The combined action of a passive exoskeleton and an EMG-controlled neuroprosthesis for upper limb stroke rehabilitation: First results of the RETRAINER project

The combined use of Functional Electrical Stimulation (FES) and robotic technologies is advocated to improve rehabilitation outcomes after stroke. This work describes an arm rehabilitation system developed within the European project RETRAINER. The system consists of a passive 4-degrees-of-freedom exoskeleton equipped with springs to provide gravity compensation and electromagnetic brakes to hold target positions. FES is integrated in the system to provide additional support to the most impaired muscles. FES is triggered based on the volitional EMG signal of the same stimulated muscle; in order to encourage the active involvement of the patient the volitional EMG is also monitored throughout the task execution and based on it a happy or sad emoji is visualized at the end of each task. The control interface control of the system provides a GUI and multiple software tools to organize rehabilitation exercises and monitor rehabilitation progress. The functionality and the usability of the system was evaluated on four stroke patients. All patients were able to use the system and judged positively its wearability and the provided support. They were able to trigger the stimulation based on their residual muscle activity and provided different levels of active involvement in the exercise, in agreement with their level of impairment. A randomized controlled trial aimed at evaluating the effectiveness of the RETRAINER system to improve arm function after stroke is currently ongoing.

[Effect of body position on coordination of breathing and swallowing]

BACKGROUND

To allow passage of food, the swallowing process closes off the larynx and interrupts respiratory flow. Both the timing of the interruption of respiratory flow and the body position can affect the results of the swallowing process.

OBJECTIVE

The effect of body position on the swallowing process and the coordination of breathing and swallowing is investigated.

MATERIALS AND METHOD

A combined EMG/bioimpedance measurement system and a piezoelectric sensor were used to investigate coordination of breathing and swallowing of a range of food consistencies in three different body positions (90°, 45° and 0°) in healthy subjects.

RESULTS

Investigations were carried out on 21 healthy subjects (12 ♂, 9 ♀). 762 swallows were recorded. Changing body position was found to have a statistically significant effect on swallow-related parameters (maximum laryngeal elevation and speed of laryngeal elevation) and breathing pattern (pre- and post-swallow breathing phases). The laryngeal elevation as well as the speed of the laryngeal elevation is influenced significantly by the consistency to be swallowed. The breathing pattern changes from saliva to solid food of inspiration/swallow/inspiration to expiration/swallow/expiration. A change of body position influences the parameters specific for swallowing and the breathing patterns significantly.

CONCLUSIONS

This study demonstrates that body position affects coordination of breathing and swallowing and swallow-related parameters in healthy subjects. Our results indicate that patients should be enabled to adopt a position in which they are sitting at an angle of at least 45°.

The effect of using variable frequency trains during functional electrical stimulation cycling

Objectives.  This paper describes an experimental investigation of variable frequency stimulation patterns as a means of increasing torque production and, hence, performance in cycling induced by functional electrical stimulation. Materials and Methods.  Experiments were conducted on six able-bodied subjects stimulating both quadriceps during isokinetic trials. Constant-frequency trains (CFT) with 50-msec interpulse intervals and four catchlike-inducing trains (CIT) were tested. The CITs had an initial, brief, high-frequency burst of two pulses at the onset of or within a subtetanic low-frequency stimulation train. Each stimulation train consisted of the same number of pulses. The active torques produced by each train were compared. Parametric main effect ANOVA tests were performed on the active torque-time integral (TTI), on the active torque peaks and on the time needed to reach those peaks (T2P). Results.  The electrical stimulation of the quadriceps produced active torques with mean peak values in the range of 1.6-3.5 Nm and a standard error below 0.2 Nm. CITs produced a significant increase of TTI and torque peaks compared with CFTs in all the experimental conditions. In particular, during the postfatigue trials, the CITs with the doublet placed in the middle of the train produced TTIs and torque peaks about 61% and 28% larger than the CFT pattern, respectively. In addition, the CITs showed the lowest reduction of the performance between prefatigue and postfatigue conditions. Conclusions.  The use of CITs improves the functional electrical stimulation cycling performance compared with CFT stimulation. This application might have a relevant clinical importance for individuals with stroke where the residual sensation is still present and thus the maximization of the performance without an excessive increase of the stimulation intensity is advisable. Therefore, exercise intensity can be increased yielding a better muscle strength and endurance that may be beneficially for later gait training in individuals with stroke.

