Fifteen-minute consultation: Approach to the infant with stridor and suspected laryngomalacia.

Stridor in an infant is a significant clinical sign; the primary objectives are to ensure that the airway is safe and to arrange timely, appropriate management. A structured history, examination and targeted investigations will determine the cause and guide care.Laryngomalacia is the most common cause of stridor in an infant. The stridor tends to start shortly after birth, classically presenting as a positional stridor in the first month, which gradually resolves before 12-18 months of age in mild cases. There is a wide spectrum of severity; few require surgical intervention. This article will outline how the infant is appropriately assessed and managed.

Emergent and urgent ventral hernia repair: comparing recurrence rates amongst procedures utilizing mesh versus no mesh.

BACKGROUND: The decision for emergent and urgent ventral hernia repair (VHR) is driven by acute symptomatology, concern for incarceration and strangulation, and perforation. Although mesh has been established to reduce hernia recurrences, the potential for mesh complications may impact the decision for utilization in emergent repairs. This study evaluates hernia repair outcomes in the emergent setting with/without mesh. METHODS: An IRB-approved review of NSQIP and retrospective chart review data of emergent/urgent VHRs performed between 2013 and 2017 was conducted at a single academic institution. Six-month postoperative emergency department and surgery clinic visits, hospital readmissions, and hernia recurrences were recorded. Patients were grouped based on mesh utilization. Perioperative and outcome variables were compared using Chi-square, Fisher's exact, and t-tests. RESULTS: Among 94 patients, 41 (44%) received mesh; 53 (56%) did not. Synthetic mesh was used in 27 cases (65.9%); bioresorbable or biologic mesh was used in 14 cases (34.1%). ASA class (p = 0.016) was higher in the no-mesh group, as were emergent vs. urgent cases (p ≤ 0.001). Preoperative SIRS/Sepsis, COPD, and diabetes were increased in the no-mesh group. Hernia recurrence was significantly higher in the no-mesh group vs. the mesh group (24.5% vs. 7.3%, p = 0.03). No difference was found in wound complications between groups. ED visits occurred almost twice as often in the mesh group (42% vs. 23%, p = 0.071). Postoperative surgery clinic visits were more frequent among the mesh group (> 1 visit 61% vs. 24%, p = 0.004). CONCLUSIONS: Mesh-based hernia repairs in the urgent/emergent patient population are performed in fewer than half of patients in our tertiary care referral center. Repairs without mesh were associated with over a three-fold increase in recurrence without a difference in the risk of infectious complications. Efforts to understand the rationale for suture-based repair compared to mesh repair are needed to reduce hernia recurrences in the emergent population.

Level of exoskeleton support influences shoulder elevation, external rotation and forearm pronation during simulated work tasks in females.

Despite growing literature, limited research details the influence of passive upper limb exoskeletons on upper limb kinematics. Two bolting tasks and a tracing task were completed at two heights (overhead and between waist and overhead height) for four exoskeleton conditions (no exoskeleton, and 3 levels of exoskeleton assistance) by female participants. Motion capture data, ratings of perceived exertion and discomfort, and task duration were recorded. Exoskeleton condition increased minimum shoulder elevation by 35-36% (Δ10.5-10.7°) at 1.81 kg and 2.72 kg of support, mean shoulder external rotation by 316% (Δ24.6°) at 0.91 kg of support and mean forearm pronation by 30.9% (Δ14.6°) at 0.91 kg of support. Exoskeleton condition reduced ratings of perceived exertion and discomfort, but not significantly. Task duration was unaffected. Exoskeleton use at any of three different settings modestly affected some joint kinematics for the tasks examined, which may merit consideration when deciding on occupational exoskeleton implementation.

Regional Electromyography of the Infraspinatus and Supraspinatus Muscles During Standing Isometric External Rotation Exercises.

