Mattress may help prevent surgical pressure ulcers
Studies point to better outcomes
No one can say for certain how often lengthy surgical procedures and recovery periods result in pressure ulcers. But there is enough evidence to indicate that a connection exists. A key question is, what can be done to prevent them?
Thus far, products in this market have primarily been mattress overlay systems designed for the operating room and postoperative care. In limited clinical trials, their effects have been mixed.
The most aggressive contender, from a marketing standpoint, has been the MicroPulse system (MicroPulse Inc., Portage, MI), a patient support surface described by its manufacturer as pad filled with "more than 2,500 air cells that systematically inflate and deflate to maintain blood circulation." The MicroPulse mattress currently rents for $300 a month; there is no outright purchase plan.
Sharon Aronovitch, PhD, RN, CETN, an education, research, and medical-legal consultant in Delmar, NY, has tested MicroPulse. She says the system contains thousands of bubble cells enclosed in a replaceable bacteriostatic material. The mattress pad hooks to a control box via hoses that deliver air to the system. As some cells inflate, others deflate, in a cycle lasting from about three to five minutes. The motion is supposed to constantly relieve and redistribute pressure across the body.
Because each cell is so small, intense pressure only occurs over a very small area. When it is relieved by the undulation of the mattress, blood flow is replenished very quickly, so the theory goes.
In two week-long trials financed by MicroPulse, researchers compared the mattress to conventional surfaces used in the operating room. At St. Paul's Hospital in Vancouver, BC, researcher Vince Dunlop, critical trials coordinator, reached this conclusion: "The MicroPulse mattress is effective in decreasing the incidence of pressure ulcers compared to the regular conventional mattress system in cardiac surgical patients." Several previous studies, according to Dunlop and other sources, have shown that the risk for OR-acquired pressure ulcers is relatively high for cardiac surgical patients, in part because their operations last so long.
Patients selected for the study were at least 18 years old, scheduled for cardiothoracic surgery of at least three hours, and did not have any evidence of a pressure ulcer at the baseline visit. Patients randomized to the experimental group (97) were placed on the MicroPulse surface both in the OR and during recovery in their hospital beds. Patients randomized to the control group (98) were placed on a gel pad in the OR and on the standard hospital mattress postoperatively.
Pressure ulcer incidence lower than expected
In the MicroPulse group, 1% acquired a pressure ulcer, compared with 6% of the control group. The low incidence in both groups surprised Dunlop, who had expected incidences of 15% in the control group and 5% in the MicroPulse group. "We're not sure if the low numbers were associated at all with the possibility that the patients and some of the staff knew what we were up to," Dunlop says. "We're always conscious of skin care at this hospital, and I think we generally have a lower incidence than average."
In addition, most of the patients in the study population were independent, ambulatory, and self-sufficient prior to surgery. They generally recovered quickly, which may make the study subjects at relatively low risk for pressure ulcers to begin with, Dunlop speculates.
In similar seven-day pilot study at the Albany (NY) Medical Center, Aronovitch compared MicroPulse to conventional OR mattresses. Once again, patients were placed either on a MicroPulse unit or on standard support surfaces during surgery and recovery. The primary efficacy variable was the occurrence of a pressure ulcer at any time within seven days of surgery. The same criteria for age and length of surgery that were used in the Vancouver study were used in the Albany study, but surgeries were not limited to the realm of cardiology.
Ninety patients were put on the MicroPulse surface during surgery, and 80 on a conventional surface. None of the MicroPulse patients developed pressure ulcers, while seven (8.75%) of those who were placed on conventional surfaces did. Four patients developed one ulcer, two developed two ulcers, and one developed three ulcers. One of the ulcers was stage 1, four were stage 2, and six were unstageable.
The investigators concluded that the MicroPulse surface was safe and effective for reducing pressure ulcer incidence in patients undergoing surgeries of three hours and longer. As expected, a few patients had difficulty adjusting to the novel surface during recovery. Nevertheless, the overall benefits of the MicroPulse surface far exceed any potential risks associated with the use of the device, says Aronovitch. "We were very excited by the results," she says, adding that that even if only 5% or 6% of surgical patients develop pressure ulcers, the number is still significant and deserves consideration.
MicroPulse studies not blinded
Critics of the MicroPulse studies fault the study design for not switching patients from the MicroPulse surface to a conventional surface during recovery to help isolate the effects of the test mattress during surgery itself. In addition, "people who are examining the skin know which surface the patient is on, so the studies really aren't blinded, which creates a source of bias," commented one source who asked not to be identified. The fact that MicroPulse funded both studies also was cited as a reason to view the results cautiously.
While the MicroPulse surface fared well in these two trials, another OR mattress overlay underwhelmed researchers. Alyce Schultz, PhD, RN, a nurse researcher at Maine Medical Center in Portland, conducted a study to evaluate the effectiveness of a special operating room mattress overlay and heel and elbow protectors in preventing the development of pressure ulcers. The Association of Operating Room Nurses funded the study. Schultz declined to mention the mattress under study because her research team has not filed the final study results.
In prior research beginning in 1994, Schultz found that surgical patients at her facility were 90% more likely to develop a pressure ulcer than were nonsurgical patients. "That's a snapshot of a particular day, but we didn't know when the wound started because we hadn't collected prospective data." She hypothesized that the incidence of pressure ulcers would be 40% lower in patients who used a mattress overlay and special protectors as compared with patients on the standard OR bed with routine padding.
Schultz randomized 413 patients to receive either typical operative care on a conventional mattress or on the new mattress overlay and protectors. No statistical differences were found between the control and experimental groups. Subjects were inspected for skin changes daily for six days. If discharged early, patients were made aware of suspicious areas and were phoned on day six. Schultz emphasizes that the study involved tightly controlled randomization and blinding. "Research assistants who examined the subjects did not know which patients had been on which type of mattress," she says. That wasn't true of the Vancouver and Albany studies - a factor that could have affected the results.
The results surprised Schultz. Overall, 89 subjects (21.5%) developed at least one pressure ulcer. Eighty subjects developed Stage I ulcers only, and nine developed Stage II ulcers (2.2%). One patient developed a Stage IV ulcer (this patient was very ill and subsequently died). Fifty-five (62%) of the 89 patients who developed pressure sores were on the study mattress. "We concluded that the mattress didn't do the job it was designed to do," Schultz says. She adds that the incidence for Stage I ulcers was higher than expected, while that of Stage II and higher was lower.
The relatively high overall incidence of pressure sores might be explained by the fact that 50% of the study population were inpatients prior to surgery, which indicates a sicker population than in the MicroPulse studies. "We sought to oversample inpatients because we believed they were the group most at risk for developing pressure ulcers, " explains Schultz.
Does the apparent success of the MicroPulse overlay in two studies mean hospitals should stock up to protect themselves from litigation? We'll consider that question in the next issue.
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