41 Clinical Trials for Various Conditions
The aim of this randomized, double-blind, placebo-controlled crossover trial is to determine the effects of caffeine vs. placebo on psychomotor vigilance and carbon dioxide tolerance during graded hypercapnia.
It is estimated that 1,275,000 people in the United States alone live with spinal cord injury, including around 100,000 Veterans with spinal cord injury, making the V.A. the largest integrated health care system in the world for spinal cord injuries injury care. New therapies are needed to prevent the morbidities and mortalities associated with the high prevalence of respiratory disorders in Veterans with spinal cord injury. The current research project and future studies would set the base for developing innovative therapies for this disorder. This proposal addresses a new therapeutic intervention for sleep apnea in spinal cord injury. The investigators hypothesized that daily hypercapnia treatments improve respiratory symptoms and alleviate sleep apnea in patients with chronic spinal cord injury. The investigators will perform a pilot study to examine the impact of daily hypercapnia treatments for-two week durations among Veterans with spinal cord injury. The investigators believe that this novel approach to treating sleep apnea and will yield significant new knowledge that improves the health and quality of life of these patients.
The aim of this randomized, single-blind, placebo-controlled crossover trial is to determine the effects of graded hypercapnia (0, 2, and 4% inspired CO2) on endurance performance. Twelve healthy and fit young adults (men and women) will complete this study. Participants will perform experimental trials on 3 separate days (one each breathing 0%, 2%, and 4% inspired CO2-all with normal 21% oxygen). During each trial, they will perform 10 minutes of submaximal treadmill walking exercise and then complete a self-paced 2-mile treadmill run time-trial.
The investigators will simulate the conditions of a working, helmeted diver by using exercising, "head out" immersed subjects to test the following hypotheses: 1. An algorithm can be developed which predicts cognitive performance in immersed exercising divers, based on the exhaled carbon dioxide (PETCO2) and the diver's inspired partial pressures of oxygen and nitrogen (PIO2 and PIN2). 2. PETCO2 using mass spectrometry is an accurate estimate of arterial carbon dioxide (PaCO2) at rest and during immersed exercise and can be used as a PaCO2 surrogate at levels exceeding 50 mmHg and depths up to 158 fsw (gas density 6.4 g/l, similar to 165 fsw density of 6.8 g/l).
The proposed study will measure the time from the end of surgery until the time patients meet the discharge criteria from the postoperative anesthesia care unit and the time from the end of surgery until the patients regained cognitive function after anesthesia.
The investigators will test the hypotheses that mild hypercapnia and supplemental oxygen reduce wound infection risk in patients undergoing colon resection. The investigators will simultaneously test the hypothesis that low-dose dexamethasone (a common treatment for postoperative nausea and vomiting) does not increase infection risk.
This study will evaluate magnetic resonance imaging (MRI ) methods for measuring changes in the brain's blood flow during hypercapnia (a condition of excess carbon dioxide in the blood). MRI is a diagnostic tool that uses a large magnet and radio waves to produce images of the body without X-rays. Healthy normal volunteers in this study may have as many as six MRI scans over a 2-year period. For this procedure, the person lies on a stretcher placed in a strong magnetic field produced by the MRI machine. During the scan, the person's blood carbon dioxide (CO2 ) levels will be increased either by: 1) breathing air mixtures containing up to 5% CO2; or 2) receiving an intravenous (I.V.) injection of a drug called acetazolamide. Persons who breathe CO2 will have their heart rate, blood pressure and oxygen levels monitored throughout the procedure. Those receiving acetazolamide will have the drug injected intravenously (I.V.) into an arm vein. If the volunteer experiences any unpleasant side effects from the CO2 or acetazolamide, the study will be stopped. The information gained from this study will be used to develop better ways to study brain function, possibly leading to better diagnostic and treatment methods.
This study will evaluate the ability of High Velocity Nasal Insufflation \[HVNI\] to effect ventilation and related physiologic responses in hypercapnic patients when compared to noninvasive positive pressure ventilation \[NIPPV\].
This is a prospective, longitudinal observational study to provide data regarding the natural course of hypercapnia in premature infants with bronchopulmonary dysplasia using both available blood pCO2 and measured capnography, as well as relate the degree and trend of hypercapnia to later respiratory outcomes.
