POTENTIAL FOR BED SORES DUE TO HIGH PRESSURES : INFLUENCE OF BODY SITES,BODY POSITION,AND MATTRESS DESIGN

SUMMARY Pressures were measured on 10 subjects, supine and sitting, under six anatomical sites prone to bed sores on three different mattresses. Studied were the Clinifloat and Therarest specialist replacement mattresses, and a standard hospital mattress. Mean supine pressures were less than 5 kPa under four sites. Average supine buttock pressure was 2.93 kPa. Occiput and heel pressures were much higher than under other sites, being on average 2.6 and 4.5 times greater respectively than the mean buttock pressure. On sitting up, buttock pressure increased by a factor of 1.7 on average, to a level higher than the accepted capillary closing pressure. Measurements were consistent with mattress design, specific features of which can significantly affect pressure under certain sites.     

Supine interface pressure in children

The effectiveness of using 2-inch and 4-inch convoluted foam overlays to protect children from developing pressure sores was investigated in 13 healthy children ranging in age from ten weeks to 13.5 years. Interface pressures were measured under the occipital, sacral, and scapular areas of children as they lay on a standard mattress, then on 2-inch and 4-inch foam overlays. The differences in pressures between the occiput and scapula, occiput and sacrum, and scapula and sacrum were significant (p less than .001), with the highest pressures recorded under the occipital area. Occipital pressures decreased from 45.7mmHg on the standard mattress to 22.3mmHg on the 4-inch overlay in ages 0 to 2, 54.3mmHg to 30.5mmHg in ages 2 to 10, and 78.0mmHg to 42.4mmHg in ages 10 to 14. Sacral pressures were highest in older and larger children, increasing from 17mm Hg in ages 0 to 2 to 34mmHg in ages 10 to 14, and when body surface area was greater than 1m2. These results indicate that the site of greatest pressure changes with increasing age from the occipital area to the sacral area. Therefore, different pressure relief considerations are necessary in treating pediatric patients than in managing pressure under adults.     

Effectiveness of mattress overlays in reducing interface pressures during recumbency

This study evaluates the pressure-reduction characteristics of seven mattress overlays. Thirty subjects were evaluated on each support surface to determine the interface pressures that are generated under the most common pressure sore sites. The results of this study indicate that there is great variability in the effectiveness of traditional mattress overlays. The most effective overlays are the Roho and Akros DFD mattresses; whereas 2-inch thick convoluted foam provides no significant protection for the trochanter when the subjects were lying on their sides (lateral position).     

Effects of position and mattress overlay on sacral and heel pressures in a clinical population.

A comparison of pressure reducing properties of alternating air, static air, and water mattress overlays was conducted with 57 patients in a surgical intensive care unit. Sacral and heel pressures in both recumbent and semi-Fowler's positions were tested for each surface using a repeated measures design. Mean pressures for the alternating air mattress were significantly higher than pressures with other surfaces, regardless of position or site. There were significant main effects for position and site, with higher pressures in the semi-Fowler's position and at the sacral site. A significant interaction between surface, site, and position was found. Pressure sores developed in eight patients, but the incidence was not significantly different across groups. A pressure measuring device constructed from available clinical materials proved to be both sensitive and reliable. The findings suggest alternating air overlays should be avoided, and that positioning and periodic position change to reduce sacral pressures for patients requiring prolonged upper body elevation is important.     

