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
Critiquing treatment and setting ventilatory parameters by using physiological modeling.
A modeling system is presented that can be used to predict the effects of ventilatory settings on the blood gases of patients on mechanical ventilation. The system uses a physiological model of the patient that includes lungs, body tissue, and brain tissue compartments. The model includes the effects of changes in the cardiac output and cerebral blood flow and lung mechanical factors. The system has applications in critiquing different treatment options and can be used alone or in combination with decision support systems to set ventilatory parameters and optimize treatment for patients on mechanical ventilation.
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Conf Proc IEEE Eng Med Biol Soc · Jan 2009
Electrode design for high frequency block: effect of bipolar separation on block thresholds and the onset response.
The delivery of high frequency alternating currents (HFAC) to peripheral nerves has been shown to produce a rapid and reversible nerve conduction block at the site of the electrode, and holds therapeutic promise for diseases associated with undesired or pathological neural activity. It has been known since 1939 that the configuration of an electrode used for nerve block can impact the quality of the block, but to date no formal study of the impact of electrode design on high frequency nerve block has been performed. Using a mammalian small animal model, it is demonstrated that the contact separation distance for a bipolar nerve cuff electrode can impact two important factors related to high frequency nerve block: the amplitude of HFAC required to block the nerve (block threshold), and the degree to which the transient "onset response" which always occurs when HFAC is first applied to peripheral nerves, is present. This study suggests that a bipolar electrode with a separation distance of 1.0 mm minimizes current delivery while producing high frequency block with a minimal onset response in the rat sciatic nerve.
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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.