Self-Tuning Extended Kalman Filter Parameters to Identify Ankle's Third-Order Mechanics.

The estimation of human ankle's mechanical impedance is an important tool for modeling human balance. This work presents the implementation of a parameter-estimation approach based on a state-augmented extended Kalman filter (AEKF) to infer the ankle's mechanical impedance during quiet standing. However, the AEKF filter is sensitive to the initialization of the noise covariance matrices. In order to avoid a time-consuming trial-and-error method and to obtain a better estimation performance, a genetic algorithm (GA) is proposed to best tune the measurement noise (Rk) and process noise covariances (Q) of the extended Kalman filter (EKF). Results using simulated data show the efficacy of the proposed algorithm for parameter-estimation of a third-order biomechanical model. Experimental validation of these results is also presented. They suggest that age is an influencing factor in the human balance.

Estimating Deep Muscles Activation from High Density Surface EMG Using Graph Theory.

In the recent years important steps forward have been made in the field of signal processing on muscle signals for hand prosthetics control. At the state of the art different algorithms and techniques allow a precise estimation of hand movements. However, they mostly work exclusively on the electrode space, not seeking for any information about the currents on the contracted muscles.In this study we propose a novel simplified method to estimate the muscles currents in the forearm, along with a first experimental application on two simple movements to assess its performance. We modeled the signal propagation from muscles to electrodes using a purely resistive electrical networks and afterwards apply the graph theory to assess the muscle currents. The proposed method considerably simplify the estimation of muscle's current, decreasing the problem complexity, and therefore potentially it can be a suitable approach for future prosthetics' control.

A Simple Method to Estimate Muscle Currents from HD-sEMG and MRI using Electrical Network and Graph Theory.

In the last years the spread of hand prosthetics has fueled the research on the field of signal processing applied on physiologic data. At the state of the art there are different algorithms that allow a precise estimation of hand movements, the majority of whom work just on the electrode space. Even though there are signal processing methods that access single muscle information, they are still premature for a real application on prosthetics. We present a novel method that exploit the information extracted from a magnetic resonance image (MRI) and a single row of high-density surface electromyography (HD-sEMG) electrodes to estimate the muscles currents in the forearm, providing a first experimental application on two simple wrist movements to assess its performance. The results show that the proposed method is able to identify the correct muscle with a single muscle-contraction task, whereas for a 2 muscle task it shows a high variance in the results. The method models the signal propagation from muscles to electrodes using a simple resistive electrical network and uses the graph theory to calculate the muscle currents. It brings a considerably simpler muscle's current estimation method, significantly decreasing the problem complexity, and therefore becoming a potential effective approach for future prosthetics' control.

Therapist recognition of impaired muscle groups in simulated multi-joint hypertonia.

It is common in today's clinical practice for a therapist to physically manipulate patients' limbs to assess hypertonic conditions (e.g. spasticity, rigidity, dystonia, among others). We present a study that evaluates the capabilities of expert therapists to correctly identify the location of a hypertonic impairment of an arm through standard manipulation. Therapists interacted with a hypertonic virtual arms rendered on a robotic device. Our results show that testing joints independently can cause misjudgment of the mechanical contributions of pluri-articular muscles to multi-joint impairment.

Haptic recognition of dystonia and spasticity in simulated multi-joint hypertonia.

This paper investigates the capability of naïve individuals to recognize dystonic- or spastic- like conditions through physical manipulation of a virtual arm. Subjects physically interact with a two-joint, six-muscle hypertonic arm model, rendered on a two degrees-of-freedom robotic manipulandum. This paradigm aims to identify the limitation of manual manipulation during diagnosis of hypertonia. Our results indicate that there are difficulties to discriminate between the two conditions at low to medium level of severity. We found that the sample entropy of the executed motion and the force experienced during physical manipulation, tended to be higher during incorrectly identified trials than in those correctly assessed.

Haptic perception of multi-joint hypertonia during simulated patient-therapist physical tele-interaction.

A potential solution to provide individualized physical therapy in remote areas is tele-interaction via robotic devices. To maintain stability during tele-interaction, transmission delay-compensation algorithms bound the impedance between the patient and the therapist. This can compromise the haptic perception of the patient being assessed, which can in turn lead to a bad diagnosis or intervention. We investigated how the perception of the severity of hypertonia (a common condition after neurological disorders) varied by modifying the connection impedance on a physical simulator. We found that assessing hypetonia using a low impedance connection may result in an overestimation of mild impairments.

