Abstract-Oscillometric blood pressure devices tend to overestimate systolic blood pressure and underestimate diastolic blood pressure compared with sphygmomanometers. Recent studies indicate that discrepancies in performance between these devices may differ between healthy and diabetic subjects. Arterial stiffness in diabetics could be the underlying factor explaining these differences. We studied differences between a Dinamap oscillometric blood pressure monitor and a random-zero sphygmomanometer in relation to arterial stiffness in 1808 healthy elderly subjects. The study was conducted within the Rotterdam Study, a population-based cohort study of subjects aged 55 years and older. Systolic and diastolic blood pressure differences between a Dinamap and a random-zero sphygmomanometer were related to arterial stiffness, as measured by carotid-femoral pulse wave velocity. Increased arterial stiffness was associated with higher systolic and diastolic blood pressure readings by the Dinamap compared with the random-zero sphygmomanometer, independent of age, gender, and average mean blood pressure level of both devices. Key Words: blood pressure monitoring Ⅲ oscillometry Ⅲ sphygmomanometry Ⅲ arterial stiffness A utomatic oscillometric blood pressure devices are frequently used to measure blood pressure. Several studies, evaluating their performance in comparison with a Hawksley random-zero or conventional sphygmomanometer, showed that oscillometric devices tend to overestimate systolic blood pressure (SBP) and underestimate diastolic blood pressure (DBP) compared with sphygmomanometers. 1-4 Recent studies indicate that differences in performance between these devices may diverge between healthy and diabetic subjects. [5][6][7] One study, comparing a Dinamap 8100 oscillometric device with a Hawksley random-zero sphygmomanometer in diabetic subjects, found that the Dinamap overestimated SBP Ͻ118 mm Hg and underestimated SBP Ͼ152 mm Hg, while DBP was underestimated over the whole range of pressures. 5 Another study compared a SpaceLabs 90207 oscillometric device with a sphygmomanometer in diabetic subjects and healthy controls. The SpaceLabs device overestimated SBP in both diabetic subjects and controls, but the overestimation was more pronounced in the diabetic subjects. DBP was underestimated in both groups but was less pronounced in diabetic subjects. 6,7 An oscillometric blood pressure device determines blood pressure by detecting a sequence of oscillations in cuff pressure while the pressure is reduced. 8 Since diabetic patients have stiffer arteries than nondiabetic subjects, 9 arterial stiffness could be the underlying mechanism of the more pronounced differences between oscillometric devices and sphygmomanometers in this group. We evaluated determinants of differences between an oscillometric blood pressure device and a sphygmomanometer in a large population-based cohort of elderly subjects. Methods Study DesignThis study was conducted within the Rotterdam Study. The Rotterdam Study is a population-based cohort ...

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

A customized filtering technique is introduced and compared with fast Fourier transformation (FFT) for analyzing heart rate variability (HRV) in neonates from short-term recordings. FFT is classically the most commonly used spectral technique to investigate cardiovascular fluctuations. FFT requires stability of the physiological signal within a 300 s time window that is usually analyzed in adults. Preterm infants, however, show characteristics of rapidly fluctuating heart rate and blood pressure due to an immature autonomic regulation, resulting in non-stationarity of these signals. Therefore neonatal studies use (half-overlapping or moving) windows of 64 s length within a recording time of 2-5 min. The proposed filtering technique performs a filtering operation in the frequency range of interest before calculating the spectrum, which allows it to perform an analysis of shorter periods of only 42 s. The frequency bands of interest are 0.04-0.15 Hz (low frequency, LF) and 0.4-1.5 Hz (high frequency, HF). Although conventional FFT analysis as well as the proposed alternative technique result in errors in the estimation of LF power, due to spectral leakage from the very low frequencies, FFT analysis is more sensitive to this effect. The response times show comparable behavior for both the techniques. Applying both the methods to heart rate data obtained from a neonate before and after atropine administration (inducing a wide range of HRV), shows a very significant correlation between the two methods in estimating LF and HF power. We conclude that a customized filtering technique might be beneficial for analyzing HRV in neonates because it reduces the necessary time window for signal stability.