Microclimate Management

This page provides an overview of microclimate management testing and the results of testing on a diverse cohort of wheelchair cushions.

Test Overview and Methodology

Microclimate testing evaluates a cushion’s ability to control heat and humidity at its interface. These characteristics are evaluated as relative humidity and temperature as a Thermodynamic Rigid Cushion Loading Indenter (TRCLI) applies a water vapor and heat load to the test cushion. Test methods per the most recent DRAFT ISO standard for Cushion Heat & Water Vapor Testing (ISO 16840-7 September 2018) were applied to 14 cushions from our 50+ cushion cohort. Figure 1 shows a visualization of the microclimate test procedures followed from the ISO 16840-7 September 2018 draft standard.

Water vapor transfer rate for the TRCLI was measured to be 1.5 g/hr using the verification procedure outlined in ISO 16840-7 for determining desiccant-absorbed moisture for 125g of desiccant over 4 hours. It is important to note that ISO 16840-7 is a working draft and is subject to change. For this testing, three trials were completed per cushion.

There are two key outcomes of this test: Temperature and Relative Humidity (%RH). These two metrics are recorded throughout the duration of cushion loading and unloading at each of five sensor locations (Figure 1A). Data from the five sensor locations are averaged. The average temperature and %RH for all sensors at 1 hr, 2 hrs and 3 hrs is reported.

Summary Results (n=14)

Descriptive statistics for n=14 cushions are presented in the table below. Six cushions in the sample were three cushion models tested with two different covers – a standard stretch cover and a microclimate management cover (“w/MCM”). Cushion AE product information states that it contains material that actively lowers the seated skin temperature by acting as a heat sink.

Data presented includes the average temperature and percent relative humidity (%RH) of all five sensors at the 3-hour timepoint averaged from the three trials. The average %RH for just the two sensors placed at the base points of the TRCLI, simulating the ischial tuberosities (IT sensors), is also presented.

Note 1: Cushion K is a 3” reference foam cushion
Note 2: Interpretation of , e.g., “H w/MCM” is that this indicates the cushion coded “H” was tested in a second configuration with a “microclimate management” cover

Individual Cushion Results

Below are data from a representative trial (1 of 3 trials) for each cushion tested. The left graph presents temperature over the entire trial and the right graph presents percent relative humidity over the entire trial.

This first image is a key for how to interpret the graphs.