Alternating pressure air mattresses as prevention for pressure ulcers: a literature review

OBJECTIVES: The purpose of this paper is to examine and synthesise the literature on alternating pressure air mattresses (APAMs) as a preventive measure for pressure ulcers. DESIGN: Literature review. DATA SOURCES: PubMed, Cinahl, Central, Embase, and Medline databases were searched to identify original and relevant articles. Additional publications were retrieved from the references cited in the publications identified during the electronic database search. RESULTS: Thirty-five studies were included. Effectiveness and comfort of APAMs were the main focuses of the studies evaluating APAMs. Pressure ulcer incidence, contact interface pressure, and blood perfusion were the most frequently used outcome measures to evaluate the effectiveness of APAMs. Fifteen randomised controlled trials (RCTs) analysed the pressure ulcer incidence. One RCT compared a standard hospital mattress with an APAM and found that the APAM was a more effective preventive measure. RCTs comparing APAMs with constant-low-air mattresses resulted in conflicting evidence. There was also no clear evidence as to which type of APAM performed better. All RCTs had methodological flaws. The use of contact interface pressure and blood perfusion measurements to evaluate the effectiveness of APAMs is questionable. Comfort of APAMs was the primary outcome measure in only four studies. Different methods for assessment were used and different types of APAMs were evaluated. Better measures for comfort are needed. A few studies discussed technical problems associated with APAMs. Educating nurses in the correct use of APAMs is advisable. CONCLUSION: Taking into account the methodological issues, we can conclude that APAMs are likely to be more effective than standard hospital mattresses. Contact interface pressure and blood perfusion give only a hypothetical conclusion about APAMs' effectiveness. Additional large, high-quality RCTs are needed. No conclusions can be drawn regarding the comfort of APAMs. A number of technical problems associated with APAMs are related to nurses' improper use of the devices.     

Comparison of transcutaneous oxygen and carbon dioxide monitors in normal adults and critically ill patients.

The performance characteristics of two transcutaneous combined PO2 (tcPO2) and PCO2 (tcPCO2) sensors were compared with single tcPO2 and tcPCO2 electrodes in critically ill patients. The relationship between arterial blood gases (PaO2, PaCO2) and transcutaneous values was linear. Correlation coefficients (r) varied from 0.79 to 0.87 for tcPO2 and 0.92 to tcPCO2. The tcPO2 readings were always lower than PaO2 values, but the tcPCO2, with modified calibration of the electrodes, did not differ significantly from PaCO2. There was no significant difference of clinical importance in the performance of the three monitoring systems.     

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.     

Effect of intermittent pneumatic compression on lower limb oxygenation

The effect of intermittent pneumatic compression (IPC) of the lower limbs on transcutaneous oxygen tension (tcPO2) was studied in 14 healthy volunteers and the same number of elderly patients. The oxygen sensor was calibrated at 37C in room air. This temperature was also used for measurements. Compression pressure in the IPC garment was standardized to 50mmHg inflation and zero mmHg deflation. Cycle time was set to 30 seconds inflation and 30 seconds deflation. It was found that using this combination of pressure and cycle times, tcPO2 fell during compression in all subjects and returned to the precompression level after the treatment. Although reactive hyperemia of various intensities occurred in some subjects after compression, tcPO2 did not rise significantly above the resting level. This suggests that the symptomatic improvement reported by patients treated with IPC was more likely to be due to enhanced removal of metabolites and supply of nutrients than to an improvement in leg oxygenation.     

Use of Pressurease and Airform mattresses in pressure ulcer care

Large cell dynamic air mattresses are effective in the prevention of pressure ulcers but they still have inherent problems, e.g. the ability of the mattresses to move patients along the mattress through the inflation and deflation of the cells. Also, there have been reports that the inflation and deflation of cells can cause motion sickness. This article reviews two mattresses from Sareo Healthcare Ltd: a static system, Pressurease; and a unique dynamic system, Airform. These two systems offer a cost-effective and clinically effective method of pressure ulcer prevention and therapy.     

Forensic analysis of crib mattress properties on pediatric CPR quality—Can we balance pressure reduction with CPR effectiveness?

Introduction

Single mode, pressure reduction (PR) crib mattresses are increasingly employed in hospitals to prevent skin injury and infection. However, single mode PR mattresses risk large mattress deflection during CPR chest compressions, potentially leading to inadequate chest compressions.

