title: Multivariate autoregressive modelling combined with transcephalic electrical impedance: method to relate neonatal systemic circulation and respiration to cerebral circulation.
abstract: We studied the pulsatile component of cerebral circulation with transcephalic electrical impedance (delta Z) in six preterm newborns, three of whom had severe cerebral bleeding, peri-intraventricular haemorrhage (PIVH). The transcephalic electrical impedance delta Z signal, ECG, arterial blood pressure, (aBP) and respirogram were recorded on analogue magnetic tape for 30 min. Artefact-free stationary segments (lasting for 2 min) of the four signals were digitised. A digital multivariate autoregressive (MAR) model was used to study frequency-specific variability in the signals and to quantify interrelations between the variabilities of delta Z, HR, aBP and respiratory signals. MAR modelling describes a system where all the signals simultaneously explain each other. The inherent variability of delta Z was lower and the influences of respiration and aBP on delta Z significantly greater in infants with severe PIVH than in controls. These changes were observed at high frequencies corresponding to respiration and heart rate. This may be interpreted as a marker of pressure passivism in the cerebral circulation following PIVH. We conclude that in preterm babies the application of MAR modelling, together with transcephalic impedance, may be a new, helpful and quantitative method for the study of simultaneous interrelations between variables of cerebral and systemic circulations and respiration.
authors.affiliation: Department of Physiology, University of Turku, Finland.
authors.forename: J U
authors.initials: JU
authors.lastname: Grönlund
authors.forename: J
authors.initials: J
authors.lastname: Jalonen
authors.forename: I
authors.initials: I
authors.lastname: Korhonen
authors.forename: P
authors.initials: P
authors.lastname: Rolfe
authors.forename: I A
authors.initials: IA
authors.lastname: Välimäki
mesh_terms: D002543:Cerebral Hemorrhage / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D017097:Electric Impedance; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D007235:Infant, Premature, Diseases / Q000503:physiopathology*; D008954:Models, Biological; D012119:Respiration / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted