Portable haptic device for lower limb amputee gait feedback: Assessing static and dynamic perceptibility.

Loss of joints and severed sensory pathway cause reduced mobility capabilities in lower limb amputees. Although prosthetic devices attempt to restore normal mobility functions, lack of awareness and control of limb placement increase the risk of falling and causing amputee to have high level of visual dependency. Haptic feedback can serve as a cue for gait events during ambulation thus providing sense of awareness of the limb position. This paper presents a wireless wearable skin stretch haptic device to be fitted around the thigh region. The movement profile of the device was characterized and a preliminary work with able-bodied participants and an above-knee amputee to assess the ability of users to perceive the delivered stimuli during static and dynamic mode is reported. Perceptibility was found to be increasing with stretch magnitude. It was observed that a higher magnitude of stretch was needed for the stimuli to be accurately perceived during walking in comparison to static standing, most likely due to the intense movement of the muscle and increased motor skills demand during walking activity.

A Real-Time Gait Event Detection for Lower Limb Prosthesis Control and Evaluation.

Lower extremity amputees suffer from mobility limitations which will result in a degradation of their quality of life. Wearable sensors are frequently used to assess spatio-temporal, kinematic and kinetic parameters providing the means to establish an interactive control of the amputee-prosthesis-environment system. Gait events and the gait phase detection of an amputee's locomotion are vital for controlling lower limb prosthetic devices. The paper presents an approach to real-time gait event detection for lower limb amputees using a wireless gyroscope attached to the shank when performing level ground and ramp activities. The results were validated using both healthy and amputee subjects and showed that the time differences in identifying Initial Contact (IC) and Toe Off (TO) events were larger in a transfemoral amputee when compared to the control subjects and a transtibial amputee (TTA). Overall, the time difference latency lies within a range of ±50 ms while the detection rate was 100% for all activities. Based on the validated results, the IC and TO events can be accurately detected using the proposed system in both control subjects and amputees when performing activities of daily living and can also be utilized in the clinical setup for rehabilitation and assessing the performance of lower limb prosthesis users.

A wearable skin stretch haptic feedback device: Towards improving balance control in lower limb amputees.

Haptic feedback to lower limb amputees is essential to maximize the functionality of a prosthetic device by providing information to the user about the interaction with the environment and the position of the prostheses in space. Severed sensory pathway and the absence of connection between the prosthesis and the Central Nervous System (CNS) after lower limb amputation reduces balance control, increases visual dependency and increases risk of falls among amputees. This work describes the design of a wearable haptic feedback device for lower limb amputees using lateral skin-stretch modality intended to serve as a feedback cue during ambulation. A feedback scheme was proposed based on gait event detection for possible real-time postural adjustment. Preliminary perceptual test with healthy subjects in static condition was carried out and the results indicated over 98% accuracy in determining stimuli location around the upper leg region, suggesting good perceptibility of the delivered stimuli.

Real-time gait event detection for lower limb amputees using a single wearable sensor.

This paper presents a rule-based real-time gait event/phase detection system (R-GEDS) using a shank mounted inertial measurement unit (IMU) for lower limb amputees during the level ground walking. Development of the algorithm is based on the shank angular velocity in the sagittal plane and linear acceleration signal in the shank longitudinal direction. System performance was evaluated with four control subjects (CS) and one transfemoral amputee (TFA) and the results were validated with four FlexiForce footswitches (FSW). The results showed a data latency for initial contact (IC) and toe off (TO) within a range of ± 40 ms for both CS and TFA. A delay of about 3.7 ± 62 ms for a foot-flat start (FFS) and an early detection of -9.4 ± 66 ms for heel-off (HO) was found for CS. Prosthetic side showed an early detection of -105 ± 95 ms for FFS whereas intact side showed a delay of 141 ±73 ms for HO. The difference in the kinematics of the TFA and CS is one of the potential reasons for high variations in the time difference. Overall, detection accuracy was 99.78% for all the events in both groups. Based on the validated results, the proposed system can be used to accurately detect the temporal gait events in real-time that leads to the detection of gait phase system and therefore, can be utilized in gait analysis applications and the control of lower limb prostheses.

Real-time gait event detection for transfemoral amputees during ramp ascending and descending.

Events and phases detection of the human gait are vital for controlling prosthesis, orthosis and functional electrical stimulation (FES) systems. Wearable sensors are inexpensive, portable and have fast processing capability. They are frequently used to assess spatio-temporal, kinematic and kinetic parameters of the human gait which in turn provide more details about the human voluntary control and ampute-eprosthesis interaction. This paper presents a reliable real-time gait event detection algorithm based on simple heuristics approach, applicable to signals from tri-axial gyroscope for lower limb amputees during ramp ascending and descending. Experimental validation is done by comparing the results of gyroscope signal with footswitches. For healthy subjects, the mean difference between events detected by gyroscope and footswitches is 14 ms and 10.5 ms for initial contact (IC) whereas for toe off (TO) it is -5 ms and -25 ms for ramp up and down respectively. For transfemoral amputee, the error is slightly higher either due to the placement of footswitches underneath the foot or the lack of proper knee flexion and ankle plantarflexion/dorsiflexion during ramp up and down. Finally, repeatability tests showed promising results.

Selective electronalysis of peracetic acid in the presence of a large excess of H2O2 at Au(111)-like gold electrode.

Peracetic acid (PAA) has been selectively electroanalyzed in the presence of a large excess of hydrogen peroxide (H(2)O(2)), about 500 fold that of PAA, using Au (111)-like gold electrode in acetate buffer solutions of pH 5.4. Au(111)-like gold electrode was prepared by a controlled reductive desorption of a previously assembled thiol, typically cysteine, monolayer onto the polycrystalline gold (poly-Au) electrode. Cysteine molecules were selectively removed from the Au(111) facets of the poly-Au electrode, keeping the other two facets (i.e., Au(110) and Au(100)) under the protection of the adsorbed cysteine. It has been found that Au(111)-like gold electrode positively shifts the reduction peak of PAA, while, fortunately, shifts the reduction peak of H(2)O(2) negatively, achieving a large potential separation (around 750 mV) between the two reduction peaks as compared with that (around 450 mV) obtained at the poly-Au electrode. This large potential separation between the two reduction peaks enabled the analysis of PAA in the presence of a large excess of H(2)O(2). In addition, the positive shift of the reduction peak of PAA gives the present method a high immunity against the interference of the dissolved oxygen.

Pharmacokinetics of artesunate following oral and rectal administration in healthy Sudanese volunteers.

The aims of this study were to determine the pharmacokinetic parameters of a single dose of 200 mg oral and rectal artesunate in healthy volunteers, and to suggest a rational dosage regimen for rectal administration. The study design was a randomized open cross-over study of 12 healthy volunteers; the analytical method used was a reversed phase high performance liquid chromatography with post column derivatization and subsequent ultraviolet detection. Pharmacokinetic parameters were derived from the main metabolite alpha-dihydroartemisinin data due to the rapid disappearance of artesunate from the plasma. Dihydroartemisinin following oral administration of artesunate had a significantly higher AUC(0-infinity) (P<0.05 95% confidence interval (CI) -1168.73, -667.61 ng x h/mL(-1)) and Cmax (P<0.05; 95% CI -419.73, -171.44 ng/mL(-1)), and had shorter tmax (P<0.05; 95% CI -0.97, -0.10 h) than that following rectal artesunate. There was no statistically significant difference in the elimination half-life between both routes of administration (P>0.05; 95% CI -0.14, 0.53 h). The relative bioavailability of rectal artesunate was [mean (coefficient of variation %) 54.9 (24.8%) %]. On the basis of these data an 8 hourly dosing regimen per day with rectal artesunate is proposed.

Descriptive study on the efficacy and safety of artesunate suppository in combination with other antimalarials in the treatment of severe malaria in Sudan.

Documentation on the efficacy of artesunate in Africa is limited, and no experience of artesunate use in Sudan is documented. Severe malaria in rural areas of Sudan, where facilities for the safe and effective use of parenteral quinine are lacking, is a frequent problem. Early treatment with artesunate suppositories would provide a simple method for use by unskilled staff and would be an alternative approach to treat malaria in settings with poor resources. We describe a hospital-based study of rectal artesunate in 100 adult patients with severe falciparum malaria with a dose derived from pharmacokinetic data (200 mg every 8 hours) over 3 days, which halted progression of severe disease and had a low fatality rate. The dosage schedule led to a rapid clinical response and reduced parasite clearance and fever subsidence times of (31.5 +/- 10.1 hours) and (31.4 +/- 11.1 hours). The sequential treatment of rectal artesunate with either doxycycline or pyrimethamine/sulfadoxine or mefloquine resulted in similar clinical cure rates of around 100%, and the combination of artesunate with either doxycycline or pyrimethamine/sulfadoxine was equally effective as mefloquine in preventing recrudescence. There were no significant adverse effects or signs of toxicity related to the treatment observed during the 28-day follow-up. The combination regimens could be used in areas where there is limited access to parenteral therapy for malaria.

Simultaneous electroanalysis of peroxyacetic acid and hydrogen peroxide.

The electrochemical behavior of peroxyacetic acid (PAA) in the presence of hydrogen peroxide (H2O2) has been investigated using cyclic voltammetry and hydrodynamic techniques [rotating disk electrode (RDE) voltammetry and rotating ring-disk electrode (RRDE) voltammetry]. The results have been analyzed aiming at simultaneous electroanalysis of both species. Glassy carbon and gold electrodes were used for this investigation. It was found that the reduction of PAA, as well as H2O2, is highly sensitive to the electrode material; for example, at 100 mV s-1, the reduction peak potentials of PAA were 0.2 and -1.1 V at gold and glassy carbon electrodes, respectively. The well-separated steady-state limiting currents were obtained using a gold electrode for the reduction of both PAA and H2O2 and also a well-defined one for the oxidation of H2O2. On the basis of the RDE experiments, good calibration curves were obtained for both species over a wide range of their concentrations, for PAA and H2O2 in the range of 0.36 to 110 and 0.11 to 34 mM, respectively. The simultaneous and selective electroanalysis of PAA and H2O2 in their coexistence is demonstrated for the first time.

Determination of sodium artesunate in plasma using ion-pairing high-performance liquid chromatography.

A chromatographic method is described for the determination of sodium artesunate in plasma. This includes cetyltrimethylammonium bromide as a cationic pairing ion in a reversed-phase system using an octadecylsilica 100 x 4.6 mm I.D. 3 microm analytical column with a mobile phase of acetonitrile/acetate buffer at pH7. Column switching incorporating a 5 microm octadecylsilica 100 x 4.6 mm I.D. precolumn is used in addition to off-line solid-phase extraction for pretreatment of plasma samples in order to eliminate interference from endogenous components. Detection is by post-column derivatisation with 1.0 M methanolic KOH followed by UV detection at 289 nm. Calibration is linear over the range 100-1600 ng ml(-1) and the limit of detection is estimated as 20 ng ml(-1). Illustrative results are shown of the artesunate plasma levels determined by the proposed method following the administration of artesunate as tablets and as suppositories to healthy volunteers.