Postural Responses to Achilles Tendon Vibration Depend on Feet Positioning

Mechanical vibration of the Achilles tendon is widely used to analyze the role of proprioception in postural control. The response to this tendon vibration (TV) has been analyzed in the upright posture, but the feet positions have varied in past research. Moreover, investigators have addressed only temporal parameters of the center of pressure (CoP). We investigated the effect of TV on both temporal and spectral characteristics of the CoP motion. Eighteen healthy young adults, stood barefoot, with one foot on each side of a dual platform, wearing glasses with opaque lenses. We applied 20 seconds of Achilles TV (bilaterally with inertial vibrators at a frequency of 80 Hz and an amplitude of .2-.5 mm). We analyzed CoP signals pre-vibration (PRE,4-seconds), during vibration (VIB,20 seconds), and after vibration cessation (REC,20 seconds). We repeated this protocol in natural and standardized positions (15° feet angular opening). For determining CoP amplitude and velocity, we divided the 20 seconds into five phases of four seconds each and calculated spectral parameters for the whole 20-second signals. There was an adaptation process in the speed of the CoP mediolateral (p < .01) and anteroposterior (p < .01) and in the displacement of the CoP anteroposterior (p < .01), with higher values in the VIB condition. Velocity and displacement decreased progressively in the REC condition. Median and peak frequencies were higher in the VIB condition when compared to the REC condition, but only in the mediolateral direction (p = .01). The standardized foot position led to increased speed in CoP mediolateral, anteroposterior, and mediolateral displacement (p < .01). CoP spectral characteristics were not affected by foot positioning. We concluded that adaptation of CoP motion in the presence of TV and after its cessation are observable both in time and frequency domains. Feet positioning influenced CoP motion in the presence of TV and after its cessation but it did not affect its spectral characteristics.

Identification of a PRDM1-regulated T cell network to regulate T cell driving plaque inflammation in human and mouse atherosclerosis

 

T cells have a prominent role in the pathogenesis of atherosclerosis, although their exact function remains elusive. Here, we pursued a network-driven approach to identify T cell-associated gene programs driving the transition from low- to high-risk human plaques.

In this study 43 human carotid arterial plaques were collected and stratified based on absence (low-risk) or presence (high-risk) of intraplaque haemorrhage (IPH). Lesion RNA was subjected to microarray gene expression analysis and analysed by Weighted Gene Co-expression Network Analysis (WGCNA). We identified a co-expressed gene cluster displaying a strong T cell signalling signature in high- versus low-risk plaque, which was tightly connected to subnetworks of angiogenesis and interferon-signalling. WGCNA-based Bayesian network inference, cell-type deconvolution and single-cell gene expression revealed that this T cell-associated gene program was likely linked to effector-memory cytotoxic CD8+ T cells, underpinning the central role of T cells in plaque destabilization. Gene regulatory analysis identified cytotoxic T cell-related transcription factors, like PRDM1, regulating this plaque T cell gene program. Moreover, we demonstrated in LDL receptor knockout mice with T cell-specific Prdm1 deficiency, that lack of Prdm1 in T cells resulted in larger, more advanced plaques.

In conclusion, our study reveals a PRDM1-regulated T cell footprint in high- versus low-risk human atherosclerotic lesions and murine atherosclerotic plaque development, thereby identifying this network as a potential target for intervention in adverse T cell responses.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): The European Research Area Network on Cardiovascular Diseases (ERA-CVD and Dutch Heart Foundation)

Identification of physically fatiguing tasks performed during aircraft open-basket ground de-icing activities

BACKGROUND

Airplane de-icing technicians work from either an open-basket or closed-basket.

OBJECTIVE

The objective of this study is to identify the tasks that have an influence on the physical fatigue of open-basket aircraft de-icing technicians.

METHODS

In a Canadian airport during the winter of 2016-2017, a field study was conducted in which the heart rate of 12 volunteer participants was collected. The data was analyzed along with the 22 tasks that make up the activity of open-basket aircraft de-icing. For each participant, the mean absolute cardiac cost per task was compared. The evolution of the cardiac signal based on the resting heart rate and steady state limit was also characterized.

RESULTS

According to the cumulative results fatigue occurs for periodic tasks as well as double tasks. More precisely, the most physically fatiguing tasks are spraying de-icing and anti-icing fluids, moving the basket and truck, as well as tactile control and de-icing quality control at ground level.

CONCLUSIONS

Similar studies would need to be conducted in other aircraft de-icing facilities to improve the generalization of the results.

Assessing the visual vertical: how many trials are required?