Hypothesis

New, dual mode PR crib mattress technology provides less mattress deflection during chest compressions (CCs) with similar PR characteristics for prevention of skin injury.

Methods

Epochs of 50 high-quality CCs (target sternum–spine compression depth ≥38 mm) guided by real-time force/deflection sensor (FDS) feedback were delivered to CPR manikin with realistic CC characteristics on two PR crib mattresses for four conditions: (1) single mode + backboard; (2) dual mode + backboard; (3) single mode − no backboard; and (4) dual mode − no backboard. Mattress displacement was measured using surface reference accelerometers. Mattress displacement ≥5 mm was prospectively defined as minimal clinically important difference. PR qualities of both mattresses were assessed by tissue interface pressure mapping.

Results

During simulated high quality CC, single mode had significantly more mattress displacement compared to dual mode (mean difference 16.5 ± 1.4 mm, p < 0.0001) with backboard. This difference was greater when no backboard was used (mean difference 31.7 ± 1.5 mm, p < 0.0001). Both single mode and dual mode met PR industry guidelines (mean surface pressure <50 mmHg).

Conclusions

Chest compressions delivered on dual mode pressure reduction crib mattresses resulted in substantially smaller mattress deflection compared to single mode pressure reduction mattresses. Skin pressure reduction qualities of dual mode pressure reduction crib mattress were maintained. We recommend that backboards continue to be used in order to mitigate mattress deflection during CPR on soft mattresses.     

Development and evaluation of an air mattress structure and function for reducing discomfort when elevating the head-of-bed

Purpose: To develop a new structure and function of alternating pressure air mattress (APAM) which reduces discomfort during head-of-bed (HOB) elevation and evaluate the effectiveness.

Method: An observational study (Study 1) and randomized crossover experiment (Study 2) were conducted in healthy adult volunteers. External force (interface pressure and shear force), body shift, discomfort (pushing feeling and pulling feeling) and HOB elevation angle were measured in Study 1. We developed a new APAM according to these findings. Study 2 compared the external force and discomfort of the new APAM with a control APAM. The magnitude of the discomfort was measured by visual analogue scale. Results: Study 1 clarified that the external force and discomfort during HOB elevation are positively correlated, and that discomfort can be reduced by decreasing the external force. Thus, we designed an APAM with a low friction layer and a novel mattress air-cell pressure control function to reduce the external force. Study 2 confirmed that the external force and discomfort were significantly decreased in the developed APAM. Conclusions: In this study, we developed a new APAM to reduce discomfort during HOB elevation and confirmed its effectiveness.

• Implications for Rehabilitation

• A positive correlation exists between the external force and the discomfort that arises during head-of-bed (HOB) elevation, and a mattress could be developed to reduce the discomfort by decreasing the external force.

• A new alternating pressure air mattress (APAM) with a low friction layer structure and novel control of mattress air-cell pressure that responds to HOB elevation angle can reduce discomfort during HOB elevation.

• This new APAM should allow more comfortable rehabilitation in bed-bound patients with mobility impairments.

     

The Theracute alternating pressure replacement mattress

The use of alternating pressure mattresses is still acknowledged as an effective adjunct in the prevention and treatment of pressure damage; however, with the plethora of equipment now available, there is an increasing need to provide information that supports the practitioners' decisions ensuring individual patients' clinical needs are met. This article reviews a new addition to the Talley Medical range of alternating pressure mattresses, the Theracute mattress replacement system.     

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.     

MEASUREMENTS OF INTERFACE PRESSURE BETWEEN BODY SITES AND THE SURFACES OF FOUR SPECIALISED AIR MATTRESSES

SUMMARY Four specialised air mattresses had interface pressure measured under six body sites prone to pressure sores in 10 subjects, supine and sitting. The mattresses were the Clinirest (SSI) and FirstStep (KCI) continuous airflow mattress overlays, and Airwave (Pegasus) and Nimbus (Huntleigh) alternating pressure air mattresses. On the mattress overlays, average supine interface pressures were 2.33 kPa (scapula), 4.15 kPa (elbow), 1.94 kPa (sacrum) and 2.79 kPa (buttock), although they were higher at the occiput (7.97 kPa) and heel (11.7 kPa). The alternating pressure air mattresses had an average minimum interface pressure close to zero for three sites, rising to 4.28 kPa under the heel. Average maximum interface pressures were 8.61 kPa (occiput), 5.21 kPa (scapula), 4.90 (elbow), 4.85 kPa (sacrum), 4.61 kPa (buttock) and 13.2 kPa (heel). No accepted scientific method exists for comparing the two types of mattress. Our data suggest a clinical benefit at the occiput and heel (supine) in using an alternating pressure air mattress and a benefit in using a continuous airflow mattress overlay at other sites.     

