Braking electric-powered wheelchairs: effect of braking method, seatbelt, and legrests

Factors associated with injury severity among users of powered mobility devices

Objective

To examine the features of powered mobility device-related injuries and identify the predictors of injury severity in such settings.

Methods

Emergency Department-based Injury In-depth Surveillance data from 2011 to 2018 were used in this retrospective study. Participants were assigned to the mild/moderate and severe groups based on their excess mortality ratio–adjusted injury severity score and their general injury-related factors and injury outcome-related factors were compared.

Results

Of 407 patients, 298 (79.2%) were assigned to the mild/moderate group and 109 (26.8%) to the severe group. The severe group included a higher percentage of patients aged 70 years or older (43.0% vs. 59.6%, P=0.003), injuries incurred in the daytime (72.6% vs. 82.4%, P=0.044), injuries from traffic accidents and falls (P=0.042), head injuries (38.6% vs. 80.7%, P<0.001), torso injuries (16.8% vs. 32.1%, P=0.001), overall hospital admission (28.5% vs. 82.6%, P<0.001), intensive care unit admission (1.7% vs. 37.6%, P<0.001), death after admission (1.4% vs. 10.3%, P=0.034), and total mortality (0.7% vs. 9.2%, P<0.001). The odds ratios (ORs) for injury severity were as follows: age 70 years or older (OR, 2.124; 95% confidence interval [CI], 1.239–3.642), head injury (OR, 10.441; 95% CI, 5.465–19.950), and torso injury (OR, 4.858; 95% CI, 2.495–9.458).

Conclusion

The proportions of patients aged 70 years or older, head and torso injuries, injuries from traffic accidents and falls, and injuries in the daytime were higher in the severe group. Our results highlight the need for measures to address these factors to lower the incidence of severe injuries.

Acute injuries resulting from accidents involving powered mobility devices (PMDs)-Development and outcomes of PMD-related accidents in Sweden

Objective: Powered mobility devices (PMDs) are commonly used as aids for older people and people with disabilities, subgroups of vulnarable road users (VRUs) who are rarely noted in traffic safety contexts. However, the problem of accidents involving PMD drivers has been reported in many countries where these vehicles have become increasingly popular. The aim of this study is to extract and analyze national PMD-related accident and injury data reported to the Swedish Traffic Accident Data Acquisition (STRADA) database. The results will provide valuable insight into the risks and obstacles that PMD drivers are exposed to in the traffic environment and may contribute to improving the mobility of this group in the long term. Methods: The current study is based on data from 743 accidents and 998 persons. An analysis was performed on a subset of data (N = 301) in order to investigate the development of accidents over a period of 10 years. Thereafter, each accident in the whole data set was registered as either single (N = 427) or collision (N = 315). Results: The results show that there was a 3-fold increase in the number of PMD-related accidents reported to STRADA during the period 2007-2016. With regard to single accidents, collisions, as well as fatalities, the injury statistics were dominated by males. Single accidents were more common than collisions (N = 427 and N = 316, respectively) and the level of injury sustained in each type of accident is on par. The vast majority of single accidents resulted in the PMD driver impacting the ground (87%), due to either PMD turnover (71%) or the driver falling out of the PMD (16%). The reason for many of the single accidents was a difference in ground level (34%, typically a curb). Cars, trucks, or buses were involved in 67% of collision events; these occured predominantly at junctions or intersections (70%). Abbreviated Injury Scale (AIS) 3+ injuries were dominated by hip and head injuries in both single accidents and collision events. Conclusions: The present study shows that further research on PMD accidents is required, with regard to both single accidents and collision events. To ensure that appropriate decisions are made, future work should follow up on injury trends and further improve the quality of PDM-related accident data. Improved vehicle stability and design, increased usage of safety equipment, proper training programs, effective maintenance services, and development of a supporting infrastructure would contribute to increased safety for PMD drivers.

Automatic Detection and Classification of Unsafe Events During Power Wheelchair Use

Using a powered wheelchair (PW) is a complex task requiring advanced perceptual and motor control skills. Unfortunately, PW incidents and accidents are not uncommon and their consequences can be serious. The objective of this paper is to develop technological tools that can be used to characterize a wheelchair user’s driving behavior under various settings. In the experiments conducted, PWs are outfitted with a datalogging platform that records, in real-time, the 3-D acceleration of the PW. Data collection was conducted over 35 different activities, designed to capture a spectrum of PW driving events performed at different speeds (collisions with fixed or moving objects, rolling on incline plane, and rolling across multiple types obstacles). The data was processed using time-series analysis and data mining techniques, to automatically detect and identify the different events. We compared the classification accuracy using four different types of time-series features: 1) time-delay embeddings; 2) time-domain characterization; 3) frequency-domain features; and 4) wavelet transforms. In the analysis, we compared the classification accuracy obtained when distinguishing between safe and unsafe events during each of the 35 different activities. For the purposes of this study, unsafe events were defined as activities containing collisions against objects at different speed, and the remainder were defined as safe events. We were able to accurately detect 98% of unsafe events, with a low (12%) false positive rate, using only five examples of each activity. This proof-of-concept study shows that the proposed approach has the potential of capturing, based on limited input from embedded sensors, contextual information on PW use, and of automatically characterizing a user’s PW driving behavior.