Background

The visual vertical (VV) consists of repeated adjustments of a luminous rod to the earth vertical. How many trials are required to reach consistency in this measure? This question has never been addressed despite the widespread clinical use of the measurement in stroke rehabilitation.

Methods

VV perception was assessed (10 trials) in 117 patients undergoing rehabilitation after a first hemisphere stroke. The intraclass correlation coefficient (ICC) and standard error of measurement (SEM) were calculated for each patient category: with contralesional VV bias (n = 48), ipsilesional VV bias (n = 17) and normal VV (n = 52).

Results

For patients with VV biases, 6 trials were required to reach high inter-trial reliability (contralesional: ICC = 0.9, SEM = 1.36°; ipsilesional: ICC = 0.896, SEM = 0.96°). For patients with normal VV, a minimum of 10 trials was required (ICC = 0.728, SEM = 1.13°). A set of 6 trials correctly classified 96 % of patients.

Conclusions

In the literature, 10 is the most frequently used number of trials used to assess VV orientation. Our study shows that 10 trials are required to adequately measure VV orientation in non-selected subacute stroke patients. For complex protocols imposing a decrease in the number of trials in each condition, 6 trials are needed to identify VV biases in most patients.

Surgery and radiotherapy for typical carcinoid of the nasopharynx: a case report

BACKGROUND

Carcinoid tumours are rare, particularly in the head and neck region. When occurring in this area, they mainly affect the larynx. The first case of primary well-differentiated carcinoid tumour arising from the nasopharynx was documented in 2009 and treated by combined external beam radiation and cold somatostatin analogue with a fatal outcome. To our knowledge, no case of this type of lesion has been successfully treated with surgery and radiotherapy until now.

OBJECTIVE

To make physicians aware that typical carcinoid nasopharyngeal tumour can be treated by surgery and adjuvant radiotherapy.

METHOD

We report the management of a typical carcinoid nasopharyngeal tumour in a 68-year-old female successfully treated with endoscopic surgery and adjuvant radiotherapy. We also review the relevant literature.

CONCLUSION

Patients with close margins at the time of the surgery may need adjuvant radiotherapy to prevent recurrence. After a negative octreotide scintigraphy, periodical follow-up only is sufficient.

[Early treatment with Nd:YAG laser for Valsalva retinopathy: results of five cases and literature review]

INTRODUCTION

According to the literature, the treatment of retinopathy of Valsalva (VR) by laser is recommended when the macular hemorrhage has not regressed after 3 weeks.

PATIENTS AND METHODS

We report five cases of VR treated early (≤ 24 hours) by Nd:YAG laser membranotomy (LM). Clinical examination was performed before and after LM (D1, D7, M1, M3 and M6). Optical coherence tomography (OCT) analysis was performed to determine the precise location of the macular hemorrhage.

RESULTS

Good visual recovery was obtained early by LM with a stable outcome at 6 months. The hemorrhage was located under the internal limiting membrane (ILM) and posterior hyaloid in two patients and only under the ILM in three patients.

DISCUSSION

The literature review and our study confirm the good functional results for patients treated by LM for VR. Furthermore, very few side effects are reported with this type of treatment compared with the natural course of the disease, which may certainly regress spontaneously, but carries a risk of secondary preretinal fibrosis. However, to obtain optimal efficacy, the treatment should be carried out as soon as possible, in order to avoid clotting of the hematoma, preventing any subsequent evacuation by laser.

CONCLUSION

LM for VR is an effective, safe and inexpensive technique compared to the surgical management of these patients presenting with a persistant premacular hematoma after a period of observation.

[Serous central chorioretinopathy and tadalafil: a case report]

We report a case of central serous chorioretinopathy in a 46-year-old man with no risk factors except for erectile dysfunction agent use: Tadalafil (Cialis(®)). An association between tadalafil and central serous chorioretinopathy could involve phosphodiesterase type 5 inhibitors and be a risk factor of central serous chorioretinopathy.

Standing balance assessment in ASIA D paraplegic and tetraplegic participants: concurrent validity of the Berg Balance Scale

STUDY DESIGNS

Longitudinal and correlational study with repeated measures.

OBJECTIVES

The aim of this study was to test the concurrent validity of the Berg Balance Scale (BBS) for a spinal cord injury (SCI) population.

PARTICIPANTS

A total of 32 individuals with an ASIA D SCI walking 10 m independently, with or without walking assistive devices.

SETTING

An intensive rehabilitation center in Montréal, Canada.

METHODS

Subjects were evaluated on the BBS, the Walking Index for Spinal Cord Injury (WISCI II), the Spinal Cord Injury Functional Ambulation Inventory (SCI-FAI), the 10-m walk test (10MWT) and the Timed Up and Go (TUG). Individuals were reassessed during rehabilitation when progressing to a device providing less support or to unassisted gait.

