14 Clinical Trials for Various Conditions
Pregnancy elicits adaptive changes in uteroplacental blood flow, which are altered at high altitude and may contribute to the observed 3-fold increase in intrauterine growth restriction (IUGR) and preeclampsia (PreE). The investigators propose to collect myometrial, cord blood, and placental tissue samples from women at high altitude (Summit County) and low altitude (Denver) in Colorado in order to determine if residence at altitude during pregnancy changes the vasoreactivity of myometrial arteries (MA). If altered MA vasoreactivity is found, further studies may be able to link these changes to the increased rates of PreE and IUGR at altitude and contribute to the understanding of these two disorders.
The main purpose of this study is to determine if a drug (acetyl-cysteine or ACCY) can increase the amount of oxygen in your body at a high altitude of 11,500 feet. ACCY is approved by the Food and Drug Administration (FDA) as a treatment or antidote for Tylenol overdoses. Other forms of ACCY are also sold over-the-counter as nutritional supplements. In this study, the FDA-approved form of ACCY will be used "off-label" (meaning in a way not approved by the FDA). This study is being conducted by researchers from the United States Army Research Institute of Environmental Medicine (USARIEM). The study will take place in the Altitude Chamber located in the basement of USARIEM. A total of approximately 30 volunteers (men and women, military and civilians) will take part in the study. They can expect to be in the study for a minimum of a few hours each day for two weeks. The investigators hypothesize that ACCY will improve ventilation and oxygenation while at altitude.
This research will evaluate nutrition requirements for missions at high altitude (i.e. \>7800 feet above sea level) and the information obtained can be used to optimize nutrient content specifications for combat rations. The objectives are: 1. Determine whether loss of lean body mass resulting from negative calorie balance over a 22-d period at high altitude can be prevented by increasing dietary protein intake. 2. Determine the efficacy of carbohydrate (glucose and fructose) supplementation on aerobic exercise performance at sea level, acute exposure to high altitude, and in response to 22-d period of negative calorie balance at high altitude. 3. Determine cognitive function, sleep patterns, and behavioral responses to high altitude and underfeeding. 4. Determine appetite and eating behavior in response to high altitude and sustained underfeeding. 5. Examine the effects of high altitude, negative calorie balance, dietary intake manipulations on gut health.
The overall goal of this study is to detect preclinical signs of HAPE by lung ultrasonography and evaluate the effectiveness of acetazolamide at decreasing pulmonary edema by using ultrasound.
This study is to determine whether bosentan will alter exercise capacity after rapid ascent to high altitude. We hypothesize that bosentan administration will improve arterial oxygenation and exercise capacity.
The goal of this study is to learn if the probiotic SLAB51 (Sivomixx800®) works to enhance acclimatization to high altitude in humans. The main questions it aims to answer are: Does SLAB51 improve oxygen saturation during high-altitude exposure? Researchers will compare SLAB51 to a placebo (a substance that contains no probiotic) to see if SLAB51 works to enhance high-altitude acclimatization. Participants will: Take SLAB51 or a placebo three times daily during two separate three-night acclimatization periods at high altitude, spaced at least six weeks apart. Complete baseline measurements at sea level. Visit the high-altitude Barcroft Station (3,801 m) at the University of California White Mountain Research Center for physiological measurements and assessments. Undergo assessments including oxygen saturation, ventilation, heart rate, blood pressure, sleep studies, cognitive assessments, exercise capacity, Acute Mountain Sickness scores, and provide blood, fecal, and urine samples for advanced analyses.
Apparent hypoxia-induced insulin insensitivity along with alterations in glucose kinetics suggests reduction in glucose uptake by the peripheral tissue is a primary factor contributing to reductions in exogenous glucose oxidation at HA. As such, the primary objective of this study is to determine the ability of an insulin sensitizer (Pioglitazone, PIO) to enhance exogenous glucose oxidation and metabolic clearance rate during metabolically-matched, steady-state exercise during acute HA exposure compared to placebo (PLA) in native lowlanders. Secondary objective of this study will be to assess the impact of PIO on markers of inflammation and iron status compared to PLA. This randomized crossover placebo control double blinded study will examine substrate oxidation and glucose kinetic responses to ingesting supplemental carbohydrate (glucose) during metabolically-matched, steady-state exercise with acute (\~5 h) exposure to HA (460 mmHg, or 4300m, barometric pressure similar to Pike's Peak) after receiving PIO (HA+PIO), or after receiving a matched placebo (HA+PLA). Eight healthy, recreationally active males between the ages of 18-39 yrs will be required to complete this study. Following a 4 day glycogen normalization period receiving PIO or PLA daily, volunteers will complete two 80-min trials, performing metabolically-matched, steady-state aerobic (same absolute workload corresponding to \~55 ± 5% of V̇O2peak at HA) exercise on a treadmill, and consuming 145 g of glucose (1.8 g/min); one trial with HA+PIO and the other with HA+PLA. A dual glucose tracer (13C-glucose oral ingestion and \[6,6-2H2\]-glucose primed, continuous infusion) technique and indirect calorimetry will be used to selectively analyze endogenous and exogenous glucose oxidation, as well as glucose rate of appearance (Ra), disappearance (Rd) and metabolic clearance rate (MCR). Serial blood samples will be collected during each trial to assess endocrine and circulating substrate responses to exercise, carbohydrate, and hypoxia with or without PIO. All trials will occur at the same time of day in the USARIEM hypobaric/hypoxic chamber and be separated by a minimum 10-d washout period. The primary risks associated with this study include those associated with acute hypobaric hypoxia, exercise, and blood sampling.