BACKGROUND: Whole-muscle electromyography (EMG) data of the rotator cuff support external rotation (ER) strengthening exercises during shoulder rehabilitation. However, distinct neuroanatomic regions in the supraspinatus and infraspinatus exist. Differences in regional muscle activity occur during rehabilitation exercises, but little information is available for ER exertions. HYPOTHESIS: Regional infraspinatus and supraspinatus muscle activity during standing ER exertions will differ with posture and intensity. STUDY DESIGN: Descriptive laboratory study. LEVEL OF EVIDENCE: Level 5. METHODS: Twenty healthy individuals (12 men, 8 women) participated. Fine wire electrodes were inserted into 2 supraspinatus and 3 infraspinatus muscle regions. EMG data were recorded during standing isometric ER exertions at 2 intensities (maximal, submaximal) and in 7 postures defined by the angle (0°, 30°, 90°) and plane (abduction, scaption, flexion) of arm elevation. EMG data were normalized to maximum voluntary isometric contraction (% MVIC) to examine the influences of posture, intensity and their interaction on muscle activity. RESULTS: Superior infraspinatus activity was higher in 0° of elevation (50.9% ± 5.7% MVIC) versus 30° of flexion (37.4% ± 3.9% MVIC) at maximal intensity. Inferior infraspinatus activity was higher in 90° of scaption (max = 59.8% ± 2.8% MVIC, submax = 29.4% ± 1.9% MVIC) versus 0° of elevation (max = 42.3% ± 4.5% MVIC, submax = 22.4% ± 2.8% MVIC) (P = 0.02, P = 0.05, respectively). Anterior supraspinatus activity was highest in 90° of adbuction (max = 61.6% ± 3.1% MVIC; submax = 39.1% ± 3.8% MVIC) and lowest in 30° of flexion (max = 29.0% ± 3.4% MVIC, submax = 15.6% ± 1.7% MVIC) and 90° of flexion (max = 34.6% ± 2.4% MVIC, submax = 14.8% ± 1.9% MVIC). Posterior suprasptinatus activity was lowest in 0° of elevation (34.2% ± 3.0% MVIC), 30° of flexion (33.0% ± 3.6% MVIC) and highest in 90° of abduction (56.2% ± 4.1% MVIC) and 90° of scaption (46.7% ± 2.8% MVIC) (all Ps < 0.04). CONCLUSION: Regional infraspinatus and supraspinatus muscle activity differed with posture and intensity. Superior and middle infraspinatus muscle activities were similar across postures, but inferior infraspinatus activity was highest in 90° of arm elevation. Anterior and posterior supraspinatus activities were higher in the abduction and scaption planes, especially at 90° of elevation, as compared with the flexion plane. CLINICAL RELEVANCE: In shoulder rehabilitation of supraspinatus tendon injuries, ER exercises in the flexion plane challenge the whole infraspinatus muscle and require lower supraspinatus muscle activity.

MuscleNET: mapping electromyography to kinematic and dynamic biomechanical variables by machine learning.

Objective.This paper proposes machine learning models for mapping surface electromyography (sEMG) signals to regression of joint angle, joint velocity, joint acceleration, joint torque, and activation torque.Approach.The regression models, collectively known as MuscleNET, take one of four forms: ANN (forward artificial neural network), RNN (recurrent neural network), CNN (convolutional neural network), and RCNN (recurrent convolutional neural network). Inspired by conventional biomechanical muscle models, delayed kinematic signals were used along with sEMG signals as the machine learning model's input; specifically, the CNN and RCNN were modeled with novel configurations for these input conditions. The models' inputs contain either raw or filtered sEMG signals, which allowed evaluation of the filtering capabilities of the models. The models were trained using human experimental data and evaluated with different individual data.Main results.Results were compared in terms of regression error (using the root-mean-square) and model computation delay. The results indicate that the RNN (with filtered sEMG signals) and RCNN (with raw sEMG signals) models, both with delayed kinematic data, can extract underlying motor control information (such as joint activation torque or joint angle) from sEMG signals in pick-and-place tasks. The CNNs and RCNNs were able to filter raw sEMG signals.Significance.All forms of MuscleNET were found to map sEMG signals within 2 ms, fast enough for real-time applications such as the control of exoskeletons or active prostheses. The RNN model with filtered sEMG and delayed kinematic signals is particularly appropriate for applications in musculoskeletal simulation and biomechatronic device control.

Wrapping technique and wrapping height interact to modify physical exposures during manual pallet wrapping.

