Acute intermittent hypoxia (AIH) involves brief (1 min), repeated episodes (\~15) of breathing low oxygen air to stimulate spinal neuroplasticity. Animal and human studies show that AIH improves motor function after spinal cord injury, particularly with slightly increased carbon dioxide (hypercapnic AIH; AIHH) and task-specific training. Using a double blind cross-over design, the study will test whether AIHH improves breathing more than AIH and whether specific genetic variations are related to individuals' intervention responses.
This study will consist of two parts - single-session testing days, and respiratory strength training blocks. If a participant is not eligible to enroll in single-day testing, they will be asked to enroll in only the respiratory strength training blocks. On single-session testing days, participants will be asked to come in on three separate days they will complete a battery of tests, then be given one of three interventions, and then complete the same battery of tests. The three interventions are acute intermittent hypoxia (AIH), acute intermittent hypercapnic-hypoxia (AIHH), or sham acute intermittent hypoxia (sham AIH). These interventions are explained in more detail below. During respiratory strength training blocks, participants will receive five days of AIH, AIHH, or sham AIH in combination with respiratory strength training, which uses small hand-held devices to strengthen the muscles used for breathing. Participants will be asked to complete all three blocks to receive all three interventions. In addition to 5 days of interventions and respiratory strength training, the respiratory strength training blocks include testing 1 day, 3 days, and 7 days after the 5 days of respiratory strength training.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
62
AIH (acute intermittent hypoxia) consists of short episodes of low oxygen (9% O2).
AIHH consists of short episodes of low oxygen (9% O2) and elevated carbon dioxide (4% CO2).
A single session of sham AIH with episodes of normal room air (21% O2).
Brooks Rehabilitation
Jacksonville, Florida, United States
RECRUITINGChange in motor evoked potential
The change in peak-to-peak amplitude of the motor evoked potential of the diaphragm will be tested using transcranial magnetic stimulation.
Time frame: Baseline, and 45-60 minutes after intervention on AIH day, AIHH day, and Sham AIH day
Change in maximal inspiratory pressure
Maximal inspiratory pressure is a non-invasive measure of the maximal force achieved when breathing in against an occluded airway.
Time frame: Baseline, 1 day, 3 days, and 7 days after intervention blocks (daily AIH + respiratory strength training, daily AIHH + respiratory strength training, daily sham AIH + respiratory strength training.)
Change in maximal expiratory pressure
Maximal expiratory pressure is a non-invasive measure of the maximal force achieved when breathing out against an occluded airway.
Time frame: Baseline, 1 day, 3 days, and 7 days after intervention blocks (daily AIH + respiratory strength training, daily AIHH + respiratory strength training, daily sham AIH + respiratory strength training.)
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