RESULTS

All walking tests were highly correlated with the BBS (0.714<Rs<0.816, P<or=0.01). A significant ceiling effect was found on the BBS, the WISCI and on most subsections of the SCI-FAI. Assistive devices used for walking relate well to the BBS score (Spearman's rho 0.714, P<0.01).

CONCLUSION

The BBS is an appropriate assessment of standing balance for individuals with SCI. Complementary evaluation with the 10MWT or the 2MWT is recommended to supplement the ceiling effect on the BBS.

Destabilizing and stabilizing forces to assess equilibrium during everyday activities

Postural stability is essential to functional activities. This paper presents a new model of dynamic stability which takes into account both the equilibrium associated with the body position over the base of support (destabilizing force) and the effort the subject needs to produce to keep his/her centre of mass inside the base of support (stabilizing force). The ratio between these two forces (destabilizing over stabilizing) is calculated to provide an overall index of stability for an individual. Preliminary results from data collected during walking at preferred and maximal safe speed in four older adults (aged from 64 to 84yr) showed that both forces are lower for subjects with reduced maximal gait speed. In addition, the stabilizing force increases by 2-3 times from preferred to maximal speed, while the destabilizing force barely changes with gait speed. Overall, the model through the index of stability attributes lower dynamic stability to subjects with lower maximal gait speed. These preliminary results call for larger-scale studies to pursue the development and validation of the model and its application to different functional tasks.

The comparison of wavelet- and Fourier-based electromyographic indices of back muscle fatigue during dynamic contractions: validity and reliability results

The purpose of this study was to compare the electromyographic (EMG) fatigue indices computed from short-time Fourier transform (STFT) and wavelet transform (WAV), by analyzing their criterion validity and test-retest reliability. The effect of averaging spectral estimates within and between repeated contractions (cycles) on EMG fatigue indices was also demonstrated. Thirty-one healthy subjects performed trunk flexion-extension cycles until exhaustion on a Biodex dynamometer. The load was determined theoretically as twice the L5-S1 moment produced by the trunk mass. To assess reliability, 10 subjects performed the same experimental protocol after a two-week interval. EMG signals were recorded bilaterally with 12 pairs of electrodes placed on the back muscles (at L4, L3, L1 and T10 levels), as well as on the gluteus maximus and biceps femoris. The endurance time and perceived muscle fatigue (Borg CR-10 scale) were used as fatigue criteria. EMG signals were processed using STFT and WAV to extract global (e.g, median frequency and instantaneous median frequency, respectively) or local (e.g., intensity contained in 8 frequency bands) information from the power spectrum. The slope values of these variables over time, obtained from regression analyses, were retained as EMG fatigue indices. EMG fatigue indices (STFT vs. WAV) were not significantly different within each muscle, had a variable association (Pearson's r range.: 0.06 to 0.68) with our fatigue criteria, and showed comparable reliability (Intra-class correlation range: 0.00 to 0.88), although they varied between muscles. The effect of averaging, within and between cycles, contributed to the strong association between EMG fatigue indices computed from STFT and WAV. As for EMG spectral indices of muscle fatigue, the conclusion is that both transforms carry essentially the same information.

Caregivers attitudes for very premature infants: what if they knew?

BACKGROUND

Decisions about resuscitation of extremely premature babies are controversial. Such decisions may reflect poor understanding of outcomes.

OBJECTIVE

To compare caregivers' attitudes towards the resuscitation of a premature infant if they are only told the infant's gestational age or if they are only given prognostic information for infants at that gestational age.

DESIGN/METHODS

Residents and nurses involved in perinatal care were asked whether they would resuscitate a depressed AGA 24-week gestation infant at birth. In another question they were asked whether they would resuscitate a depressed preterm infant with a 50% chance of survival, knowing that of those who survived, 50% would have a development 'within normal limits', 20-25% a serious handicap and 40% with behavioural and/or learning disability.

RESULTS

Two hundred and seventy-nine caregivers responded (91% response rate). In the scenario that only presented gestational age, 21% of respondents would resuscitate. In the scenario that only presented prognostic statistics, 51% of respondents would resuscitate (p<0.05).

CONCLUSIONS

Providers of perinatal health care respond to vignettes differently depending upon the format in which information is provided. The relative unwillingness to resuscitate a baby of 24-week gestation is surprising since outcomes for such babies are the same or better than those we described in the scenario that provided only outcome data without specifying gestational age. Two explanations are possible: (1) respondents have irrational negative associations with low gestational ages or (2) respondents are unaware of actual outcomes.

