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1

The sources of errors in the oscillometric blood pressure measurements

Juroszek B.

Metrology and Measurement Systems

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2008

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Vol. 15, nr 4

539-549

EN

This report presents an analysis of the source of errors in the blood pressure measurements which use the oscillometric method. The basis of this method are the blood pressure oscillations in the occluding cuff which are used to evaluate systolic and diastolic pressures. They are found during calculations with the use of fixed constants. These numbers, having a statistical meaning, are the main source of a measuring error. The respective theoretical considerations are presented. Here they have been confirmed by the example of comparison of the measuring results obtained from two different blood pressure devices. During tests the instruments were connected together to the same occluding cuff A statistical method was used for evaluation of the results: the coefficient of variation and the reliability coefficient.

2

Two-dimensional simulations of the effect of the reservoir region on the pressure oscillations observed in the stick-slip instability regime

Taliadorou E., Georgiou G., Alexandrou A.

International Journal of Applied Mechanics and Engineering

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2006

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Vol. 11, no 2

245-254

EN

The time-dependent, two-dimensional compressible Newtonian flow over the reservoir-die region is solved assuming that slip occurs along the die wall following a nonmonotonic slip law. The combination of compressibility and nonlinear slip leads to self-sustained oscillations of the pressure drop and of the mass flow rate at constant piston speed, when the latter falls into the unstable negative slope regime of the flow curve. The effect of the reservoir volume on the amplitude, the frequency and the waveform of the pressure oscillations is studied and comparisons are made with experimental observations concerning the stick-slip polymer extrusion instability.

3

Metody wyznaczania krzywej oscylometrycznej

Wilk B.

Zeszyty Naukowe Politechniki Rzeszowskiej. Elektrotechnika

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2005

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z. 28 [223]

267-274

PL

W pracy zaprezentowano i porównano kilka metod do wyznaczania obwiedni amplitudowej sygnału reprezentującego oscylacje ciśnienia mankiecie okluzyjnym podczas deflacji. Wykazano, ze proponowana metoda bazująca na interpolacji wielomianem umożliwia wyznaczenie obwiedni badanego sygnału z dużą dokładnością, co w znacznym stopniu wpływa na końcowy wynik pomiaru.

EN

This paper deals with some problems of digital signal processing occurring during arterial blood pressure measurement using the oscillometric method. The amplitude envelope of pressure oscillations was estimated by various methods (i.e. the average energy or the average amplitude, and the Hilbert transform). The polynomial interpolalion was proposed for creating the oscillometric curve. The results suggested that this method was superior in estimating the signal envelope.

4

Local cavitation due to water hammer

Mitosek M., Kodura A., Rybak-Wilusz E.

Archives of Hydro-Engineering and Environmental Mechanics

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2003

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Vol. 50, nr 1

59-72

EN

The phenomenon of vapour cavitation due to water hammer is investigated ex-perimentally using high frequency pressure transducers (piezoelectric and strain gauges). The water hammer is caused by a sudden closure of a ball valve mounted at the end of the steel pipe. A short-duration pressure pulse, as well as high frequency cavitation pressure oscillations is observed. The high frequency pressure oscillations appear just after the vapour cavity collapse, whereas the pressure pulse does not occur immediately after collapse but is delayed from 0 to the water hammer period $2L/c$, s. The experiments have shown that the maxi-mum high frequency pressure oscillation, directly proportional to the pressure wave velocity, can be many times higher than the maximum water hammer pres-sure amplitude as well as short-duration pressure pulse. The influence of liquid evaporation duration and the steady state losses on the maximum high frequency cavitation pressure oscillation are shown. Growing pressure reduction is accom-panied by gas desorption from the liquid. The liberated air reduces the amplitude of the pressure increase and prolongs the period of oscillations. The experiments have shown that there are three phases of the maximum amplitude of high fre-quency pressure oscillations for each fixed steady state loss. The frequency of va-pour cavitation pressure oscillations depends on the duration of the oscillations. For the test cases, the frequency increases during the cavitation from ca. 400 to 900 Hz for steel pipes.