What is Differential Air Pressure?

Astronaut in Space

Breakthroughs in technology are taking modern physical therapy to new heights. As we learned in the previous post in this series, physical therapy technology has come a long way, with new advancements in the ways physical therapists assess, monitor, and rehabilitate patients.

While many of these advancements can be found in AlterG® physical therapy tools, differential air pressure (DAP) remains the cornerstone technology on which the AlterG® Anti-Gravity Treadmill™ is based. Here’s a closer look at what makes DAP such a milestone in PT innovation.

What is Differential Air Pressure (DAP)?

Differential air pressure (DAP) is a patented technology developed by NASA engineer Dr. Robert Whalen. Initially, Dr. Whalen was tasked with finding a way for astronauts to run and keep in shape while in outer space.

Eventually, Dr. Whalen arrived at DAP, a pressurized bubble of sorts that held astronauts down on a treadmill using the principles of differential pressure. It was this patented technology on which the first Anti-Gravity Treadmill prototype, launched in 2005, was based.

“Differential air pressure (DAP) is a pressurized, variable lifting force used to decrease the impact of gravitational forces and body weight during walking, running, or exercise. DAP is frequently used in various physical therapy applications for safely training and rehabilitating patients.”

How AlterG® Integrates DAP for PT and Athletic Conditioning

Rather than help astronauts exercise, though, the Anti-Gravity Treadmill uses DAP to help humans defy gravity here on earth. The AlterG® Anti-Gravity Treadmill integrates DAP, allowing PTs to make incremental adjustments to variables like incline, body weight, and speed.

To use DAP, patients wear specifically designed shorts that create an airtight enclosure attached to the treadmill system. After the PT calibrates the person’s size and weight, they can then determine how much strain can be put on the patient’s body for the purposes of rehab.

During a workout, the air pressure system can be used to reduce body weight in increments as small as one percent. Body weight can be reduced up to 80%. For example, imagine a patient who weighs 200 pounds, but whose injury only allows for 40 pounds of body-weight support to exercise safely. With DAP, this clinical application is possible.

The air pressure system can reduce body weight in increments as small as one-percent increment. Body weight can be reduced up to 80%.

Why Should Clinicians Care about DAP?

DAP and the Anti-Gravity Treadmill are not the only technologies available to physical therapists. Harnesses and water-based systems, for example, can also be used to reduce body weight impact or fall risk. And while these tools have their place for certain clinical applications, DAP has a number of advantages:

  • More precise than water rehabilitation, including the ability to precisely and incrementally change the amount of patient support
  • More realistic support of the lower limbs in the free-swing phase, allowing the legs to swing more normally
  • Safer training and rehabilitation environment, helping control variables that sometimes cause injury and discomfort
  • Objective data helps optimize rehab and limit liability issues when making clinical recommendations for insurance considerations

How Patients Benefit from Differential Air Pressure

At its core, DAP enables patients to exercise during rehabilitation without the fear of pain or re-injury—without compromising the natural gait and form crucial to proper rehabilitation. A lack of confidence due to a serious injury is a common impediment to effective PT. A patient with a torn ACL, for example, might be reluctant to put weight on the injured limb.

Most importantly, differential air pressure is part of a suite of AlterG® technologies helping PTs deliver more precise rehabilitation protocols. These can cut down the time it takes people to get people back on their feet and doing the things they know and love.

To learn more about differential air pressure technology, take a peek at the introductory video below. And stay tuned to the AlterG® blog for the next post in our series on the technologies driving PT forward. In our next post, we’ll take a closer look at Stride Smart Gait Analytics.