Howard Chen

Characterization of printable cellular micro-fluidic channels for tissue engineering

Tissue engineering has been a promising field of research, offering hope of bridging the gap between organ shortage and transplantation needs. However, building three-dimensional (3D) vascularized organs remains the main technological barrier to be overcome. One of the major challenges is the inclusion of a vascular network to support cell viability in terms of nutrients and oxygen perfusion. This paper introduces a new approach to the fabrication of vessel-like microfluidic channels that has the potential to be used in thick tissue or organ fabrication in the future. In this research, we investigate the manufacturability of printable micro-fluidic channels, where micro-fluidic channels support mechanical integrity as well as enable fluid transport in 3D. A pressure-assisted solid freeform fabrication platform is developed with a coaxial needle dispenser unit to print hollow hydrogel filaments. The dispensing rheology is studied, and effects of material properties on structural formation of hollow filaments are analyzed. Sample structures are printed through the developed computer-controlled system. In addition, cell viability and gene expression studies are presented in this paper. Cell viability shows that cartilage progenitor cells (CPCs) maintained their viability right after bioprinting and during prolonged in vitro culture. Real-time PCR analysis yielded a relatively higher expression of cartilage-specific genes in alginate hollow filament encapsulating CPCs, compared with monolayer cultured CPCs, which revealed that printable semi-permeable micro-fluidic channels provided an ideal environment for cell growth and function.

Accuracy and repeatability of an inertial measurement unit system for field-based occupational studies

Abstract The accuracy and repeatability of an inertial measurement unit (IMU) system for directly measuring trunk angular displacement and upper arm elevation were evaluated over eight hours (i) in comparison to a gold standard, optical motion capture (OMC) system in a laboratory setting, and (ii) during a field-based assessment of dairy parlour work. Sample-to-sample root mean square differences between the IMU and OMC system ranged from 4.1° to 6.6° for the trunk and 7.2°–12.1° for the upper arm depending on the processing method. Estimates of mean angular displacement and angular displacement variation (difference between the 90th and 10th percentiles of angular displacement) were observed to change <4.5° on average in the laboratory and <1.5° on average in the field per eight hours of data collection. Results suggest the IMU system may serve as an acceptable instrument for directly measuring trunk and upper arm postures in field-based occupational exposure assessment studies with long sampling durations. Practitioner Summary: Few studies have evaluated inertial measurement unit (IMU) systems in the field or over long sampling durations. Results of this study indicate that the IMU system evaluated has reasonably good accuracy and repeatability for use in a field setting over a long sampling duration.

A comparison of instrumentation methods to estimate thoracolumbar motion in field-based occupational studies

The performance of an inertial measurement unit (IMU) system for directly measuring thoracolumbar trunk motion was compared to that of the Lumbar Motion Monitor (LMM). Thirty-six male participants completed a simulated material handling task with both systems deployed simultaneously. Estimates of thoracolumbar trunk motion obtained with the IMU system were processed using five common methods for estimating trunk motion characteristics. Results of measurements obtained from IMUs secured to the sternum and pelvis had smaller root-mean-square differences and mean bias estimates in comparison to results obtained with the LMM than results of measurements obtained solely from a sternum mounted IMU. Fusion of IMU accelerometer measurements with IMU gyroscope and/or magnetometer measurements was observed to increase comparability to the LMM. Results suggest investigators should consider computing thoracolumbar trunk motion as a function of estimates from multiple IMUs using fusion algorithms rather than using a single accelerometer secured to the sternum in field-based studies.

Evaluation of four sensor locations for physical activity assessment.

