The Impact of Transfer Setup on the Performance of Independent Transfers: Phase I Final Report

Chapter 4: Implications for standards and design

Expert opinion on the current knowledge

Our review of the literature revealed a small number of studies that directly relate to the influence of transfer setup on performing independent transfers and thus points to a critical need for more studies in this area. All the studies identified also involved small groups of subjects and all of them included either subjects with SCI or unimpaired subjects except for one study (8) and thus a vast majority of them would not be generalizable to other populations who do independent transfers.  There is not enough evidence in the literature or studies at the present time to determine the limits of setup that would make transfers in the built environment accessible to a majority of wheelchair users. 

Transfer boards are a common aid used to facilitate transfers for those who have limited arm strength and/or situations where the height differential between the initial and target seats or gap difference is too large for them to negotiate without assistance.  As the latter is a function of environment, we hoped to find studies that addressed the use of transfer boards or other similar technologies for circumventing environmental barriers. 

In addition to transfer aids, experts also felt none of the original research studies were relevant to the issue of constrained space available for transfers.  This item was geared to identifying issues concerning transfers into/out of an airplane seat, amusement park ride, or motor vehicle, by which the individual has a limited space to position the feet or legs when moving over to or from the target surface.

All the studies were conducted in laboratory settings versus ‘real-world’ environments with experimental setups that appeared free from any barriers that would limit leg/foot placement.  Proper positioning of the feet is believed clinically to be a very important consideration for setting up for a safe and efficient transfer (9, 10) and thus may be critical for space planning in public areas where transfers are expected.

Physical obstacles and barriers are commonly observed for transfers to and from airline seats (e.g. arm rest is fixed) and amusement park rides (e.g. ride side rail/guard is fixed).  Boats, kayaks, and other sorts of recreational equipment pose a similar barrier to transfers.  None of the research identified described how well individuals are able to overcome physical barriers in between the wheelchair and target surfaces.  In our own observations we see individuals going around or over the top of obstacles (e.g. transferring onto the obstacle first and then down into the seat/surface).  The later is an example of a scenario that was scored separately for the item ‘number of transfers to go from the initial location to the final destination’ which was another aspect of setup reviewers identified as lacking evidence.  There is no evidence suggesting how large (e.g. how high, tall and wide) an obstacle can be and still be accessible to a majority of wheelchair users. 

Another area lacking sufficient evidence concerns the location and characteristics of effective supports to aid with transferring.  This item encompassed for example the use of handholds, grab bars, or other environmental fixtures designed to facilitate a transfer to a target surface. 

Evaluation of transfers

Our results clearly indicate that height above and below WMD seat height, gaps and obstacles can pose serious transfer-related accessibility problems for WMD users. Based on the guideline criteria in Table 13 pertaining to transfer heights alone (e.g. no gap and no obstacle), 15% of the sample could not transfer to a surface 24” high or higher and 57% of the sample could not transfer to a surface 14” high or lower. Note that none of the subjects had WMD with seats lower than 17 in which explains the lower percentages of subjects who could transfer to the recommended maximum low transfer heights compared to the higher heights (Table 13).  A majority of our subjects (92% of the sample, CI[86%,96%]) managed a height at 22” (51cm) with no gap in place which is more similar to their own seat height. Thus it follows that transfers are the easiest to achieve when the height of surface to transfer onto is at the same height as the WMD (seat height + cushion). This is consistent with other research results that have found that level transfers require less exertion of the upper limb (3, 4, 6) . Study results suggest that an element’s height should fall within a range of 19”-23” to include 88% and within 21”-23” to include 90% of our sample.

A 2” transfer step height was acceptable for 86% of our sample; while current guidelines for pools and spas say step heights up to 8” are acceptable (11).  It’s important to note that the step height in this study was a calculated value determined by subtracting the WMD seat height from the maximum (or minimum) target surface height to obtain a relative height difference.  The 8” step in the pool/spa guideline refers to the height difference between two flat, step-like smooth surfaces and the wheelchair is not part of the transfer process. These types of transfers were not evaluated in our study.  A future study is being developed to further evaluate transfer step possibilities (e.g. design features) for various kinds of transfer elements (e.g. amusement park rides) and allowances (e.g. height differences for multi-step or multi-tiered transfers).

