Impact of Prophylactic Dressings Using in Vitro Body Analog
Impact of Prophylactic Dressings Using in Vitro Body Analog
A sweating thermodynamic rigid cushion loading indenter (TRCLI) as described by Ferguson-Pell et al was employed for prophylactic dressing testing. Dressings were tested by applying them to the approximasacral location of the TRCLI, and placement was done to reflect typical application and functional anatomy for dressings applied to the body while supine in bed (Figure 1).
(Enlarge Image)
Figure 1.
TRCLI with dressing applied.
(Enlarge Image)
Figure 2.
Moisture trapped in the dressing vs escaped through the dressing
Each dressing was centered on the TRCLI and positioned to cover the typical sacral location. The TRCLI is intended to test a larger surface area than the dressings covered, so each dressing was placed as previously described, and the remaining TRCLI test surface was left unmodified. This arrangement was also selected to provide a microclimate comparable to that created by the body when lying supine on a support surface. A photograph of the dressing placement is shown in Figure 1.
Eight commercially available dressings (Table 1) were tested in triplicate. Dressings as close to the same size as possible were obtained, however, due to differences in dressing design, intended function, and manufacturer offerings, there were significant differences in size of the dressings.
All trials were conducted in a temperature and humidity controlled laboratory maintained at 23° C +/- 2° C and 50% RH +/- 5% as per International Organization for Standardization 554–1976(E). The TRCLI was charged with a 50/50 ethylene glycol/water solution and a circulating water bath (Forma Scientific Model 2095) maintained circulation through the indenter at a constant temperature of 37° C +/- 0.1° C.
The TRCLI has been shown to deliver 3.6 grams of insensible water vapor per 3-hour trial, and the resolution of the system is 1% relative humidity and 0.1° C. The TRCLI was brought to set point and held for 60 minutes to allow for equilibration prior to each trial. The sweat chamber of the TRCLI was charged with deionized water and recharged following each test to ensure that the starting sweat volume was identical for each trial. The charged, dressed, and equilibrated TRCLI was loaded onto a mattress surrogate consisting of a water-impermeable mattress cover over a high resilience-45 (firm) foam mattress analog.
Temperature and humidity data were logged using a Sensirion EK-H3 system (Sensirion Inc, Westlake Village, CA) with 11 combined thermistor-based temperature and silicone wafer humidity sensors from the same company. Sensors were calibrated prior to use with the saturated salts method. Duplicate sensors were placed at each of the following 5 locations, one inside and one outside the dressing; right and left ischial tuberosities, the perineum and the right and left thigh. When dressing size limited the number of sensors that could be placed under the dressing, the compliment of sensors was reduced to 3 locations, the right and left ischial tuberosities and the perineum.
Each test consisted of a 60-minute equilibration period, a 180-minute test period, then a 45-second raising of the indenter intended to represent the repositioning of the patient, followed by a 15-minute replacement in the test position. The apex of the TRCLI was placed 13 cm from the edge of the support surface surrogate so that no edge effect would confound the test data.
The 11 sensors were continuously sampled with data logged at a rate of 0.5 Hz throughout the test period. Data was stored in a comma-delimited format that allowed it to be imported into a spreadsheet for analysis. The average temperature, average relative humidity, difference between pairs of sensors both inside and outside the dressing, and the difference between the dressing and the support surface surrogate were calculated.
Materials and Methods
A sweating thermodynamic rigid cushion loading indenter (TRCLI) as described by Ferguson-Pell et al was employed for prophylactic dressing testing. Dressings were tested by applying them to the approximasacral location of the TRCLI, and placement was done to reflect typical application and functional anatomy for dressings applied to the body while supine in bed (Figure 1).
(Enlarge Image)
Figure 1.
TRCLI with dressing applied.
(Enlarge Image)
Figure 2.
Moisture trapped in the dressing vs escaped through the dressing
Each dressing was centered on the TRCLI and positioned to cover the typical sacral location. The TRCLI is intended to test a larger surface area than the dressings covered, so each dressing was placed as previously described, and the remaining TRCLI test surface was left unmodified. This arrangement was also selected to provide a microclimate comparable to that created by the body when lying supine on a support surface. A photograph of the dressing placement is shown in Figure 1.
Eight commercially available dressings (Table 1) were tested in triplicate. Dressings as close to the same size as possible were obtained, however, due to differences in dressing design, intended function, and manufacturer offerings, there were significant differences in size of the dressings.
All trials were conducted in a temperature and humidity controlled laboratory maintained at 23° C +/- 2° C and 50% RH +/- 5% as per International Organization for Standardization 554–1976(E). The TRCLI was charged with a 50/50 ethylene glycol/water solution and a circulating water bath (Forma Scientific Model 2095) maintained circulation through the indenter at a constant temperature of 37° C +/- 0.1° C.
The TRCLI has been shown to deliver 3.6 grams of insensible water vapor per 3-hour trial, and the resolution of the system is 1% relative humidity and 0.1° C. The TRCLI was brought to set point and held for 60 minutes to allow for equilibration prior to each trial. The sweat chamber of the TRCLI was charged with deionized water and recharged following each test to ensure that the starting sweat volume was identical for each trial. The charged, dressed, and equilibrated TRCLI was loaded onto a mattress surrogate consisting of a water-impermeable mattress cover over a high resilience-45 (firm) foam mattress analog.
Temperature and humidity data were logged using a Sensirion EK-H3 system (Sensirion Inc, Westlake Village, CA) with 11 combined thermistor-based temperature and silicone wafer humidity sensors from the same company. Sensors were calibrated prior to use with the saturated salts method. Duplicate sensors were placed at each of the following 5 locations, one inside and one outside the dressing; right and left ischial tuberosities, the perineum and the right and left thigh. When dressing size limited the number of sensors that could be placed under the dressing, the compliment of sensors was reduced to 3 locations, the right and left ischial tuberosities and the perineum.
Each test consisted of a 60-minute equilibration period, a 180-minute test period, then a 45-second raising of the indenter intended to represent the repositioning of the patient, followed by a 15-minute replacement in the test position. The apex of the TRCLI was placed 13 cm from the edge of the support surface surrogate so that no edge effect would confound the test data.
The 11 sensors were continuously sampled with data logged at a rate of 0.5 Hz throughout the test period. Data was stored in a comma-delimited format that allowed it to be imported into a spreadsheet for analysis. The average temperature, average relative humidity, difference between pairs of sensors both inside and outside the dressing, and the difference between the dressing and the support surface surrogate were calculated.
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