Can a simulator that regenerates physiological waveforms evaluate oscillometric non-invasive blood pressure devices?
ABSTRACT A simulator has been developed that enables previously recorded clinical oscillometric waveforms to be regenerated for testing oscillometric non-invasive blood pressure measurement devices. Two non-invasive blood pressure devices were evaluated using the simulator with its database of 243 waveforms, to assess the value of a simulator for such evaluations.
Two oscillometric non-invasive blood pressure devices, both of which had previously been validated against auscultatory references, were selected. The Omron HEM-907 (Omron, Hoofddorp, The Netherlands) measures the pressure during linear cuff deflation and the GE ProCare 400 (GE Healthcare, Tampa, Florida, USA) measures during step deflation. Each non-invasive blood pressure device was attached to the simulator and pressures were recorded from all 243 waveforms. The differences between the systolic and diastolic pressures measured by each non-invasive blood pressure device and the auscultatory references for each waveform were calculated. These were assessed with the European and American validation standards and with the British Hypertension Society protocol.
The paired pressure differences (non-invasive blood pressure device minus auscultatory reference) for each device complied partly, but not fully, with the standards or protocol. The means (+/-standard deviation) of the paired systolic and diastolic pressures differences for the Omron were -2.4 mmHg (+/-5.9 mmHg) and -8.9 mmHg (+/-6.5 mmHg), and for the ProCare were -6.5 mmHg (+/-10.4 mmHg) and -2.9 mmHg (+/-7.0 mmHg), respectively. The pressures recorded by the Omron device met the standards for systolic pressures but failed for diastolic pressures and conversely for the ProCare.
This represents the first evaluation of non-invasive blood pressure devices with a simulator that generates previously recorded clinical oscillometric waveforms. It allowed data from over 100 study participants to be used. Both devices had been previously clinically validated, but their evaluation using the simulator with its regenerated waveforms only partly met the required criteria. Although the results did not fully match previous clinical validations, these initial results give encouragement that a simulator with sufficient stored waveforms might be able to replace the difficult and expensive clinical evaluation of non-invasive blood pressure devices that has prevented many devices from being fully evaluated.
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ABSTRACT: Non-invasive blood pressure (NIBP) simulators are electro-mechanical devices used for testing and evaluating oscillometric non-invasive blood pressure monitors. Simulators are used mainly in clinical environment to assist with routine and after-repair testing of NIBP monitors. In this paper we suggest basic procedures for evaluating a NIBP simulator; assessing its suitability and quality. Proposed evaluation procedure consists of a static calibration and a dynamic evaluation. In static calibration the simulator is calibrated as a common indicating barometer. In dynamic evaluation the output waveforms are investigated (repeatability of the output according to different static pressures and heart rates, repeatability of the output at a constant blood pressure magnitude). Proposed evaluation procedure represents a minimal set of tests to ensure the simulator can be used for testing NIBP monitors. A commercial simulator SmartArm (by Clinical Dynamics, USA) was evaluated according to it and the results are presented.12/2006: pages 342-345;
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ABSTRACT: Oscillometric noninvasive blood pressure devices measure blood pressure using an indirect method and proprietary algorithms and hence require validation in clinical trials. Clinical trials are, however, expensive and give contradictory results, and validated devices are not accurate in all patient groups. Simulators that regenerate oscillometric waveforms promise an alternative to clinical trials provided they include sufficient physiological and pathological oscillometric waveforms. Simulators should also improve the understanding of the oscillometric method.Blood Pressure Monitoring 09/2007; 12(4):251-3. DOI:10.1097/MBP.0b013e3280b10bd8 · 1.18 Impact Factor
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ABSTRACT: Oscillometric noninvasive blood pressure (NIBP) devices determine pressure by analysing the oscillometric waveform using empirical algorithms. Many algorithms analyse the waveform by calculating the systolic and diastolic characteristic ratios, which are the amplitudes of the oscillometric pulses in the cuff at, respectively, the systolic and diastolic pressures, divided by the peak pulse amplitude. A database of oscillometric waveforms was used to study the influences of the characteristic ratios on the differences between auscultatory and oscillometric measurements. Two hundred and forty-three oscillometric waveforms and simultaneous auscultatory blood pressures were recorded from 124 patients at cuff deflation rates of 2-3 mmHg/s. A simulator regenerated the waveforms, which were presented to two NIBP devices, the Omron HEM-907 [OMRON Europe B.V. (OMCE), Hoofddorp, The Netherlands] and the GE ProCare 400 (GE Healthcare, Tampa, Florida, USA). For each waveform, the paired systolic and paired diastolic pressure differences between device measurements and auscultatory reference pressures were calculated. The systolic and diastolic characteristic ratios, corresponding to the reference auscultatory pressures of each oscillometric waveform stored in the simulator, were calculated. The paired differences between NIBP measured and auscultatory reference pressures were compared with the characteristic ratios. The mean and standard deviations of the systolic and diastolic characteristic ratios were 0.49 (0.11) and 0.72 (0.12), respectively. The systolic pressures recorded by both devices were lower (negative paired pressure difference) than the corresponding auscultatory pressures at low systolic characteristic ratios, but higher than the corresponding auscultatory pressures at high systolic pressures. Conversely, the differences between the paired diastolic pressure differences were higher at low diastolic characteristic ratios, compared with those at high diastolic characteristic ratios. The paired systolic pressure differences were within +/-5 mmHg for those waveforms with systolic characteristic ratios between 0.4 and 0.7 for the Omron and between 0.3 and 0.5 for the ProCare. The paired diastolic pressure differences were within +/-5 mmHg for those waveforms with diastolic characteristic ratios between 0.4 and 0.6 for the Omron and between 0.5 and 0.8 for the ProCare. The systolic and diastolic paired oscillometric-auscultatory pressure differences varied with their corresponding characteristic ratios. Good agreement (within 5 mmHg) between the oscillometric and auscultatory pressures occurred for oscillometric pulse amplitude envelopes with specific ranges of characteristic ratios, but the ranges were different for the two devices. Further work is required to classify the different envelope shapes, comparing them with patient conditions, to determine if a clearer understanding of the different waveform shapes would improve the accuracy of oscillometric measurements.Blood Pressure Monitoring 11/2007; 12(5):297-305. DOI:10.1097/MBP.0b013e32826fb773 · 1.18 Impact Factor