Preterm infants, less than 37 weeks gestation with respiratory distress syndrome, who remain ventilated between 7 and 14 days after birth will be randomized to a ventilator strategy of either a higher level of permissive hypercapnia or of a lower level of permissive hypercapnia to determine if either strategy will increase the number of alive ventilator-free days in the 28 days after randomization.
In the US, every year approximately 30,000 infants are born very prematurely, with birth weight less than 1000 grams. These infants usually require ventilators to help them breath normally during the first few weeks of life. Although the ventilator is lifesaving, it can also injure the very fragile lungs of these infants. Thus, a ventilation strategy, called permissive hypercapnia (high carbon dioxide), is widely used to prevent lung injury. Importantly, there is new research showing that high carbon dioxide may cause brain injury. In our proposed research, we will use magnetic resonance imaging methods to evaluate the brain in 40 very premature infants at term-equivalent age (Half of them had permissive hypercapnia ventilation, the other half did not) to see if permissive hypercapnia has adverse effect on brain development.
This study will use magnetic resonance imaging (MRI) to examine and compare changes in blood flow and blood volume in the brains of normal volunteers and patients with multiple sclerosis (MS). Patients with MS-an inflammatory disease that attacks the brain and spine-may have new blood vessel formation (called angiogenesis) within the brain that may or may not contribute to the disease or help in repairing the brain. It is not known if these new vessels behave in the same way as the naturally occurring vessels. MRI uses a strong magnetic field and radio waves to generate brain images that provide information on brain chemistry, function, and blood flow. The results of this study may lead to a better understanding of MS. Healthy normal volunteers and patients with multiple sclerosis 18 years of age and older may be eligible for this study. Normal volunteers must have no history of signs or symptoms of central nervous system disease. Patients with MS will be recruited from the NIH Neuroimmunology MS clinic. All participants will undergo MRI. For this procedure, the subject lies still on a table that slides into a narrow metal cylinder (the MRI scanner). Scanning varies from 20 minutes to 3 hours, with most scans lasting between 45 and 90 minutes. During the scan, the subject wears earplugs to muffle loud knocking noises caused by electrical switching of the radio frequency circuits. The subject can communicate with the MRI staff at all times during the procedure. During the scan, the subject wears a mask and breathes in room air or air containing 6% carbon dioxide (CO2). (Room air contains approximately 0.04% CO2, which is about 150 times less than the 6% CO2. Air that is normally breathed out contains about 5% CO2.) Breathing 6% CO2 increases the amount of blood flow in the brain that can be measured using MRI. The total duration of a single 6 percent CO2 inhalation will not exceed 10 minutes. A catheter (thin plastic tube) is placed in a vein in the subject's arm before he or she enters the scanner. At some point during the scan, a contrast agent called gadolinium DTPA is injected into the vein through the catheter. This agent enables clearer images of the brain.
In light of the ongoing COVID-19 pandemic, wearing a mask has become a universal standard as an attempt to reduce the spread of COVID-19. As of 2020, more than half of all U.S. states have implemented a state wide mandated mask policy. There are many schools of thought regarding the benefits and risks of donning a mask to prevent the spread of COVID-19. There is an unproven theory among some that wearing a mask interferes with our natural respiratory function, causing hypoxia, altered mental status and other various health issues. This dangerous perception has led some to believe wearing a mask is harmful, and encourages against wearing a mask in public. This theory, recently refuted by a study investigating oxygen levels while participants wore masks, performed in 2020 encouraged increased compliance with wearing masks. Another study, preformed by evaluated whether gas exchange abnormalities occurred with the use of surgical masks in subjects with and without lung function impairment. The conclusions of the study showed that regardless of lung function impairment, the presence of surgical masks did not impact gas exchange. Additionally, a more recent study concluded that the presence of a facemask did not have a significant change in physiologic parameters while during exercise. Although there is evidentiary support that facemasks do not negatively affect oxygen status and physiologic capacity, there is not strong evidence examining the relationship between ETCO2 and facemasks. The relationship between ETCO2 and facemasks is one of importance because mild decreases in oxygen have much less dangerous effects compared to the effects of rapid accumulations of carbon dioxide. Increases in end tidal carbon dioxide lead to confusion, acidosis and in severe cases, respiratory distress and failure. A study performed in 1989 showed that hypercapnia has greater increases in blood pressure, minute ventilation and sympathetic nerve activity than hypoxia. In this newly proposed study, healthy volunteers will all wear the same type of three layer surgical mask. Their end tidal carbon dioxide will be measured while at rest without a mask, while resting with a mask and then after walking 100 meters in the mask. While previous studies have focused on changes in oxygen, there is a lack of research dedicated to analyzing end tidal carbon dioxide. This study will hope to show evidence supporting that there is no increase in end tidal carbon dioxide while wearing a mask.
