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The Effect of Using a Low-Air-Loss Surface on the Skin Integrity of Obese Patients: Results of a Pilot Study

Empirical Studies

The Effect of Using a Low-Air-Loss Surface on the Skin Integrity of Obese Patients: Results of a Pilot Study


Obese patients often are immobile, acutely ill, and at high risk for developing pressure ulcers when admitted to acute care facilities. Pressure-relieving mattresses are an integral part of a pressure ulcer prevention plan of care.

Patients with a body mass index (BMI) >35, weight between 250 and 500 lb, and a minimum 3-day length of stay were recruited to participate in a pilot study to evaluate the safety and use of a new low-air-loss, continuous lateral rotation bariatric bed. Skin inspection was performed at the beginning and end of the study (maximum 7 days). Participants included 21 consecutively admitted patients (10 men, 11 women, average age 51.7 years [range 32 to 76], average BMI = 51.4 [range 37 to 71]) with an average Braden pressure ulcer risk score of 14.7 (range 9 to 21). Most (n = 11) were receiving treatment in the intensive care unit. Six patients had 10 pressure ulcers (six Stage I, four Stage II). Average length of stay on the surface was 4.8 days (range: 2 to 8 days); ulcers decreased from an average size of 5.2 cm2 to 2.6 cm2. No new pressure ulcers developed. Controlled clinical studies to assess the efficacy of pressure redistribution mattresses in this high-risk population are needed.

     One in 10 patients admitted to healthcare facilities in the United States is morbidly obese.1 Obesity is a condition that substantially raises the risk of comorbid conditions such as hypertension, dyslipidemia, type 2 diabetes, coronary heart disease, stroke, gall bladder disease, osteoarthritis, sleep apnea, and respiratory problems.2-4 More than 250,000 deaths annually are attributed to obesity in the US.5

     Obese patients often are immobile and acutely ill when they present to the hospital.6 Unique factors such as poor vascularization of adipose tissue and a large amount of weight distribution over the entire supine surface area increase pressure ulcer risk in the bariatric patient.7,8 A recent analysis9 of 2006–2007 pressure ulcer prevalence survey data (N = 167,936) showed that patients >300 lb had overall pressure ulcer prevalence rates ranging from 11.4% to 28.6% compared to 10.7% to 13.1% in persons weighing 151 to 300 lb. Pressure ulcers have been associated with lengthened hospital stays, increased costs of care, 10-12 and higher mortality rates.13-15 The ability to manage these complex patients in the acute care facility is crucial in today’s hospital environment.

     Pressure-relieving mattresses are an important part of an overall pressure ulcer prevention plan of care. Low-air-loss surfaces have been used for patients at significant risk for pressure ulcer formation according to existing clinical protocols within facilities, which include the Braden Scale for Pressure Ulcer Risk for pressure ulcer formation, and for patients with existing pressure ulcers.16,17 Although evidence in the available literature may be limited,6 low-air-loss surfaces may assist in skin microclimate management by wicking excess moisture away from the skin, a specific concern for the bariatric patient.

     To assess the safety and clinical use of a new low-air-loss surface, a pilot study was conducted among obese inpatients in a tertiary care facility. Study patients were placed on the TotalCare® Bariatric Plus Therapy System (Hill-Rom, Inc., Batesville, IN) surface, which features Advanced MicroclimateTM Technology and provides continuous lateral rotation therapy (CLRT).


     After obtaining Institutional Review Board (IRB) and hospital nursing council approval to use a product that had not been released for marketing by the US Food and Drug Administration (FDA) at the time of the research, a convenience sample of 21 patients at a nonprofit, 710-bed tertiary care facility in Texas was selected to participate in a pilot study. Patients with a body mass index (BMI) >35 and weight between 250 and 500 lb were eligible to participate if they, or their legal representative, were willing and able to provide informed consent. Study candidates were recruited from the general hospital population, admitted to the study consecutively, and expected to remain on the study mattress for a minimum of 3 to a maximum of 7 days. Patients who were clinically unstable were allowed to remain on the surface for >7 days until clinically stable. The presence or absence of a pressure ulcers did not affect eligibility but patients using only one turning surface were excluded from the study. Turning surfaces are defined as the number of turning options for a body surface other than the surface with the pressure ulcer. If a patient has multiple pressure ulcers in various body locations, the ability to turn to relieve pressure becomes more limited; thus, these patients may require a specialty bed.