Driving performance in a power wheelchair simulator

PURPOSE

A power wheelchair simulator can allow users to safely experience various driving tasks. For such training to be efficient, it is important that driving performance be equivalent to that in a real wheelchair. This study aimed at comparing driving performance in a real and in a simulated environment.

METHOD

Two groups of healthy young adults performed different driving tasks, either in a real power wheelchair or in a simulator. Smoothness of joystick control as well as the time necessary to complete each task were recorded and compared between the two groups. Driving strategies were analysed from video recordings. The sense of presence, of really being in the virtual environment, was assessed through a questionnaire.

RESULTS

Smoothness of joystick control was the same in the real and virtual groups. Task completion time was higher in the simulator for the more difficult tasks. Both groups showed similar strategies and difficulties. The simulator generated a good sense of presence, which is important for motivation.

CONCLUSIONS

Performance was very similar for power wheelchair driving in the simulator or in real life. Thus, the simulator could potentially be used to complement training of individuals who require a power wheelchair and use a regular joystick. [Box: see text].

Review of the Use of Physical Restraints and Lap Belts With Wheelchair Users

Wheelchair-related physical restraints, lap belts, and other alternatives are intended to provide safe and adequate seating and mobility for individuals using wheelchairs. Physical restraints and lap belts are also helpful for positioning people in their wheelchairs to reduce the risk of injury during wheelchair tips and falls. However, when used improperly or in ways other than intended, injury or even death can result. Although widely prescribed, little evidence is available to direct professionals on the appropriate use of these restraints and lap belts and for whom these restraints are indicated. The purpose of this study was to conduct a review of available literature from 1966-2006 to identify the risks and benefits associated with lap belts while seated in wheelchairs. Twenty-five studies that met the inclusion criteria were reviewed. Nine studies reported the frequency of asphyxial deaths caused by physical restraints, nine studies reported the long-term complication and indirect adverse effects of physical restraints and lap-belt use, and seven studies reported the benefits of physical restraints and lap belts with individuals using wheelchairs. Despite the weak evidence, the results suggest a considerable number of deaths from asphyxia caused by the use of physical restraints occurred each year in the U.S. The majority of the deaths occurred in nursing homes, followed by hospitals, and then the home of the person. Most deaths occurred while persons were restrained in wheelchairs or beds. Based on that, caution needs to be exercised when using restraints or positioning belts. In addition, other seating and environment alternatives should be explored prior to using restraints or positioning belts, such as power wheelchair seating options. Positioning belts may reduce risk of falls from wheelchairs and should be given careful consideration, but caution should be exercised if the individual cannot open the latch independently. Also, the duration of use of the physical restraint should be limited. Therefore, several factors should be considered when devising a better quality of physical-restraint services provided by health care professionals. These efforts can lead to improved safety and quality of life for individuals who use wheelchairs.

Engineering better wheelchairs to enhance community participation

With about 2.2 million Americans currently using wheeled mobility devices, wheelchairs are frequently provided to people with impaired mobility to provide accessibility to the community. Individuals with spinal cord injuries, arthritis, balance disorders, and other conditions or diseases are typical users of wheelchairs. However, secondary injuries and wheelchair-related accidents are risks introduced by wheelchairs. Research is underway to advance wheelchair design to prevent or accommodate secondary injuries related to propulsion and transfer biomechanics, while improving safe, functional performance and accessibility to the community. This paper summarizes research and development underway aimed at enhancing safety and optimizing wheelchair design.

Influence of wet surfaces and fall height on pediatric injury risk in feet-first freefalls as predicted using a test dummy

INTRODUCTION

Falls are a major cause of morbidity and mortality in children, but are also reported falsely in child abuse. Therefore, it is of interest to understand those factors which may lead to a higher likelihood of injury in a feet-first freefall.

METHODS

We used laboratory freefall experiments and a 3-year-old Hybrid III anthropomorphic test dummy (ATD) to assess head and femur injury risk. Wet and dry linoleum impact surfaces were used from three fall heights: 22, 35 and 47 in.