Quantification of pressure relief using interface pressure and tissue perfusion in alternating pressure air mattresses

OBJECTIVE: To examine whether the interface pressure (IP) relief provided by alternating pressure air mattresses (APAMs) is matched with maintenance of tissue perfusion over the points of contact by measuring transcutaneous oxygen and carbon dioxide (tcPO2, tcPCO2). DESIGN: Comparative analysis of 2 APAMs with a 2-parameter continuous time-based method for quantifying pressure relief (PR) and transcutaneous gas measurement for assessing tissue perfusion. SETTING: Rehabilitation research facility in a university hospital. PARTICIPANTS: Eleven able-bodied adult postgraduate student volunteers. MAIN OUTCOME MEASURES: Two full-replacement APAM systems were used. For each mattress the mean maximum and minimum interface pressures; mean peak air pressures in the mattresses; interface pressure durations below 30, 20, and 10 mmHg over a 60-minute period; mean maximum tcPCO2 and minimum tcPO2; and mean area under the tcPO2 and tcPCO2 curves were measured for each subject. RESULTS: IP on the sacrum was held below thresholds of 30, 20, and 10 mmHg longer on a 2-cell, low pressure system than on a 3-cell, high pressure system (p < .001). Integrated over time, tcPO2 levels also indicated that the 2-cell system retained oxygen levels closer to the unloaded baseline than did the 3-cell system (p < .01). tcPCO2 levels did not rise significantly (p > 0.1) compared with the baseline measurement in both mattresses. CONCLUSIONS: PR was sensitive to the design of the APAM, especially its inflation pressure, cycle time, and inflation sequence. If future trials demonstrate that PR values and transcutaneous blood gas measurements correlate significantly with the clinical incidence of pressure sore formation, then this technique may prove useful in assessing the effectiveness of alternating pressure support surfaces.     

AN INVESTIGATION OF INTERFACE PRESSURES IN LOW AIR LOSS BEDS

Prospective randomised trials indicate that the low air loss bed is a successful method of treatment for pressure sores. To study the properties of these beds interface pressures were measured in two different low air loss beds. Ten healthy volunteers had eight readings at six different body sites taken supine and sitting. Occipital and heel pressures for both products exceeded 4.7 kPa, the accepted capillary closing pressure, while pressures at other sites were below this. These findings suggest that pressure relief alone is not the sole reason for the clinical acceptance of low air loss beds in the treatment of pressure sores.     

Preventing pressure ulcers: an evaluation of four operating-table mattresses.

Pressure is a major factor in the development of pressure ulcers. This research focused on assessing the pressure-reducing effects of operating-table mattresses. Five mattresses were tested: a standard operating-table mattress, a foam mattress, a gel mattress, a visco-elastic polyether mattress, and a visco-elastic polyurethane mattress. Four intraoperative postures were evaluated: supine, lateral, fossa, and the Miles-Pauchet position. Interface pressure measurements were performed on 36 healthy volunteers. The foam mattress and the gel mattress seem to have little or no pressure-reducing effect; the polyurethane mattress and the polyether mattress reduce interface pressure significantly better (p < .001); but none of the mattresses reduce pressure sufficiently to prevent the occurrence of pressure ulcers.     

The new QUATTRO PLUS mattress replacement system

Since the early development of alternating pressure air mattresses (APAMs) there have been regular alterations in design. These designs have led to improved reliability and performance. This article outlines the changes made by Talley Medical to the QUATTRO PLUS replacement mattress. Improved safety features and design modifications continue the process commenced many years ago which has seen the use of alternating pressure air mattresses become widespread throughout the UK.     

Skin blood flow in relation to external pressure and temperature in the supine position on a standard hospital mattress

The purpose of this investigation was to study the relationship between skin blood flow, external pressure and temperature in the skin over bony prominences and muscle padded areas, when healthy individuals and patients with hemiplegia were lying in the supine position on a standard hospital mattress. The pressure values under the gluteus maximus muscle and the sacrum increased significantly in the supine position with bent knees. The heels resting on the mattress gave very high pressure values. Some patients had no observable skin blood flow in the skin over the sacrum and the gluteus maximus muscle. In many individuals there was no observable blood flow in the skin over the heel among both healthy individuals and patients, which was confirmed by very high post-ischemic reactive hyperaemia. There is also a heat accumulation when lying on the mattress which increases the requirement for skin blood flow.     

