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The heart rate response to tilting was investigated in active and quiet sleep in 19 normal newborns (age 1–7 days) and 11 healthy premature infants (age 2–19 days). RR intervals were determined by computer from the ECG for 30–60 s periods immediately before and after each tilt. Term infants had a significant (p < 0.005) decrease in RR interval for head-up tilting and significant (p < 0.005) increase in RR with head down tilts. There was no significant difference in the magnitude of RR change between upward and downward tilt or between active and quiet sleep. For premature infants, the response to tilting was similar to that of the term infants, especially with allowance for the faster heart rates of the former. Respiratory rate changes were an important source of variability in the heart rate response to tilting and are likely the source of previous inconsistencies. Our results indicate that healthy newborns have a well-developed heart rate response to tilting, suggesting considerable maturity of neural control of heart rate.

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