Occupational tasks often involve musculoskeletal demands that contribute to injury risk. In pallet wrapping tasks, 36% of workplace claims involve over exertion and repetitive exposures (Workplace Safety and Prevention Services, 2012). Tools that modify how the wrap is handled by workers have been introduced to help mitigate over exertion and extreme postures wherever possible. A novel device has been introduced that places the required tension on the roll to mitigate these factors. However, the effect of reducing the necessary tension on the roll during pallet wrapping in limiting muscular demand and extreme postures is unknown. Fourteen healthy university aged participants completed 12 wrapping trials on a simulated pallet (2 repetitions of 2 wrapping techniques (device, hand wrapping) at 3 wrapping heights (low, medium, high)). Surface electromyography (sEMG) was measured on 6 shoulder and 2 low back muscles; anterior and middle deltoids, biceps brachii, infraspinatus, supraspinatus, upper trapezius, and erector spinae (T8 & L3). Kinematic data were collected for the torso and upper extremity and global to torso, and torso to upper arm angles were computed. Repeated measures ANOVAs were performed for the following experimental factors: 1) technique used (device or hand wrapping) and 2) the wrapping height (low, medium, high) for each muscle (8), angle (5), rating of perceived discomfort (1) and rating of perceived exertion (1). Pallet wrapping without a device required greater trunk flexion at lower heights and thoracohumeral elevation at higher wrapping heights as compared to using the device. Muscular activation increased when using the device, specifically at the higher and lower heights. Posture and muscular demands during pallet wrapping tasks are sensitive to both wrapping technique and wrapping height. Ergonomics interventions such as this device may mitigate postural risks associated with manual material handling tasks.

Upper extremity and trunk body segment parameters are affected by BMI and sex.

Although body mass index (BMI) relates to body segment parameters (BSPs), unknowns persist over whether: 1) BSPs relate to BMI group classifications, 2) sex influences BMI/BSP relationships, and 3) simple anthropometric measures sufficiently predict BSPs. Dual energy X-ray absorptiometry (DXA) scans and anthropometric measures were obtained from 76 participants (33M, 43F) of varying body composition. Trunk, neck and head (TNH), arm, forearm and hand masses were obtained from DXA scans and center of mass locations (COM) estimated from geometric models. Groups with larger BMIs had lesser hand and forearm mass (%total body mass; p<0.001) and greater TNH mass (p=0.014). Males had greater hand, forearm, and arm masses (p<0.05). TNH COM was inferior in groups with larger BMI (p<0.01) and in males (p=0.006). In females, arm COM was distal in Obese II/III versus Normal (p=0.024). Two sets of linear models were created to predict BSPs; a simplified set with only BMI, height, weight, sex and mass potential predictors and a complex set with additional anthropometric measures. Complex arm and TNH mass models (arm R2=0.43, TNH R2=0.61) explained more variance than simplified models (arm R2=0.1, TNH R2=0.33). Complex hand mass, forearm mass and TNH COM models had smaller R2 increases versus simplified models (hand=0.05, forearm=0.06, TNH=0.08). Explained variance in forearm COM (R2=0.2) and arm COM (R2=0.27) complex models was low, suggesting a constant may provide reasonable estimates. Certain BSPs can be estimated using simplified measures, whereas prediction of other BSPs markedly improves if additional anthropometric measures are included.

Determining best practices for manual pill crushing through evaluation of upper extremity muscle exposures.

Nurses in long-term care homes often crush pills into a fine powder using a manual pill crushing device. This study provides novel quantitative data on muscle loading experienced during pill crushing. The influence of surface height, number of pills and device orientation were studied in twelve muscles of the upper extremity. Variations in the work surface height and number of pills crushed resulted in static shoulder and forearm muscle activations that exceeded recommended static limits. In most cases, working at approximately a 50th percentile female's hip height (87 cm) reduced the level of muscle activity, often to below the EMG-based exposure limit, compared to higher heights. A perpendicularly oriented device required substantially lower muscle activity in some shoulder muscles, with marginal differences occurring in muscles of the elbow and wrist. These data can inform practical design and work practice recommendations to reduce muscular activity while performing this important healthcare task.