Matching patient need for pressure sore prevention with the supply of pressure redistributing mattresses

The authors have conducted a series of pressure sore prevalence surveys within one health district over a 4-year period. Additional surveys of the availability and deployment of pressure redistributing (PR) bed mattresses have also been made within the same district. The prevalence of pressure sores increased from 6.8% (1986) to 14.2% (1989) while the available stocks of PR mattresses increased from 69 (1987) to 186 (1989). Our results appear to question the common assumption that successful pressure sore prevention can be achieved through expanding the stocks of PR mattresses. Five possible reasons why the increase in mattress provision was matched with an increased prevalence of pressure sores are forwarded. The use of measures of prevalence rather than incidence rates to monitor the effects of clinical initiatives is discussed.     

Development and evaluation of a self-regulating alternating pressure air cushion

Purpose: To investigate the effect of alternating air cells of a newly developed dynamic cushion on interface pressure and tissue oxygenation levels. Method: This cross-over experimental study included 19 healthy volunteers. The dynamic cushion used has an automatic self-regulating alternating pressure air-cell system with 35 small and four large air cells for maintaining posture while seated. This cushion also has 17 bottoming-out detectors that automatically inflate the air cells to release a high interface pressure. To assess the effect of this alternating system, participants sat on the new cushion with an alternating system or static system for 30?min and then performed push-ups. The interface pressure was monitored by pressure-sensitive and conductive ink film sensors and tissue oxygenation levels were monitored by near-infrared spectroscopy. A reactive hyperaemia indicator was calculated using tissue oxygenation levels as an outcome measure. Results: The peak interface pressure was not significantly different between the groups. The reactive hyperaemia indicator was significantly higher in the static group than in the alternating group. Conclusions: An alternating system has beneficial effects on blood oxygenation levels without increasing interface pressure. Therefore, our new cushion is promising for preventing pressure ulcers with patients with limited ability to perform push-ups.

• Implications for Rehabilitation

• A dynamic cushion was developed, which consists of a uniquely-designed air-cell layout, detectors for bottoming out, and an alternating system with multiple air-cell lines.

• The alternating system did not increase interface pressure and it significantly reduced reactive hyperaemia after 30?min of sitting in healthy volunteers.

• This cushion is a new option for individuals who require stable posture but have limitations in performing scheduled push-ups for prevention of pressure ulcers.

     

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.     

Prevention of ventilatory disturbance while in the face-down position after macular hole surgery

The aim of the present study was to assess the effects of the face-down position on ventilatory function after macular hole surgery. The transcutaneous carbon dioxide tensions (tcPCO2) were measured in five patients who had undergone intraocular tamponade and in 17 normal subjects. The tcPCO2 measurements were done in patients following vitrectomy in the sitting position and in the prone position with their faces down over the semi-closed spaces of the conventional mats. In normal subjects, minute ventilatory volumes (V.E) were measured simultaneously with tcPCO2 in the sitting position and prone position. The newly introduced face-down mats (new mats) for the prone position were also tested in the normal subjects. In normal subjects, VE in the prone position with the conventional mats was significantly lower than that found in the sitting position (5.06 +/- 1.55 vs 6.06 +/- 1.64 L/min; P < 0.002). The tcPCO2 in the prone position was significantly higher than that in the sitting position (41.7 +/- 2.1 vs 38.0 +/- 1.9 mmHg; P < 0.0001). In post-vitrectomy patients, tcPCO2 in the prone position with the conventional mats was significantly higher than that in the sitting position (41.4 +/- 1.7 vs 38.6 +/- 2.2 mmHg; P < 0.02). The tcPCO2 in the prone position in normal subjects was significantly lower using new mats than that when using conventional mats. The use of conventional mats during a prone position, increased the tcPCO2 values when compared to the tcPCO2 values obtained during the sitting position in patients following vitrectomy. This could be due to either a decrease of the VE caused by limited thoracic movement or rebreathing of the exhaled gas over the semi-closed space, or both. The new mats might be useful in alleviating the increase of tcPCO2 by eliminating the rebreathing of the exhaled gas.     

