Differential Pressure Walking Assist

Differential Pressure Walking Assist - an inflatable walking support

Charles Burgar, MD; Douglas Schwandt, MS; James Anderson, JEM; Robert Whalen, PhD; Gregory Breit, PhD

Need - The Differential Pressure Walking Assist (DPWA), which comfortably reduces the ground reaction force and lower limb muscle and joint forces, is intended for patients recovering from neurologic diseases and orthopedic procedures.

Concept - The lower body differential pressure concept was invented at the Life Science Division of NASA-Ames Research Center to investigate space exercise applications, and to simulate hypo- and hyper-gravity effects on biomechanics and cardiovascular physiology.

The DPWA consists of an inflatable vinyl skirt with a flexible, air-tight neoprene waist seal enclosing the subject' lower body. The skirt is attached to a wooden treadmill enclosure. A lifting force equal to the pressure difference times the waist cross-sectional area supports the subject during ambulation, removing half of the subject's effective weight with 1 psi (50 mmHg) differential pressure. Since the upper and lower body air pressures are uniformly distributed over the body surfaces, the subject simply feels lighter, similar to being buoyed up by waist-deep water. The lifting force can easily be controlled by adjusting chamber pressure to adapt to an individual patient's needs as he or she progresses through rehabilitation

Figure 1. The inflatable walking support provides controlled reduction of patient effective weight.

Work Accomplished - During an initial study to investigate cardiovascular effects on able-bodied subjects during standing, buoyant forces up to 100% of body weight were demonstrated without adverse cardiovascular effects (the changes in heart rate and mean arterial blood pressure did not differ significantly from those experienced when moving from supine to standing). An improved system has been completed that incorporates a transparent vinyl enclosure supported by netting. A zipper has been added to facilitate entry and exit of the device for patients with limited mobility.

Future Plans - We will confirm the safety of the DPWA for subjects with cardiovascular disease common in the older patient population the DPWA is intended to serve. Additional studies will focus on the efficacy of the DPWA in treating specific neuromuscular and orthopedic conditions. If results continue to be encouraging, a commercial version of the device will be developed in collaboration with an industrial partner.

Republished from the 1996 Rehabilitation R&D Center Progress Report. For current information about this project, contact: Charles Burgar.