Automatic electrical stimulation of abdominal wall muscles increases tidal volume and cough peak flow in tetraplegia

<p>Paralysis of the respiratory muscles in people with tetraplegia affects their ability to breathe and contributes to respiratory complications. Surface functional electrical stimulation (FES) of abdominal wall muscles can be used to increase tidal volume (V_{T}) and improve cough peak flow (CPF) in tetraplegic subjects who are able to breathe spontaneously.</p> <p>This study aims to evaluate the feasibility and effectiveness of a novel abdominal FES system which generates stimulation automatically, synchronised with the subjects' voluntary breathing activity. Four subjects with complete tetraplegia (C4-C6), breathing spontaneously, were recruited.</p> <p>The automatic stimulation system ensured that consistent stimulation was achieved. We compared spirometry during unassisted and FES-assisted quiet breathing and coughing, and measured the effect of stimulation on end-tidal CO_2 (EtCO_2) during quiet breathing.</p> <p>The system dependably recognised spontaneous respiratory effort, stimulating appropriately, and was well tolerated by patients. Significant increases in V_T during quiet breathing (range 0.05–0.23 L) and in CPF (range 0.04–0.49 L/s) were observed. Respiratory rate during quiet breathing decreased in all subjects when stimulated, whereas minute ventilation increased by 1.05–2.07 L/min. The changes in EtCO_2 were inconclusive.</p> <p>The automatic stimulation system augmented spontaneous breathing and coughing in tetraplegic patients and may provide a potential means of respiratory support for tetraplegic patients with reduced respiratory capacity.</p&gt

Arm-cranking exercise assisted by Functional Electrical Stimulation in C6 tetraplegia: a pilot study

Tetraplegic volunteers undertook progressive exercise training, using novel systems for arm-cranking exercise assisted by Functional Electrical Stimulation (FES). The main aim was to determine potential training effects of FES-assisted arm-crank ergometry (FES-ACE) on upper limb strength and cardiopulmonary {fitness} in tetraplegia. Surface FES was applied to the biceps and triceps during exercise on an instrumented ergometer. Two tetraplegic volunteers with C6 Spinal Cord Injury (SCI) went through muscle strengthening, baseline exercise testing and three months of progressive FES-ACE training. Repeat exercise tests were carried out every four weeks during training, and post-training, to monitor upper-limb strength and cardiopulmonary fitness. At each test point, an incremental test was carried out to determine peak work rate, peak oxygen uptake, gas exchange threshold and oxygen uptake-work rate relationship during FES-ACE. Peak oxygen uptake for Subject A increased from 0.7 l/min to 1.1 l/min, and peak power output increased from 7 W to 38 W after FES-ACE training. For Subject B, peak oxygen uptake was unchanged, but peak power output increased from 3 W to 8 W. These case studies illustrate potential benefits of FES-ACE in tetraplegia, but also the differences in exercise responses between individuals. Keywords: electrical stimulation; spinal cord injury; cardiopulmonary fitness; rehabilitation; tetraplegi

Online identification and nonlinear control of the electrically stimulated quadriceps muscle

A new approach for estimating nonlinear models of the electrically stimulated quadriceps muscle group under nonisometric conditions is investigated. The model can be used for designing controlled neuro-prostheses. In order to identify the muscle dynamics (stimulation pulsewidth-active knee moment relation) from discrete-time angle measurements only, a hybrid model structure is postulated for the shank-quadriceps dynamics. The model consists of a relatively well known time-invariant passive component and an uncertain time-variant active component. Rigid body dynamics, described by the Equation of Motion (EoM), and passive joint properties form the time-invariant part. The actuator, i.e. the electrically stimulated muscle group, represents the uncertain time-varying section. A recursive algorithm is outlined for identifying online the stimulated quadriceps muscle group. The algorithm requires EoM and passive joint characteristics to be known a priori. The muscle dynamics represent the product of a continuous-time nonlinear activation dynamics and a nonlinear static contraction function described by a Normalised Radial Basis Function (NRBF) network which has knee-joint angle and angular velocity as input arguments. An Extended Kalman Filter (EKF) approach is chosen to estimate muscle dynamics parameters and to obtain full state estimates of the shank-quadriceps dynamics simultaneously. The latter is important for implementing state feedback controllers. A nonlinear state feedback controller using the backstepping method is explicitly designed whereas the model was identified a priori using the developed identification procedure