RESULTS

For a given fall height, dry surfaces were associated with higher head injury criteria (HIC) values than wet surfaces. Changes in fall height 22-47 in. did not significantly affect HIC values for falls onto either surface. Generally, compressive and bending femur loading increased significantly for wet as compared to dry linoleum.

CONCLUSIONS

In simulated feet first freefall experiments up to 47 in. using a 3-year-old test dummy, a low risk of contact type head injury and femur fracture was found. However, both fall height and surface conditions influenced femur loading and head injury measures. Future efforts should explore the risk of head injury associated with angular acceleration in freefalls.

Influence of fall height and impact surface on biomechanics of feet-first free falls in children

OBJECTIVE

The objectives of our study were to assess biomechanics associated with feet-first free falls in 3-year-old children and to investigate the influence of impact surface type and fall height on key biomechanical measures associated with injury risk.

METHODS

Repeatable feet-first free fall experiments were conducted in a laboratory mock-up environment using an instrumented Hybrid II 3-year-old test dummy. Impact surface type and fall height were varied to examine their influence on biomechanical measures.

RESULTS

Feet-first falls from short distances (27 in.) (0.69 m) were found to have a low risk of contact-type head injury, regardless of impact surface type. When comparing different types of impact surfaces in a 27 in. (0.69 m) fall, head acceleration associated with falls onto playground foam was significantly less than that associated with falls onto wood, linoleum or padded carpet. For falls onto playground foam, femoral compressive loads and bending moments were found to significantly increase as fall height increased.

CONCLUSIONS

Impact surface type and fall height were found to influence biomechanics associated with injury risk in feet-first free falls as assessed through experimental mock-ups using an instrumented child test dummy. Feet-first falls from short distances (27 in.) (0.69 m) were associated with a low risk of contact-type head injury as assessed using HIC, irrespective of impact surface type.

Tips and falls during electric-powered wheelchair driving: effects of seatbelt use, legrests, and driving speed

OBJECTIVE

To measure the response of a test dummy while traversing common obstacles encountered by users of electric-powered wheelchairs (EPWs) to determine whether optimal wheelchair fit, use of seatbelts, and driving speed affect the frequency and severity of EPW tips and falls.

DESIGN

Repeated-measures comparison study.

SETTING

Constructed environment both in and around a Veterans Affairs medical center.

PARTICIPANT

A 50th percentile Hybrid II anthropometric test dummy (ATD) was used to simulate a person driving an EPW.

INTERVENTIONS

The ATD was driven in 4 different EPWs over commonly encountered obstacles at speeds of 1 and 2m/s, with and without the use of a seatbelt, and at varying legrest heights.

MAIN OUTCOME MEASURES

The response and motion of the ATD were observed and recorded as no fall, loss of control (the ATD falls forward or sideways but remains in the EPW), the ATD falls out of the EPW, or the EPW tips completely.

RESULTS

A total of 97 adverse events out of 1700 trials were recorded: 88 were losses of control (instability) and 9 were ATD falls. No complete tips of any EPW occurred. Univariate statistical analysis indicated a significant relationship between the adverse events and the use of seatbelts, legrest condition, and test obstacles (P<.05). A mixed-model analysis confirmed the significant relationships between the adverse events and the use of seatbelts, legrest condition, and test obstacles (P<.05). However, the mixed model indicated that (1) there was no significant relationship between the adverse events and driving speed and (2) no one obstacle was designated to be the most problematic.

CONCLUSION

Persons who use EPWs should use seatbelts and legrests while driving their EPWs, and clinicians should include common driving tasks when assessing the proper set-up of EPWs.

Kinematic comparison of Hybrid II test dummy to wheelchair user

Hybrid test dummies provide a safe alternative to human subjects when investigating mechanisms of wheelchair tips and falls. The data that researchers acquire from these test dummies are more useful if the test dummy represents the population being studied. The goal of this study was to measure the validity of a 50th percentile Hybrid II test dummy (HTD) as an accurate representation of a wheelchair user. A test pilot with T8 paraplegia due to traumatic spinal cord injury served as a basis for validation. Simple modifications were made to the HTD to approximate the trunk stability characteristics of a person with a spinal cord injury. An HTD, a modified HTD, and a human test pilot were seated in an electric-powered wheelchair and several braking tests performed. The standard HTD underestimated the kinematics when compared to the test pilot. The modified HTD had less trunk stability than the standard HTD during all braking methods. The modified HTD and wheelchair test pilot had similar trunk stability characteristics during kill switch and joystick full-reverse braking conditions. The modified HTD is a satisfactory representation of a wheelchair user with a spinal cord injury; however, the modified test dummy underestimates the trunk dynamics during the less extreme joystick release braking. Work should continue on the development of a low-speed, low-impact test dummy that emulates the wheelchair user population.