IEEE transactions on bio-medical engineering
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We have studied the effect that learning a new stimulus-response (SR) relationship had within a neuronal network cultured on a multielectrode array. For training, we applied repetitive focal electrical stimulation delivered at a low rate (<1/s). Stimulation was withdrawn when a desired SR success ratio was achieved. ⋯ However, a local (path-specific) component to learning was also found by analyzing profiles of single-electrode-activity phase profiles. Phase profiles that were not part of the SR relationship changed far less during CRS than the phase profiles of the electrodes that were part of the SR relationship. Finally, the manner in which phase profiles changed shape varied and could not be linked to the SR relationship.
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IEEE Trans Biomed Eng · Apr 2009
A least mean-square filter for the estimation of the cardiopulmonary resuscitation artifact based on the frequency of the compressions.
Cardiopulmonary resuscitation (CPR) artifacts caused by chest compressions and ventilations interfere with the rhythm diagnosis of automated external defibrillators (AED). CPR must be interrupted for a reliable diagnosis. However, pauses in chest compressions compromise the defibrillation success rate and reduce perfusion of vital organs. ⋯ The sensitivity and specificity were above 95% and 85%, respectively, for a wide range of working conditions of the LMS filter. Our results show that the CPR artifact can be accurately modeled using only the frequency of the compressions. These can be easily registered after small changes in the hardware of the CPR compression pads.
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IEEE Trans Biomed Eng · Apr 2009
Design of a new somatosensory stimulus delivery device for measuring laryngeal mechanosensory detection thresholds in humans.
Laryngeal control is essential for airway protection, breathing, deglutition, speech, and voice. Unfortunately, integration of laryngeal sensory assessment in research and clinical practice is limited by technical and practical limitations of commercially available technology. A commercial device is available, but reported limitations include procedural complexity requiring two or three individuals to operate, limited stimulus dynamic range, device generated noise, and questionable stimulus reproducibility. ⋯ Testing with the new device revealed laryngeal mechanosensory detection thresholds in an individual with Parkinson's disease that were seven times higher than those of healthy controls. These data would have otherwise gone undetected due to limited stimulus dynamic range in the commercial device. The new design resulted in a new assessment instrument that is simple to use for routine clinical assessment, yet sufficiently versatile for integration within rigorous clinical research protocols.
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IEEE Trans Biomed Eng · Mar 2009
Low-oxygen-saturation quantification in human arterial and venous circulation.
Conventional pulse oximetry has limited accuracy in measuring blood oxygen saturation in low-saturation and -perfusion scenarios. This limits the application of pulse oximetry in patients suffering from peripheral vascular afflictions. We present a novel pulse oximetry system that proposes solutions to these low-saturation and -perfusion scenarios by inducing an artificial pulse in the detected photoplethysmograph (PPG). ⋯ The arteriovenous hypothesis was validated, indicating that venous saturation can be extracted from the artificial PPG. The results indicate that the proposed system might be able to accurately monitor arterial and venous saturation in low- or no-perfusion scenarios. It is recommended that further studies into the system's performance are conducted.
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IEEE Trans Biomed Eng · Mar 2009
Noninvasive intracranial compliance from MRI-based measurements of transcranial blood and CSF flows: indirect versus direct approach.
Intracranial compliance (ICC) determines the ability of the intracranial compartment to accommodate an increase in volume without a large increase in intracranial pressure (ICP). The clinical utilization of ICC is limited by the invasiveness of current measurement. Several investigators attempted to estimate ICC noninvasively, from magnetic resonance imaging (MRI) measurements of cerebral blood and cerebral spinal fluid flows, either using indirect measures of ICC or directly by measuring the ratio of the changes in intracranial volume and pressure during the cardiac cycle. ⋯ In vivo volumetric blood and CSF flows measured by MRI phase contrast from healthy volunteers and from patients with elevated ICP were used for the comparison. An RLC circuit model of the craniospinal system was utilized to simulate the effect of a change in ICC on the CSF flow waveform. The simulations demonstrated that amplitude-based measures of ICC are considerably more sensitive than phase-based measures, and among the amplitude-based measures, the ICC index provides the most reliable estimate of ICC.