     Each patient’s admitting diagnosis, nutritional status, Braden Risk score, demographic information, and medical history (including comorbid conditions and physical assessment data) were collected on entry into the study. Because this bed system was designed to prevent and manage existing pressure ulcers, study variables included assessment of overall product functionality in the hospital critical care and medical settings and daily skin examinations to assess the presence of new or existing pressure ulcers. Skin assessments included manual measuring of length and width of any pressure ulcers present for each patient at initial placement of the product, at day 3/4, and at day 7 (end of study). Ulcers were staged using National Pressure Ulcer Advisory Panel definitions.18 The two principal investigators, both certified wound ostomy continence nurses, performed all pressure ulcer measurements (no formal inter-rater reliability was established). Unexpected patient skin deterioration (based on condition at admission) was to be reported to the study sponsor and the clinical treatment team assessed whether the patient should be removed from the study. Patients with pressure ulcers received standard pressure ulcer treatment per hospital guidelines throughout the study. Bed system safety was assessed continually by detailing any problems in functionality of the bed frame or if skin breakdown occurred. Study data were recorded on a case report form provided by the sponsor (Hill-Rom, Inc., Batesville, IN). If new ulcers occurred, they were recorded, along with staff concerns regarding the functionality of the bed system.

     In addition, surveys were placed in the units and on participating patient charts for completion by the primary caregivers and ancillary staff, including patient care assistants, physical therapists, and respiratory therapists, integral components of the patient care team. Questions related to patient mobility and repositioning, bed maneuverability, use of CLRT and percussion and vibration, whether caregivers thought the bed kept the patient dry and comfortable, and whether the bed controls were easy to operate for the caregivers; answers were provided using a 4-point Likert scale (1 = very dissatisfied to 4 = very satisfied). Completed surveys were placed in a private collection box in the unit.

     Cognitively able patient participants completed patient comfort surveys, which were part of the case report form. Patients rated the bed’s comfort in different positions, firmness, perceived ability to ingress and egress both from the side and foot of the bed, and noise level of the bed’s blower using a multiple choice questionnaire where 1 = very uncomfortable to 4 = very comfortable. Survey results were averaged and provided an overall assessment of comfort.

     Data analysis. Due to the limited number of subjects enrolled, descriptive analysis was applied to the study data. To evaluate change in pressure ulcer size, ulcer length and width were multiplied and percent healing calculated by dividing final wound surface area by initial surface area. Only change in surface area was used to measure pressure ulcer healing.


     Twenty-one patients, predominantly in the intensive care setting (n = 11) were enrolled, including 10 men and 11 women, average age of 51.7 years (± 14, range 32 to 76). Patients spent an average of 4.8 days (± 2.5, range 2 to 8 days) on the mattress. Average patient height was 66.2˝ (± 3.8, range 59˝ to 74˝) and average weight 319.9 lb (± 35.9, range 262 to 347 lb). Average BMI was 51.4 (± 10.3, range 37 to 71) and average Braden pressure ulcer risk score was 14.7 (± 3.4, range 9 to 21) Braden Scores were distributed as follows: four patients >19 (slight to no risk), one patient 17–18 (mild risk), four patients 15–16 (mild risk), eight patients 12–14 (moderate to high risk), and four patients <12 (high to very high risk). Patients with existing pressure ulcers (n = 6) had lower Braden Scores than patients without ulcers (average 11.8, ± 2.6, and 15.8, ± 3.2, respectively). Of the 21 participants, one (5%) had paraplegia and nine (43%) were cognitively impaired (mostly due to sedation). Almost all study participants needed some respiratory support: eight (38%) required mechanical ventilation, 10 (48%) had oxygen delivered through nasal cannulae, and seven (33%) were on Bi-Pap (see Table 1).