Control strategies for integration of electric motor assist and functional electrical stimulation in paraplegic cycling: Utility for exercise testing and mobile cycling

AIM: The aim of this study was to investigate feedback control strategies for integration of electric motor assist and functional electrical stimulation (FES) for paraplegic cycling, with particular focus on development of a testbed for exercise testing in FES cycling, in which both cycling cadence and workrate are simultaneously well controlled and contemporary physiological measures of exercise performance derived. A second aim was to investigate the possible benefits of the approach for mobile, recreational cycling. METHODS: A recumbent tricycle with an auxiliary electric motor is used, which is adapted for paraplegic users, and instrumented for stimulation control. We propose a novel integrated control strategy which simultaneously provides feedback control of leg power output (via automatic adjustment of stimulation intensity) and cycling cadence (via electric motor control). Both loops are designed using system identification and analytical (model-based) feedback design methods. Ventilatory and pulmonary gas exchange response profiles are derived using a portable system for real-time breath-by-breath acquisition. RESULTS:We provide indicative results from one paraplegic subject in which a series of feedback-control tests illustrate accurate control of cycling cadence, leg power control, and external disturbance rejection. We also provide physiological response profiles from a submaximal exercise step test and a maximal incremental exercise test, as facilitated by the control strategy. CONCLUSION: The integrated control strategy is effective in facilitating exercise testing under conditions of well-controlled cadence and power output. Our control approach significantly extends the achievable workrate range and enhances exercise-test sensitivity for FES cycling, thus allowing a more stringent characterization of physiological response profiles and estimation of key parameters of aerobic function.We further conclude that the control approach can significantly improve the overall performance of mobile recreational cycling

Methods and protocols for incremental exercise testing in tetraplegia, using arm-crank ergometry assisted by Functional Electrical Stimulation

Cervical spinal cord injury (SCI) leads to tetraplegia, with paralysis and loss of sensation in the upper and lower limbs. The associated sedentary lifestyle results in an increased risk of cardiovascular disease. To address this, we require the design of exercise modalities aimed specifically at tetraplegia and methods to assess their efficacy. This paper describes methods for arm-crank ergometry (ACE) assisted by Functional Electrical Stimulation (FES) applied to the biceps and triceps. The instrumented ergometer enables work-rate control during exercise, implemented here for incremental exercise testing during FES-ACE. Detailed protocols for the tests are given. Experimental data collected during exercise tests with tetraplegic volunteers are provided to illustrate the feasibility of the proposed approach to testing and data analysis. Incremental tests enabled calculation of peak power output and peak oxygen uptake. We propose that the high-precision exercise testing protocols described here are appropriate to assess the efficacy of the novel exercise modality, FES-ACE, in tetraplegia

Iron nutrition and possible lead toxicity: an appraisal of geophagy undertaken by pregnant women of UK Asian communities

A cultural transfer of geophagy is evident in the UK, with soils imported from Bengal being deliberately consumed mainly by pregnant Asian women. Two samples purchased from ethnic shops were subjected to a 2-part acid–alkaline in vitro physiologically based extraction test (PBET) procedure, representing the stomach and small intestine of the human digestive system respectively, to determine the bioaccessibility of elements. Despite the low bioaccessibility of Fe, with the quantity of soil consumed one sample can provide 41–54% of this mineral nutrient required by a 15–18 year old female, with the other sample providing 90–119%. Significant amounts of Ca, Cu and Mn are also supplied to the consumer, whilst further research investigating the possible effects of Pb toxicity on the geophagist would seem to be justifie

Comparison of stimulation patterns for FES-cycling using measures of oxygen cost and stimulation cost

