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Preventive Effect of a Microclimate-Regulating System on Pressure Ulcer Development: A Prospective, Randomized Controlled Trial in Dutch Nursing Homes

van Leen, Martin MD, PhD; Halfens, Ruud PhD; Schols, Jos MD, PhD

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Advances in Skin & Wound Care: January 2018 - Volume 31 - Issue 1 - p 1-5
doi: 10.1097/01.ASW.0000527288.35840.0a
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In nursing homes, pressure ulcers (PrUs) result in suffering and a substantial loss in quality of life of the residents involved.1,2 They are also associated with considerable extra healthcare cost.3–6

Incidence measurements in various healthcare settings are an indicator for the relevance of PrUs. Vanderwee et al7 found an incidence rate of category 2, 3, and 4 PrUs of 6.8% in hospital wards, during an observation period of 16 days. Meesterberends et al8 reported an incidence of category 2, 3, and 4 PrUs of 22% and 7.8% in Dutch and German nursing homes, respectively, for newly admitted residents who were followed up longitudinally for a period of 12 weeks. De Souza and De Gouveia Santos9 found an incidence of 11.7% category 2 PrUs over a period of 90 days in long-term-care facilities. In addition, most PrUs in nursing home residents occur in the sacral region and at the heels, and many of them are slow to heal.10–12 These studies clearly show that PrUs are a highly relevant problem in the nursing home population.

Next to paying attention to the health status of the residents, normally the first step in PrU prevention involves the use of pressure-reducing systems in bed and on (wheel)chairs. For sacral ulcers, this means redistributing pressure forces over a larger part of the body with pressure-relieving systems (mattresses and cushions) and shortening the period of pressure at 1 spot through repositioning.13,14 The current international guidelines for PrU prevention recommend the use of a viscoelastic foam mattress and repositioning on a schedule (every 3 hours by day and 4 hours by night) as first-line preventive measures.15 Preventing heel ulcers is normally facilitated by redistribution surfaces or off-loading devices such as heel protection devices or pillows under the calf; the aim is to achieve zero pressure on the heel bone.15

Pressure has long been considered the only important extrinsic factor causing PrUs. However, since 1985, shear and friction have been studied to determine their role in PrU etiology.16 Recent and ongoing research has revealed that the skin microclimate also has a significant impact in the complex pathophysiology of PrUs.17

Pressure is defined as the amount of perpendicular force/load applied per unit surface area of application. A force applied over a small area will produce greater pressure than the same force over a larger area.

When forces are oriented or exerted parallel to the skin, they are considered shearing or shear forces. Tissues attached to the bone are pulled in 1 direction, while surface tissues remain in place. Shearing can damage deep tissues, including muscle tissue. Shearing in bed most commonly occurs when the head of the bed is elevated and the resident slides downward.

Friction is the mechanical force of 2 surfaces (eg, the skin and a bed or chair) moving across each other. Friction can lead to tissue damage, including blisters and abrasions. Residents who cannot lift themselves during repositioning and transferring are at high risk of friction injuries. Friction forces in bed are most common when residents are turned or pulled up in bed.17

In addition, the phenomenon of microclimate has gained interest recently. Microclimate refers to the skin temperature and moisture conditions at the skin-surface interface.18 Maintaining a balanced microclimate is a key component of the ability of the skin and underlying soft tissue to withstand prolonged stress.19 Disturbances of the microclimate worsen both PrU risk and PrU incidence.

It is still unclear what the best methods are for maintaining a balanced microclimate. An imbalanced microclimate is characterized by a temperature that is too high or too low and a humidity of the skin surface that is too high or too low.18 A rise in skin temperature results in a 10% rise in cell metabolism, which in turn can lead to tissue damage from a reduction in blood flow.20,21

Excessive moisture (perspiration, urine, or feces) can weaken the skin surface considerably.22 This may result in a higher skin coefficient of friction (COF), leading to more damage from friction and shear stress.17 Very dry skin can also be a problem. Drier and/or locally rougher skin can lead to higher friction on a support surface (a sticking effect). Often occurring in frail older adults, dry skin has reduced lipid levels (necessary for cohesion of epidermal cells), water content, tensile strength, and adhesion between the epidermis and dermis, all of which can leave the skin vulnerable.23,24

Measurable microclimate parameters for resident support interfaces, sheets, and mattresses are water vapor resistance, resulting humidity and temperature after water absorption, and dry heat flux.25 Yusuf et al26 measured the ability of the resident support interface to cool down after heating (dry heat flux) and its ability to transfer water vapor (water vapor resistance or Ret value). Their conclusion was that increasing skin temperature can be used as a quantitative measurement to predict the development of PrUs and superficial skin changes and to evaluate support surface capability against negative microclimate factors.26

