The effect of change in sympatho-vagal balance on heart rate and blood pressure variability in the foetal lamb.

Cardiac and vascular function is mainly under autonomic nervous control within seconds to minutes, although the control is not mature at birth. We studied sympathovagal control of heart rate and blood pressure in chronically catheterized foetal lambs in the last trimester of gestation. Power spectral analysis was used to quantitate the frequency-specific heart rate variability (HRV) and blood pressure variability.

Computer analysis of heart rate variation and breathing movements in fetal lambs.

A quantitative method for studying the frequency-specific relationships between heart rate (HR) and fetal breathing movements (FBM) was developed. The reactivity of periodic HR variation in relation to FBM was investigated by means of power spectral analysis. Seven fetal lambs were studied during the third trimester of gestation using a chronic animal model.

Association of breathing movements to the variability of heart rate and blood pressure in foetal lambs.

Heart rate (HR) variability and arterial blood pressure (BP) variability were analysed as functions of foetal breathing movements (FBMs) by means of power spectral analysis in seven foetal lambs during the third trimester of gestation. No evidence of FBM-related changes, either in mean HR, mean systolic or diastolic arterial pressures, were found. Mean arterial pulse pressure, HR variability, and BP variability increased during FBMs.

Do beta-adrenergic blockade and sleep state affect cardiorespiratory control in neonatal lambs? Multivariate autoregressive modeling approach.

Beta-Blockers are used in pregnancy-associated hypertension and in postnatal cardiac arrhythmias, and the neonate may get them in breast milk. We therefore studied the effects of beta-adrenergic medication on interrelations between heart rate (HR), respiration, and arterial blood pressure (aBP) in newborn lambs. The influence of sleep state on these cardiorespiratory interrelations was also examined.

Regulation of heart rate variation by the autonomic nervous system in neonatal lambs.

We studied the role of the autonomic nervous system in the regulation of heart rate variation (HRV) in 12 chronically instrumented neonatal lambs. HRV was quantified from ECG tracings by computing periodic HRV distributions at frequencies of 0.02-1.