Interface pressure comparison of healthy premature infants with various neonatal bed surfaces

PURPOSE: The aim of this study was to determine interface pressure between the occiput of healthy premature infants and 5 different bed surfaces used in special care nurseries. SUBJECTS: Thirteen healthy premature infants comprised the convenience sample enrolled 1 to 3 weeks prior to discharge. DESIGN: A quasi-experimental design was used with the dependent variable being the interface pressures obtained under the occiput and the independent variables as the bed surfaces. METHODS: Order of bed surfaces was randomized and standardization of the infant positioning and measuring procedure maintained. Measurements were made between the infant's occiput and the bed surface and interface pressures recorded in millimeters of mercury. The 5 bed surfaces were standard crib mattress with or without foam, gel donut, gel mattress, and water pillow. MEASURES: Interface pressure measurements were obtained using the Mini-Texas Interface Pressure Evaluator (Mini-TIPE, Tee-Kay Applied Technology, Inc, Stafford, Texas). RESULTS: A 1-way blocked analysis of variance was conducted to evaluate the relationship between the mattress surfaces and the interface pressure measurements. A significant difference in the mean of the interface pressures among the 5 mattress bed surfaces was determined, F(4,46) = 33.267, P < .001, with the lowest being the foam overlay. The standard crib mattress had the highest interface pressure that exceeded 100 mm Hg. Post hoc comparisons showed a significant difference between the standard crib mattress with and without foam and the other surfaces. CONCLUSIONS: Interface pressure is an important consideration when choosing a support surface for premature infants susceptible to tissue compromise and head molding. Variations in interface pressures between neonatal bed surfaces are apparent. Comparison studies of interface pressures using these and other neonatal bed surfaces will be valuable in determining appropriate products for both premature and neonatal populations with lengthy intensive care stays.     

The effect of a double-regression hospital bed on interface pressure

This study examines, for the first time, the differences of interface pressure in different positions on a standard hospital bed and a double-regression hospital bed. For both beds, the interface pressure was recorded in four supine positions and three lateral positions in 49 healthy volunteers (30 men and 19 women). The results demonstrate, independently of the bed type, that when a supine and lateral position is indicated, the 0° and 30° positions, respectively, are preferable. We also show that patients requiring prolonged upper body elevation may benefit from the use of a double-regression hospital bed that reduces the maximum pressure and the pressure surface greater than 32 mm Hg at the sacrum and heel sites.     

A Phantom-Based Method to Assess X-Ray Table Mattress Interface Pressures

BackgroundPressure redistribution performance of x-ray table mattresses can influence the development of pressure ulcers in at-risk populations. Interface pressure analysis, with human participants, is a common method to assess mattresses. This approach has limitations that relate to the lack of standardisation between and within humans.AimThis study aimed to develop and validate an anthropomorphic phantom-based method to assess x-ray table mattress interface pressures as an index of mattress performance.MethodsA three dimensional phantom simulating an adult’s head, pelvis, and heels was printed from x-ray computed tomography image data and attached to a metal frame 175 cm in length. Dry sand was added to the phantom head, pelvis, and heels to represent a range of human weights. Pressure distribution was assessed using XSensor. Phantom validation was achieved by comparing phantom mattress interface pressure characteristics, for five human equivalent weights, against 27 sets of human mattress interface pressure data.ResultsUsing the correlation coefficient R, phantom and human pressure data showed good correlation for the five phantom weights (R values: head = 0.993, pelvis = 0.997, and heels = 0.996).ConclusionA novel method to test x-ray mattresses for interface pressure was developed and validated. The method could have utility in the testing of x-ray mattresses that are in routine use and for new mattress development. Phantom interface pressure data could be provided by manufacturers to help inform procurement decisions when matching mattress characteristics to medical imaging demands and the underlying patient populations.     

