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Postnatal development of baroreflex sensitivity in infancy
Author(s) -
Yiallourou Stephanie R.,
Sands Scott A.,
Walker Adrian M.,
Horne Rosemary S. C.
Publication year - 2010
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2010.187070
Subject(s) - baroreflex , sensitivity (control systems) , medicine , neuroscience , cardiology , psychology , blood pressure , heart rate , electronic engineering , engineering
Baroreflex sensitivity (BRS) using spontaneous sequence analysis in the time domain is not fully applicable in infancy, as the time delay for heart period to change (heart period delay, HPD) after an arterial pressure change is unknown. We estimated and compared HPD and BRS in the frequency (BRS sp , HPD sp ) and time domains (BRS seq , HPD seq ) from systolic blood pressure (SBP) and heart period fluctuations. Continuous SBP, using photoplethysmography, and heart period measurements were performed on 30 term infants at 2–4 weeks, 2–3 months and 5–6 months postnatal age. Cross‐spectral analysis between SBP and heart period fluctuations was used to estimate BRS sp and HPD sp . Spontaneous sequence analysis was used to estimate BRS using a fixed beat delay of 1–12 beats (BRS seq ) or a variable delay identified by a novel method accounting for epoch–epoch variability in HPD (BRS seqvar ). HPD sp averaged 3.4 s (∼7 beats); BRS sp averaged 11.4 ms mmHg −1 . BRS seq and BRS seqvar were consistently lower than BRS sp ( P < 0.05), but the three BRS estimates were strongly correlated using a HPD of ∼5–6 beats. BRS seqvar resulted in the average estimate (8.9 ms mmHg −1 ) closest to BRS sp and overall had the strongest correlation with BRS sp ( R 2 = 0.61; P < 0.001). All three BRS estimates increased progressively with postnatal age, with BRS sp averaging 6.4, 10.5 and 16.0 ms mmHg −1 at 2–4 weeks, 2–3 months and 5–6 months, respectively ( P < 0.05). Accounting for the HPD of infancy provides estimates of BRS in the time domain that closely parallel spectral estimates, and provides a novel analytical tool to assess normal development and dysfunction of the baroreflex in infants.