Ratings of perceived fatigue predict fatigue induced declines in muscle strength during tasks with different distributions of effort and recovery.

The purpose of this study was to quantify the relationship between ratings of perceived fatigue (RPF), using a modified Borg CR-10 scale, and muscle fatigue accumulation, as defined by maximal voluntary contraction strength (MVC) declines, during two complex MVC-relative tasks (conditions) that cause muscle fatigue and allow recovery. Nine female participants completed the fatiguing tasks, composed of a series of submaximal, isometric efforts (task plateaus) requiring isometric flexion at the distal interphalangeal joint of the thumb. Significant partial correlations between RPF and MVC, while controlling for task plateau intensity (%MVC), were found in 6/9 participants. A significant linear regression model, explaining 86.2% of the variance in mean MVC decline, was obtained with 3 predictor variables: mean RPF (p < 0.001), Task Plateau (p < 0.001), and the interaction between mean RPF and Task Plateau (RPF × Task Plateau; p = 0.014). The observed linear relationship between RPF and MVC declines, both at the participant and group level support, the use of RPF to estimate the instantaneous fatigue status of the muscle in tasks that allow both muscle fatigue and recovery.

Algorithmically detectable directional changes in upper extremity motion indicate substantial myoelectric shoulder muscle fatigue during a repetitive manual task.

Repetitive workplace tasks are associated with fatigue-induced changes to shoulder muscular strategies, potentially altering kinematics and elevating susceptibility to tissue overexposures. Accessible and reliable methods to detect shoulder muscle fatigue in the workplace are therefore valuable. Detectable changes in joint motion may provide a plausible fatigue identification method. In this investigation, the onset of the first kinematic changes, as identified by a symbolic motion representation (SMSR) algorithm, and the onset of substantial surface electromyography (sEMG) mean power frequency (MPF) fatigue were not significantly different, both occurring around 10% of task duration. This highlights the potential utility of SMSR identified directional changes in joint motion during repetitive tasks as a cue of substantial muscle fatigue, enabling ergonomics responses that can mitigate shoulder muscular fatigue accumulation and its associated deleterious physical effects. Practitioner Summary: The onset of substantial muscle fatigue during a repetitive dynamic task was assessed using kinematics and myoelectric-based techniques. Algorithmically detectable directional changes in upper extremity joint motion occurred with the onset of substantial muscle fatigue, highlighting the potential of this as a useful approach for workplace fatigue identification.

Arm posture influences on regional supraspinatus and infraspinatus activation in isometric arm elevation efforts.

This study aimed to evaluate the effect of arm posture on activation of the anterior and posterior regions of supraspinatus and the superior and middle regions of infraspinatus during resisted isometric arm elevations. Thirty-one healthy participants performed 18 isometric resistance exertions against a force cube in three elevation planes (flexion, scaption, abduction) and three elevation angles (30°, 90°, 150°) in maximal and sub-maximal resistance conditions. EMG data were obtained using four pairs of fine wire electrodes. The mean activation of each region and the activation ratios were compared across postures using ANOVAs. Supraspinatus anterior was significantly more active during abduction and scaption, and in higher elevation angles, while the posterior region showed similar activation levels across postures. Infraspinatus regions were more active during flexion with more relative activation of the infraspinatus superior at 90° flexion. The results suggest that regional activation of supraspinatus and infraspinatus should be considered for assessment and rehabilitation purposes. In any clinical setting where it is important to reduce the stress on the supraspinatus anterior, isometric flexion exercises performed with arm in low elevation angles could provide the opportunity to strengthen the posterior region of supraspinatus with limited stress on the anterior region. Beside external rotation exertions, resisted flexion tests may be useful for evaluation of infraspinatus regions.

Phosphine-mediated partial reduction of alkynes to form both (E)- and (Z)-alkenes.

A mild, phosphine-mediated partial reduction of alkynyl carbonyls to the corresponding alkenes was developed. Tuning of the reaction conditions led to either the (E)- or (Z)-diastereomer with high selectivity. A range of alkynyl esters, amides, and ketones were reduced to form alkenes in good to high yields and with excellent functional group tolerance.

Maximal voluntary isometric contraction tests for normalizing electromyographic data from different regions of supraspinatus and infraspinatus muscles: Identifying reliable combinations.

