By Randy D Trumbower
Spinal cord injury can cause lifelong paralysis by damaging the connections between the brain and spinal cord. Most injuries are incomplete, which means residual connections between the brain and spinal cord allow residual movement but recovery remains limited. As few therapeutic options exist for patients with these types of chronic injuries, there is a critical need for new therapies that enable patients to stand, walk within the home, or negotiate spaces not accessible to wheelchairs. Such benefits can translate into significant health advantages and improved quality of life for those with lifelong struggles due to lost function.
Exciting new findings suggest that breathing brief bouts of lower oxygen (intermittent hypoxia) may promote functional recovery in people with chronic incomplete spinal cord injury by inducing positive changes in the neurochemical environment of the spinal cord. In our study in Neurology, 19 patients with incomplete spinal cord injuries were exposed to a low oxygen therapy for approximately 40 minutes each day for five days. During this therapy (termed acute intermittent hypoxia), participants received low oxygen through a mask for 90-second intervals interspersed with 60-seconds of room air. Walking speed and endurance were tested before the study, after the first day of treatment, the fifth day of treatment and at one and two weeks after the treatment was completed.
Participants showed significant improvements in both walking speed and endurance. They significantly increased their walking speed after just one exposure to low oxygen only therapy compared with when they received room air only—walking an average of 3.8 seconds faster. However, participants showed even greater gains when low oxygen therapy was combined with daily walking therapy. This finding was particularly true for walking endurance, which showed an average improvement of nearly 100 metres. Many of these gains were considered clinically meaningful, with more than 30% of patients improving walking speed by more than 0.13 metres per second and more than 70% improving walking endurance by more than 50 metres. Finally, these improvements persisted for at least three days in 18 of 19 participants.
These promising findings suggest that intermittent low oxygen therapy may be a powerful therapeutic for restoring walking function after spinal cord injury. The sustained improvements in walking are especially striking given that the course of the therapy was only five days. We speculate that intermittent low oxygen therapy may enhance the capacity to restore mobility in patients with chronic incomplete spinal cord injury, which could be further improved by task-specific training. However, further study is warranted to determine the enduring effects of this therapy in a larger cohort of patients with spinal cord injury.
Randy D Trumbower, assistant professor, Department of Rehabilitation Medicine, Division of Physical Therapy, and Neuroscience Graduate Program, Emory University, School of Medicine, Atlanta, USA. He is also the program faculty in the Department of Biomedical Engineering at Georgia Institute of Technology, Atlanta, USA