Direct measurements of physical activity (PA) obtained with inertial measurement units (IMUs) secured to the upper arms and trunk of 36 registered nurses working a full shift were compared to measurements obtained with a commercially-available PA monitor (ActiGraph wGT3X-BT) worn at the waist. Raw accelerations from each device were summarized into PA counts/min and metabolic equivalent (METs) categories using standard definitions. Differences between measurements were examined using repeated measures one-way analyses of variance (ANOVA) and agreement was assessed using Bland-Altman plots. Statistically significant differences were observed between all sensor locations for all PA summary metrics except for between the left and right arm for percentages of work time in the light and moderate counts/min categories. Bland-Altman plots suggested limited agreement between measurements obtained with the IMUs and measurements obtained with the wGT3X-BT waist-worn PA monitor. Results indicate that PA measurements vary substantially based on sensor location.

Working postures and physical activity among registered nurses.

Nurses report a high prevalence of musculoskeletal discomfort, particularly of the low back and neck/shoulder. This study characterized the full-shift upper arm and trunk postures and movement velocities of registered nurses using inertial measurement units (IMUs). Intensity of occupational physical activity (PA) was also ascertained using a waist-worn PA monitor and using the raw acceleration data from each IMU. Results indicated that nurses spent a relatively small proportion of their work time with the arms or trunk in extreme postures, but had few opportunities for rest and recovery in comparison to several other occupational groups. Comparisons between nurses in different PA groups suggested that using a combination of accelerometers secured to several body locations may provide more representative estimates of physical demands than a single, waist-worn PA monitor. The findings indicate a need for continued field-based research with larger sample sizes to facilitate the development of maximally effective intervention strategies.

A Comparison of Examination Equipment Used During Common Clinical Ophthalmologic Tasks

OCCUPATIONAL APPLICATIONS Ophthalmologists and other eye-care physicians frequently use clinical examination equipment that restricts access to patients and requires the adoption of sustained, non-neutral working postures of the neck and shoulders. The use of ergonomic principles in the design of examination equipment could help reduce these physical demands, which may be partly responsible for the high prevalence of neck and shoulder pain among ophthalmologists. This study compared the effects of a set of this alternative “ergonomic” equipment to a set of conventional equipment on measures of neck and shoulder muscle activity and upper arm posture during simulations of common clinical ophthalmologic tasks. Results suggested that some aspects of the alternative equipment may help reduce exposures to sustained, non-neutral working postures of the neck and shoulder among ophthalmologists. Ophthalmologists and other eye-care physicians may consider implementing similar alternative equipment interventions into their practices. TECHNICAL ABSTRACT Background: Ophthalmologists report a high prevalence of work-related musculoskeletal symptoms, particularly of the neck and shoulders. Improving the design of equipment used in the clinical environment may reduce exposures to physical risk factors (e.g., sustained muscular exertions and non-neutral postures) associated with neck and shoulder pain among ophthalmologists. Purpose: This study compares estimates of neck and shoulder muscle activity and upper arm posture during use of conventional and alternative examination equipment common in clinical ophthalmologic practice. Methods: Fifteen ophthalmologists performed one mock clinical examination using conventional equipment and one mock clinical examination using alternative equipment with the potential to reduce exposure to sustained muscular exertions and non-neutral upper arm postures. The alternative equipment included a slit lamp biomicroscope with inclined viewing oculars, adjustable elbow supports, and a wider tabletop with more room for supporting the arms in comparison to the conventional slit lamp biomicroscope. A wireless binocular indirect ophthalmoscope was also evaluated that had a more even weight distribution than the conventional design. Measurements of upper trapezius and anterior deltoid muscle activity, upper arm posture, and perceived usability were used to compare the conventional and alternative equipment. Results: In comparison to the conventional slit lamp biomicroscope, the alternative slit lamp biomicroscope led to (i) 12% to 13% reductions in upper trapezius muscle activity levels, (ii) a 9% reduction in left anterior deltoid muscle activity levels, and (iii) a 15% reduction in the percentage of work time spent with the left upper arm elevated in positions greater than 60º. In addition, participants rated the comfort and adjustability of both the alternative slit lamp biomicroscope and binocular indirect ophthalmoscope more favorably than the conventional equipment. Conclusions: The results suggest that the alternative slit lamp biomicroscope may help to reduce overall muscular demands and non-neutral postures of the neck and shoulder region among ophthalmologists.

