February 2002

Evaluating the Options

By Michelle L. Lange, OTR, ABDA, ATP

Evaluating the options
The pros and cons of dependent mobility systems.

Dependent mobility systems (DMSs) are a group of mobility bases that are designed to look different from manual wheelchairs, offer specialized features that are often unavailable in manual wheelchairs, and rarely provide any self-propulsion. They are sometimes referred to as adapted strollers, but are generally called dependent mobility systems to improve reimbursement. So how do these DMSs compare to standard strollers and manual wheelchairs? This is important to know in order to determine if a DMS is the most appropriate base for the client.

Standard Strollers
Standard strollers are popular for very young children as this equipment is viewed as "normal." Strollers generally fold very easily and are lightweight (particularly umbrella style). The umbrella style often holds hypotonic infants or toddlers very well as their bottoms sink down into a well. Standard strollers often provide various back angles up to full recline, which allow infants to lie down. However, standard strollers provide very little positioning, particularly umbrella strollers, which tend to place the young child in a significant posterior pelvic tilt. These strollers cannot hold medical equipment, such as vent trays and oxygen tanks. Little growth is available, as they are designed for infants to use until they can walk longer distances.

Manual Wheelchairs
The chief advantage of a manual wheelchair (MWC) over a DMS is that a manual wheelchair is generally set up for self-propulsion. Even if clients cannot move the base efficiently, if they can move the MWC, they have some independent mobility. MWCs often have more growth available than DMSs. Aggressive seating options are more readily available in MWCs as well. For the older child, an MWC is more age appropriate-a DMS can appear babyish as it is designed to look more like a stroller than a wheelchair.

On the other hand, fewer MWCs are crash tested than DMSs. An MWC can be more difficult to fold, particularly if a tilt or recline is present. Very few pediatric reclining MWCs are available either. Finally, an MWC can look far more medical than a DMS.

Important Features
Following are some of the major features that should be compared to client needs and should ease the requirements placed on the caregiver:

• Seating Options
  Some DMSs have virtually no seating beyond a sling seat and back. Other systems offer solid linear seats and backs and a variety of components including hip guides, lateral chest pads, anterior trunk supports, seat belts, headrests, armrests, foot plates or platforms, and ankle straps. Typically, these components are mounted to a shell, rather than a wheelchair frame.
• Growth and Weight Limits
  DMSs vary tremendously in available growth in seat width and depth, back height, and lower leg length. Some systems offer very small starting dimensions for the neonate. While others offer limited growth, DMSs have weight limits that may restrict how long a child can continue using the system.
• Weight of DMS
  The weight of the base and seating system also varies with the DMS chosen and the particular configuration specified. As a DMS is usually the first base ordered for a child, the family's home and vehicle are often inaccessible. The family has not yet built a ramp or bought a van. This system is often lifted in and out of vehicles and carried up steps, so the weight of the base is critical.
• Foldability
  Some DMSs fold only with the seating system removed, creating another step for the caregivers. Removing the seat, however, can also greatly reduce the weight of the system, as the caregiver is now lifting two lighter pieces. Some DMSs can be very challenging to fold.
• Tilt and Recline
  The system may offer tilt, recline, or both. Many DMSs have a fixed tilt built into the system. This can be problematic for clients who do not tolerate being seated in a tilt or who have resulting reflex activity from being tilted (ie, symmetrical tonic neck reflex). Systems that offer an adjustable tilt and/or recline vary in the degree of adjustment available. The tilt is usually a component of the base, while the recline is usually built into the seating system. Many clients require a tilt and/or recline to assist in feeding, respiration, or control of specific medical conditions (ie, blood pressure issues, seizures). Very young children are not yet able to sit upright and so require a tilt or recline to compensate. Adjustable tilts and/or reclines are generally available only on pediatric DMSs.
• Rear-facing
  Some DMSs offer a rear-facing feature. Either the stroller handle can be moved from front to back or the entire seating system is removed and then reattached facing the opposite direction. This feature can be critical for infants or young children with medical issues that require close monitoring by the caregiver. This feature is generally available only on pediatric DMSs.
• IV Pole
  Many DMSs offer an IV pole. Not too many clients require an IV very often, but many infants and young children do receive gastrostomy tube feedings. The IV pole is a great place to hang a feeding pump and formula bags.
• Oxygen Tank Holder

