Effect on signal-to-noise ratio of splitting the continuous contacts of cuff electrodes into smaller recording areas.

BackgroundCuff electrodes have been widely used chronically in different clinical applications. This neural interface has been dominantly used for nerve stimulation while interfering noise is the major issue when employed for recording purposes. Advancements have been made in rejecting extra-neural interference by using continuous ring contacts in tripolar topologies. Ring contacts provide an average of the neural activity, and thus reduce the information retrieved. Splitting these contacts into smaller recording areas could potentially increase the information content. In this study, we investigate the impact of such discretization on the Signal-to-Noise Ratio (SNR). The effect of contacts positioning and an additional short circuited pair of electrodes were also addressed.MethodsDifferent recording configurations using ring, dot, and a mixed of both contacts were studied in vitro in a frog model. An interfering signal was induced in the medium to simulate myoelectric noise. The experimental setup was design in such a way that the only difference between recordings was the configuration used. The inter-session experimental differences were taken care of by a common configuration that allowed normalization between electrode designs.ResultsIt was found that splitting all contacts into small recording areas had negative effects on noise rejection. However, if this is only applied to the central contact creating a mixed tripole configuration, a considerable and statistically significant improvement was observed. Moreover, the signal to noise ratio was equal or larger than what can be achieved with the best known configuration, namely the short circuited tripole. This suggests that for recording purposes, any tripole topology would benefit from splitting the central contact into one or more discrete contacts.ConclusionsOur results showed that a mixed tripole configuration performs better than the configuration including only ring contacts. Therefore, splitting the central ring contact of a cuff electrode into a number of dot contacts not only provides additional information but also an improved SNR. In addition, the effect of an additional pair of short circuited electrodes and the "end effect" observed with the presented method are in line with previous findings by other authors

Analysis and Design of RF Power and Data Link Using Amplitude Modulation of Class-E for a Novel Bone Conduction Implant

This paper presents analysis and design of a radio frequency power and data link for a novel Bone Conduction Implant (BCI) system. Patients with conductive and mixed hearing loss and single-sided deafness can be rehabilitated by bone-anchored hearing aids (BAHA). Whereas the conventional hearing aids transmit sound to the tympanic membrane via air conduction, the BAHA transmits sound via vibrations through the skull directly to the cochlea. It uses a titanium screw that penetrates the skin and needs life-long daily care; it may cause skin infection and redness. The BCI is developed as an alternative to the percutaneous BAHA since it leaves the skin intact. The BCI comprises an external audio processor with a transmitter coil and an implanted unit called the bridging bone conductor with a receiver coil. Using amplitude modulation of the Class-E power amplifier that drives the inductive link, the sound signal is transmitted to the implant through the intact skin. It was found that the BCI can generate enough output force level for candidate patients. Maximum power output of the BCI was designed to occur at 5-mm skin thickness and the variability was within 1.5 dB for 1–8-mm skin thickness variations

Feedback Analysis in Percutaneous Bone-Conduction Device and Bone-Conduction Implant on a Dry Cranium

Hypothesis: The bone-conduction implant (BCI) can use a higher gain setting without having feedback problems compared with a percutaneous bone-conduction device (PBCD). Background: The conventional PBCD, today, is a common treatment for patients with conductive hearing loss and single-sided deafness. However, there are minor drawbacks reported related to the percutaneous implant and specifically poor high-frequency gain. The BCI system is designed as an alternative to the percutaneous system because it leaves the skin intact and is less prone to fall into feedback oscillations, thus allowing more high-frequency gain. Methods: Loop gains of the Baha Classic 300 and the BCI were measured in the frequency range of 100 to 10,000 Hz attached to a Skull simulator and a dry cranium. The Baha and the BCI positions were investigated. The devices were adjusted to full-on gain. Results: It was found that the gain headroom using the BCI was generally 0 to 10 dB better at higher frequencies than using the Baha for a given mechanical output. More specifically, if the mechanical output of the devices were normalized at the cochlear level the improvement in gain headroom with the BCI versus the Baha were in the range of 10 to 30 dB. Conclusion: Using a BCI, significantly higher gain setting can be used without feedback problems as compared with using a PBCD

Treatment of phantom limb pain (PLP) based on augmented reality and gaming controlled by myoelectric pattern recognition: a case study of a chronic PLP patient

