Heart Rate Response to Tilting in Newborns in Quiet and Active Sleep

Abstract

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.

Factors Affecting Heart Rate Variability and Heart Rate Responses to Tilting in Infants Aged 1 and 3 Months

“…Following the head-up tilt, the stable HR response was very strongly associated with sleep state, both with and without movement in the analysis. In contrast, studies of preterm and term infants slowly tilted head-up to 30°or 60°( so as not to induce sighs or movement), found no association between the stable heart rate change and sleep state (24,25).…”

“…We found the ratio measure to be higher in older infants suggesting a larger reflex response to the tilt, findings that were reproduced by defining the profile of the response but not apparent once the heart rate reached a stable level. However with a rapid tilt, sighs, apneas, and movement are common and some stress the importance of measuring heart rate responses only in the absence of these (24,25). By excluding movement in our analysis, the maturational effect remained for the reflex response.…”

“…The methodology for this test varies, in the timing and degree of tilts, age ranges studied, study conditions used and methods of analysis of the heart rate response (23). Analyses of the responses include 1) quantitative measures of the changes in heart rate from rest immediately following the tilt (7,20) and the changes to a new stable rate (24,25) and, 2) qualitative measures in terms of profiling the heart rate response (22). It has been shown that some infants who experienced apparent life-threatening events (ALTE) had a normal heart rate response to head-up tilting measured quantitatively, but abnormal by qualitative terms (22).…”

Effect of Head-Up Body Tilt Position on Autonomic Function and Cerebral Oxygenation in Preterm Infants

“…Recordings made after infants were allowed to settle at least 3-5 min in HETP did not reveal significant changes in heart rate and blood pressure. Conflicting data in the heart rate response of preterm infants to positional changes in former studies resulted mainly from different time schedules during evaluation and different ages of populations [7][8][9].…”

Cardiovascular Consequences of Preterm Birth in the First Year of Life

“…In the latter study, blood pressure was also unchanged on tilting however peripheral vascular resistance increased significantly, and there was no correlation between cardiovascular parameters and gestational or chronological age (Lagercrantz et al, 1990). In contrast, Finley et al, (Finley et al, 1984) showed that both term infants studied in the first week after birth and preterm infants (born at 33 -37 week GA) studied at 2 -29 d had significant increases in heart rate on head-up tilting (30) and significant decreases on head-down tilting, results were however very variable between infants. In addition, there was no difference in responses between sleep states, and they concluded that control of heart rate was well developed at term.…”