Multijoint arm stiffness during movements following stroke: implications for robot therapy.

Impaired arm movements in stroke appear as a set of stereotypical kinematic patterns, characterized by abnormal joint coupling, which have a direct consequence on arm mechanics and can be quantified by the net arm stiffness at the hand. The current available measures of arm stiffness during functional tasks have limited clinical use, since they require several repetitions of the same test movement in many directions. Such procedure is difficult to obtain in stroke survivors who have lower fatigue threshold and increased variability compared to unimpaired individuals. The present study proposes a novel, fast quantitative measure of arm stiffness during movements by means of a Time-Frequency technique and the use of a reassigned spectrogram, applied on a trial-by-trial basis with a single perturbation. We tested the technique feasibility during robot mediated therapy, where a robot helped stroke survivors to regain arm mobility by providing assistive forces during a hitting task to 13 targets covering the entire reachable workspace. The endpoint stiffness of the paretic arm was estimated at the end of each hitting movements by suddenly switching of the assistive forces and observing the ensuing recoil movements. In addition, we considered how assistive forces influence stiffness. This method will provide therapists with improved tools to target the treatment to the individual's specific impairment and to verify the effects of the proposed exercises.

Factors associated with emergency department visits due to acute asthma

It is important to identify characteristics related to poor disease control and frequent visits to the emergency department (ED). The objective of the present study was to compare the characteristics of patients attending the adult ED for treatment of asthma exacerbation with those attending an asthma specialist clinic (AC) in the same hospital, and to determine the factors associated with frequent visits to the ED. We conducted a cross-sectional survey of consecutive patients (12 years and older) attending the ED (N = 86) and the AC (N = 86). Significantly more ED patients than AC patients reported ED visits in the past year (95.3 vs 48.8 percent; P < 0.001) and had difficulty performing work (81.4 vs 49.4 percent; P < 0.001. Significantly more AC than ED patents had been treated with inhaled corticosteroids (75.6 vs 18.6 percent; P < 0.001) used to increase or start steroid therapy when an attack was perceived (46.5 vs 20.9 percent; P < 0.001) and correctly used a metered-dose inhaler (50.0 vs 11.6 percent; P < 0.001). The history of hospital admissions (odds ratio, OR, 4.00) and use of inhaled corticosteroids (OR, 0.27) were associated with frequent visits to the ED. In conclusion, ED patients were more likely than AC patients to be dependent on the acute use of the ED, were significantly less knowledgeable about asthma management and were more likely to suffer more severe disease. ED patients should be considered an important target for asthma education. Facilitating the access to ambulatory care facilities might serve to reduce asthma morbidity.

Factors associated with emergency department visits due to acute asthma.

It is important to identify characteristics related to poor disease control and frequent visits to the emergency department (ED). The objective of the present study was to compare the characteristics of patients attending the adult ED for treatment of asthma exacerbation with those attending an asthma specialist clinic (AC) in the same hospital, and to determine the factors associated with frequent visits to the ED. We conducted a cross-sectional survey of consecutive patients (12 years and older) attending the ED (N = 86) and the AC (N = 86). Significantly more ED patients than AC patients reported ED visits in the past year (95.3 vs 48.8%; P < 0.001) and had difficulty performing work (81.4 vs 49.4%; P < 0.001. Significantly more AC than ED patents had been treated with inhaled corticosteroids (75.6 vs 18.6%; P < 0.001) used to increase or start steroid therapy when an attack was perceived (46.5 vs 20.9%; P < 0.001) and correctly used a metered-dose inhaler (50.0 vs 11.6%; P < 0.001). The history of hospital admissions (odds ratio, OR, 4.00) and use of inhaled corticosteroids (OR, 0.27) were associated with frequent visits to the ED. In conclusion, ED patients were more likely than AC patients to be dependent on the acute use of the ED, were significantly less knowledgeable about asthma management and were more likely to suffer more severe disease. ED patients should be considered an important target for asthma education. Facilitating the access to ambulatory care facilities might serve to reduce asthma morbidity.