Bed-bound patients – those who may be obese, in hospice care, or recovering from wounds or bed sores – often find relief on an air-inflated mattress that spreads their weight over a larger area to provide increased pressure relief than would be possible with a conventional mattress. But more than a mattress filled with air, this medical device boasts of carefully placed small air holes that keep patients cool and dry. The bed was invented in the 1950s in Europe, but since coming to America it has been improved with new varieties, new materials, better blowers that keep it inflated, and controls that provide more than inflation.

“Patients who are bed bound develop pressure sores on their coccyx, the bone mid buttocks, so we provide specialty air-mattresses that replace a conventional mattress to provide pressure relief,” says Brian Emich, President of Galaxy Medical in Akron, Ohio. “One of the air mattresses we use has an AMETEK blower in the pump that keeps the mattress inflated. This product has been around for a while. One reason the system is so durable is the blower inside the pump unit,” he adds.

The point of low pressure

Sometimes called therapeutic air, the design has about 30 cells each with three or four pinholes. The patient’s weight is distributed so the pressure on the body’s pressure points is minimized. “It’s almost as if they are floating in a pool,” says Emich. “This lets blood flow into the coccyx area and prevents the skin from breaking down.”

The point of a low air-loss system, says Gregg Garland, CEO of support-surface manufacturer Moxi Enterprises, “is to redistribute the patient weight over the largest area possible, immerse the patient, and wick away moisture to keep the patient cool and dry. When a patient spends long periods in bed, the escaping air helps to remove humidity from underneath the patient because heat and moisture can contribute to tissue damage. So, reducing the humidity lowers the risk of wounds,” says Garland.

“Most equipment we distribute is for hospice patients throughout Ohio,” adds Emich. “People at end stages of life need medical equipment to get them through that journey as comfortably as possible. So we provide hospital beds, oxygen concentrators, wheel chairs, and air mattresses to patients in homes and nursing homes.”

Durability is important to Emich and his clients. When equipment is returned to the warehouse, it is cleaned and restocked. “We have Moxi air-mattress systems that are up to ten years old that are in daily use,” he says.

Early bed designs used a compressor to stay inflated, says Moxi’s Garland. “We started using AMETEK blowers in the 1990s. The beds and surfaces have changed mostly with new materials and features. We are sensitive to a couple more factors in wound care that is high friction and shearing forces. So the material should have a low-friction surface and

low shear. The material must also be waterproof because most patients are incontinent. It must also be durable and washable.”

In the last ten years, moisture wicking has become a predominant material characteristic. The medical industry was first to realize its importance. “I have been using the term ever since entering this business over 20 years ago, and now many consumer brands offer the feature in clothes to sports enthusiasts,” says Garland.

He adds that the industry is now dominated by adding new features. “We have the science down so now we compete on features. For instance, we have an automatic setup mode. It uses algorithms to set up the system based on the patient’s weight distribution. Also, when the bed frame is elevated, so the patient can sit up, the patient goes from flat to elevated, centering the weight distribution more around the trunk area of the body. So the power unit responds by pumping about 25 to 30% more air into the trunk area of the mattress to prevent the patient from bottoming out,” he says.

The mattresses are sold through a nationwide network so it is not uncommon for someone to call and ask for a new feature or tweak. “For instance, safety is a great concern, especially regarding patients who might fall out of bed. For them, we provide an optional safety cover with foam bolsters on the surface to prevent the patient from rolling off. Two bolsters are in the shoulder area and two in the calf area. We cannot restrain the patient so we have to devise clever ideas to prevent falls without restraints,” he says.

A range of sizes is another feature. “These are the many different widths, heights, lengths, and versions. For example, the bariatric world – for the morbidly obese – has a heavy-duty model. A standard mattress is 36-in. wide but can be had up to 60-in. wide. A full mattress depth is 8 to 10-in. but an overlay, a topper that goes on a standard foam mattress, is only about three to five-in. deep. And there are about five different power options that depend on the features selected.

Regarding the blower, Garland says his engineers prefer those from Ametek because they are durable and reliable. “It is a work horse. It has safety features to address overheating that make it unlike other blowers. The system is a little more expensive than some of the imported products, but we differentiate ourselves with a five-year warranty, which is unusual in this industry because the mattress works 24/7. We would not feel comfortable doing that if not for that blower and its reliability. In fact, some competitive products still use compressors, not blowers, because they are less expensive, so their warranties might be one or two years at most.”

A closer look at the blowers

Blowers selected by engineers at Moxi Enterprises are manufactured by AMETEK Dynamic Fluid Solutions and go into a range of hospital and healthcare beds. “In those applications, most designers select 5-in. Minijammers and 5.7-in. Windjammer blowers,” says AMETEK Application Engineering Manager Kevin Martin. The numbers refer to the diameter of the fan. Martin adds that the compressors used in other brands of medical mattresses resemble those used in ordinary aquariums. “For some beds the issue is not just pressure. There are flow requirements and that is where the generic compressors don’t stack up.” Compressors on low-cost mattresses just blow up the topper as if it were a conventional air mattress.

Martin says his company provides more than hardware. “We can do custom work for companies that need assistance, such as particular performance from the blower. For example, one high-end bed manufacturer asked for assistance making sure the mattress inflated at the right speed, provided the right pressure, and deflated as needed.”

Fluidized beds are an interesting variation to low-loss toppers, says Martin. “Technically it is an air bed but air flows through glass fluidized beads to provide another level of comfort and support for patients. Another treatment tactic is to vary the pressure at different areas of the mattress. It is usually done by using a controller to open and close simple valves. Another mattress pad uses the technique to inflate and roll the patient to avoid bed sores and provide climate control. This cannot be done with a compressor. It calls for a blower.”

The blowers are also considered more reliable than compressors. Martin says there are at least three reasons. “First, the company has been manufacturing blowers for more than 30 years. And we use brushless motors. Compressors use brushed technology, and brushes wear out. Hence, the blowers last longer. Also, in manufacturing, all bearing bores are machine to tight tolerances so fan alignment is better than on less expensive, competing units. And, rotor balancing makes for a quiet and long-life blower.”

Electronic controls on the high-end blowers allow fine tuning the operating parameters. “Recently, for one design, a team of engineers from AMETEK and the customer worked together to get perfect the blower operation. The application engineering team tuned the software to the exact performance and response necessary. The task was to match the operating parameters, find the right signal level, and minimal noise on the system,” says Martin.