heart rate following head-up tilting are no longer apparent at the older ages. These results are consistent with the hypothesis that, during the period of maximum risk for SIDS, infants may have reduced ability to compensate for challenges that lead to decreases in blood pressure.