Characterizing exposure to physical risk factors among reforestation hand planters in the Southeastern United States

Low back and neck/shoulder pain are commonly reported among reforestation hand planters. While some studies have documented the intensive cardiovascular demands of hand planting, limited information is available regarding exposures to physical risk factors associated with the development of musculoskeletal disorders (MSDs) among hand planters. This study used surface electromyography (EMG) and inertial measurement units (IMUs) to characterize the muscle activation patterns, upper arm and trunk postures, movement velocities, and physical activity (PA) of fourteen Southeastern reforestation hand planters over one work shift. Results indicated that hand planters are exposed to physical risk factors such as extreme trunk postures (32.5% of time spent in ≥45° trunk flexion) and high effort muscle exertions (e.g., mean root-mean-square right upper trapezius amplitude of 54.1% reference voluntary exertion) that may place them at increased risk for developing MSDs. The findings indicate a need for continued field-based research among hand planters to identify and/or develop maximally effective interventions.

Usability Evaluation and Implementation of a Health Information Technology Dashboard of Evidence-Based Quality Indicators

Health information technology dashboards that integrate evidence-based quality indicators can efficiently and accurately display patient risk information to promote early intervention and improve overall quality of patient care. We describe the process of developing, evaluating, and implementing a dashboard designed to promote quality care through display of evidence-based quality indicators within an electronic health record. Clinician feedback was sought throughout the process. Usability evaluations were provided by three nurse pairs and one physician from medical-surgical areas. Task completion times, error rates, and ratings of system usability were collected to compare the use of quality indicators displayed on the dashboard to the indicators displayed in a conventional electronic health record across eight experimental scenarios. Participants rated the dashboard as “highly usable” following System Usability Scale (mean, 87.5 [SD, 9.6]) and Poststudy System Usability Questionnaire (mean, 1.7 [SD, 0.5]) criteria. Use of the dashboard led to reduced task completion times and error rates in comparison to the conventional electronic health record for quality indicator–related tasks. Clinician responses to the dashboard display capabilities were positive, and a multifaceted implementation plan has been used. Results suggest application of the dashboard in the care environment may lead to improved patient care.

Comparing Fatigue, Physical Activity, and Posture among Nurses in Two Staffing Models

The high variability and complexity of patient care needs have led to the development of various nurse staffing models. While “pod nursing” has been observed to result in favorable outcomes such as improved patient access, professional communication, and job satisfaction among nurses, the effects of pod nursing on important metrics related to nurse health have not been previously reported. This study compared self-reported estimates of fatigue and directly measured estimates of physical activity and exposure to non-neutral working postures of the trunk and upper arms obtained from registered nurses working in a pod nursing model to estimates obtained from registered nurses working in a total patient care (TPC) model. Results suggested that nurses working in the pod model had similar exposures to nurses working in the TPC model. Consistent with previous work, nurses were observed to spend a small percentage of work time performing moderate or greater intensity physical activity.

Development of a Multi-Arm Bioprinter for Hybrid Tissue Engineering

This paper highlights the development of a multi-arm bioprinter (MABP) capable of concurrent deposition of multiple materials with independent dispensing parameters including deposition speed, material dispensing rate and frequency for functional zonal-stratified articular cartilage tissue fabrication. The MABP consists of two Cartesian robots mounted in parallel on the same mechanical frame. This platform is used for concurrent filament fabrication and cell spheroid deposition. A single-layer structure is fabricated and concurrently deposited with spheroids to validate this system. Preliminary results showed that the MABP was able to produce filaments and spheroids with well-defined geometry and high cell viability. The resulting filament width has a variation of +/-170 μm and the center-to-center filament distance was within 100 μm of the specified distance. This fabrication system is aimed to be further refined for printing structures with varying porosities to mimic the natural cartilage structure in order to produce functional tissue-engineered articular cartilage using cell spheroids containing cartilage progenitor cells (CPCs).Copyright