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Previously, we found evidence that bisferiens peaks in the radial artery pressure wave in the newborn infant may suggest the presence of a left-to-right shunt through a patent ductus arteriosus (PDA). The purpose of the present study was to analyze the origin of this pulsus bisferiens. Starting from the assumption that the radial artery pressure wave form is similar to the aortic pressure wave form, as described previously, we attempted to explain the bisferiens peaks on the basis of echocardiographically obtained ascending aortic flow. We studied 11 preterm mechanically ventilated infants with a left-to-right shunt through a PDA and 7 without. Aortic volume flow was established echocardiographically, and radial artery blood pressure measurement was performed with a high fidelity cathetermanometer system. Ascending aortic peak flow during PDA was significantly higher in the case of PDA, compared with the case without PDA. An augmented peak flow with an abrupt decline after the high peak in PDA, resulting in a sharp pressure peak with a steep decline after the peak, was thought to explain the first sharp peak of pulsus bisferiens. An abrupt decline of flow after peak flow is thought to be due to the fast runoff of blood through the ductus. According to the pulsatile pressure dynamics theories, which state that pressure wave forms consist of forward and backward wave forms, the second peak of the pulsus bisferiens can be explained by the return of the reflected (backward) wave form when the forward wave form has already considerably decreased. We conclude that the bisferiens peaks found in PDA result from a combination of large stroke volume (augmented first peak) and large runoff (quick decline of the forward wave) before the return of the reflected wave.

Previously, we found evidence that radial artery pressure wave forms in newborns represent central aortic wave forms, provided that pressure is measured with adequate accuracy. Therefore, we postulated that the neonatal radial artery wave form, like the adult aortic wave form, may contribute to cardiovascular diagnosis. We investigated whether radial artery wave forms in infants suffering from patent ductus arteriosus (PDA) are different from the wave forms as seen without the presence of PDA. We studied 34 newborn infants with a radial artery line and with the possible clinical diagnosis of PDA with left-to-right shunt. On the basis of echocardiographic examination to assess PDA, these infants were divided in two groups: infants with PDA (n = 24) and without PDA (n = 10). In 15 out of 24 infants with PDA, recordings were repeated after ductal closure. Blood pressure measurement was performed with a high fidelity cathetermanometer system using a tip-transducer (natural frequency 95 Hz, damping coefficient 0.15). Contour analysis was performed by describing morphology of the waves during PDA and without PDA. In 23 out of 24 infants with PDA, a pulsus bisferiens was present: two peaks separated by a deep cleft. The average pressure difference between the first pressure peak and the cleft [delta Ppeak1] was 0.35 +/- 0.19 kPa, and the average difference between the cleft and the second pressure peak [delta Ppeak2] was 0.44 +/- 0.23 kPa. the ratio of mean magnitude of delta Ppeak1 and delta Ppeak2 was 0.81 +/- 0.26. None of the 10 infants without PDA showed pulsus bisferiens.(ABSTRACT TRUNCATED AT 250 WORDS)

To achieve accurate blood pressure measurement through radial artery catheters in infants, we previously developed an experimental high-fidelity catheter-manometer system (CMS). As this system lacks facilities for flushing and for blood sampling, we aimed to further develop this technique in order to make the system suitable for clinical practice. In addition, we aimed to develop methods to automate processing of the pressure wave forms. The high-fidelity system to be improved consisted of a 24 Gauge catheter, a threeway stopcock and a tip-manometer. We inserted this system in the catheter-manometer system as routinely used i.e. the remaining end of the stopcock was connected to the fluid-filled CMS as used routinely. This combined system became clinically applicable, since blood samples could be obtained and flushing could be performed. The measurement chain was completed by application of a modified physiological monitor and a computerized method to analyze pressure wave forms. In this manner accurate beat-to-beat pressure parameters were obtained. This technique was applied to 25 neonates admitted for intensive care and requiring arterial access. Gestational age of these infants ranged from 25-40 (median 29) weeks and birth weight ranges from 500-3375 (median 1060) grams. In all infants the technique was found to be convenient and the high-fidelity blood pressure measurements were performed without any problems. The advantage of the present system is the potential for both correct intermittent recordings of arterial wave forms in close relation to clinical condition and for the establishment of accurate radial artery beat-to-beat pressure values in clinical practice.

The aim of this study was to document arterial blood pressure wave forms at two sites along the arterial tree of the neonate: in the radial and posterior tibial arteries. Using a high-fidelity catheter tip-transducer system, peripheral arterial blood pressure wave forms in 26 critically newborn infants were studied. In 14 infants the radial artery and in 12 infants the posterior tibial artery was cannulated. Radial artery blood pressure waves resembled those of proximal aortic rather than those of the radial artery in adults. Quantitative analysis of the waves was performed to reassure this finding. Blood pressure waves obtained from posterior tibial artery resembled those of femoral artery rather than those of posterior tibial artery waves in adults. We conclude that radial and posterior tibial artery wave forms in neonates appear to have a central appearance. This phenomenon might be explained by the close proximity of the radial and posterior tibial artery to the central aorta and femoral artery respectively, due to the small and short limbs of the neonate. The finding allows an "easy central pressure look" at both ends of the neonatal aorta.

Mean arterial pressure (MAP) is the area under the pressure wave form averaged over the cardiac cycle. A widely used rule of thumb to estimate MAP of peripheral arterial pressure waves in adults is adding one-third of the pulse pressure (PP) to diastolic arterial pressure (DAP). However, radial artery pressure waves in newborns differ from those in adults and resemble proximal aortic pressure waves, so that the above-mentioned calculation of MAP may not be correct. The present study was set up to obtain an arithmetical approximation to derive MAP from blood pressure waves measured in the radial artery of the neonate. We accurately recorded about 300 invasively obtained blood pressure curves in the radial artery of 10 neonates admitted for intensive care. We found that MAP in the radial artery in these neonates can be well approximated by adding 46.6% PP to DAP (range 43.0-50.1%). We suggest that the rule of thumb to derive MAP from radial artery waves in the neonate to be approximately the average of systolic and diastolic pressure, as opposed to adding one-third of the pulse pressure to the diastolic value in the adult.