Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference
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Conf Proc IEEE Eng Med Biol Soc · Jan 2009
In-vivo evaluation of a fiber-optic splanchnic photoplethysmographic sensor during open laparotomy.
There is a need for a reliable and continuous monitoring of abdominal organ oxygen saturation (SpO(2)). Splanchnic ischemia may ultimately lead to cellular hypoxia and necrosis and may well contribute to the development of multiple organ failures and increased mortality. A new prototype reflectance fiber optic photoplethysmographic sensor and signal processing system was evaluated on six anaesthetized patients undergoing elective laparotomy. ⋯ The normalized amplitudes of the splanchnic PPG signals were in good agreement with those obtained from the periphery using an identical fiber optic sensor. Furthermore, average SpO(2) values were in good agreement and showed correlation with those obtained from a commercial system. These preliminary results suggest that a miniaturized 'indwelling' fiber optic sensor may be a suitable method for pre-operative and post-operative evaluation of splanchnic organ SpO(2) and their health.
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Conf Proc IEEE Eng Med Biol Soc · Jan 2009
Noninvasive cardiac output estimation using a novel photoplethysmogram index.
Cardiac output (CO) monitoring is essential for indicating the perfusion status of the human cardiovascular system under different physiological conditions. However, it is currently limited to hospital use due to the need for either skilled operators or big, expensive measurement devices. Therefore, in this paper we devise a new CO indicator which can easily be incorporated into existing wearable devices. ⋯ After least squares linear regression, the precision between CO(imp) and CO estimated from IHAR (CO(IHAR)) was 1.40 L/min. The total percentage error of the results was 16.2%, which was well below the clinical acceptance limit of 30%. The results suggest that IHAR is a promising indicator for wearable and noninvasive CO monitoring.
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Conf Proc IEEE Eng Med Biol Soc · Jan 2009
Using A-weighting for psychoacoustic active noise control.
Conventional adaptive active noise control (ANC) methods aim to attenuate the acoustic noise over the frequency band of interest indiscriminately using the sound pressure level (SPL) measurement (or the measurement of the residual error variance). However, SPL does not correctly reflect the human perception of attenuated noise due to the frequency selective sensitivity of human hearing system. A-weighting is a commonly used weighting filter for measuring the noise. ⋯ In this paper, we aim to improve the performance of adaptive noise cancellation method from the psychoacoustic point of view by incorporating the A-weighting into the ANC system design. Loudness is used as the psychoacoustic criterion for evaluating the ANC system performance. Simulation results illustrate the effectiveness of the proposed method.
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Conf Proc IEEE Eng Med Biol Soc · Jan 2009
Estimation of the aortic pressure waveform from a radial artery pressure waveform via an adaptive transfer function: Feasibility demonstration in swine.
We previously proposed a new technique to estimate the physiologically and clinically more relevant central aortic pressure (AP) waveform from a conveniently and safely measured peripheral artery pressure (PAP) waveform distorted by wave reflections. In contrast to conventional generalized transfer function (GTF) techniques, the technique is able to adapt the transfer function relating PAP to AP to the inter-patient and temporal variability of the arterial tree by defining it through a tube model and invoking the fact that aortic flow is negligible during diastole to estimate the unknown model parameters. We conducted feasibility testing of this adaptive transfer function technique here with respect to radial artery pressure (RAP) waveforms, for the first time, as well as femoral artery pressure (FAP) waveforms from four swine instrumented with AP catheters during several hemodynamic conditions. Our results showed that the AP waveforms estimated by the technique from the RAP and FAP waveforms were in superior agreement to the measured AP waveforms (overall respective errors of 4.1 and 4.8 mmHg) than the two unprocessed PAP waveforms (9.1 and 8.1 mmHg) and a previous GTF technique trained on a subset of the same data (5.0 and 5.8 mmHg).
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Conf Proc IEEE Eng Med Biol Soc · Jan 2009
Detection of respiratory rhythm from photoplethysmographic signal by adaptive morphological filter.
An approach using morphological filter technique is proposed to determine the respiratory rhythm from the photoplethysmographic (PPG) signal. As the structuring elements of morphological filter have a decisive effect on the analysis result, in the study the structuring elements are determined by the individual heart rate adaptively. ⋯ Furthermore, the low computational complexity of the algorithm may make it easy to be implemented on Microprogrammed Control Units (MCU) for real-time processing. More experimental data is necessary to improve the reliability and robustness of the algorithm.