Evaluation of a Vibrotactile Biofeedback System Targeting Stance Time Symmetry Ratio of Individuals with Lower-limb Amputation: A Pilot Study

Individuals with lower-limb amputation (LLA) often exhibit atypical gait patterns and asymmetries. These patterns can be corrected using biofeedback (BFB). Real-time BFB strategies have demonstrated to be effective to various degrees in BFB systems. However, no studies have evaluated the use of corrective vibrotactile BFB strategies to improve temporal gait symmetry of LLA. The aim of this study was to evaluate a wearable vibrotactile BFB system to improve stance time symmetry ratio (STSR) of LLA, and compare two corrective BFB strategies that activate either one or two vibrating motors at two different frequency and amplitude levels, based on a pre-set STSR target. Gait patterns of five unilateral LLA were assessed with and without BFB. Spatiotemporal and kinematic gait parameters were measured and assessed using a wearable motion capture system. Usability and workload were assessed using the System Usability Scale and NASA Task Load Index questionnaires, respectively. Results showed that participants significantly (p<0.001) improved STSR with BFB; however, this coincided with a reduction in gait speed and cadence compared to walking without feedback. Knee and hip flexion angles improved and changes in other parameters were variable. Immediate post-test retention effects were observed, suggesting that gait changes due to BFB were preserved for at least a short-time after feedback was withdrawn. System usability was found to be acceptable while using BFB. The outcomes of this study provide new insights into the development and implementation of clinically practical and viable BFB systems. Future work should focus on assessing the long-term use and retention effects of BFB outside controlled-laboratory conditions.

P942 Outcome prediction by exercise stress echocardiography and cardiopulmonary exercise testing assessment in patients with heart failure

Background

Cardiopulmonary exercise testing (CPX) is essential to the assessment of functional impairment and prognosis in patients with heart failure (HF). Peak oxygen consumption (peak VO2) continues to be considered the gold standard for assessing prognosis in HF. The minute ventilation-carbon dioxide production (VE-VCO2) slope has recently demonstrated prognostic significance in patients with HF. Ergometer stress echocardiography (Erg-Echo) is useful to evaluate the exercise-induced pulmonary hypertension and the potential cardiac dysfunction that are difficult to evaluate in the resting state.

Objective

The aim of this study is to evaluate the relationship between CPX and Erg-echo indices, and the usefulness of Erg-echo to determine the severity of cardiac dysfunction and the prognosis in patients with HF.

Methods

We studied 58 patients with HF (age 65.2 ± 11.9 years) and performed CPX and Erg-Echo. The peak VO2 and the VE-VCO2 slope were measured by CPX. Cardiac output (CO) and estimated mean pulmonary artery pressure (mPAP) were measured by Erg-Echo at rest and peak exercise load, and the change ratio (ΔmPAP / ΔCO) were calculated. We evaluated the clinical outcome during a1 year period.

Results

The ΔmPAP / ΔCO was significantly correlated with the peak VO2 (R = -0.6767, P &lt;0.0001) and the VE-VCO2 slope (R = 0.6809, P &lt;0.0001). Cardiovascular events (1 patient of cardiovascular death, 8 patients of re-hospitalization due to HF, 4 patients of myocardial ischemia, 2 patients of Cardiac Resynchronization Therapy (CRT) devices implantation, 1 patient of ventricular tachycardia) developed in 16 of the 58 patients (27.5%: Group CE) during the 1 year. The peak VO2 was significantly lower (12.1 ± 2.5 vs. 16.1 ± 3.1ml/min/kg, P &lt;0.0001) and the VE-VCO2 slope was significantly higher (41.1 ±. 12.3 vs. 31.8 ± 6.1ml/ml, P &lt;0.0001) in Group CE compared to the other 42 patients (Group N). The ΔmPAP was significantly higher (19.1 ± 4.4 vs. 14.9 ± 6.4, P = 0.0408) and the ΔCO was significantly lower (2.4 ± 1.2 vs. 4.1 ± 2.0, P = 0.0078), and the ΔmPAP / ΔCO was significantly higher (9.7 ± 4.6 vs. 4.4 ± 2.4, P &lt;0.0001) in Group CE compared to Group N.

Conclusions

The ΔmPAP/ ΔCO by Erg-Echo is useful to evaluate the severity of cardiac dysfunction and the prognosis of HF patients.

Metabolic encephalopathy in Egyptian children

Fatty Acid Oxidation disorders represent an expanding group of inborn errors of metabolism. Clinical manifestations include episodic encephalopathy, hypoketotic hypoglycemia, Reye like episodes, hepatic, muscular, cardiac affection and sudden death. Analysis of urinary organic acids and plasma fatty acids of 44 clinically suspected patients by Gas Chromatography Mass spectrometry revealed 4 cases of Medium chain acyl-CoA dehydrogenase deficiency (MCADD), 3 cases of Very long chain acyl-CoA dehydrogenase deficiency, 9 cases of multiple defects of acyl-CoA dehydrogenation in addition to 3 patients with other metabolic disorders. Timely detection of these disorders including screening for MCADD can have a favorable impact on the outcome of these patients (Tab. 11, Fig. 3, Ref. 24) Full Text (Free, PDF).

Isoform-dependent differences in feedback regulation and subcellular localization of serine acetyltransferase involved in cysteine biosynthesis from Arabidopsis thaliana

Serine acetyltransferase (SATase; EC 2.3.1.30), which catalyzes the formation of O-acetyl-L-serine (OAS) from acetyl-CoA and L-serine, plays a regulatory role in the biosynthesis of cysteine by its property of feedback inhibition by cysteine in bacteria and certain plants. Three cDNA clones encoding SATase isoforms (SAT-c, SAT-p, and SAT-m) have been isolated from Arabidopsis thaliana. However, the significance of the feedback regulation has not yet been clear in these different isoforms of SATase from A. thaliana. We constructed the overexpression vectors for cDNAs encoding three SATase isoforms of A. thaliana and analyzed the inhibition of SATase activity by cysteine using the recombinant SATase proteins. In the case of SAT-c, the activity was feedback-inhibited by a low concentration of cysteine (the concentration that inhibits 50% activity; IC50 = 1.8 microM). By contrast, SAT-p and SAT-m were feedback inhibition-insensitive isozymes. We also determined the subcellular localization of three SATase isozymes by the transient expression of fusion proteins of each SATase N-terminal region with jellyfish green fluorescent protein (GFP) in 4-week-old Arabidopsis leaves. The SAT-c-GFP fusion protein was stayed in cytosol, whereas SAT-p-GFP and SAT-m-GFP fusion proteins were localized in chloroplasts and in mitochondria, respectively. These results suggest that these three SATase isoforms, which are localized in the different organelles, are subjected to different feedback regulation, presumably so as to play the particular roles for the production of OAS and cysteine in Arabidopsis cells. Regulatory circuit of cysteine biosynthesis in the plant cells is discussed.

Delivery and discrimination: the Seine protocol

We present two protocols for information exchange between multiple identical senders and a single receiver. At each instant, every sender sends one bit, and the bits from all of senders are or-ed together into one bit before being received by the receiver. If a sender has a data message to send, it sends the message bits one by one; otherwise it sends zero bits. Clearly, if the sending of two messages by two senders overlap, then the resulting “collision” can result in a corrupted message, i.e., one that was not sent by either sender. The function of the protocol is to deliver those and only those messages that are not corrupted by collision. (In other words, the receiver acts as a discriminating seine that catches and delivers only uncorrupted messages; hence the title.) The two protocols presented here are based on Manchester codes and general balanced codes, respectively.