Randomized clinical trial comparing 2 support surfaces: results of the Prevention of Pressure Ulcers Study.

OBJECTIVE: To determine whether a viscoelastic polymer (energy absorbing) foam mattress was superior to a standard hospital mattress for pressure ulcer prevention and to analyze the cost-effectiveness in comparison with standard hospital mattresses. DESIGN: Unblinded, randomized, prospective trial. SETTING: Elderly acute care, rehabilitation, and orthopedic wards at 3 hospitals in the United Kingdom. PARTICIPANTS: 1168 patients at risk of developing pressure ulcers (Waterlow score, 15 to 20), with a median age of 83 years (25th to 75th percentile range, 79-87). INTERVENTIONS: Participants were allocated to either the experimental equipment (CONFOR-Med mattress/cushion combination) or a standard mattress/cushion combination; all were given standard nursing care. Pressure areas were observed daily. MAIN OUTCOME MEASURE: Development of nonblanching erythema. RESULTS: A significant decrease in the incidence of blanching erythema (26.3% to 19.9%; P =.004) and a nonsignificant decrease in the incidence of nonblanching erythema occurred in participants allocated to the experimental equipment. However, when the survival curve plots were analyzed at 7 days, both categories showed statistically significant decreases (P =.0015 and P =.042, respectively). Participants on standard equipment had a relative odds ratio of 1.36 (95% confidence interval [CI], 1.10-1.69) for developing blanching erythema or worse and 1.46 (95% CI, 0.90-1.82) for developing nonblanching erythema or worse. To prevent nonblanching erythema, the number needed to treat (NNT) was 41.9 (95% CI, -82.6-15.3). To prevent any erythema (blanching or nonblanching), the NNT was 11.5 (95% CI, 41.6-9.3). Participants with blanching or nonblanching erythema were significantly less mobile than participants with normal skin and more likely to have worsening mobility (P <.001). For participants with similar pressure ulcer status, mattress type was not associated with difference in mobility. CONCLUSIONS: Regardless of prevention routine, pressure ulcers occur. In this study, the experimental equipment showed statistical significance to standard equipment for prevention of blanching erythema; significance was not achieved for nonblanching erythema. Trend and survival analysis show that a larger study is required to determine whether this nonsignificant difference is genuine.

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.

Assessment of alternating-pressure air mattresses using a time-based pressure threshold technique and continuous measurements of transcutaneous gases.

Alternating-pressure air mattresses (APAMs) are used increasingly for the prevention and treatment of pressure sores. Laboratory evaluation techniques have centred largely on interface pressure (IP) measurement, typically analysing discrete maximum and minimum levels, or average pressure. However, since pressure relief varies with time, a time-based analysis technique has been developed for performance assessment. IP was recorded continuously, and the duration of pressures below three thresholds (30, 20 and 10 mmHg) was calculated automatically using a computerized rig. Fifteen healthy volunteers were used to evaluate the pressure-relieving characteristics of four APAMs, including one overlay. Results indicated significant differences (P < 0.001) between products when durations below the 20 and 10 mmHg thresholds were analysed, showing that some devices were only capable of momentarily relieving pressure. Maximum contact pressures on the sacrum were significantly lower (P < 0.0001) on devices whose inflation pressure was adjusted according to subject's body mass. This technique could assist in the selection of alternating or dynamic surfaces of any description with further clinical validation.

A study of infection in elderly nursing/residential home and community-based residents.

It is commonly believed that patients admitted to hospital from nursing homes/residential homes (NHRH) with infections are less likely to respond to treatment and have a higher fatality rate than counterparts admitted from their own homes ('the Community'). It is also believed that NHRH's harbour a reservoir of unusual and resistant organisms. These preconceptions may influence how these patients are managed. A database of 10593 sequential admissions to a Geriatric Medical unit over a three-year period was used to identify NHRH and community populations with a principal diagnosis of infection. They were investigated using the Department of Microbiology's database. The admission rate in the NHRH group was twice that of the community group. There were no significant differences in length of stay (LOS) [16 +/- 2 vs 17 +/- 2 days (s.e.m.)], or mean survival time (ST)(61 days (37-84) vs 48 days (25-72): 95% confidence intervals) between the two groups. Subgroups of the NHRH group did have significantly different survival times. Fatality rate was not significantly different between the NHRH (40%) or Community (35%) groups. Both the NHRH and community group underwent very similar levels of investigation (189 vs 200 investigations performed). The types and frequencies of pathogen seen in the two groups were very similar.

Assessment of alternating air mattresses using a time-based interface pressure threshold technique.

Laboratory evaluation techniques for support surfaces have centered largely around interface pressure (IP) measurement, typically analyzing discrete maximum and minimum levels, or calculating the average pressure. Nowadays, alternating pressure air mattresses (APAMs) are used increasingly for the prevention and treatment of pressure sores. Pressure relief (PR) provided by an APAM is time-varying. A computerized system that measures IP, air pressure, and pressure-time characteristics of dynamic support surfaces has been developed for performance assessment. Using this system, IP was recorded continuously and the durations of pressures below three thresholds (30, 20, and 10 mmHg) were calculated automatically. Fifteen sound volunteers were used to evaluate the pressure-relieving characteristics of four APAMs, including one overlay. Results indicated significant differences (p < 0.001) between products when durations below 20 and 10 mmHg thresholds were analyzed, showing some devices were only capable of momentarily relieving pressure. Maximum contact pressures on the sacrum were significantly lower (p < 0.0001) on devices where inflation pressure was adjusted according to the body mass of the subject. With further clinical validation, this tool could assist in the selection of alternating surfaces of any description.

Effect of intermittent pneumatic compression on lower limb skin perfusion.

Transcutaneous oxygen (tcPO2) and carbon dioxide (tcPCO2) measurements were used before, during, and after intermittent pneumatic compression (IPC) to assess lower limb skin perfusion in 21 healthy adult volunteers and 23 elderly patients. The temperature of the sensors was set at 44 degrees C during calibration and maintained throughout all tests. Resting tcPO2 was significantly lower (p less than 0.01) in patients than in controls. In all subjects tcPO2 decreased and tcPCO2 increased during compression. Patients showed a highly significant increase (p less than 0.001) in tcPCO2 during and after the treatment. Results of this study indicate that the symptomatic improvement, in peripheral vascular disease and wound healing following IPC, is not due to improved skin perfusion or enhancement of oxygenation and CO2 removal.