This study aimed to identify optimal sets of maximal voluntary isometric contractions (MVICs) for normalizing EMG data from anterior and posterior regions of the supraspinatus, and superior, middle and inferior regions of the infraspinatus. 31 right-handed young healthy individuals (15 males, 16 females) participated. EMG activity was obtained from two regions of supraspinatus and three regions of infraspinatus muscles via fine wire electrodes. Participants performed 15 MVIC tests against manual resistance. The EMG data were normalized to the maximum values. Optimal sets of MVIC combinations, defined as those which elicited >90% MVIC activation in the muscles of interest in >80% and >90% of the population, were obtained. EMG data from the inferior region of infraspinatus were removed from analysis due to technical problem. No single test achieved maximal activation of both regions of either the supraspinatus or infraspinatus. Instead, a combination of 6-8 MVICs were required to reach >90% MVIC activation in both parts of those muscles. In all regions of the rotator cuff muscles, the optimal combination was obtained with 8-10 MVICs. The proposed combinations can reduce inter-participant variability in generating maximal activation from different regions of the supraspinatus and infraspinatus muscles.

Application of a symbolic motion structure representation algorithm to identify upper extremity kinematic changes during a repetitive task.

Efficient and holistic identification of fatigue-induced movement strategies can be limited by large between-subject variability in descriptors of joint angle data. One promising alternative to traditional, or computationally intensive methods is the symbolic motion structure representation algorithm (SMSR), which identifies the basic spatial-temporal structure of joint angle data using string descriptors of temporal joint angle trajectories. This study attempted to use the SMSR to identify changes in upper extremity time series joint angle data during a repetitive goal directed task causing muscle fatigue. Twenty-eight participants (15 M, 13 F) performed a seated repetitive task until fatigued. Upper extremity joint angles were extracted from motion capture for representative task cycles. SMSRs, averages and ranges of several joint angles were compared at the start and end of the repetitive task to identify kinematic changes with fatigue. At the group level, significant increases in the range of all joint angle data existed with large between-subject variability that posed a challenge to the interpretation of these fatigue-related changes. However, changes in the SMSRs across participants effectively summarized the adoption of adaptive movement strategies. This establishes SMSR as a viable, logical, and sensitive method of fatigue identification via kinematic changes, with novel application and pragmatism for visual assessment of fatigue development.

Controlled Rh-Catalyzed Mono- and Double-decarbonylation of Alkynyl α-Diones To Form Conjugated Ynones and Disubstituted Alkynes.

A Rh-catalyzed controlled decarbonylation of alkynyl α-diones is described. By using different ligand and solvent combinations, mono- and double-decarbonylation can be selectively achieved to give conjugated ynones and disubstituted alkynes, respectively. A fundamental study on catalytic activation of unstrained C-C bonds under nonoxidative conditions is presented.

Rh-Catalyzed Decarbonylation of Conjugated Ynones via Carbon-Alkyne Bond Activation: Reaction Scope and Mechanistic Exploration via DFT Calculations.

In this full article, detailed development of a catalytic decarbonylation of conjugated monoynones to synthesize disubstituted alkynes is described. The reaction scope and limitation has been thoroughly investigated, and a broad range of functional groups including heterocycles were compatible under the catalytic conditions. Mechanistic exploration via DFT calculations has also been executed. Through the computational study, a proposed catalytic mechanism has been carefully evaluated. These efforts are expected to serve as an important exploratory study for developing catalytic alkyne-transfer reactions via carbon-alkyne bond activation.

Rh(I)-catalyzed decarbonylation of diynones via C-C activation: orthogonal synthesis of conjugated diynes.

Utilization of C-C bond activation as a unique mode of reactivity for constructing C-C bonds provides new strategies for preparing important organic molecules. Development of a Rh(I)-catalyzed C-C activation of diynones to synthesize symmetrical and unsymmetrical conjugated diynes through decarbonylation is reported. This C-C cleavage strategy takes advantage of the innate reactivity of conjugated ynones without relying on any ring strain or auxiliary directing group. This alkynation method also has orthogonal properties compared to typical cross-coupling reactions.