[Electric stimulation in dysphagia therapy--a review]

In the last years an increased interest in the electrical stimulation has consisted in the treatment of dysphagia. In the article we introduce the anatomical and physiological premises for the method. In a critical analysis the present state of art is represented, the clinical results are checked and the chances for the future are examined.

Impacts of Wireless Power on Medical Device Design Safety

Wireless power holds great promise for solving many power distribution problems. Medical device designers will need to understand the impact of the electromagnetic coupling used for wireless power systems to design safe electromagnetic environments and safe medical devices. One question for designers will be whether or not current standards and requirements used for testing the electromagnetic compatibility (EMC) of medical devices and human exposure go far enough to insure safe environments and safe and reliable medical devices in the presence of wireless power. Electromagnetic energy can be transferred in three ways: through induction, radio frequency waves, or resonant evanescent coupling. Nonradiative inductive coupling uses the magnetic fields created when current is passed through one coil to create a current in a second coil that is located very near the first coil. These systems usually operate in the 50 KHz to 10 MHz range. Radio frequency energy can be transferred through radiating electromagnetic waves over great distances at frequencies from the upper KHz to many GHz. Most recently, work has been done on resonant evanescent coupling which transfers power between resonant objects over a distance of a couple of meters at frequencies from 1–10 MHz. Safety and reliability of medical devices is confirmed by testing EMC emissions and susceptibility to IEC60601-1-2 and supporting standards. For example, one of the supporting standards, CISPR 11 calls for measuring the electric field of radiated emissions over 30 MHz and the magnetic field below 30 MHz at distances of 3–10 meters. Many of the effects of wireless power systems are in the near field and are not covered in the current test standards. The AAMI PC69 series of standards have some near field requirements but these standards tend to be industry specific – such as drug pumps or pacemakers. EMC immunity standards used to test EMC susceptibility barely mention magnetic immunity. The only test for magnetic fields recommends testing fields at the power frequencies of 50 and 60 Hz. There are few standards detailing safe limits for human exposure to the near field effects of wireless power as well. Historically human exposure standards have been based on time average thermal effects on tissue and not medical devices. IEEE's C95.1b has requirements for specific absorption rate limits averaged over a 6 minute period. A pulsed wireless power system could meet these requirements and be safe for exposed tissue, but if a patient has an implanted device, or is wearing an external medical device, the pulsed EM energy could affect it during the pulse. The German BGV B11 standard lists human exposure limits for electric and magnetic fields based on a time average and limits exposure based on which portion of the body is exposed. However, it is meant as a workplace standard not a medical device standard. Currently the FDA does not require meeting either of these standards. It is necessary to determine the appropriate limits and tests to ensure that medical devices safely use wireless power and continue to operate safely in the presence of wireless power.

Misregulated RNA Pol II C-terminal domain phosphorylation results in apoptosis

Misregulation of the level of RNA polymerase II carboxyl-terminal domain (CTD) phosphatase, Fcp1, in Drosophila results in high level of caspase-mediated apoptosis. Apoptosis induction by Fcp1 misregulation requires the presence of Drosophila melanogaster (Dm)p53, but occurs without the transcriptional activation of Dmp53 proapoptotic targets rpr, ark, and hid. Overproduction of a transcription activation-defective mutant Dmp53 protein increases, while Dmp53 null background decreases significantly the level of apoptosis in Fcp1-misregulated animals. Generating the apoptotic signal does not require the function of the ATM and Rad3-related kinase (ATR), and no significant level of nucleo-cytoplasmic translocation of Dmp53 is detectable in cells expressing Fcp1 at an abnormal level. Immunostaining of larval salivary gland polytene chromosomes with anti-Dmp53 antibodies indicates Dmp53 localization at several transcriptionally active chromosomal regions in wild-type cells, while in Fcp-misregulated cells the association of Dmp53 with specific chromosomal sites is decreased.

First-aid sensor system: new methods for single-point detection and analysis of vital parameters such as pulse and respiration

The paper describes a first aid medical sensor system that is able to detect pulse and respiration. According to an opinion poll 79% of unexperienced first aiders were looking forward to use a system that supports them in first aid situations. Such a device has to be reliable and available in everyday use (e.g. as a keychain or in a first-aid kit). Therefore we investigated a single point sensor that is able to detect both respiration and blood flow at the same point of the body, for instance on the neck. Compared to ECG-derived methods absent pulse due to pulseless electrical activity (PEA) will be recognized as such. Tests have shown that the sensor can also be used to detect deglutition and other body motion sequences.