Noninvasive Assessment of Blood Pressure Variability in Preterm Infants

Abstract

The feasibility of measuring blood pressure (BP) variability by a noninvasive beat-to-beat finger arterial BP device (Finapres) was assessed in preterm infants. By application of the finger cuff around the infant's wrist, time and frequency domain (spectral power) analysis of noninvasive beat-to-beat BP signals were compared with intra-arterial measurements. A fast Fourier Transform was used to compute the spectral power density from 128-s periods. The low-frequency band (LF; 0.04 -0.15 Hz) is partly associated with baroreflex activity. The high-frequency band (HF; 0.4 -1.5 Hz) is associated with respiratory activity. In eight subjects above 1000 g, reliable signals could be obtained. We observed a high correlation between noninvasive and intraarterial beat-to-beat systolic BP values (mean r value Ϯ SD, 0.87 Ϯ 0.11), with a gain close to 1 (mean gain Ϯ SD, 1.0 Ϯ 0.4 mm Hg/mm Hg). Finapres estimated beat-to-beat systolic BP changes more accurately than diastolic values. We found a very high amount of linear coupling, expressed as coherence function, between the power spectra of noninvasive and intra-arterial systolic BP measurements. For systolic BP, the (pooled) group mean Ϯ SEM coherence values were 0.93 Ϯ 0.00 and 0.91 Ϯ 0.01 for LF and HF fluctuations, respectively (NS). The wrist method of Finapres in neonates has limited value in estimating absolute BP but is useful in a clinical research situation, where identification of beat-to-beat changes in systolic BP is more important. Finapres (FINger Arterial PRESsure) is a noninvasive blood pressure (BP) method that is based on the volume-clamp principle (1). The device is based on a photoplethysmographic system applied to the finger and provides a continuous beatto-beat waveform. Several studies of Finapres have been reported and have shown good agreement with intra-arterial measured BP, in both adults and children (2-4). Despite abundant literature about the application of Finapres in adults, very little is known in neonates. Drouin et al. (5) published in 1997 about the accuracy of Finapres measurements in the neonate. Because no appropriately sized cuff exists for neonates, Drouin placed the finger cuff around the wrist of the baby. Absolute Finapres BP values were compared with intraarterial BP for selected periods of 5 s, and it was concluded that both methods gave similar results. However, no information was given about the accuracy of measuring BP fluctuations over longer periods of time. We do know from studies in adults, however, that Finapres may overestimate the lowfrequency (LF) fluctuation (6). The reliability of Finapres to produce frequency domain analysis in neonates has not been assessed. The aim of this study was to determine 1) the accuracy of Finapres in measuring BP absolute values and beat-to-beat changes and 2) the accuracy of Finapres in studying BP variability by frequency domain analysis. METHODSThe study was performed in 12 preterm infants (gestational age, 26 -33 wk; birth weight, 750 -2215 g) whose intensive

Abnormal Circulatory Stress Responses of Preterm Graduates

“…5). These findings are remarkable in view of the relatively small number of infants studied and the fact that we used indirect (although validated) techniques to measure arterial CO 2 and pressures (13,16,17). Clearly, short-term circulatory control is altered by being born too soon and may be further compromised by perinatal complications.…”

“…BP was recorded from a wrist cuff (Finometer, FMS, The Netherlands; for accuracy, the "physiocal" function was always enabled) (13). To alleviate venous congestion in the hand, cuff inflations were limited to 10 min (several inflations were needed to complete the protocol).…”

Characteristics of Arterial Stiffness in Very Low Birth Weight Premature Infants

“…Currently there are no other alternative methods that can provide noninvasive, continuous arterial blood pressure tracing in neonates. Although the use of the Finapress technique did not allow measurement of arterial pressure at sites other than the wrist, Finapress wrist pulse pressure has been shown to be close to aortic PP in neonates (20,28). To reduce the PP amplification between central and peripheral circulation, the continuous tracing of arterial blood pressure was initially calibrated on brachial arterial pressure recorded by oscillometric method.…”

Evidence for Cardiovascular Autonomic Dysfunction in Neonates With Coarctation of the Aorta

“…Bias was defined as the average of the differences between Portapres and arterial line values. 25 The SD of the bias is an index of intrapatient variation. Comparisons between CoA and controls were made with unpaired 2-tailed t tests for normally distributed data and Mann-Whitney rank sum tests for data that were not normally distributed.…”

“…[25][26][27] We studied infants shortly after feeding when they were settled and sleeping. No formal determination of sleep state was measured.…”