The goal of this study is to clarify mechanisms of acute intermittent hypoxia and to examine the effect on lower limb function in persons with chronic, incomplete spinal cord injury.
The goal of this study is to clarify mechanisms of acute intermittent hypoxia by examining changes in blood biomarkers, neural excitability, and hemoglobin mass. We also aim to clarify how these changes relate to changes in lower limb function in persons with chronic, incomplete spinal cord injury by measuring force steadiness and voluntary muscle activation.
Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
100
4 consecutive days of 15, 1.5 min episodes at 9% O2 (AIH) alternating with 21% O2 at 1 min intervals
Andrew Tan
Boulder, Colorado, United States
Change in Serum Blood Brain Derived Neurotrophic Factor
Serum blood brain derived neurotrophic factor (pg/mL) will be assessed using enzyme-linked immunosorbent assay. Blood will be sampled prior to AIH and within 1 hour following the 1st, 3rd, and 4th AIH exposure.
Time frame: Baseline, Day 1, Day 3, and Day 4
Change in Serum Serotonin
Serum serotonin (ng/mL) be assessed using enzyme-linked immunosorbent assay. Blood will be sampled prior to AIH and within 1 hour following the 1st, 3rd, and 4th AIH exposure.
Time frame: Baseline, Day 1, Day 3, and Day 4
Change in the Transcranial Magnetic Stimulation Recruitment Curve Slope
The mean motor evoked potential response will be plotted against the corresponding stimulation intensity (% resting motor threshold) to produce a stimulus-response curve at 20% and 40% of maximum. We will measure TMS before the start of 4 consecutive days of AIH exposure. We will measure TMS within 24 hours of the final AIH exposure.
Time frame: Baseline and Day 4
Change in Force Steadiness
The coefficient of variation of force will be calculated in both plantarflexion and dorsiflexion at 20% and 40% of maximum. We will measure coefficient of variation of force before the start of 4 consecutive days of AIH exposure. We will measure coefficient of variation of force within 24 hours of the final AIH exposure.
Time frame: Baseline and Day 4
Change in Central Activation Ratio
We will measure the central activation ratio using supramaximal electrical stimulus over a peripheral nerve during maximum voluntary activation. We will measure the central activation ratio before the start of 4 consecutive days of AIH exposure. We will measure the central activation ratio within 24 hours of the final AIH exposure.
Time frame: Baseline and Day 4
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Change in hemoglobin mass
Using the optimized carbon monoxide rebreathing procedure we will evaluate hemoglobin concentration, carboxyhemoglobin, and hematocrit to calculate total hemoglobin mass, blood volume, and plasma volume. The optimized carbon monoxide rebreathing procedure will be done prior to the first hypoxia exposure and following the 4th hypoxia exposure.
Time frame: Baseline and Day 4
Change in Serum Erythropoetin
Serum erythropoetin (mU/mL) will be assessed using enzyme-linked immunosorbent assay. Blood will be sampled prior to AIH and within 1 hour following the 1st, 3rd, and 4th AIH exposure.
Time frame: Baseline, Day 1, Day 3, and Day 4
Axial damage ratio
Using MRI, we will quantify the axial damage ratio. Prior to participation in the study we will obtain an MRI for quantification of axial damage ratio
Time frame: Baseline
6-Minute Walk Test
We will assess the distance walked in 6-minutes. The 6-minute walk test will be completed prior to the first exposure to hypoxia and following the 4th exposure of hypoxia.
Time frame: Baseline and Day 4
10-Meter Walk Test
We will assess how long it takes subjects to walk 10 meters. The 10-Meter walk test will be done prior to the first hypoxia exposure, and following the 4th hypoxia exposure.
Time frame: Baseline and Day 4