This study is designed to evaluate the effects of the coadministration of paroxetine or escitalopram with an opioid on ventilation. Ventilation will be assessed using a rebreathing methodology. This study will evaluate chronic and acute dosing of paroxetine and escitalopram combined with an opioid as well as chronic and acute dosing of the two drugs without coadministration of an opioid. This study is a 3-period, randomized, placebo-controlled crossover study conducted with 25 healthy participants. Each participant will receive each of the 3 treatments (placebo/oxycodone, paroxetine/oxycodone, escitalopram/oxycodone) in a randomized order.
Opioids can decrease breathing and co-administration of benzodiazepines with opioids can further decrease breathing. It is unknown whether certain other drugs also decrease breathing when co-administered with opioids. The objective of this study is to determine whether certain drugs combined with an opioid decrease breathing compared to breathing with an opioid alone. In order to assess this, this study will utilize the Read Rebreathing method, where study participants breathe increased levels of oxygen and carbon dioxide. The increased levels of carbon dioxide cause the study participants to increase breathing. This increased breathing response can be decreased by opioids and benzodiazepines, and potentially other drugs. Using this procedure, low doses of opioids or benzodiazepines can be administered that have minimal-to-no effects on breathing when study participants are going about normal activities breathing room air, however breathing increases less than expected as carbon dioxide levels are increased. This study will also obtain quantitative pupillometry measurements before and after each rebreathing assessment to allow for comparisons of pupillary changes to ventilatory changes when subjects receive different drugs and drug combinations. This study includes three parts: A Lead-In Reproducibility Phase and two main parts (Part 1 and Part 2). The Lead-In Reproducibility Phase will measure the variability between study participants and between repeated uses of the method in the same study participant within a day and between days. Part 1 will study an opioid alone, benzodiazepine alone, and their combination to show the methodology will detect changes in breathing at low doses of the drugs that are known to affect breathing. Part 2 will assess whether two drugs, selected due to their effects on breathing in a nonclinical model, decrease the breathing response when combined with an opioid compared to when an opioid is administered alone.
Use of trancutaneous CO2 (TC02) monitoring to aide in titration of sedation of midazolam and fentanyl. Trancutaneous readings validated with invasively obtained specimens from existing arterial sheaths required during AF and VT ablations (trans-septal and retrograde aortic respectively)
The goal of this clinical trial is to learn about the mechanisms of oxygen toxicity in scuba divers. The main questions it aims to answer are: * How does the training of respiratory muscles affect oxygen toxicity? * How do environmental factors, such as sleep deprivation, the ingestion of commonly utilized medications, and chronic exposure to carbon dioxide, impact the risk of oxygen toxicity? * How does immersion in water affect the development of oxygen toxicity? Participants will be asked to do the following: * Undergo a basic screening exam composed of health history, vital signs, and some respiratory function tests * Train their respiratory muscles at regular intervals * Exercise on a cycle ergometer both in dry conditions and underwater/under pressure in the context of medication, sleep deprivation, or carbon dioxide exposure Researchers will compare the performance of each subject before and after the possible interventions described above to see if there are changes in exercise performance, respiratory function, cerebral blood flow, and levels of gene expression.
This study will evaluate the ability of a new High Velocity Nasal Insufflation \[HVNI\] device design to effect ventilation and related physiological responses relative to the current HVNI device design.
This study will evaluate the ability of High Velocity Nasal Insufflation \[HVNI\] next generation nasal cannula designs to effect ventilation and related physiological responses relative to the conventional legacy cannula design.
