Knowing where to start when prescribing a mobile over-toilet shower commode chair can be difficult. This quick guide to choosing a mobile shower commode outlines the 10 most important questions that I ask myself or the user, once it has been established that a mobile shower commode is required. Choosing the best piece of equipment relies on asking the right questions and matching the answers to the most useful features. Before I start asking these questions, I've generally already checked that the user's bathroom includes enough circulation space and a level-access shower, and we've had a discussion about how the mobile shower commode will be used (e.g. in the shower, over the toilet, or both).

Prescription of any equipment always needs to consider the user's preferences, safety, and sound clinical judgement. The questions I use to guide my reasoning probably won't apply directly to your situation, but I thought I'd share this to give my fellow therapists some general information and ideas.

With so many options it can be hard to make the right choice.

These first four questions are really to help narrow down the range of products to consider.

1. Can the user self-propel?

A self-propelling mobile shower commode has big wheels at the back (or front), and two small castors at the front (or back). Attendant-propelled shower commodes just have four small wheels, so the user is unable to move themselves. Some manufacturers only provide attendant propelled shower chairs.

I tend to prescribe a self-propelling mobile shower commode where ever the user is physically and cognitively able to push themselves, and the circulation space of the environment allows. This gives the user more freedom and independence, which is also be important in situation where their safety may be compromised.

2. What are the user's body proportions like?

To answer this question, I take a general look at the user, and take some measurements (width and weight) if unsure. It's important that the shower commode seat fits well and is comfortable. The user's body and feet need to be well supported. Standard shower commode seats are generally square, except the bariatric sizes, which are wider than their depth.

• Is the user fairly "standard" in their proportions, so they could fit a standard adult size shower commode (440 x 440mm seat)?

• Are they a child or very small, so they would best fit a paediatric size (330 x 330mm seat)?

• Are they smaller than a standard adult, but too big for paediatric, so a Junior size would fit best (400 x 400mm seat)?

• Are they very big, so they would need a bariatric size (550-900mm seat width)?

• Are they disproportionate? Would minor modifications, or a custom build be required? A user with very long legs may require a longer seat depth, and longer leg rests. A user with short legs and a short torso may require modified or paediatric leg rests, a shorter seat depth, and a lower backrest height.

3. How good is the user's postural control?

Consider what postural support the user requires in other seats. If they have specialised seating on their wheelchair, it may need to be replicated on the mobile shower commode. Some mobile shower commodes (such as the Goanna chair or the Seahorse paediatric shower chair) include a very supportive moulded seat and backrest, which is great for those who need it, but can be a barrier to thorough washing and limit independence. If the user has reasonable balance and postural control, I would steer away from this style.

Minor postural adjustments can be made to many mobile shower commodes, such as adding a lap belt, chest strap, lateral positioning wedges, or a higher backrest.

4. Will the user require "tilt in space"?

Some users may have medical conditions that require them to be laid back in a hurry. For others, tilt in space is required so they can achieve a functional position for using the toilet, a safe transfer, or for hygiene. While tilt in space is often prescribed on wheelchairs for pressure relief, this is generally not the case for mobile shower commodes due to the much shorter sitting time.

The mechanics required for tilt in space add weight and bulk to the chair, not to mention the extra expense. More moving parts also means more that can break, so I tend to prescribe tilt in space only when absolutely necessary.

The next six questions are directed towards narrowing down on specific features or accessories.

5. How will the user transfer into the mobile shower commode?

There are three main transfer options:

• Standing transfer: If the user is able to sit into the commode seat from a standing position, swing away leg rests are usually the best option.

• Side transfer: If the user is transferring sideways from one seat to another, the height of the shower commode may need to be adjusted to be closer to the height of the other seat. I have had to lower shower commode seats in the past because the user was transferring from a wheelchair, which was much lower. This can be a dangerous game though! If you lower it too much the shower commode won't fit over the toilet! Check your measurements carefully and allow at least an inch (25mm) clearance. For user who are side transferring, the location and style of the brakes need to be checked so they are accessible and not interfering with the transfer. Swing-away arm rests are usually required.

• Hoist transfer: If the user is hoisted or lifted into the mobile shower commode, tilt in space may be required. The shower commode should also have brakes on every wheel (locking castors). It's important to talk through the transfer with the user (and carers if applicable) to make sure the equipment will be compatible.

6. How often and for what duration will the equipment be used?

If the mobile shower commode is used only occasionally, or short-term (e.g. post-surgery), perhaps a lighter weight, more simple option would be suitable. Some users need their shower commode for up to 2 hours every day. In this case, it is important to consider comfort features, such as padded arm rests, and durability of construction.