Reducing pressure ulcer incidence in a long-term setting

Selection of appropriate pressure prevention equipment relies on risk assessment and clinical assessment of the resident/patient. Decisions are then made in combination with manufacturer's recommendations, such as interface pressure testing. However, risk assessments can over-predict and laboratory investigations do not necessarily provide an accurate picture of how individual patients will react to pressures from support services. There are few studies on visco-elastic mattresses and their benefits in reducing pressure ulcer incidence. Therefore, a small study was undertaken to review the efficacy of a pressure-reducing visco-elastic foam mattress. For the benefit of the study, a 20-bedded nursing home was provided with 20 visco-elastic mattresses (Pressurease) and 20 pressure-reducing cushions (Mediform Visco). The study aimed to demonstrate a reduction in pressure ulcer prevalence. The study involved 21 residents over a 6-month period. There was a 58.3% prevalence (of Stirling grade 1-2 pressure damage) at trial initiation. The results showed an 85.7% decrease of pressure ulcers within 4 weeks, and an overall decrease of 82.5% over the 6-month period. Comfort levels, scored by residents on a visual analogue scale, demonstrated the Pressurease mattress to be superior to the nursing home standard mattress.     

Special mattresses: effectiveness in preventing decubitus ulcers in chronic neurologic patients

Thirty-two chronic neurologic patients between 19 and 60 years of age were randomly assigned, for a period of three months, to either an alternating air mattress or a silicore mattress to test the preventive qualities of special mattresses in the occurrence of decubitus ulcers. The two groups were comparable on the variables of age, weight, diagnoses, history of disease process, history of being wheelchair bound, history of previous pressures, and mean scores on Norton's scale of risk, which is based on the subject's physical condition, mental alertness, ambulation, mobility and incontinence. No significant differences were observed in the preventive qualities of the two types of special mattresses in terms of the incidence, location, severity, or healing duration of the subjects' decubitus ulcers. Improved studies of common special mattresses are suggested.     

Factors affecting the pressure-distributing properties of foam mattress overlays

A universal concern of those in nursing care is the occurrence of decubitus ulcers. To minimize this problem foam overlays are routinely used on hospital beds throughout the country. This study was undertaken to develop laboratory testing procedures which will reliably predict the support characteristics of mattress overlays in clinical service. Initially, test methods based on constant load and constant deformation boundary conditions were developed. These methods were applied to measure the pressure-distributing properties of 10 polyurethane foams fabricated in a wide range of pliancies and densities. Based on these laboratory data, a single index was developed to express the effectiveness of each overlay in distributing interface pressures. This index was found to be influenced by the stiffness (ILD), density, and thickness of each device. These data were then compared with measurements of interface pressure obtained from volunteer subjects who were supported on mattress overlays fabricated from each of the original foams. Correlation of these data with the laboratory results demonstrated that the effectiveness index was an accurate predictor of mattress overlay performance under end-use conditions.     

A review of pressure reduction device studies.

When considering patient morbidity, mortality and costs, pressure sore formation is a major health care concern. An adjunct to the nursing care plan for prevention and treatment is the selection of a pressure reduction/relief device. This review of four pressure reduction device studies is intended to increase the vascular nurse's knowledge base concerning pressure reduction device efficacy. Each study is reviewed and graphed to identify like patterns within each study. Foam is judged to be least effective. Air cell and air mattress overlays are found to be intermediate devices and the low air loss beds appear to be the most effective. Few of the tested devices reduced pressure below 32mmHg at the heel site, leaving the heel at risk for breakdown.     

Efficacy and cost-effectiveness of the Thermo contour mattress

Use of air mattresses in reduction of pressure sore incidence is an important part of quality patient care. However, there will never be enough air mattresses to match the demand as increased education and an increase in the general provision of air mattresses can lead to an unrealistic expectation of obtaining air mattresses when required for patients. This raises the demand for air mattresses and increases costs within hospital trusts. This study examined a way to redress the balance through use of an alternative, cost-effective type of mattress (thermoelastic polymer) in the prevention of pressure sores. Prime consideration was given to the comfort of the patient. The claims of the manufacturers, Barrington Healthcare, that 'patients with Waterlow scores of 23 can be nursed safely on this product' were explored as part of the study. A total of 407 patients took part over a 6-month period. Twenty-four Thermo contour mattresses were loaned to one ward for the study and patients were allocated to the mattress through admission to the experimental ward. Patients were then split into two groups on two wards. Group B were allocated to a Thermo contour mattress and group A were nursed on air mattresses and foam mattresses generally used throughout the trust. Results showed that more patients were comfortable on the Thermo contour mattresses than on all other mattresses. Patients with Waterlow scores under 25 did not develop pressure sores on the Thermo contour mattress. However, the sample of patients with a Waterlow score of between 20 and 25 was small and therefore further research is required.     