Many clients who require a DMS have medical issues that require oxygen. Even if the client requires oxygen only some of the time, the DMS must support the tank. Even though many DMSs offer an oxygen tank holder, they often support only the older, round tanks. If the client uses a different style, the supplier may need to fashion a custom holder or the tank may be hung from the push handles, which can interfere with pushing the base or be unsafe if an infant is in the rear facing position. Regardless of how the tank is attached, do not forget to add this to the weight limit of the base.
• Ventilator Base
  Just as many clients have medical issues requiring oxygen, some clients may be on a ventilator, particularly the neonates just leaving the hospital. Just as with oxygen tanks, ventilators come in a variety of sizes and weights. The platform holding the ventilator is generally placed low and toward the center of the DMS to prevent tipping the base over. Clients who require a ventilator often need oxygen, which makes a rear facing option important so that the caregiver can monitor the child and a tilt/recline to accommodate respiratory needs. The ventilator often affects the weight limit of the base and sometimes is available only on a larger model base. In these cases, a smaller seat is still used if required by client size. Ventilator trays are generally only available on pediatric DMSs.
• Tray
  Some DMSs offer a tray that can be adjusted to remain parallel to the floor if the seat is tilted. This is important with young children, so they do not end up with a lap full of toys. The seat to floor height of many DMSs prevents children from sitting in the base with their knees under a table. In a preschool setting, the tables are also very low. A tray provides a play surface for the child. A tray may also hold food for the child, allowing the DMS to function as a high chair. Most children using DMSs are unable to sit in a standard high chair due to insufficient support. Finally, a tray can provide support to the upper extremities. Many DMSs have no armrests and so provide no support to the arms.
• Crash Tested
  Dependent mobility bases are often crash tested for use in vehicles and have tie-down attachment points on the base. This allows the client to ride in the base, rather than in a standard child car seat or standard vehicle passenger seat. This is usually required if a child rides the school bus. Several DMS seating systems are actually a removable adaptive car seat. Many more DMSs are crash tested than manual wheelchairs, perhaps because only one type of seating system is generally available on each DMS (though with different components) and manual wheelchairs can be used with a wide variety of seating systems. The base and seat are crash tested together, so testing a manual wheelchair with every possible seating system is not cost-effective.
• Aesthetics
  Two DMSs may offer identical features and yet look very different. For the very young child, the decision is made by the caregiver. The style is often very important for families just beginning to deal with the reality of their child's disability. It is important to be family centered and offer DMS options that meet the criteria you have determined in your assessment.
• Other Bases
  Some pediatric DMSs offer a separate base on which the seating system can be placed. This base may be on wheels, but is not designed for dependent mobility. These bases are generally designed to place the child at a lower height than the mobility base. These are sometimes referred to as feeder bases as they can be used like a high chair. Some of these bases include tilt and various seat height options. Some DMSs are specifically designed to accommodate a child wearing a spica cast following surgery. A spica cast places the legs in abduction, hip flexion, and knee extension. As a result, the seat depth is short, seat width is wide, and a pad is often placed under the legs.
  
  Occasionally, twins will both require a DMS. Several DMS manufacturers offer a twin version with the seating systems side- by-side or in front of one another. One manufacturer offers a DMS that will support one to four seating systems, front to back. The seating system consists of a shell, so other components must be attached as needed. This DMS does not fold or offer tilt or recline. If one child requires a specialized seating system and the other does not, some parents still request a twin DMS, just as many parents of typical twins use a twin stroller. This is almost always a funding issue and the family may have to pay the difference between the cost of a single DMS and the twin version.
• Accessories
  Available accessories include sunshades, rain canopies, grab bars, and baskets. Some of these accessories can be difficult to get funded unless they are offered as part of a package including medically necessary items.
Other factors to keep in mind are durability, manufacturer warranty, and support and cost. Some of these DMSs are made outside of the United States, which can affect ease of reimbursement, timely delivery of the base, and availability of any needed parts in the future.

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