This research study will evaluate changes in resting metabolic rate, appetite, and heart rate variability following overnight exposure (8 h/night) to normobaric hypoxia (NH) or normobaric normoxic (NN). In randomized order, participants will sleep one night in NH conditions (\~15% oxygen; achieved with nitrogen dilution, equivalent to \~8500 feet elevation) and another night in NN (control) conditions (\~20% oxygen; achieved with nitrogen dilution, equivalent to \~1000 feet elevation).
Low oxygen at altitude causes pauses in breathing during sleep, called central sleep apnea. Central sleep apnea causes repeated awakenings and poor sleep. Low oxygen itself and the induced oxidative stress can damage mental function which is likely worsened by poor sleep. Reduced mental function due to low oxygen can pose a serious danger to mountain climbers. However there is also mounting evidence that even in populations of people that live at high altitudes and are considered adapted, low oxygen contributes to reductions in learning and memory. Therefore there is a serious need for treatments which may improve sleep, control of breathing and mental function during low oxygen.Therefore this study aims to determine how melatonin effects control of breathing, sleep and mental performance during exposure to low oxygen.
Ibuprofen is often taken by travelers to high altitude to treat the symptoms of acute mountain sickness such as headache and malaise. However, the blunting of inflammation by ibuprofen may slow the process of acclimatization to altitude, which relies on mediators of inflammation for adjustments in breathing. The study randomizes healthy subjects to receive ibuprofen or placebo and then ascend to altitude (12,500 feet). Blood cytokines and non-invasive measurements of blood and tissue oxygen levels will be made for 48 hours at altitude. The hypothesis being tested is that subjects receiving ibuprofen will have lower blood and tissue oxygen levels after 48 hours at altitude than will placebo subjects.
During ascent to high altitude there is a physiologic response to hypoxia that results in an elevated pulmonary arterial pressure associated with decreased exercise performance, altitude-induced pulmonary hypertension, and high altitude pulmonary edema (HAPE). Riociguat is a novel agent from Bayer Pharmaceuticals that has already demonstrated effectiveness in the treatment of pulmonary hypertension, and it may prove to be beneficial in cases of altitude-induced pulmonary hypertension or HAPE. This research study, composed of 20 healthy volunteers ages 18-40 years, will attempt to mimic the decreased oxygen supply and elevated pulmonary artery pressures found in conditions of high altitude, allowing observation of the effects of riociguat and exercise on pulmonary arterial pressure, arterial oxygenation, and exercise performance. Prior to entering the hypobaric chamber, subjects will have radial arterial lines and pulmonary artery catheters placed to obtain arterial and pulmonary artery pressure measurements. Subjects will then enter the hypobaric chamber and perform exercise tolerance tests at a simulated altitude of 15,000 feet on an electrically braked ergometer (exercise bike) before and after administration of riociguat. If, after administration of riociguat and exposure to a simulated altitude of 15,000 feet, the exercise performance is improved and observed pulmonary artery pressures are lower than those measurements seen prior to administration of riociguat, this could lead to development of a prophylactic and/or treatment strategy for HAPE and high-altitude pulmonary hypertension. Statistical analysis will compare the variables of pulmonary artery pressure, radial arterial pressure, ventilation rate, cardiac output, PaO2, and work rate at exhaustion before and after administration of the drug riociguat. The investigator's hypothesis is that riociguat will decrease pulmonary artery pressure and improve gas exchange and exercise performance at altitude.
The objective of this study is to determine if single dose administration of inhaled iloprost will reduce pulmonary artery pressure, reduce hypoxic pulmonary vasoconstriction and improve arterial oxygenation at rest and during exercise at high altitude.
Hypobaric hypoxia (decreased oxygen supply to body tissues due to low atmospheric pressure) caused by exposure to high altitude disrupts sleep. Sleep deprivation is associated with degraded post-sleep performance of neurobehavioral tasks. The lowest altitude at which sleep and/or post-sleep performance are affected is not known. The study hypothesis is that sleep and/or post-sleep performance of neurobehavioral tasks will occur due to hypobaric hypoxia at altitudes of 8,000 or less.
The purpose of this study is to look at how a reduction in oxygen levels (hypoxia) influences insulin sensitivity and carbohydrate metabolism. It is expected that 10 nights of exposure to moderate hypoxia (\~ 15% O2, similar to conditions at an altitude of \~7500 feet) will improve glucose metabolism.