     At the start of the study, six patients had 10 pressure ulcers — six were Stage I and four were Stage II (see Table 2). The average ulcer surface area measured 5.2 cm2 (± 5.2, range: 0.3 cm2 to 12 cm2) at admission and 2.6 cm2 (± 5.0, range 0 cm2 to 12 cm2) at discharge. Five ulcers on three patients healed during the study (length of stay on mattress ranging from 5 to 6 days). No nosocomial pressure ulcers developed during the study period.

     The average overall caregiver satisfaction rating with the pilot version of the bed system was 3.6; patient-reported comfort reported averaged 3.9. Patients (n = 14) interviewed by the Principal Investigator reported being comfortable while resting in bed.

     Patients were allowed to utilize CLRT while in the study; however, no CLRT-specific data were collected.


     After being placed on the study surface, no new pressure ulcers developed in any of the 21 patients (BMI range 51 –77) enrolled. Six patients had 10 existing ulcers; five ulcers healed, two decreased in size, and three remained the same size (surface area). None of the ulcers enlarged in size. More than 50% of patients entered into study were at moderate risk for developing pressure ulcers (Braden ≤14) and four were at high risk (Braden ≤12), with an average Braden Risk Score of 14.7. Although this is a small study sample, it has provided some initial data that indicate this bed system is safe and may provide positive skin outcomes in acutely ill bariatric patients.

     Providing pressure-redistributing surfaces for at-risk patients is an important part of a pressure ulcer prevention program. The Centers for Medicare and Medicaid Services19 (CMS) developed a list of conditions defined as “reasonably preventable through proper care” and for which Medicare will no longer pay at a higher rate if the patient acquires them during a hospital stay; this list includes pressure ulcers. As of October 1, 2008, hospitals will not receive payment for a pressure ulcer that is not present on admission.20 As a result and as a part of general efforts to improve quality care, hospitals are now developing aggressive pressure ulcer prevention programs.

     Obese patients have been shown to be at greater risk than persons of normal weight for developing pressure ulcers. Patients weighing >351 lb had a 9% to 99% greater prevalence of actual pressure ulcers than would have been expected in a normal distribution.9 Patients weighing >300 lb have been found to have overall prevalence rates ranging from 11.4% to 28.6% as compared to the 10.7% to 13.1% range in weights 151 to 300 lb.9 Patients weighing ≥351 lb also have lower average Braden Scale® risk scores (15–17) than patients at lower weights (18–19) through >100 lb and an average Braden score of 16.9 Patients who weigh more than 351 lb also have higher overall prevalence and nosocomial prevalence than patients of weights ranging from 151 to 350 lb.8

     Obese patients may have extended length of stay due to complications associated with comorbidities. These patients also are more difficult than the general hospital population to mobilize and reposition.21 In many cases, it may take several caregivers to perform routine tasks. The current nursing shortage has had a negative impact on the patient care process. Nurses report their ability to ensure overall patient safety and detect patient complications early has been compromised.22 With all of these current challenges, providing optimal pressure-redistributing surfaces on admission to patients at high risk for developing pressure ulcers will be a key component of overall preventative care.


     The results of this study must be interpreted prudently due to the small sample size and lack of a comparator arm. No formal inter-rater reliability was established. In addition, sample size was further reduced because not all patients were able to complete the patient comfort survey.


     The results of this small, non-randomized pilot study of 21 hospitalized obese patients suggest that the new pressure-redistribution, low-air-loss support surface evaluated is safe and may help in the prevention and management of Stage I and Stage II pressure ulcers. Further studies comparing specific clinical outcomes, including pressure ulcer prevalence, incidence, and pulmonary outcomes utilizing CLRT, are needed to allow staff to make evidence-based decisions regarding the surface of choice for specific patient populations.