7. What seat shape will be needed?

Some shower commode manufacturers (such as K-Care and Otto Bock) sell seats separately to the mobile shower commode frame. This allows us to match the seat with the needs of the user. It is important to understand and consider all the self-care activities the user needs to perform in the mobile shower commode. Most shower commode seats are made with a ply wood base, foam top, and waterproof vinyl covering. They have an aperture (the hole in the middle), which can vary in shape, size and location. They can be closed front (first two pictured), open front (third picture), rear or side opening (less common). The can have a 'bite', a cut-out from the side, to allow more access without compromising the structural integrity of the seat. The Queensland Spinal Cord Injury Service has some great templates for measuring and drawing custom-designed seats.

Three examples of common mobile shower commode seats.

The main decisions to make:

• Machine-made vs Hand-made: Machine-made seats (pictured above, centre) are generally much cheaper than hand-made, however they often have a heat-welded seam along the inside of the aperture and around the sides of the seat, which can cause problems for fragile skin. Machine-made seats are often less durable as the seams can split. Hand-made seats are a must for anyone with sensation-loss, as the foam is wrapped from the top through the aperture, so the user's bottom isn't resting on the wooden base. They are also carefully made with no rough edges. I have never prescribed a machine-made seat, but they may be appropriate for occasional or short-term users.

• Closed front vs Open front: Open front generally gives better access for washing and some toileting procedures. Closed front gives better support to the legs, and may be required for good positioning. Rear or side opening may be required depending on the user's bowel management routine.

• Size of Aperture: The default aperture sizes vary according to the manufacturer, and the size of seat chosen (paediatric/junior/adult). A smaller aperture may be required for users who have wasting of their gluts (resulting in bony bottoms), as they may tend to sink too far down through a large aperture, which is an issue for skin stretching and clearance to roll over the toilet. Smaller apertures can also assist with maintaining posture.

8. What seat padding will be needed?

There are usually at least two, and often three, standard levels of pressure redistribution in shower commode seat ranges. The basic level might include a plastic, moulded foam, or machine-made ply and foam seat. The next level up is generally a hand-made padded seat. The top level is called different things depending on the manufacturer: "pressure care special", "Dartex" (has extra-stretchy black covering as well as extra foam), "JPTR", etc. The top level seats often have dual-layer foam and a stretchy covering. The foam is usually higher. Keep this difference in mind if you need to specify the seat to floor height. The vast majority of mobile shower commode users are catered for within this selection.

For those with a very high risk of pressure injury, an extra pressure relief layer can be added, such as a gel commode seat topper (available in adult standard size only, closed and open front), ROHO commode seat cushion (can be made to order), or I've cut a hole in an Equagel cushion, which worked quite well.

9. How will the new piece of equipment fit into the user's lifestyle?

Do they travel? If so, a folding shower commode might be required. The ability to adjust the height may also be useful. Depending on the circumstances, the user might have an ideal mobile shower commode for home use, and a more portable alternative for travel.

Do they have to sit for long periods? Users with neurogenic bowel, such as people with spina bifida or spinal cord injury, may have to sit for long periods due to their bowel routine. Sometimes, they may want the option of sitting somewhere other than the bathroom. A suitable pan and rack would be needed, and a splash guard. Unfortunately not many mobile shower commodes have options for the type of pan/bowl provided, so this may involve some creativity.

Who else lives in their household? This may impact on storage options. If the bathroom is used by others, the mobile shower commode may need to be stored somewhere else. It's good to have a plan for storage before the equipment arrives.

10. How are the user's needs likely to change over time?

Imagine how the user is likely to change over the next few years, and go back over all the questions above considering the possible changes. Will your original prescription still be valid? I look at getting adjustable features to manage predictable changes, such as growth in children. With children, we plan for them to become more independent over time. For someone with a progressive condition, the ideal shower commode will be easily modified in future with more support, a higher pressure care seat, or other features they may benefit from.

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That's the end of my "quick" guide to mobile shower commode prescription. They can be quite straight-forward or a bit tricky to get right, depending on your level of experience and the complexity of the user. If you're just starting out, it's a great idea to get someone to supervise your first few prescriptions, as mistakes can be very costly and time consuming, not to mention embarrassing! I've been prescribing mobile shower commodes regularly for 5 years and I still talk through most scripts with a colleague before submitting them, especially the trickier ones. Good luck!

If you have some mobile shower commode questions or tips - don't be shy.