The methodology of Doppler-derived central blood flow measurements in newborn infants

Abstract

Central blood flow (CBF) measurements are measurements in and around the heart. It incorporates cardiac output, but also measurements of cardiac input and assessment of intra- and extracardiac shunts. CBF can be measured in the central circulation as right or left ventricular output (RVO or LVO) and/or as cardiac input measured at the superior vena cava (SVC flow). Assessment of shunts incorporates evaluation of the ductus arteriosus and the foramen ovale. This paper describes the methodology of CBF measurements in newborn infants. It provides a brief overview of the evolution of Doppler ultrasound blood flow measurements, basic principles of Doppler ultrasound, and an overview of all used methodology in the literature. A general guide for interpretation and normal values with suggested cutoffs of CBFs are provided for clinical use.

Figure 1

Compartments of the circulation where blood flow can be measured. The central circulation includes the pulmonary and systemic circulation. Organ circulation includes each organ and the peripheral circulation. All organs have their local afferent and/or efferent regulation system. Blood pressure in newborns is measured in the central circulation (descending aorta) or in the peripheral circulation (limbs).

Figure 2

Methods of determination of LVO diameter. 2D ascending aorta dimensions are inner wall dimensions. 2D aortic annulus dimensions are taken at the valve hinges. Trailing edge technique measures the inner diameter of a vessel in M mode from the posterior portion of the anterior aortic wall to the inner boundary of the posterior aortic wall. Leading edge technique measures from the anterior portion of the anterior aortic wall to the inner boundary of the posterior aortic wall.