The purpose of this research study is to better understand how blood flow and metabolism are different between normal controls and patients with disease. The investigators will examine brain blood flow and metabolism using magnetic resonance imaging (MRI). The brain's blood vessels expand and constrict to regulate blood flow based on the brain's needs. The amount of expanding and contracting the blood vessels can do varies by age. The brain's blood flow changes in small ways during everyday activities, such as normal brain growth, exercise, or deep concentration. Significant illness or physiologic stress may increase the brain's metabolic demand or cause other bigger changes in blood flow. If blood vessels are not able to expand to give more blood flow when metabolic demand is high, the brain may not get all of the oxygen it needs. In less extreme circumstances, not having as much oxygen as it wants may cause the brain to grow and develop more slowly than it should. One way to test the ability of the blood vessels to expand is by measuring blood flow while breathing in carbon dioxide (CO2). CO2 causes blood vessels in the brain to dilate without increasing brain metabolism. The study team will use a special mask to control the amount of oxygen and carbon dioxide patients breath in so that we can study how their brain reacts to these changes. This device designed to simulate carbon dioxide levels achieved by a breath-hold and target the concentration of carbon dioxide in the blood in breathing patients. The device captures exhaled gas and provides an admixture of fresh gas and neutral/expired gas to target different carbon dioxide levels while maintaining a fixed oxygen level. The study team will obtain MRI images of the brain while the subjects are breathing air controlled by the device.
Assessment of Spry Health's Loop oximetry accuracy in profound hypoxia Assessment of Spry Health's Respiratory rate accuracy in normal conditions and profound hypoxia
Chronic obstructive pulmonary disease (COPD) is a highly prevalent condition worldwide and is a cause of substantial morbidity and mortality. Unfortunately, few therapies have been shown to improve survival. The importance of systemic effects and co-morbidities in COPD has garnered attention based on the observation that many patients with COPD die from causes other than respiratory failure, including a large proportion from cardiovascular causes. Recently, two high profile randomized trials have shown substantial improvements in morbidity and mortality with use of nocturnal non-invasive ventilation (NIV) in COPD patients with hypercapnia. Although the mechanisms by which NIV improves outcomes remain unclear, the important benefits of NIV might be cardiovascular via a number of mechanisms. In contrast to prior trials of NIV in COPD that did not show substantial benefit, a distinguishing feature of these encouraging recent NIV clinical trials was a prominent reduction of hypercapnia, which might be a maker or mediator of effective therapy. Alternatively, improvements might be best achieved by targeting a different physiological measure. Additional mechanistic data are therefore needed to inform future trials and achieve maximal benefit of NIV. Recent work in cardiovascular biomarkers has identified high-sensitivity troponin to have substantial ability to determine cardiovascular stress in a variety of conditions - even with only small changes. In COPD, a number of observational studies have shown that high-sensitivity troponin increases with worsening disease severity, and that levels increase overnight during sleep. This biomarker therefore presents a promising means to study causal pathways regarding the effect of NIV in patients with COPD. With this background, the investigator's overall goals are: 1) To determine whether the beneficial effect of non-invasive ventilation might be due to a reduction in cardiovascular stress, using established cardiovascular biomarkers, and 2) To define whether a reduction in PaCO2 (or alternative mechanism) is associated with such an effect.
Humidified Nasal High-flow with Oxygen (HNHF-O2) therapy has been reported to have acute beneficial effects in patients with hypoxemic respiratory failure who have been hospitalized. The usefulness of this therapy in the outpatient setting is unproven. This pilot study will test the feasibility of using this therapy in the outpatient setting and its effects on sleep.
Elucidating cerebrovascular control mechanisms during physiologic stress may help identify novel therapeutic targets aimed at preventing or reducing the impact of cerebrovascular disease. The physiological stressors of hypoxia and hypercapnia will be utilized to elicit increases in cerebral blood flow (CBF), and intravenously infused drugs will allow for the testing of potential mechanisms of cerebrovascular control. Specifically, the contributions of nitric oxide synthase (NOS), cyclooxygenase (COX), and reactive oxygen species (ROS) to hypoxic and hypercapnic increases in CBF will be examined. The concept that these mechanisms interact in a compensatory fashion to ensure adequate CBF during both hypoxia and hypercapnia will also be tested. \~25 young, healthy men and women will be tested at rest and during hypoxia and hypercapnia. Subjects will participate in two randomized, counterbalanced study visits under the following conditions: inhibition of NOS, NOS-COX, and NOS-COX-ROS or inhibition of COX, COX-NOS, COX-NOS-ROS. During hypoxia, arterial oxygen saturation will be lowered to 80% and end-tidal carbon dioxide will be maintained at basal levels. During hypercapnia arterial carbon dioxide will be increased \~10 mmHg above basal levels and arterial oxygen saturation will be maintained. Blood flow velocity will be measured with transcranial Doppler ultrasound in the anterior (middle cerebral artery; MCA) and posterior (basilar artery; BA) circulations as a surrogate for CBF. It is hypothesized that both NOS and COX independently contribute to hypoxic and hypercapnic vasodilation in the MCA and BA, combined NOS-COX contribute to hypoxic and hypercapnic vasodilation in MCA and BA to a greater extent than either NOS or COX alone, and NOS-COX-ROS contribute to hypoxic and hypercapnic vasodilation in the MCA and BA to a greater extent than NOS-COX.
