This study will examine if acute intermittent hypoxia (brief episodes of breathing lower oxygen), which has been shown to enhance plasticity and motor output, can enhance functional outcomes and muscle activation in individuals with spinal cord injury. Our aim is to assess breathing, sitting, standing and walking functional ability before and after acute intermittent hypoxia, compared to a sham treatment. This information may be useful in advancing rehabilitation for people with spinal cord injuries.

Recent evidence has shown that acute intermittent hypoxia can strengthen motor pathways after spinal cord injury, and enhance walking outcomes after walking rehabilitation compared to walking rehabilitation alone. A single session of acute intermittent hypoxia has also been shown to temporarily enhance breathing and limb strength in people with spinal cord injury. Further evidence supports the hypothesis that acute intermittent hypoxia acts on all motor pathways, and thus can enhance the strength of most muscles in the body.

Spinal cord injury affects the muscles that control respiration. Decreased respiratory muscle function can lead to diseases of the respiratory system, which are the primary cause of death and significant cause of re-hospitalization after spinal cord injury. Deficits in postural muscle function affect one's ability to balance, safely maintain a seated position, or ambulate after spinal cord injury, severely impacting daily activities such as self-care and feeding skills.

This study will test the hypothesis that a single session of acute intermittent hypoxia will increase strength and activation of the muscles that control respiration and posture, leading to improved scores on functional assessments in individuals with chronic spinal cord injury. Our long term goal is to better understand the therapeutic potential of acute intermittent hypoxia combined with physical rehabilitation for individuals with chronic spinal cord injury.

Inclusion criteria:

1. Male or female, ages 18-65
2. Greater than 6 months post-spinal cord injury
3. Spinal cord injury affecting segments between C4-T12
4. No other known neurological disorders
5. Able to provide informed consent
6. no severe musculoskeletal impairments, open wounds, or skin lesions that would limit participation in functional assessments.

Exclusion criteria:

1. Presence of a self-reported uncontrolled medical condition including, but not limited to: cardiovascular disease; sleep apnea; obstructive lung disease; severe neuropathic or chronic pain; severe recurrent autonomic dysreflexia
2. Severe, untreated bladder or urinary tract infection
3. Presence of severe musculoskeletal impairments, open wounds, or skin lesions that would limit participation in functional assessments
4. Women who report being pregnant or test positive on a pregnancy test

3 weeks

The study was low risk and there were no adverse events. Participants were monitored for safety as described in the protocol. As required, a cumulative adverse event table was submitted annually to the IRB.

Subjects will be asked to participate in two visits at least 7 days apart. Subjects will be assessed on various clinical outcomes before and after an exposure to one of two treatments. In one visit, subjects will be assessed before and after acute intermittent hypoxia, consisting of brief exposures of breathing low oxygen air, alternated with brief exposures to room air. In the other visit, subjects will be assessed before and after an exposure to a sham treatment, consisting of breathing brief exposures of normal oxygen air, alternated with brief exposures to room air. Subjects will undergo acute intermittent hypoxia or a sham treatment in a randomized order.