Evaluation of Generic Shape Contoured cushion for Wheelchair Users Based on the Development of Body-Seat Interface Shape Measurement Instrument

Evaluation of Generic Shape Contoured cushion for Wheelchair Users

Based on the

Development of Body-Seat Interface Shape Measurement Instrument

Yue Li

Planification et analyse statistique d'exp é riences

MTH6301 April 21, 2001

Presentation Structure

• Problem & Objective

• Methodology

— Description of input variables

— Description of response variables

— Choice of design

• Statistical analysis

Problem & Objective (1)

Pressure &

deformation of the body-seat interface

Internal characteristics of the wheelchair user

External characteristics of the wheelchair user

Type of cushion

Posture

Moisture

Tissue stiffness

Gender Nutrition

Weight Height

Skin temperature

Age

Type of disability

Time spending on the wheelchair

Leg-rest angle Seat angle Backrest angle

Foot-rest angle Material

Shape Active or static

ã ã General objective: Minimum the pressure and deformation

Problem & Objective (2)

1. Average pressure 2. Maximum pressure 3. Peak pressure gradient 4. Maximum deformation

Slump posture Forward trunk flexion posture

Mid-line posture Flat foam cushion

ISCUS cushion Generic shape contoured cushion

ã ã Specific objective: Minimum the 4 response variables &

confirm that Generic shape contoured cushion (GSCC) is better

Posture

Wheelchair configuration

Type of cushion

Problem & Objective (3)

Example of Generic shapes

Methodology (1)

Description of input variables

• Controllable input variables

— Type of cushion: 3 levels

1. Flat foam cushion

2. ISCUS cushion (Orthofab Inc, Montreal)

3. Generic shape contoured cushion (developing in the project)

— Posture: 3 levels

1. Mid-line posture

2. Forward trunk flexion posture 3. Slump posture

• Uncontrollable variable

— Body type of the subject (thin, average, obese)

Methodology (2)

Description of response variables

1. Average pressure 2. Maximum pressure

3. Peak pressure gradient

4. Maximum deformation

ð Pressure measurement:

Force Sensing Array (FSA) pad (Vista Medical, Manitoba, Canada)

ð Deformation measurement:

Shape Sensing Array (SSA) pad (developing from Shape Tape - Measurand Inc, Fredericton, NB, Canada)

IB 1 IB 2 IB 3 IB 4 IB 5

IB 7 IB 8 IB 6

Computer

Methodology (3)

Choice of design

Constraints:

Number of subjects ( ≤ 20)

Number of maximum treatments per subject: 4

• 3

full factorial design è è 9 treatments per subject x

• Central composite design: quantitative variable only x

• Balanced incomplete block design [[

t = Number of treatments = 9

b = Number of blocks = 18 (number of subject)

k = Block size = 4

r = Number of replicates of each treatment = 8

N = tr = bk = total number of observations = 72

Methodology (4)

Balanced incomplete block design

• Each subject represents one block

• Four treatments per subject

• Treatments are based on a full factorial design (3

= 9 treatments)

• Three repeat measurements

•

(1,2,3,4); (1,2,5,6); (1,2,7,8); (1,3,5,7); (1,4,6,8); (1,3,6,9);

(1,4,8,9); (1,5,7,9); (2,3,8,9); (2,4,5,9); (2,6,7,9); (2,3,4,7);

(2,5,6,8); (3,5,8,9); (4,5,7,9); (3,4,5,6); (3,6,7,8); (4,5,7,8);

flat cushion ISCUS GSCC

Mid-line 1 2 3

Forward 4 5 6

Slump 7 8 9

Statistical analysis

• ANOVA (study the relationship between the body types and response variables)

• ANOVA (test the hypothesis that the

treatment effects are zero)