Pulmonary arterial wedge pressure measurement can modify pulmonary hae mo dynamics in patients with chronic lung disease

Summary. In 20 patients with chronic lung disease in stable condition, haemodynamic values were compared during wedging of a Swan-Ganz catheter, either in a distal branch of the pulmonary artery, or by balloon inflation (with 1 ml) in a proximal branch, mostly excluding right lower lobe perfusion. Average pulmonary arterial wedge pressure, systemic arterial pressure, transcutaneous and mixed venous oxygen saturation, cardiac output and pulmonary blood volume (PBV) were not statistically different during distal and proximal wedging, but systolic pulmonary arterial pressure and pulmonary vascular resistance were slightly higher during balloon inflation (P < 0.05). In four patients, PBV decreased by 20% or more; cardiac output was reduced and mean systemic arterial pressure diminished by 10 mmHg or more in three patients. Of the two patients with the lowest PBV, one did not tolerate the balloon inflation because of dyspnoea, and the other showed dramatically haemodynamic changes. These were more likely to occur when the occlusion lead to the exclusion of a still well perfused area. Our results support optimal matching between ventilation and perfusion in patients with chronic lung disease, although both are inhomogeneous. When pulmonary vascular restriction can be suspected, pressure obtained during catheter wedging by balloon inflation should be interpreted with caution. Monitoring arterial oxygen saturation and systemic arterial pressure before and during the manoeuver could help to diagnose haemodynamic effects of the balloon inflation in a proximal pulmonary artery.     

A descriptive study of skin temperature, tissue perfusion, and tissue oxygen in patients with chronic venous disease

Chronic inflammation and microcirculatory disturbances of the skin have been implicated as causative factors of complications associated with chronic venous disease (CVD). The purpose of this study is to describe the mean differences between and correlations among three measures of microcirculation: skin temperature (Tsk), tissue perfusion/blood flow (BF), and tissue oxygen (tcPO(2)) of CVD-inflamed skin compared to normal controls. In a convenience sample of 55 patients with CVD (n = 31) and without CVD (n = 24), Tsk was measured with an infrared thermometer, BF with a laser Doppler flowmeter, and tcPO( 2) with a transcutaneous oximeter across three measurements periods 1 week apart (Times 1, 2, and 3) at the medial aspect of both lower legs. Tsk was higher (1.2 degrees C) across all measurement periods (p < .05), BF was higher at Times 1 and 3 (p = .002 and .012, respectively), and tcPO(2) was lower at Times 1 and 3 (p = .013 and .050, respectively) in the CVD group as compared to the non-CVD group. BF and Tsk were positively correlated at Times 1 and 2 (r = .516, p < .005; r = 0.278, p = .04) but not at Time 3 (r = 0.235, p > .05). No consistently significant correlations were found between tcPO(2) and BF or tcPO(2) and Tsk (p > .05). Tsk and BF were higher in the skin of lower legs affected by CVD than in those not affected. Pathological processes in the skin produce heat detectable by an infrared thermometer. Measurement and monitoring of Tsk can augment clinical findings and guide treatment when localized inflammation is suspected. Future studies of Tsk should be directed toward the usefulness of infrared technology to develop a CVD leg ulcer prediction model.     

Lower body positive pressure by anti-G garment inflation: a suitable method to increase pulmonary capillary wedge pressure in healthy elderly subjects

