Measuring Pressure Redistribution Properties of 4 Hospital Bed Surfaces: A Quality Improvement Project

Pressure ulcers/injuries (PU/Is) are still highly prevalent in the acute care setting. According to the Joint Commission Center for Transforming Healthcare (2021), more than 2.5 million patients in US acute care facilities are estimated to have PU/Is each year, and 60,000 die of their associated complications.¹ PU/I development has many contributing factors, including prolonged pressure over bony prominence due to inactivity/immobility, shearing between skin surface and mattress/seating surface,² poor perfusion,³ tissue ischemia, and prolonged high surface interface pressure.^4-6 Incidence of PU/Is has been shown to be
associated with increased disease burden, financial burden, and increased in-hospital mortality rates.^2,3,7 Therefore, it is crucial that interdisciplinary teams implement the use of appropriate pressure redistribution surfaces to minimize the burden of PU/I development.

Literature review. Several studies have been conducted to examine the effectiveness of various surfaces in the acute care setting for reducing PU/Is. Kirkland-Walsh et al⁸ conducted an institutional review board–approved comparative study of 50 volunteers with various body mass indexes and examined 4 different operating room (OR) surfaces to identify the most effective pressure redistribution surface for prolonged OR procedures. The surface attributes found to provide efficient pressure redistribution included the following: the lowest average interface pressure, the lowest peak interface pressure, and the highest skin contact area. Another comparative quality improvement study conducted by Teleten et al⁶ in 5 volunteers on various OR surfaces found that the use of a static, air-filled seat cushion on top of the standard OR surface, placed in the sacral area, resulted in superior pressure redistribution properties in the bent-knee and lithotomy patient positions in the OR compared with the standard OR surface alone. The results from these studies suggest that selection of a surface with the best surface redistribution properties may decrease the incidence of PU/Is in the OR.^6,8 Further, a cross-sectional comparative study conducted by Slayton et al⁴ examined surface, mean pressure, peak pressure, and pressure area index (PAI) on 34 healthy participants seated in a standard hospital recliner in various positions. The following conditions for the standard hospital recliners were examined: no cushion, foam cushion, nonadjustable air cushion, nonadjustable air/foam cushion, and adjustable air cushion. The nonadjustable air and air/foam cushions were found to result in the lowest mean and average interface pressures and the highest PAI, indicating that these surfaces provided the best pressure relief out of the surfaces tested.⁴ While these studies compared various surfaces for pressure relief for OR surfaces and hospital recliners, few studies have compared the effectiveness of various surfaces in standard hospital beds in the acute care setting. Therefore, this current quality improvement study was developed to examine bed surfaces within the hospital to measure the average pressures, peak pressures, and surface area for all surfaces available for pressure redistribution to determine the effectiveness of various surfaces for pressure relief and pressure redistribution.

Previous studies for pressure mapping have been conducted by this research team for finding the best surfaces in the OR and for education on pressure mapping.^6,8 With this study, the authors measured the average pressures, peak pressures, and surface area for 4 different types surfaces available within the hospital for pressure redistribution. Only 1 study participant agreed to be pressure mapped on the 4 surfaces in both the supine and prone position.

Purpose. The purpose of this quality improvement study was to compare the pressure redistribution properties of a standard hospital mattress with that of a standard mattress with a static, air-filled bed overlay placed on top of it. The pulsing settings were also compared with the immersing settings on the specialty mattresses that provide this technology.

Conceptual framework. Pressure mapping is based on a model derived from a classic study conducted by Kosiak and a conceptual model on the etiology of PU/Is. The 1959 study evaluated the interface pressure on skin over time and explained how interface pressure over the skin in a specific area could lead to vaso-occlusion, resulting in decreased tissue perfusion and possibly ischemia in deep and superficial tissues in the area under pressure. Kosiak used a cutoff of 32 mm Hg as the upper limit for measuring surface interface pressure. An interface pressure of 32 mm Hg or less is considered to be a useful guideline for determining the efficacy of the redistribution properties of the surface being measured and for reducing the risk of PU/I.⁹

This quality improvement study involved volunteer hospital staff and multiple pressure measurements for a comparative measures design in which participants (N = 8) were evaluated while in the supine position with the head of the bed inclined 0 degrees (flat); of these 8 participants, 1 was also evaluated in the prone position with the head of bed inclined 0 degrees. Four different surfaces were evaluated. The volunteers recruited were all lift team members and nurses who had a specific interest in the relationship between pressure on the surface in the supine and prone positions. Eligibility criteria included volunteers who were willing and agreed to be pressure mapped for comparison on the standard viscoelastic mattress, the viscoelastic mattress with the static air overlay, and specialty mattresses with pulsing and immersing technologies.

Pressure mapping is a noninvasive, objective, and reliable means of measuring the interface pressure between the body and the surfaces measured. The pressure mapping technique may be used widely for both seated and lying positions. Typically, pressure mapping has been used in research and in defining the pressure redistribution properties of a surface.¹⁰

To evaluate the pressure redistribution properties of the surfaces, the authors used a full-body interface pressure mapping system for testing that has been found to be valid and reliable in measuring interface pressure.^5,6,8 Pressure mapping systems are composed of a mat that contains pressure sensing materials that send data to a computer program. The data are displayed as a color-coded map and as grids for providing numerical pressure values in each area. The numerical values are expressed in the instrument used.

