Validation test for climate control on air-loss supports

Objective: To develop a simple, reproducible validation test protocol for c lassification of air-loss support systems. Design: Simultaneous experimental measurement of moisture loss and temperat ure reduction at the air-loss support surface-human body equivalent interfa ce from a sweating human skin analogue. Setting: A hospital department of physical medicine and rehabilitation. Other Participants: These 3 manufacturers contributed 14 support surfaces. Interventions: Test support surfaces and a standard foam mattress were plac ed on a hospital bed. Water was circulated to a loading gauge, placed on a dry moisture reservoir, and connected to a water bath to keep the interface at 37 degrees +/- 0.5 degrees C. The loading gauge and support surface was adjusted 23cm below the water bath level and the air flow through the inte rface initiated. After the dry moisture reservoir came to temperature equil ibrium for 30 minutes, it was replaced with a wet one that was saturated wi th 36g of saline. The temperature change and evaporation rate were recorded throughout a 90-minute test period. Main Outcome Measures: Temperature of support surface interface and evapora tion rate. Results: Clustered data from temperature reduction and standardized rate of moisture loss yielded 3 groups of support surfaces in categories of no air loss (control), low air loss (LAL), and high air loss. The mean values of the characteristic temperature reduction and rate of moisture loss differed significantly between the groups. By multiple comparisons with Bonferroni' s adjustment, the group means differed significantly fur average temperatur e reduction (p <.017) and for standardized rate of moisture loss (p =.0001) . The measured temperature change at any instant of time reflected the effe ct of evaporation and the opposing effect of thermal conductivity. Conclusion: Measurements of support interface climate change allowed for se lective grouping of LAL surfaces according to rate of moisture evaporation and the resulting temperature reduction. Neither temperature change nor eva poration rate alone was sufficient to determine the microclimate characteri stics of the support surface. Combined, these characteristics can effective ly describe the performance of any LAL support system and may be used to de fine standards of performance.