Although gap has not been researched specifically (12), it is intuitive that the closer one is to the surface the easier it will be to move your body across. Our results also showed that fewer subjects were able to attain larger height differentials with a gap in place as compared to the setup without the gap. Therefore, attaining transfers at different heights than the WMD seat height across a gap is even more complicated.

Our results also showed that in terms of minimum space required for the transfer, the guidelines are insufficient (Table 12). Mainly because our subjects positioned their device at an angle instead of the parallel approach the guidelines suggest as well as the likelihood that today’s WMD’s vary more in size (13). ADAAG guidelines for pools and spas have recognized that people do not necessarily transfer parallel to the transfer target and suggest a clear deck area of 60” by 60” for transfer walls (11). This area could better accommodate our results’ mean plus one standard deviation of the area needed for our sample.

Introducing the side guard obstacle posed a significant barrier to transfer greatly reducing the number of subjects who were able to attain transfers at any height and/or gap. Despite the absence of recommendations regarding obstacles for transferring in the recreational facilities, guidelines for aircraft transportation for wheelchair users recognize that when the seat has a fixed armrest transferring is further complicated but it does not specifically recommend that armrest should be able to pivot (14). ADAAG guidelines for pools and spas suggest that if the lift seat has armrests, these need to be able to pivot so people can transfer from/to their WMD and the lift more easily (11). Our data suggest that adding a grab bar in front of the transfer seat helps to overcome a 6” obstacle and thus might be a worthwhile design criteria to include in future revisions of the guidelines.  When the front grab bar was added in conjunction with the side guard, it was used more often but it did not help as many subjects to attain a higher or lower transfer compared to using the front bar without the obstacle in place. There was a high frequency of lateral grab bar use and front grab bar/lateral grab bar together upon initial hand placement. However, a decreased frequency of the use of the lateral bar was found in the grab bar protocol due to increased frequency of front bar use.  Bars and the side guard were used often for repositioning the trunk and buttocks onto the platform after landing however the frequency of which these bars were used for this purpose was not documented.

Accessibility guidelines concerning handholds and grab bars where transfers are expected are not very detailed in general.  Details are absent in the guidelines for amusement park rides and briefly referred to in the play area guidelines which suggests that transfer elements should have open sides (or an open side), back supports, and hand supports to help facilitate easy transfer and access (15). There is a general recommendation regarding the height of a horizontal grab bar (parallel to the floor) to be between 33”-36” (83.8-91.4cm) for water stalls, water closets, bathtubs, and bathrooms. Our study suggests that for a horizontal grab bar mounted in front of the element, the ideal height is between 30”-33” (76.2-83.8cm) high.  One reason for the difference in heights between our study and the guidelines could be how the grab bar is used.  In our study, we noted grab bar use for the initial hand placement and when the front bar was part of the set up it was used much more for this purpose than the lateral bar (e.g. this is the reason for the drop in Table 11 results for lateral bar use in the front grab bar protocol).  Bars mounted horizontally on the side of the element may be used more to help with making adjustments onto the element once the initial transfer has occurred.  As our subjects had to enter the station from the side (versus the front) the front bar was a closer handheld to use as opposed to reaching over to the lateral bar.  Because the transfer occurs initially from a seated wheelchair position, a lower bar may help users gain the leverage necessary for lifting the body over to the new surface and back.  The next phase of study will investigate further the usefulness of different type of handhelds and grab bar positioning during transfers.