Gefen27 developed a model that quantitatively demonstrated that a rise in skin temperature, ambient temperature, relative humidity, and/or the pressure delivered to the skin from the support, as well as decreased permeability of the materials in contact with the skin or in close proximity to the skin, all increase the risk of superficial PrUs. Lachenbruch et al28 used laser Doppler flowmetry to study the effects of a higher skin temperature, pressure, and shear stress on the superficial skin layer. The results suggest that managing skin pressure and temperature may reduce the risk of ischemia/PrU development.28,29


Recently, a new multilayer mattress system (total thickness, 13 mm) was developed (Bedcare; Sense Textile, ‘s-Hertogenbosch, the Netherlands), consisting of 3 separate layers, each with an independent function34:

  1. The Mini Overlay System (MOS; thickness, 9.5 mm), a 3-dimensional pressure-relieving spacer fabric used as a supplement to the mattress; the MOS is placed on top of a normal basal mattress to assist in pressure reduction.
  2. A textile mattress cover (made of polyester and elastan, covered with polyurethane; 0.5 mm) to protect both the regular basal mattress as well as the mini mattress layer against contamination and damage.
  3. The Stay and Transfer Sheet (STS; thickness, 3 mm), a 3-dimensional knitted spacer fabric designed to replace a normal bed sheet. The STS is the actual interface between the skin and mattress, designed with a low COF to diminish shear stresses. The knitted fabric helps to regulate the microclimate through vapor uptake, fluid dispersion, evaporation, and ventilation (Figure 1). The 3 layers of the STS provide the following:
    • • A top layer made of a low-friction, very fine knitted textile fabric based on fine and smooth synthetic fibers, leading to a static and dynamic COF of 0.3 (dry sheet) and static COF 0.3 (wet sheet). These are very low COF values compared with standard cotton sheets, which show a static and dynamic COF of 0.4 (dry sheet) and 0.6 (wet sheet); this layer is in direct contact with the resident.
    • • A 3-dimensional intermediate layer with bendable pile yarns that transports fluid (perspiration, urine) away from the top surface into an area where it is more easily evaporated to lower the humidity and the temperature of the skin interface.
    • • A bottom layer made of a very fine knitted textile fabric, less permeable, based on fine and smooth synthetic fibres.

These authors hypothesized that the Bedcare system, by combining the 3 components (MOS, barrier mattress cover, and STS) into 1 unit and using it in conjunction with a new viscoelastic mattress, would achieve additional reduction of pressure, shear stress, and optimization of the microclimate. Ultimately, this would lead to a lower PrU incidence than expected with a new viscoelastic foam mattress/cotton sheet alone.

Figure 1.:


Study Design

This study was set up as a multicenter, prospective, randomized controlled trial in 21 voluntarily participating Dutch nursing homes. The total study period was 12 weeks.

Study Population and Control Versus Intervention

All residents at medium/high risk (Braden score <16; see Data Collection) of PrUs were asked to participate and observed for a period of 12 weeks. The inclusion criteria were age older than 60 years, life expectancy greater than 3 months, and informed consent. The exclusion criteria were a PrU in the last 3 months, participation in a comparable trial, or a physical and/or mental condition that could interfere with participation (such as sepsis, immune disease, palliative status).

After informed consent, randomization into 2 groups was performed by using the Castor randomization software (version 1.44; Mionix, Malmö, Sweden).35 To detect a clinically relevant reduction in the incidence of PrUs (30%) with a statistical safeguard of α = .05 and a power of 0.80, 220 residents were needed.

In order to establish uniform, standard care, the control group received a new high-quality viscoelastic foam mattress, covered with a normal cotton bed sheet, while the intervention group received the same new high-quality viscoelastic foam mattress together with the new multilayer system (Bedcare) instead of the normal cotton bed sheet. When they were out of bed, all residents sat on a PrU-preventive air pillow according to standard preventive measures in line with the international guidelines.

The Medical Ethical Committee, Brabant, Tilburg, the Netherlands, approved the study (no. NL48831.028.14/P1414). The study was also recorded in the Dutch trial register (no. 4557).

Data Collection

Four research nurses were responsible for collecting the data. The following data were recorded at the start of the study: age, gender, main diagnosis, comorbidity, medication, skin condition, incontinence (yes/no), body mass index, and type of PrU preventive measures already in use (eg, cushions in [wheel] chair, off-loading devices for the heels, repositioning, scheduled transfers in/out of bed, etc).

