Mechanical engineering researchers at the UCLA Samueli School of Engineering in the US have designed a mattress prototype that aims to improve airflow and reduce fluid buildup, commonly associated with prolonged bedrest.

The mattress helps prevents pressure ulcers by alternating pressure across the body and, at times, increasing peak pressure rather than reducing it to restore blood flow.

Commonly, pressure ulcer prevention procedures involve healthcare staff manually moving and turning patients every two hours. However, this can cause potential injuries for caregivers and be costly and cumbersome.

The researchers hope that the mattress will address this problem. Their research study is published in the journal Science Robotics.

Jonathan Hopkins, the study leader and a professor of mechanical and aerospace engineering at UCLA Samueli, explained: “We set out to build an affordable, versatile and practical mattress that would be much more effective in preventing pressure ulcers.”

With more than 1,200 linear actuators, the mattress shifts between peak and pit states, applying and relieving pressure to optimise blood flow

Jonathan’s team previously created a bed featuring 1,260 linear actuators that can be independently controlled to test how different surface patterns affect blood flow and pressure. The research findings led to the design of the alternating pressure mattress that utilises a lattice of compliant mechanisms, which enables smooth transitions between two alternating checkerboard-like surface patterns while minimising actuation energy and cost.

To demonstrate the performance of their mattress, the researchers tested their design on a standard bedframe using a sensor-equipped foam pad on top of the mattress and a 99.7kg anatomical dummy.

The sensors tracked pressure levels across the body as the mattress shifted between its two states of pressure, relieving pressure at the troughs and applying pressure to the peaks. The pressure data were capped at the average occlusion pressure threshold of 32 millimetres of mercury — an average pressure beyond which blood and lymphatic fluids are prevented from flowing into tissue, causing pressure ulcers, according to the UCLA researchers.

Nearly 30 balancing springs are incorporated into the design so that the transition between the two states of pressure is smooth and gentle. The researchers also developed a software tool using a patient’s height and weight to determine the optimal number and placement of balancing springs needed to minimise the force required to actuate the mattress for patients of varying sizes. By attaching a few low-power linear actuators to the structure, the mattress can transition between states automatically. But it can also be set in motion by a caregiver with little effort.

“Imagine that the black squares of a checkerboard rise up to support the patient while the white squares retract to provide pressure relief at their locations,” Jonathan said.

“Then, after some time, the white squares rise upward and the black squares sink to alleviate the pressure just applied — the peaks become the pits, then vice-versa. That is cyclically repeated with the hope of ensuring there’s no place where blood flow is persistently occluded.”

Findings from the research also suggested that increasing pressure differences — within comfort limits — more effectively restored circulation to areas under pressure. So instead of reducing overall peak pressure, the team focused on ensuring an increased pressure difference between the raised and lowered states and alternating which body parts bear the most force on the mattress at any given time. The alternating pressure means that the body’s points of contact under pressure are minimised to no more than 50 percent of the time.

In addition, the mattress’ design allows for finer pressure redistribution informed by real-time data and tailored to individual user characteristics, such as height and weight.

The prototype is currently undergoing volunteer testing at a professional lab to assess its effectiveness in real-world settings.