A variety of treatments have been historically used to alleviate phantom limb pain (PLP) with varying efficacy. Recently, virtual reality (VR) has been employed as a more sophisticated mirror therapy. Despite the advantages of VR over a conventional mirror, this approach has retained the use of the contralateral limb and is therefore restricted to unilateral amputees. Moreover, this strategy disregards the actual effort made by the patient to produce phantom motions. In this work, we investigate a treatment in which the virtual limb responds directly to myoelectric activity at the stump, while the illusion of a restored limb is enhanced through augmented reality (AR). Further, phantom motions are facilitated and encouraged through gaming. The proposed set of technologies was administered to a chronic PLP patient who has shown resistance to a variety of treatments (including mirror therapy) for 48 years. Individual and simultaneous phantom movements were predicted using myoelectric pattern recognition and were then used as input for VR and AR environments, as well as for a racing game. The sustained level of pain reported by the patient was gradually reduced to complete pain-free periods. The phantom posture initially reported as a strongly closed fist was gradually relaxed, interestingly resembling the neutral posture displayed by the virtual limb. The patient acquired the ability to freely move his phantom limb, and a telescopic effect was observed where the position of the phantom hand was restored to the anatomically correct distance. More importantly, the effect of the interventions was positively and noticeably perceived by the patient and his relatives. Despite the limitation of a single case study, the successful results of the proposed system in a patient for whom other medical and non-medical treatments have been ineffective justifies and motivates further investigation in a wider study

On the viability of implantable electrodes for the natural control of artificial limbs: Review and discussion

The control of robotic prostheses based on pattern recognition algorithms is a widely studied subject that has shown promising results in acute experiments. The long-term implementation of this technology, however, has not yet been achieved due to practical issues that can be mainly attributed to the use of surface electrodes and their highly environmental dependency. This paper describes several implantable electrodes and discusses them as a solution for the natural control of artificial limbs. In this context "natural" is defined as producing control over limb movement analogous to that of an intact physiological system. This includes coordinated and simultaneous movements of different degrees of freedom. It also implies that the input signals must come from nerves or muscles that were originally meant to produce the intended movement and that feedback is perceived as originating in the missing limb without requiring burdensome levels of concentration. After scrutinizing different electrode designs and their clinical implementation, we concluded that the epimysial and cuff electrodes are currently promising candidates to achieving a long-term stable and natural control of robotic prosthetics, provided that communication from the electrodes to the outside of the body is guaranteed

Phthalate Diesters and Their Metabolites in Human Breast Milk, Blood or Serum, and Urine as Biomarkers of Exposure in Vulnerable Populations

BACKGROUND: Phthalates may pose a risk for perinatal developmental effects. An important question relates to the choice of suitable biological matrices for assessing exposure during this period. OBJECTIVES: This study was designed to measure the concentrations of phthalate diesters or their metabolites in breast milk, blood or serum, and urine and to evaluate their suitability for assessing perinatal exposure to phthalates. METHODS: In 2001, 2-3 weeks after delivery, 42 Swedish primipara provided breast milk, blood, and urine samples at home. Special care was taken to minimize contamination with phthalates (e.g., use of a special breast milk pump, heat treatment of glassware and needles, addition of phosphoric acid). RESULTS: Phthalate diesters and metabolites in milk and blood or serum, if detected, were present at concentrations close to the limit of detection. By contrast, most phthalate metabolites were detectable in urine at concentrations comparable to those from the general population in the United States and in Germany. No correlations existed between urine concentrations and those found in milk or blood/serum for single phthalate metabolites. Our data are at odds with a previous study documenting frequent detection and comparatively high concentrations of phthalate metabolites in Finnish and Danish mothers' milk. CONCLUSIONS: Concentrations of phthalate metabolites in urine are more informative than those in milk or serum. Furthermore, collection of milk or blood may be associated with discomfort and potential technical problems such as contamination (unless oxidative metabolites are measured). Although urine is a suitable matrix for health-related phthalate monitoring, urinary concentrations in nursing mothers cannot be used to estimate exposure to phthalates through milk ingestion by breast-fed infants

SmokeHaz: systematic reviews and meta-analyses of the effects of smoking on respiratory health

Background: Smoking tobacco increases the risk of respiratory disease in adults and children, but communicating the magnitude of these effects in a scientific manner that is accessible and usable by public and policymakers presents a challenge. We have therefore summarised scientific data on the impact of smoking on respiratory diseases to provide the content for a unique resource, SmokeHaz. Methods: We conducted systematic reviews and meta-analyses of longitudinal studies (published to 2013) identified from electronic databases, grey literature, and experts. Random effect meta-analyses were used to pool the findings. Results: We included 216 papers. Among adult smokers, we confirmed substantially increased risks of lung cancer (Risk Ratio (RR) 10.92, 95% CI 8.28-14.40; 34 studies), COPD (RR 4.01, 95% CI 3.18-5.05; 22 studies) and asthma (RR 1.61, 95% CI 1.07-2.42; 8 studies). Exposure to passive smoke significantly increased the risk of lung cancer in adult non-smokers; and increased the risks of asthma, wheeze, lower respiratory infections, and reduced lung function in children. Smoking significantly increased the risk of sleep apnoea, and asthma exacerbations in adult and pregnant populations; and active and passive smoking increased the risk of tuberculosis. Conclusions: These findings have been translated into easily digestible content and published on the SmokeHaz website (www.smokehaz.eu)