Assessment of agonist-antagonist shoulder torque ratios in individuals with paraplegia: a new interpretative approach

STUDY DESIGN

Cross-sectional study.

OBJECTIVE

To evaluate isokinetic shoulder flexor-extensor (F/E) and abductor-adductor (Ab/Ad) torque ratios in individuals with paraplegia using a new interpretative approach. We proposed to study torque ratios according to joint angle sections (15 degrees angle subgroups) over a selected range of motion.

SETTING

Pathokinesiology Laboratory, Montreal, Canada.

METHOD

Sixteen individuals with complete motor paraplegia, without shoulder pain or impairment, were included in this study. After a preloading period of 1 s, maximum isokinetic concentric contractions of all muscle groups were completed at 30, 60 and 120 degrees s(-1) over the entire tested ranges of motion (70 to -35 degrees for the flexion-extension and 15 to 60 degrees for the abduction-adduction). After the continuous torque curves were rebuilt, the mean F/E and Ab/Ad torque ratios were calculated and analyzed every 15 degrees.

RESULTS

A significant modification of the F/E (F=66.3; P<0.001) and Ab/Ad (F=100.6; P<0.001) torque ratios was observed according to the 15 degrees angle subgroup evaluated. More precisely, a progressive decline of both the F/E and Ab/Ad ratios was noted as the shoulder flexion or abduction progressed. Angular velocity did not have any influence on torque ratio values.

CONCLUSION

Angle subgroup torque ratio analysis leads to a better estimation of the balance between the agonist and antagonist muscle groups than does traditional peak torque ratio analysis. In individuals with paraplegia, this precise estimation of torque ratios may lead to the development of specific shoulder strengthening programs to prevent muscle imbalance and its consequences.

Moral distress in the neonatal intensive care unit: caregiver's experience

BACKGROUND

The Neonatal Intensive Care Unit (NICU) can be ethically charged, which can create challenges for health-care workers.

OBJECTIVE

To determine the frequency with which nurses and residents have experienced ethical confrontations and what factors are associated with increased frequency.

DESIGN/METHODS

An anonymous questionnaire was distributed to nurses in a university center, a high-risk obstetric service, a maternity hospital NICU with 85% in-born patients and an outborn NICU, most of whose preterm admissions are those with surgical complications. Obstetric and pediatric residents in the four universities of the province also received the questionnaire, which included demographics, opinions regarding the gestational age threshold at which resuscitation of a premature infant with bradycardia was appropriate, knowledge of cerebral palsy (CP) outcomes (as an indicator of knowledge about long-term sequelae of prematurity) and questions about ethical confrontation in the NICU.

RESULTS

Two hundred and seventy-nine caregivers participated (115 full time nurses and 164 residents). All the distributed questionnaires were completed. Frequent ethical confrontation was reported by 35% of the nurses and 19% of the residents. Among the nurses, moral distress differed significantly between work environments. Nurses working in an out-born NICU and obstetric nurses were more likely to overestimate CP prevalence (P<0.05). Nurses who overestimated CP rates had higher thresholds for resuscitation and were more likely to experience ethical confrontations. Of the residents, 60% were pediatric and 40% obstetric. All groups of residents frequently overestimated the prevalence of CP, and knowledge differed significantly by residency program (P<0.05). The residents who overestimated CP rates had higher thresholds for resuscitation, had more incorrect answers regarding prematurity outcomes and were less likely to have ethical confrontations.

CONCLUSIONS

A large proportion of nurses and residents report frequent ethical confrontations. Many residents and nurses have limited knowledge of outcomes and high threshold for resuscitation. Ethical confrontation is more common among nurses with poor knowledge about outcomes, and less common in residents with poor knowledge about outcomes.

Instrumented staircase for kinetic analyses of upper-and lower-limb function during stair gait

The paper describes the design, technical characteristics and first results of an adjustable staircase with commercial force plates embedded in the steps and custom force transducers as part of the handrail supports. For the railing assembly, the greatest errors (< 10% of maximum signal) and cross-talk range (0.58-6.74%) were in the medial-lateral direction and were corrected using a calibration matrix. Power spectral density analyses showed free vibration frequency responses for both the railing (15 Hz) and steps (38.6 Hz) that were relatively distinct from lower applied forces recorded during stair ascent. The creation of standardised filtering protocols was therefore possible to provide step reaction force signals identical to the literature and examples of upper-limb reaction forces that have not been shown before. Such a staircase will allow a more complete study of full body contributions to stair walking across various subject populations.