Assessing for the correct chair size

Introduction

Having the correct size chair is essential and should be the second priority after considering how a person will transfer i.e. get in and out of the recommended chair. The correct size chair supports a person by reducing the need to shuffle around in the seat of the chair and the tendency to lean to one side to obtain support, and it enables users to stay in a midline position.

This not only enhances comfort, reduces the risk of pressure areas developing and enables both safer and easier transfers, but it also lessens the need for frequent repositioning and can aid circulation, digestion and respiration.

Seat depth and height

Ideally a person should be able to sit on a chair with their back against the back rest of the chair, whilst their feet are flat on the ground or on a footplate. Their hips, knees and ankles should be at 90-degree angles, and their arms supported by the armrests.

The correct size can only be achieved if the chair is the correct seat depth and height. These two measurements are closely linked together and enable a person to sit in the chair with the ideal seated pressure distribution of :

Buttocks and thighs 75%
Feet 19%
Back 4%

Seat width

When measuring the width of a person, it is important to measure the person at the widest point; for most users this is at the hips. Keeping the tape measure straight rather than going around the abdomen is essential, as this will give you an accurate measurement of the space required between the two armrests.

In some cases, the hips are not the widest point; for example a person may have fixed abduction of the hips, making their knees the widest point. If the space between the outside of the knees and thighs is wider than the hip width, then this is the measurement that needs to be taken so that the space available will accommodate this width.

When choosing the correct size chair, consider the overall size of the user: are they an average, small, medium or large person?

Then take the following 3 key measurements in this order of priority:

Seat depth
Seat height
Seat width

When measuring the width for a riser recliner or a specialist chair, the requirements differ slightly:

Configura Rise and Recline chair:

Ideally with a riser recliner, we would like to see approximately 1- 2 inches either side between the inside of the chair and the person sitting in the chair. This reduces the risk of the skin rubbing against the inside of the chair, whilst still enabling the person to reach both armrests for support when seated and when transferring. See more information about the Configura Rise and Recline chair.

Configura Advance chair:

When using a specialist chair which provides postural support, the chair needs to be close fitting to provide support, enabling the user to obtain an upright position. This means the width of the chair is similar to the width of the person. All contact areas of the Configura Advance chairs, are made of a breathable, vapour permeable fabric, which reduces the risk of pressure areas developing.

Bariatric chair:

When measuring a plus size user for a riser recliner, there are additional considerations. The plus size user will have excess body mass which needs to be accommodated for and so the way we measure a plus size user is different. The figure below shows what is often a typical seating presentation of a plus size user.

The extra body mass has not been accommodated for. As a result, the person has not got adequate back support and the seat height is too high. The person has tilted the chair forward to enable their feet to be in contact with the floor and their head to be in contact with the top cushion. This position places the person at risk of slipping from the chair and often requires a great deal of core strength and upper body strength to retain their position. This is uncomfortable and likely to cause pressure build up in certain areas.

Seat depth and height:

The figure below shows that the actual measurement for the seat depth and seat height of a plus size user is shorter and shallower than an average sized user. This is because we need to accommodate the space required for the extra body mass under the thighs, behind the calves and behind the spine. Compare this figure with the one shown alongside seat width above, to identify the different points we measure from.

The figure below shows that the lowest cushion of the waterfall backrest has been removed to accommodate the extra body mass, which is also known as the gluteal shelf. Each cushion has removable stuffing and so in some cases it is just necessary to remove part of the stuffing, rather than the whole cushion. If space for the gluteal shelf is not considered, when the person is sitting on the chair, they will not have any back support.

Seat width:

In plus size users, the widest part when seated is from the outside of the knees. The legs need to spread to accommodate the extra body mass around the abdomen and thighs.

Whenever a measurement is taken, it is essential to ensure that the tape measure is kept straight, as this will give you an accurate measurement of the space required between the armrests.

Details on the Configura Bariatric chair can be found here.

For more information on assessing pressure care or to book seating assessment contact our team on 01223 206 100 or info@accora.care

KottnerJ, Gefen A, Lahmann N (2011) Weight and pressure ulcer occurrence: a secondary data analysis. Int J Nurs Stud 48 (11): 2608-20

MND Association Wheelchair Pathway 2021, https://www.mndassociation.org/app/uploads/2021/01/Wheelchair-pathway.pdf

Sandoz H 2012, No pressure – a study guide. Anthony Kerr, MA Healthcare Ltd. London