To assess the risk of PrUs, the Braden scale was used. This is a scale with proven validity and reliability.36,37 The scale measures PrU risk, assigning scores from 1 to 4 for mental and physical condition, activity, mobility, and incontinence. The maximum score is 23 (no risk at all), and the minimum score is 7. A score of 19 or lower indicates that the patient is at risk of PrUs; a score of 13 to 17 represents medium risk, and a score of 7 to 12 is high risk.36

Each patient’s care dependency at the start of the trial was measured by the Minimum Data Set–Activities of Daily Living (from the Resident Assessment Instrument, the section on physical functions).38 The Minimum Data Set–Activities of Daily Living measures bathing, self-care, getting dressed, mobility, transfers, toilet use, bed mobility, and eating; each item of the scale is assessed on a 6-point Likert scale, and the total score ranges from 0 to 72; the higher the score, the more care dependent the patient is.

In the follow-up period, weekly assessments of the following were conducted: inspection of skin condition, changes in use of PrU preventive measures, and monitoring for possible adverse events. Data were collected weekly, controlled by an independent research nurse.

Outcome Parameters

The primary outcome parameter was the development of a category 2, 3, or 4 PrU.15 Category 1 PrUs were excluded because of potential equivocal diagnosis. The staging of the PrUs was established by the research nurses.

Data Analysis

Statistical analyses were done with the IBM SPSS Statistics Software, version 23 (SPSS Inc, Chicago, Illinois). Differences between the control and intervention groups were tested with the Student t test for continuous variables and a χ2 test for categorical variables.


In total, 215 residents provided informed consent. Nine residents could not participate because of initial organizational problems in some of the participating nursing homes, so 206 residents were included in the study, 103 residents in each group. In total, 165 residents completed the full period and all related follow-up. Seventeen residents dropped out of their own initiative or because of hospitalization (9 in the control group and 8 in the intervention group). Twenty-four residents died, 12 in each group, in all cases not related to the study. No adverse events were reported during the study period. Table 1 shows the demographic characteristics of the participating residents.

The majority of patients were older than 80 years, female, and very care dependent. The 2 most important main diagnoses (stroke and dementia) were representative for the overall nursing home population. There were no statistically relevant differences between the control and the intervention groups.

The development of PrUs in the control and intervention groups is shown in Table 2. In the control group, 5 patients developed a PrU, and in the intervention group, 9 patients developed a PrU. This difference was not statistically significant (P = .180).


The results of this study show that the study authors’ initial hypothesis was not confirmed. The control group showed a PrU incidence of 4.9%; in the intervention group, 8.7% of patients developed a PrU. The low PrU incidence in the control group confirms the primary PrU prevention strategy of using an adequate viscoelastic foam mattress as stated in the international guideline.15

It was unclear why the expected positive additional effect of the new multilayer system was not observed in this study. To explore possible reasons for this, additional laboratory pressure tests were performed by the Institut für Textil und Verfarenstechnik Denkendorf (Germany), on the viscoelastic foam mattress used in this study and also on the mattress in combination with the pressure-relieving part of the multilayer system (MOS).39Figure 2 shows the pressure test results.

Figure 2.:
Table 1.:
Table 2.:

This graph shows how many Newtons are required to achieve the same surface contact indentation (support surface area). The more the body is indented in a support surface, the larger the contact area for pressure distribution of the body weight. These measurements show that in the intervention group the patient would not indent the mattress as much as a patient would on a control mattress. The intervention provided less indentation and therefore less surface area, resulting in higher pressure load distributed over a smaller area. If one were to calculate, for example, the weight of a foot and the surface area of a heel, or bony proximities such as ankles or hips, one might conclude that the results of load distribution here could be at least a factor of 2.2× higher than on the control mattress. Therefore, the surprising results of this test may constitute one explanation for the failed hypothesis.

The potential additional benefits of the STS part of the multilayer system related to reduction of shear stress, regulation of the microclimate, patient comfort, and nursing feasibility unfortunately could not be assessed in this study and should be explored in future studies.

Strength and Limitations

Compared with other studies, this study is one of the largest randomized controlled trials on the PrU preventive effect of mattresses/mattress overlays ever performed in nursing homes. Moreover, special attention has been paid to standardizing the basic mattress in both groups. Because it was necessary to include more than 200 residents at medium/high risk, 21 nursing homes were ultimately involved. Differences in the use of other PrU preventive measures (eg, skin care, nutritional status, fluid intake, repositioning, off-loading of heels in control group) may possibly have influenced the results, which can be considered a limitation.


This study shows that the multilayer system (MOS, barrier mattress cover, and STS), when used as an integral system and in combination with a new viscoelastic foam mattress, has no added value in preventing PrUs over the viscoelastic foam mattress/cotton sheet alone.


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    microclimate; nursing home; pressure ulcer; pressure-relieving system; ulcer prevention; viscoelastic foam mattress

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