Please cite this article in press as: Raamat R, et al. Comparison of oscillometric pulse amplitude envelopes recorded from the locally compressed radial arteries. Med Eng Phys (2010), doi:10.1016/j.medengphy.2010.08.002 ARTICLE IN PRESS G Model JJBE-1731; No. of Pages 7 Medical Engineering & Physics xxx (2010) xxx–xxx Contents lists available at ScienceDirect Medical Engineering & Physics journal homepage: www.elsevier.com/locate/medengphy Comparison of oscillometric pulse amplitude envelopes recorded from the locally compressed radial arteries R. Raamat ∗ , J. Talts, K. Jagomägi, J. Kivastik Department of Physiology, University of Tartu, Tartu, Estonia article info Article history: Received 7 March 2010 Received in revised form 1 August 2010 Accepted 7 August 2010 Keywords: Oscillometric envelope Oscillometric pattern Oscillogram Radial non-invasive blood pressure Photoplethysmographic Pneumoplethysmographic abstract Simultaneously recorded oscillometric envelopes, obtained pneumo- and photoplethysmographically from a small local pad-type pneumatic cuff on the left and from a larger cuff on the right radial artery, were compared in 17 healthy subjects. For oscillometric estimation, specific fixed ratios based on evidence in the literature were used. The obtained envelopes for each person were shifted and aligned at the point of upper arm mean arterial pressure for this person, thus eliminating the brachial-to-radial mean blood pres- sure gradient and possible left–right difference. In this way, the shape of differently recorded envelopes as a determinant of the accuracy of oscillometric estimation was studied. Results showed an advan- tage of photoplethysmographically compared to pneumoplethysmographically recorded envelopes. For a smaller cuff (diameter 40 mm), the mean difference in mm Hg ‘oscillometric estimate minus auscul- tatory reference’ and standard deviation were in the case of photo recording for systolic and diastolic pressures -0.6 (6.3) and 1.2 (3.4), respectively. In the case of pneumo recording, these parameters were considerably larger, being 12.1 (11.9) and -6.2 (10.9), respectively. For a larger cuff the same tendency was revealed. Photo recording was found to be less sensitive to alterations in the cuff size and characteristic ratios. © 2010 IPEM. Published by Elsevier Ltd. All rights reserved. 1. Introduction The oscillometric method is increasingly used in blood pres- sure (BP) measurement. Due to the simplicity and reliability of this method, the oscillometric principle is employed in the majority of present-day automatic and semiautomatic non-invasive blood pressure monitors. Oscillometric blood pressures are typically determined from the envelope of successive oscillometric pulse amplitudes obtained from the occlusive cuff during its inflation or deflation. The highest point of the envelope curve is generally regarded as the mean arte- rial pressure (MAP) [1,2]. This is consistent with the oscillometric maximum criterion described by Marey more than 130 years ago [3]. Two general types of criteria have been used to estimate systolic (SBP) and diastolic (DBP) blood pressures: height-based criteria and slope-based criteria [4]. In the height-based approach the systolic and diastolic pressures are determined using special fractions of the maximum oscillation amplitude [5,6]. These fractions are known as characteristic ratios (systolic and diastolic, respectively). In the slope-based approach the cuff pressure at which the oscillometric pulse amplitude increases rapidly is taken as the systolic pressure, ∗ Corresponding author. Tel.: +372 737 4987. E-mail address: raamat@ut.ee (R. Raamat). while that at which the amplitude decreases rapidly is taken as the diastolic pressure. Mathematically, the latter criterion defines the points at which the first derivative of the envelope curve is maximum or minimum. There are no definitive correct values for the systolic and dias- tolic characteristic ratios, but rather that different manufactures use different values. Theoretical and experimental work has sug- gested the following values for characteristic ratios: (a) systolic from 0.46 to 0.64 and diastolic from 0.59 to 0.80 (theo- retical work by Ursino and Cristalli [7]), (b) systolic 0.593 and diastolic 0.717 (theoretical work by Drzewiecki et al. [6]), (c) systolic from 0.45 to 0.57 and diastolic from 0.69 to 0.89 (exper- imental work by Geddes et al. [5]), (d) systolic (mean and SD) equal to 0.49 (0.11) and diastolic equal to 0.72 (0.12) (experimental work by Amoore et al. [8]). Specific studies have demonstrated an effect of the shapes of oscillometric pulse amplitude envelopes on the differences between auscultatory and oscillometric BP measurement [8,9]. Subsequently, recording of oscillometric envelopes of appropriate shape and stability remains a topical issue for the oscillometric method. Oscillometric wrist monitors have shown lower reliability com- pared to upper arm devices. On the other hand, oscillometric wrist 1350-4533/$ – see front matter © 2010 IPEM. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.medengphy.2010.08.002