For this comparative study, the authors used the XSENSOR X3 PX100 system (XSENSOR Technology Corp) to measure interface pressure. This system consists of a thin, 99.06 cm × 220.98 cm full-body pressure mapping pad with

1664 sensing points. The sensors in the pad have 3.175 spatial resolutions. The pad was placed between the volunteer and the support surface and connected to the X3 display for real-time pressure mapping recording.

All bed frames and types were the same, and all data were collected in 1 day.

The standard mattress was measured first with average pressures, peak pressures, and surface contact area measured in the supine flat position. The static, air-filled overlay was placed over the standard mattress for measurement, and the specialty surface mattress was measured in both the pulsing and the immersing modes.

All participants were instructed to lie in the supine flat position for 5 minutes on each surface before measurements were recorded on the pressure mapping device. This 5-minute “settling time” was recommended and performed in the authors’ previously published study of pressure mapping the OR surface.⁸ The data were displayed on the screen for a minimum of 1200 frames per participant and were recorded on each surface and in both the supine and prone positions. Although there was only one participant who agreed to be mapped in the prone position, the authors believe this information is important to report for future research. The collected data were then downloaded to a computer using the XSENSOR X3 medical v6.0 software. The peak pressures and surface contact areas recorded were then transcribed into Excel (Microsoft Corp) spreadsheets by 2 investigators; 2 different investigators validated all measurements, color coded images, and measured millimeters of mercury (mm Hg) to reflect the pressure between the body and the surface measured.

The following operational definitions were used, aligning with those used in previous studies related to pressure mapping⁸:

• Interface pressure. The pressure load between the skin and the support surface; measured in mm Hg.
• Peak interface pressure. The highest-pressure load between the skin and the support surface; measured in mm Hg.
• Average interface pressure. The average pressure load between the skin and support surface of a full body or the specific area calculated by the pressure mapping device; measured in mm Hg.
• Skin contact surface area. The total contact area between the skin and the support surface; measured in square inches (in²).
• Pressure redistribution. The pressure relief to a small, concentrated area and the distribution of the pressure over a larger surface area.

Of the 4 surfaces tested by the 8 volunteers, the combination of the standard mattress with the static, air-filled overlay on top of the standard viscoelastic mattress proved most effective for pressure redistribution in the supine position by providing lowest average pressure (19.77 mm Hg), the lowest peak pressure (34.61 mm Hg), and the highest surface area (635.15 in²) as shown in the summary of all measured mappings (Table 1). For the one participant measured in the prone position, the lowest peak pressure and the highest measured surface area were measured in the static air mattress overlay on top of the standard viscoelastic mattress (34.61 mm Hg and 635.15 in², respectively) (Table 1). Table 2, Table 3, Table 4, Table 5, and Table 6 contain images of the 8 participants on different surfaces with the pressure legend set at 32 mm Hg; see tables for more details.

In this quality improvement project, the use of a standard hospital bed with static air overlay resulted in the lowest measured peak pressure with the highest measured surface area. These findings were consistent with studies conducted by Kirkland-Walsh et al⁸ and Teleten et al,⁶ both of which found that air-inflated static seat cushions had the best pressure redistribution properties in the sacral region compared with other surfaces tested for OR use. The authors found no other published studies on full-sized mattress pressure mapping.

Similar to the Kirkland-Walsh and Teleten studies, findings from the present quality improvement study suggest that the use of static air overlay on hospital beds may provide the most effective pressure relief for patients in acute care settings. By using the most effective surface for pressure redistribution, health care providers and the interdisciplinary team members can take measures to decrease the incidence of hospital-acquired PU/Is. Furthermore, these findings can be used to educate patients who are susceptible to PU/Is on the most effective pressure redistribution surfaces to use. Initiating the use of a static air overlay may reduce the development of hospital-acquired PU/Is, which may in turn decrease disease burden, financial burden, and in-hospital mortality rates.

This study has some limitations. It was conducted with a small number of health care workers in a single site. In addition, due to time constraints and willingness of volunteers to be in the prone position, the investigators were only able to measure 1 volunteer by pressure mapping in the prone position. Future work should include patients or volunteers in the prone position, under anesthesia, and with the head of the bed inclined at 30 and 45 degrees to obtain measurements for comparison.

This quality improvement project provided measured pressure mapping comparisons of 8 participants in the supine position on 4 different surfaces, and 1 participant was evaluated in both the supine and prone positions. This project measured the lowest peak pressures and the highest surface contact area with the standard viscoelastic mattress, with and without a static air mattress overlay, and beds with pulsing and immersing technology. The outcomes can help guide surface choice for prevention of PU/Is in the hospital and in transitions of care to home or skilled nursing facilities.

Oleg Teleten, MS, RN, CWCN¹; Tatyana S. Polyak, MD¹; Jessica Espinoza, OTS²; Andrew I. Li, MD¹; Ariel J. Rodgers, MD³; and Holly Kirkland-Kyhn, PhD, FNP, GNP, CWCN, FAANP¹

¹Patient Care Services, University of California, Davis
²OT student, San Jose State University, San Jose, CA
³Medical resident, San Joaquin General Hospital, French Camp, CA

Address all correspondence to: Oleg Teleten, MS, RN, CWCN, 2315 Stockton Blvd., Sacramento, CA 95817; email: osteleten@ucdavis.edu