Laboratory performance of alternating pressure air mattresses component and sequelae

The performance of three different alternating pressure air mattresses with different geometries of air cell were compared (Nimbus 3, Heritage, Tamora Plus), using simple performance indices based on pressure mapping. The aim of this study was to examine the effect on performance of elevating the backrest and thigh section of the bed into sitting position. Ten healthy volunteers of various sizes were pressure-mapped over the full pressure cycle on three alternating pressure air mattresseses with differing cell geometries. This was then repeated with the beds profiled to a sitting position. Performance of the alternating pressure air mattresses in terms of their ability to redistribute pressure dynamically was assessed in the different positions. The different alternating pressure air mattresses performed similarly with the bed in the lying flat position, but smaller cells appeared to be more effective in the sitting position. A conclusion was made that cell geometry may have an effect on the ability of the mattress to achieve alternating behaviour in the sitting position.     

Wound healing in acute spinal cord injury: effect of anticoagulation

Medical records were surveyed to test the impression that anticoagulation therapy administered to patients hospitalized for acute spinal cord injury impaired wound healing. Records for 25 patients with 26 wounds, located over the sacrum (21), thigh (two), occiput, heel, or buttock (one each), were reviewed. Among 11 wounds not associated with concurrent anticoagulation therapy, healing was delayed beyond 75 days in two patients. Among 15 wounds associated with anticoagulation therapy (heparin or heparin followed by coumarin derivatives), healing was delayed more than 75 days in nine patients (chi 2 = 4.53, p less than 0.05). This association of anticoagulation therapy with impaired wound healing in patients with an acute spinal cord injury suggests that this factor should be considered in future studies of wound healing.     

不同间隔时间静态空气垫对卧床患者皮肤减压效果的比较

目的：探讨静态空气床垫不同间隔时间对卧床患者压疮防治效果的影响。方法采用便利抽样及自身对照的方法,选择骨科患者100例,患者均取平卧位,采用全电脑压力传感器（ Xsensor测压毯）平铺于患者身下,卧普通床垫2 h后及平卧静态空气垫2,3,4 h后,对其两侧足跟部、骶尾部的平均压强峰值进行测量比较,并监测每例患者卧床期间的皮肤完整性和压疮发生情况。结果卧普通床垫2h后发生Ⅰ期压疮3例,发生部位为左足跟1例、骶尾部2例,压疮发生率为3％;卧静态空气床垫2,3,4 h后患者未见压疮发生,皮肤完整率为100％;平卧普通床垫2 h与平卧静态空气床垫2 h后患者左足跟部平均压强峰值分别为（185．03±11．34）,（69．13±9．64）mmHg;右足跟部平均压强峰值分别为（176．03±18．64）,（76．40±11．52）mmHg;骶尾部平均压强峰值分别为（253．03±28．64）,（100．23±18．36）mmHg,两组比较,差异有统计学意义（t值分别为7．126,6．287,4．235;P＜0．05）。平卧静态空气床垫2,3,4 h,足跟部、骶尾部受压皮肤平均压强峰值的变化比较,差异无统计学意义（F值分别为5．863,3．128,4．852;P＞0．05）。结论静态空气床垫能有效降低卧床患者受压部位的表面垂直压力,翻身间隔时间可延长至4 h1次,这样既减轻频繁翻身给患者带来的痛苦,同时也减轻了护理人员的劳动强度。