Using Orthotic Design to

Manage Wheelchair Cushion

Microclimate

Daniella Giles, PT, ATP/SMS

Ride Designs, California education and sales support

Denver, CO

Microclimate

The term microclimate refers to the

skin surface temperature (heat)

and skin surface humidity

(moisture) at the body-support

surface interface.

Literature & Research Review Heat and moisture at the sitting surface are believed to be the

causative factor in superficial stage I and II pressure ulcers (Ferguson-Pell 2009)

Elevated temperature exacerbates ischemia related to sitting acquired ulcer development (Berlowitz and Brienza, 2007)

When there is an increase in temperature we can predict an increase in moisture (Ferguson-Pell 2009)

Superficial dermal injuries without deep underlying tissue damage results from moisture and shear (Berlowitz and Brienza, 2007)

Negative Effects of HeatEvery 1°C raises metabolic demands by 10%

Increased metabolic need = STRESSED OUT cells

Ischemia occurs when tissue perfusion is insufficient to meet the

needs of the tissue

Elevated tissue temperature will cause ischemia and pressure ulcer

development in a shorter period of time

When there is an increase in temperature, we can predict an

increase in moisture (Ferguson-Pell 2009)

Negative Effects of Moisture

Softening of the stratum corneum at the epidermis

Weakening of the collagen crosslinks in the dermis

Causing increased risk for damage via micro-traumas

Reduced natural skin barrier to outside toxin absorption, allowing more

toxins into the cells

Increased friction co-efficient

Microclimate Pilot Study

Primary Researcher: Evan Call, MS, CSM Weber State University, Ogden, UT

Approx. 2mm x 4mm sensor

LoggerMethodology:

Single-subject human test

6 mini temperature sensors and a

temperature and humidity “logger”

Data gathered over 24 hour period x 7

days each on air cushion and orthotic-

style cushion

Objective:

Compare sitting surface temperature

and humidity on an air cell and

orthotic- style wheelchair cushion

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

TE

MP

ER

AT

UR

E C

°

TIME

Orthotic Cushion Day 4

Right IT Right Thigh Perineum

Left Thigh Left IT Ambient

Microclimate Study Data

Temperature Date

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

55.0

60.0

65.0

70.0

75.0

TE

MP

ER

AT

UR

E C

°

TIME

Air Cushion Day 2Right IT Right Thigh Perineum

Left Thigh Left IT Ambient

05

101520253035404550556065707580859095

%R

H

TIME

Orthotic Cushion, Day 4Right IT Right Thigh Perineum

Left Thigh Left IT Ambient

Microclimate Study Data

Humidity

0.05.0

10.015.020.025.030.035.040.045.050.055.060.065.070.075.080.085.090.095.0

%R

H

TIME

Air cushion Day 3Right IT Right Thigh Perineum

Left Thigh Left IT Ambient

Calculations

Peak readings for RH and temperature indicating at risk occupancy times.

Minimum readings indicating excursions from the cushion.

Duration of readings indicating occupancy, time between repositioning/pressure

relief.

Pilot Study Results

The cushion/user interface on the orthotic style cushion was 1.6°C

cooler (2.88°F) than the 4” air cushion

This can be equated to an average of 16 to 20% decrease in

metabolic demands of the tissue (Call, 2015)

Microclimate & Immersive Cushion Design

Immersive designed cushions rely

upon mechanical pressure relief for

effective heat and moisture

management.

Microclimate & Orthotic Designed Cushion

Airflow around high risk anatomy helps

keep skin cool and dry.

Spacer mesh maintains air space

at lower risk/loaded anatomy.

Study Limitations and Future Considerations

Single subject test, should be 10 subjects

While significance statements and confidence intervals can be applied to the data, they

would only suggest the confidence we have that the readings we gathered are not in error

for this volunteer at this time.

Better logging of activities to improve correlation with temperature and RH.

The humidity data requires further analysis.

Multiple climates

Recording of core temp.

Conclusion

Research shows Stage I & II pressure ulcers are caused by heat and

moisture

A wheelchair cushion utilizing orthotic-design principles, properly

covered, has the ability to decrease heat at the sitting surface. This

can assist in the prevention of sitting acquired pressure ulcers

It is essential that a wheelchair cushion prescription address heat

and moisture build-up at the wheelchair user sitting interface

Further research needed

References:1. Clark, M, Romanelli M, Reger SI, Ranganathan VK, Black J, Dealey C.

Microclimate in context. www.woundsinternational.com pdf, pages 19-28.

2. Kakote, JY, Leland, Kj, Held, AM, et al. Temperature modulated pressure

ulcers: a porcine model. Arch Phys Med Rehabili. 1995; 76(7) 666-73.

3. Gerhardt LC, Strassle V, Lenz A, et al. Influence of epidurmal hydration on the

friction of human skin against textiles. J R Soc Interface 2008; 5(28): 1317-28.

4. Fisher SV, Szymke TE, Apte SY, Kosiak M. Wheelchair cushion effect on skin

temperature. Arch Phys Med Rehabil 1978; 59(2): 68-72.

5. Brienza DM, Gyer MJ. Using support surfaces to manage issue integrity. Adv

Skin Wound Care 2005; 18: 151-57.

6. National Pressure Ulcer Advisory Panel, NPUAP. Pressure Ulcer Prevention

Points (http://www.npuap.org/PU_Prev_Points.pdf)

7. Salzberg CA; Byrne DW; Cayten CG; Kabir R; van Niewerburgh P; Viehbeck

M; Long H;Jones EC., Predicting and preventing pressure ulcers in adults with

paralysis. Advances in Wound Care. 11(5):237-46, 1998 Sep.

8. Dan R. Berlowitz, MD, MPH; and David M. Brienza, PhD, Are All Pressure

Ulcers the Result of Deep Tissue Injury? A Review of the Literature,

9. Ostomy/Wound Management - ISSN: 0889-5899 - Volume 53 - Issue 10 -

October 2007 - Pages: 34 - 38