Many studies have evaluated current accessibility guidelines in terms of space for maneuverability and finding them insufficient for current devices sizes (16-18) . These design parameters of the standard should be revised to reflect the setup of current WMD users as devices have changed since the standards were created in the 1970s. In 25 years, many changes have occurred in WMD users demographics and body sizes, as well as equipment characteristics (13). Equipment characteristics include increased use of positioning systems (e.g. tilt, recline, or combination which increases the effective length of the WMD), use of pressure-relieving cushions, and the availability of a wider range of wheel sizes (13). 

Study limitations

There are several limitations to this study worth noting. A large number of our subjects were veterans who participated in organized sports-related events however we have found that their daily activity levels apart from the time of the event do not differ from adult WMD users who live in community (19).  If comparing the demographics of our sample to LaPlante et al (2010) who reported subject demographics among adult wheelchair users using data obtained by the US Census Bureau we find some similarities and some differences (Table 14).  It is important to note that the LaPlante (2010) statistics are inclusive of full-time, part-time WMD users and those who rely on human assistance for wheeled mobility.  The demographics of our sample resemble closely other studies that have specifically targeted independent mobility users thus further supporting the external validity of our study. For instance, a study that researched minimum space requirements for WMD maneuverability enrolled the majority of their subjects with spinal cord injury followed by central nervous system disorders ( multiple sclerosis, cerebral palsy, and spina bifida) (18). Similarly, a pilot study that investigated environmental barriers and facilitators for wheelchair users had the majority of its subjects with spinal cord injury followed by multiple sclerosis (20). Another study researched the effect of cross-slopes on the mobility of manual wheelchair users and also reported the majority of their subjects having spinal cord injury followed by multiple sclerosis, cerebral palsy, spina bifida, and amputations (21). 

The number of handhelds, their positioning, and how they were used throughout the transfer process were not comprehensively studied.  The lateral grab bar was at a fixed height, diameter, and length and always present on the station.  Only one front grab bar of variable height was introduced as an optional handheld but its horizontal distance from the platform, diameter, and length was fixed.  Its unclear what changes in the ‘fixed’ parameters could further aid users in the transfer process.

Table 14. Comparison between WMD users demographics reported by LaPlante (2010) and our study’s subjects demographics.

a Refer to Table 1 for Other type of self-reported disability in our sample
b Other in Laplante et al (2010) include diabetes, heart trouble, lung or respiratory problems, high blood pressure, blindness or vision problems, broken bone/fracture, cancer, senility/dementia/Alzheimer’s, kidney problems, mental or emotional problem, deafness or hearing problems, mental retardation and others which constituted 24.5% of the 56.5% and were not described in the article.

Table 14 Alternative Text Description: This table gives the comparison between WMD users demographics reported by LaPlante (2010) and our study’s subjects demographics. There are many similarities in the demographics between the two studies. 

Future Work

Bars and the side guard were used often for repositioning the trunk and buttocks onto the platform after landing however their use for this purpose was not documented. Grab bars and handhelds placed in other locations (e.g. in the front, on the sides, overhead, or to the element itself) could have enabled more successful transfers.  The side guard although intended to serve as an obstacle to the transfer was sometimes used to facilitate getting in and out of the station. Future studies should look into the effects of variable ‘side guard’ widths, heights, contours and shapes to see if it such as structure could act more as a benefit versus a hindrance to the transfer. The next phase of study will research alternative hand placement options for both initial hand placement and repositioning upon landing on the target surface. 

Only adult aged WMD users were studied and the sample consisted of a limited number of women and scooter users.  The next phase of study will include children, more women, and scooter users.  There is a lack of information about multi-step or multi-tiered transfers and how they can facilitate a barrier free or more level transfer for certain types of transfer elements (e.g. playground equipment, amusement park rides, medical diagnostic equipment) or places where transfers are expected (e.g. boat docks, airliners, etc.). A workshop and/or discussion panel with stakeholders (i.e. consumers, therapists, manufacturers, researchers, designers and Access Board members) is being planned to determine 1) what efforts should be made to mine the data gathered in the first phase to look at other transfer issues and 2) what other critical issues need to be addressed through research and design development in this area.