NCT07002437 · University of Florida
Hypoxia Pathways for Early Recovery After Spinal Cord Injury
(HyPER-FLO)
What this study is about
Spinal cord injury (SCI) disrupts neural pathways to respiratory motor neurons, diminishing breathing capacity and airway defense (e.g., cough). Indeed, respiratory impairment is a leading cause of infection, re-hospitalization and death after SCI. There is a critical need for new strategies to restore breathing ability and airway defense in people with SCI.
View original scientific description
Spinal cord injury (SCI) disrupts neural pathways to respiratory motor neurons, diminishing breathing capacity and airway defense (e.g., cough). Indeed, respiratory impairment is a leading cause of infection, re-hospitalization and death after SCI. There is a critical need for new strategies to restore breathing ability and airway defense in people with SCI. Acute intermittent hypoxia (AIH) - repetitive exposure to brief episodes of low inspired oxygen - is a promising strategy to restore breathing capacity by promoting spinal neuroplasticity. Exciting outcomes in \>12 SCI trials completed to date demonstrate that AIH improves human respiratory and limb function. Unfortunately, \~40% of individuals exhibit minimal response to AIH, making it essential to 1) optimize AIH protocols to maximize functional benefits; and 2) identify genetic biomarkers distinguishing those most/least likely to benefit from AIH-based treatments. The purpose of the pilot study, to be conducted in a small sample of participants with sub-acute SCI (2 weeks to 6 months post injury), is to preliminarily compare the effects of two intermittent hypoxia protocols. Since AIH-induced plasticity may be induced via serotonin or adenosine-driven mechanisms and these pathways compete and inhibit each other, each protocol favors a distinct mechanistic pathway. Our long-term objective is to test the hypothesis that a longer duration (i.e., augmented) hypoxia protocol, favoring adenosine mechanisms, enhances respiratory motor plasticity more than an AIH protocol targeting serotonin mechanisms (low O2 + CO2) in people with sub-acute SCI. Since an individual's genetics can influence the response to rehabilitation, we are also investigating how certain genes are related to breathing changes after these treatments. Data acquired through this pilot study will be used to inform a larger, more definitive clinical trial and will contribute to estimations of the magnitude and direction of effects.
Interventions
OTHER
Augmented Acute Intermittent Hypoxia (aAIH)
aAIH (augmented acute intermittent hypoxia) consists of 3, 5-minute episodes of low oxygen (9-13% O2), interspersed with 3-min room air intervals. Each study participant will complete 6 sessions of augmented AIH (aAIH), which consists of 3, 5-minute exposures. Each exposure involves a 5-minute hypoxic episode (9-13% inspired O2), with a 3-min interval of room air breathing (21% O2). Gas mixtures will be delivered via Douglas bags (pre-filled with desired gas mixture) that are coupled to a non-rebreathing valve and facemask. A manual-control valve allows seamless gas mixture switching. Participant safety will be continuously monitored in real-time using non-invasive sensors and LabChart software. For instance, inspired and expired concentrations of O2 will be monitored by continuous recordings of arterial O2 saturation and end-tidal gas, respectively. Furthermore, vital signs (respiratory rate, tidal volume, heart rate, and blood pressure) will be continuously monitored.
OTHER
Acute Intermittent Hypercapnic-Hypoxia (AIHH)
AIHH consists of 1-min episodes of low oxygen (9% O2) and elevated carbon dioxide (5% CO2), interspersed with 1.5 min room air. Each participant will complete 6 sessions of AIHH exposure, which consists of 15, 1-minute hypercapnic hypoxic episodes (4-5% inspired CO2, 9-13% inspired O2), with 1.5-minute intervals of room air breathing (21% O2). Gas mixtures will be delivered in the same manner described for AIH intervention. Participant safety will be continuously monitored in real-time using LabChart software. For instance, inspired and expired concentrations of CO2 and O2 will be monitored by continuous recordings of arterial O2 saturation and end-tidal gas, respectively. Furthermore, vital signs (respiratory rate, heart rate, and blood pressure) will be monitored.
OTHER
Sham AIH
Six sessions of sham AIH with episodes of normal room air (21% O2). Sham experiments will use methods identical to AIH/AIHH protocols except that normoxic gas (21% inspired O2) will be delivered. Since the timing and intervals vary with each protocol, the sham will use a distinct protocol involving 5, 3-min episodes with 2 min intervals between each episode. The valve on the non-rebreathing mask will be turned to deliver these episodes, but 21% O2 will be delivered throughout.
Primary outcome measures
Change in Maximal Inspiratory Pressure
Time frame: Baseline, 1-day, and 1-week following intervention
Maximal inspiratory pressure is a non-invasive measure of the maximal force achieved when breathing in against an occluded airway.
Change in Maximal Expiratory Pressure
Time frame: Baseline, 1-day, and 1-week following intervention
Maximal expiratory pressure is a non-invasive measure of the maximal force achieved when breathing out against an occluded airway.
Change in Cough Function
Time frame: Baseline, 1-day, and 1-week following intervention
Cough function will be measured by non-invasive tests of cough volume acceleration during a maximal cough.
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- Adults 18-70 years of age
- Sub-acute incomplete SCI 2 weeks to 6 months after injury, at or below C1-T6 Incomplete SCI based on residual sensory and motor function below the level of the injury or injury classification of B, C, D at initial screening according to the American Spinal Injury Association Impairment Classification and the International Standards for the Neurological Classification of SCI. -OR- Sub-acute complete SCI 2 weeks to 6 months after injury at or below C4-T6 Complete SCI based on the absence of residual sensory or motor function below the level of injury or injury classification of A at initial screening according to the American Spinal Injury Association Impairment Classification and the International Standards for the Neurological Classification of SCI.
- Medically stable with physician clearance
- SCI due to non-progressive etiology
Exclusion criteria
- Current diagnosis of an additional neurologic condition such as Multiple Sclerosis, Parkinson disease, stroke, or brain injury
- Severe illness or infection, including non-healing decubitus ulcers, untreated bladder or urinary tract infections, cardiovascular disease, lung disease, active heterotopic ossification, or uncontrolled hypertension
- Severe neuropathic pain
- Known pregnancy
- Severe uncontrolled autonomic dysreflexia
- Currently hospitalized in an acute care hospital
Where
- Jacksonville, Florida
Collaborators
Brooks Rehabilitation
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Frequently asked questions
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Data: ClinicalTrials.gov · synced Dec 3, 2025 · Source of record for eligibility and locations