Sleep-Dependent Changes in the Coupling Between Heart Period and Arterial Pressure in Newborn Lambs

Abstract

This study assessed whether sleep-dependent changes in the relationship between heart period (HP) and mean arterial pressure (MAP) occur in newborn life. Electrodes for electrocorticographic, electromyographic, and electrooculographic monitoring and an arterial catheter for blood pressure recordings were implanted in 11 newborn lambs. HP and MAP beat-to-beat values were computed from 120-s blood pressure recordings during quiet wakefulness, active sleep, and quiet sleep. For each recording, the time shift at which the maximum of the HP versus MAP cross-correlation function was attained was identified. For each lamb and wake-sleep state, an average correlation coefficient was then computed corresponding to the median value of such time shifts. The maximum of the cross-correlation function was attained with HP lagging behind MAP. The corresponding mean correlation coefficient was significantly higher in quiet sleep (0.51 Ϯ 0.05) than either in quiet wakefulness (0.31 Ϯ 0.05) or in active sleep (0.29 Ϯ 0.03). Sleep-related differences in the correlation between HP and MAP were maintained after HP and MAP data were low-pass filtered at 0. The regulation of systemic arterial pressure plays an essential role in homeostasis, as it permits coupling of blood flow to tissue metabolic needs while avoiding excessive rises in microvessel transmural pressure. Central autonomic commands, in supporting an actual or expected behavior [e.g. exercise (3), defense reaction (4)], may induce parallel changes in heart rate and in systemic vascular resistance. In adult rats, baroreflex control of heart rate prevails in quiet sleep, whereas central commands prevail in active sleep (5,6). Although effects of central autonomic commands on heart rate and arterial pressure are similar in wakefulness and in active sleep, the cause of such commands is uncertain in the latter state. Thus, central autonomic commands that occur in active sleep give rise to regulatory disturbances rather than to anticipatory regulation, as it occurs during wakefulness. It is unclear whether these conclusions apply to animals during early postnatal development, whose cardiovascular regulation undergoes functional maturation and differs in many respects from that of older animals (7-12).The aim of our study was to assess whether the relationship between heart period (HP) and arterial pressure changes during sleep in newborn lambs. We analyzed the relationship between HP and mean arterial pressure (MAP) in the time domain by Received February 11, 2004; accepted July 6, 2004

Bidirectional interactions between the baroreceptor reflex and arousal: an update

“…While transient central commands may alter baroreflex control in each sleep-wake state, an analysis of cardiovascular variability in human subjects [47] and animal models (lambs [48]; rats [49]) indicates that this occurs to different extents in different states. In particular, the baroreflex plays a greater role in driving cardiac rhythm during NREM sleep than during quiet restful wakefulness [45].…”

The low frequency power of heart rate variability is neither a measure of cardiac sympathetic tone nor of baroreflex sensitivity

“…We studied control healthy sheep as well as sheep with pacing-induced heart failure (23), which is a condition of heightened CSNA tone with significant clinical implications (3,11). We performed a cross-correlation analysis of spontaneous cardiovascular fluctuations (19,21) to investigate whether in each individual, HP was coupled to CSNA and BP. We then analyzed correlations between the values of HP, LF HRV, CSNA, and BRS obtained in individual control sheep and sheep with heart failure.…”

Estimation of Sleep Onset Latency Based on the Blood Pressure Regulatory Reflex Mechanism

“…In animal model studies, the correlation between HBI and SBP suggests a variable contribution of central and arterial baroreflex mechanisms to cardiovascular control in different wake-sleep states [12], [13]. The arterial baroreflex contribution to HBI control was most prominent during quiet sleep in lambs [13] and during nonrapid eye movement (NREM) sleep in rats [12].…”

“…The arterial baroreflex contribution to HBI control was most prominent during quiet sleep in lambs [13] and during nonrapid eye movement (NREM) sleep in rats [12]. For human subjects, the authors in [14] determined that the relationship between HBI and the previous SBP values differs substantially among sleep-wake states.…”