<b>Aim</b><p></p> The energy efficiency of FES-cycling in spinal cord injured subjects is very much lower than that of normal cycling, and efficiency is dependent upon the parameters of muscle stimulation. We investigated measures which can be used to evaluate the effect on cycling performance of changes in stimulation parameters, and which might therefore be used to optimise them. We aimed to determine whether oxygen cost and stimulation cost measurements are sensitive enough to allow discrimination between the efficacy of different activation ranges for stimulation of each muscle group during constant-power cycling. <p></p> <b>Methods</b><p></p> We employed a custom FES-cycling ergometer system, with accurate control of cadence and stimulated exercise workrate. Two sets of muscle activation angles (“stimulation patterns”), denoted “P1” and “P2”, were applied repeatedly (eight times each) during constant-power cycling, in a repeated measures design with a single paraplegic subject. Pulmonary oxygen uptake was measured in real time and used to determine the oxygen cost of the exercise. A new measure of stimulation cost of the exercise is proposed, which represents the total rate of stimulation charge applied to the stimulated muscle groups during cycling. A number of energy-efficiency measures were also estimated. <p></p> <b>Results</b><p></p> Average oxygen cost and stimulation cost of P1 were found to be significantly lower than those for P2 (paired <i>t</i>-test, <i>p</i> < 0.05): oxygen costs were 0.56 ± 0.03 l min<sup>−1</sup> and 0.61 ± 0.04 l min<sup>−1</sup>(mean ± S.D.), respectively; stimulation costs were 74.91 ± 12.15 mC min<sup>−1</sup> and 100.30 ± 14.78 mC min<sup>−1</sup> (mean ± S.D.), respectively. Correspondingly, all efficiency estimates for P1 were greater than those for P2. <p></p> <b>Conclusion</b><p></p> Oxygen cost and stimulation cost measures both allow discrimination between the efficacy of different muscle activation patterns during constant-power FES-cycling. However, stimulation cost is more easily determined in real time, and responds more rapidly and with greatly improved signal-to-noise properties than the ventilatory oxygen uptake measurements required for estimation of oxygen cost. These measures may find utility in the adjustment of stimulation patterns for achievement of optimal cycling performance. <p></p&gt

Charge order and low frequency spin dynamics in lanthanum cuprates revealed by Nuclear Magnetic Resonance

We report detailed 17O, 139La, and 63Cu Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) measurements in a stripe ordered La1.875Ba0.125CuO4 single crystal and in oriented powder samples of La1.8-xEu0.2SrxCuO4. We observe a partial wipeout of the 17O NMR intensity and a simultaneous drop of the 17O electric field gradient (EFG) at low temperatures where the spin stripe order sets in. In contrast, the 63Cu intensity is completely wiped out at the same temperature. The drop of the 17O quadrupole frequency is compatible with a charge stripe order. The 17O spin lattice relaxation rate shows a peak similar to that of the 139La, which is of magnetic origin. This peak is doping dependent and is maximal at x ~ 1/8.Comment: submitted to European Physical Journal Special Topic

Macrosegregation Caused by Thermosolutal Convection During Directional Solidification of Pb-Sb Alloys

Pb-2.2 and 5.8 wt pet Sb alloys were directionally solidified with a positive thermal gradient of 140 K cm(-1) at growth speeds ranging from 0.8 to 30 mu m s(-1), and then quenched to retain the mushy-zone morphology. Chemical analysis along the length of the directionally solidified portion and in the quenched melt ahead of the dendritic array showed extensive longitudinal macrosegregation, Cellular morphologies growing at smaller growth speeds are associated with larger amounts of macrosegregation as compared with the dendrites growing at higher growth speeds. Convection is caused, mainly, by the density inversion in the overlying melt ahead of the cellular/dendritic array because of the antimony enrichment at the array tip. Mixing of the interdendritic and bulk melt during directional solidification is responsible for the observed longitudinal macrosegregation

Automated mapping of social networks in wild birds

Growing interest in the structure and dynamics of animal social networks has stimulated major advances [1], [2] and [3], but recording reliable association data for wild populations has remained challenging. While animal-borne ‘proximity’ tags have been available for some time [4], earlier devices were comparatively heavy, had limited detection ranges and/or necessitated recovery for data retrieval. We have developed wireless digital transceiver technology (‘Encounternet') that enables automated mapping of social networks in wild birds, yielding datasets of unprecedented size, quality and spatio-temporal resolution. Miniature, animal-borne tags record the proximity and duration of bird encounters, and periodically transfer logs to a grid of fixed receiver stations, from which datasets can be downloaded remotely for real-time analysis. We used our system to chart social associations in New Caledonian crows Corvus moneduloides [5] and [6]. Analysis of ca. 28,000 encounter logs for 34 crows over a 7-day period reveals a substantial degree of close-range association between non-family birds, demonstrating the potential for horizontal and oblique information exchange