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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 (1 to 6 months post injury), is to preliminarily compare the immediate 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. The 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, investigators are also preliminarily 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.
The purpose of this study is to develop a single, standardized test to determine how individuals tolerate acute hypoxia in a stepwise fashion. We aim to evaluate the association between multiple factors, such as ventilatory compensation, heart rate response, acid-base changes, sex, pulmonary function, etc, which may explain why some individuals tolerate exercise in hypoxia better than others. Identifying these factors of association will inform future pharmacological and non-pharmacological attempts to combat acute hypoxic exercise.
The goal of this study was to evaluate the accuracy of pulse oximeters over the range of 70-100% per the International Organization for Standardization (ISO) 80601-2-61:2019. Four test devices were placed on each subject on the left or right hand with two at the finger base and two at the fingertip. Motion equipment was used to control motion of the test devices. In addition, two test devices were placed on the contralateral hand on the base of a finger and also on the fingertip. Finally, a test wrist device was placed on either the left or right wrist. SpO2 measurements from these devices were compared to sampling of arterial blood during brief stable oxygen desaturation in healthy volunteers to evaluate the claimed range.
The purpose of this study is to examine hypoxic vasodilation and the role of beta-adrenergic receptors in younger premenopausal, perimenopausal, and older postmenopausal women.
This study aims to understand the mechanisms of a novel intervention involving breathing short durations of low levels of oxygen for persons with multiple sclerosis (MS). This intervention with low levels of oxygen is called Acute Intermittent Hypoxia (AIH), the levels of oxygen experienced are similar to breathing the air on a tall mountain, for less than 1 minute at a time. Previous studies have shown that AIH is a safe and effective way to increase strength in persons with MS. Here the investigators aim to look at brain activation and ankle strength before and after AIH to gain a better understanding of how the AIH may improve strength in those persons with MS.
The aim of this project is to test the accuracy of pulse oximeters during mild, moderate and severe hypoxia. This is done by comparing the reading of the pulse oximeter during brief, steady state hypoxia with a gold-standard measurement of blood oxygen. This study will be done on healthy male or females between the age group of 18-50.
Warfighter Performance Optimization in Extreme Environments remains an area of important and intense investigation, with the following goals: (1) Optimize, sustain and augment medical readiness and physiological/ psychological performance in extreme and hazardous military operational environments and (2) develop joint DoD countermeasures and guidance to sustain performance, assess physiological status, and reduce injury risk in extreme and hazardous operational environments. Successful and safe outcomes in extreme and hazardous operational environments require that warfighters maintain optimum cognitive and exercise performance during physiologic stress. Extreme environmental conditions encountered in such environments include warfighter exposure to hypoxia and hypothermia, alone or in combination. Both hypoxia and hypothermia undermine O2 delivery system homeostasis, imposing dangerous constraints upon warfighter cognitive and exercise capacity. While red blood cells (RBCs) are commonly recognized as O2 transport agents, their function as a key signaling and control node in O2 system delivery homeostasis is newly appreciated. Through O2 content-responsive modulation of RBC energetics, biomechanics, O2 affinity and control of vasoactive effectors in plasma - RBCs coordinate stabilizing responses of the lung, heart, vascular tree and autonomic nervous system - in a fashion that maintains O2 delivery system homeostasis in the setting of either reduced O2 availability (hypobaric hypoxia) or increased O2 demand (hypothermia). Human RBCs demonstrate adaptive responses to exercise, hypoxia and hypothermia - these changes are commonly appreciated as a key element enabling high altitude adaptation. However, under conditions of hypoxia and hypothermia, without prior adaptation, RBC performance is adversely impacted and limits the dynamic range of stress adaptation for O2 delivery homeostasis - therefore limiting warfighter exercise capacity and cognitive performance in extreme environments, such as during acute mountain sickness.
Tumor hypoxia is one of the physiological factors for treatment resistance and likely contributes to poor overall survival among patients with head and neck cancer (HNC). Identifying hypoxic features of HNC may allow the personalizing treatment plan. The investigators propose multiparametric Hypoxia MR (HMR) imaging using diffusion, perfusion, and oxygenation as non-invasive, in-vivo imaging components of a hypoxia phenotype. Assessing the hypoxia phenotypes' expression will be critically important for characterizing and predicting CRT response among patients with advanced HNC. A prospective cohort study will be conducted used multiparametric MR (MPMR) imaging correlated with treatment response assessed by 3 months fluorodeoxyglucose-positron emission tomography (FDG-PET). The image analysis approach will be developed to incorporate FDG-PET and quantitative MRI characteristics of tumor (ADC, oxygen-enhanced T1 and T2\* maps, and volume transfer constant (Ktrans) to facilitate 3D visualization of multiparametric information. This proposed study's overarching goal is to develop and validate multiparametric HMR imaging using 18F - (fluoromisonidazole) FMISO-PET and immunohistochemistry (IHC) as the standard of references.
The goal of this clinical trial is the acquisition of photoplethysmography signals during periods of profound hypoxia. The study is designed in accordance with ISO 80601- 2-61,2ed:2017-12 \& 2018-02.
This study is designed to answer questions related to safety and preliminary efficacy of Acute Intermittent Hypoxia (AIH) in Traumatic Brain Injury (TBI) survivors. First, we aim to establish whether brief reductions in inhaled oxygen concentration can be safely tolerated in TBI survivors. Second, we aim to establish whether there are any effects of AIH on memory, cognition, and motor control. Participants will be monitored closely for any adverse events during these experiments. Data will be analyzed to determine if there is an improvement in key outcomes at any dose level.