In a study on non-invasive assessment of pulmonary capillary wedge pressure (PCWP), we sought a method to increase PCWP non-invasively. We hypothesized that inflation of an anti-G garment was suitable to increase PCWP non-invasively in healthy elderly subjects. In 20 subjects, aged 70 +/- 4 years (mean +/- SD), before, immediately after, and 4 min after anti-G garment inflation to 52 mmHg, PCWP and mean pulmonary artery pressure (MPAP) were measured with a Swan-Ganz catheter, and mean arterial blood pressure (MAP) with Finapres, in supine and semi-recumbent position. Supine, PCWP (mmHg, mean +/- SD) increased from 9.9 +/- 2.1 to 15.5 +/- 3.9** immediately after inflation and 13.4 +/- 3.7** at 4 min; semi-recumbent from 8.9 +/- 2.0 to 17.5 +/- 3.3** and 14.7 +/- 2.9** (*P<0.05, **P< 0.001 versus before inflation). MPAP (mmHg) increased after inflation: supine 16.9 +/- 2.3 to 22.3 +/- 4.6** and 20.6 +/- 3.9** and semi-recumbent 15.7 +/- 2.8 to 24.3 +/- 5.1** and 22.5 +/- 3.5**, suggesting that increased preload was the primary effect of anti-G garment inflation. Supine MAP (mmHg) increased from 96.0 +/- 11.3 to 101.4 +/- 13.4** and 100.5 +/- 12.7* and semi-recumbent from 102.0 +/- 8.9 to 108.3 +/- 11.4** and 106.0 +/- 11.3*, suggesting an effect of increased afterload as well. The latter was supported by an increase in total peripheral resistance (d s cm(-5)) from 1346 +/- 299 to 1441 +/- 384 after 4 min (P = 0.057) and from 1461 +/- 341 to 1532 +/- 406 (P = 0.054), supine and semi-recumbent respectively, while cardiac output remained unchanged. Complications did not occur. We conclude that in healthy elderly subjects, anti-G garment inflation is a safe, non-invasive, method to induce a significant increase in PCWP. Our findings justify its application in future studies in which non-invasive temporary increase in PCWP is required.     

经皮氧分压联合四肢多普勒早期诊断糖尿病周围血管病变

目的探讨四肢多普勒联合经皮氧分压在诊断糖尿病周围血管病变的价值。方法检测192例糖尿病患者下肢血管多普勒频谱及测定踝肱指数(ABI)、经皮氧分压(TcPO2)等值。结果踝/肱指数(ABI):34例ABI<0.9,11例ABI在0.9～1.0,134例ABI在1.0～1.3,13例ABI 1.3～1.4;经皮氧分压Tc-PO2:9例TcPO2在<20 mm Hg,101例TcPO2在20～39 mm Hg,81例TcPO2≥40 mmHg;两项检查结果完全正常者55例。结论四肢多普勒联合经皮氧分压对于早期诊断糖尿病周围血管病变尤其对无症状早期患者具有一定临床应用价值。     

Influence of external pressure on transcutaneous oxygen tension and laser Doppler flowmetry on sacral skin

Summary. The effects of external pressure upon transcutaneous oxygen tension (tcpO₂) and skin blood flow (SKBF) over the sacral area were studied in 16 healthy volunteers. Pressure was applied on the sacral area using a special device which included tcpO₂ and laser-Doppler flowmetry probes. The mean values of tcpO₂, SKBF and wave occurrence of the flow were analysed for 18 increasing pressure levels. A significant decrease of tcpO₂ was observed from 40 mmHg (5.3 Kpa) of applied pressure, while we obtained a significant decrease of SKBF when the external pressure was at 20 mmHg (2.7 Kpa). Using a non-linear regression model, we have found a fourth degree polynomial to describe the relationship between tcpO₂ and SKBF according to increasing pressure. SKBF slow wave occurrence decreased when external pressure was at 10 mmHg (1.3 Kpa), while rapid wave occurrence significantly decreased only at 120 mmHg (16.1 kPa) pressure.     

Collecting pressure ulcer prevention and management outcomes: 2

The first part of this article (Vol 11(4): 230-8) outlined the argument that a combination of efficacy and effectiveness is required to assess fully the impact of interventions such as pressure-redistributing (PR) beds and mattresses. In addition, it described the methodology of this multinational, multicentre, prospective, non-randomized cohort study designed to record the occurrence and characteristics of patients vulnerable to, or with, established pressure ulcers. This article reports further details of the characteristics of the 2507 UK adult hospital patients recruited to the study. Over 40% (42% n = 1046) of all subjects were considered to be at an elevated risk of developing ulcers (Waterlow score of 15 or greater) (Waterlow, 1985). Many were inactive with 332 (13%) confined to bed alone with a further 262 (10%) confined to bed and their chair. Most (74% n = 1868) were nursed upon PR beds and mattresses, while fewer subjects were provided with a PR seat cushion (n = 547; 27%). Two hundred and fifty-seven subjects (10%) experienced at least one change of bed mattress during their stay in hospital, with two subjects being nursed on five different mattresses during their hospital stay.