* Patients with spinal cord injury (SCI) usually breathe without any mechanical assistance, but significant breathing problems occur often during sleep, either because the upper airway closes (obstructive sleep apnea; OSA), or because of weakness/paralysis of the breathing muscles. These problems often go unrecognized, as SCI patients face logistical barriers that cause them to refuse appropriate testing in sleep laboratories. We have devised a strategy for diagnosing sleep-disordered breathing in the patient's home, using placement of noninvasive devices that monitor breathing overnight. This project is designed to test the feasibility and utility of this strategy. * After collecting baseline data on symptoms and medical events for four months, the home-based studies are performed noninvasively with FDA-approved devices: a type III sleep system and a recording oxygen saturation/ transcutaneous carbon dioxide monitor. If these studies identify sleep-disordered breathing, noninvasive ventilatory support is prescribed according to standard clinical practice. Over the following twelve months, the subjects monitor their symptoms daily, and answer quality-of-life questionnaires every three months. After 3, 6, and 12 months, blood tests are performed to measure blood sugar and cholesterol/lipids. Data is downloaded from the ventilator device to monitor compliance and ventilator performance. This study is designed to determine the prevalence of sleep-disordered breathing in SCI, the feasibility of home-based testing to establish the diagnosis, and the short term effects on symptoms, quality-of-life, and associated conditions (glucose intolerance, blood lipid disorders).
The purpose of this study is to determine the factors that are associated with improved cardiovascular function with the use of CPAP therapy on subjects diagnosed with moderate to severe obstructive sleep apnea.
This study will use magnetic resonance imaging (MRI) to examine the role of prostaglandins-a type of fatty acid with hormone-like actions-in the regulation of brain blood flow. The results will provide information on how to better use this technique to study brain function, which, in turn, may lead to a better understanding of certain illnesses and more effective treatments. Healthy normal volunteers 18 years of age and older may be eligible for this study. Participants will fill out a health questionnaire and undergo a history, physical examination and MRI studies. MRI is a diagnostic tool that uses a strong magnetic field and radio waves instead of X-rays to show structural and chemical changes in tissues. During the scanning, the subject lies on a table in a narrow cylinder containing a magnetic field. An intercom system allows the subject to speak with the staff member performing the study at all times during the procedure. Four separate studies will be done-two carbon dioxide inhalation studies and two functional activation studies-as follows: Carbon dioxide inhalation (indomethacin): This study is done in two parts. In both parts, an MRI brain scan is done. During the scan, the subject inhales an air mixture containing 6% carbon dioxide through a facemask or mouthpiece. Blood pressure and heart rate are monitored during inhalation of the mixture. For the second part of the study, indomethacin-a non-steroidal anti-inflammatory drug-is injected through a catheter (thin flexible tube) in an arm vein. Indomethacin inhibits prostaglandin production. Total scan time averages between 45 and 90 minutes, with a maximum of 2 hours. Carbon dioxide inhalation (rofecoxib and celecoxib): This study is identical to the one above, except either rofecoxib or celecoxib is given instead of indomethacin. Both of these drugs are also non-steroidal anti-inflammatory drugs that inhibit prostaglandin production. Unlike indomethacin, rofecoxib and celecoxib are given orally instead of through a vein, so, to allow time for the drug to be absorbed, the second scan is delayed for 2 hours. Functional activation (indomethacin): This study is done in two parts. In both parts, a MRI brain scan is done. During the study, the subject performs a simple motor task, such as finger tapping. For the second part of the study, indomethacin is injected through a catheter in an arm vein. Functional activation (rofecoxib and celecoxib): This study is identical to the indomethacin functional activation study, except either rofecoxib or celecoxib is given instead of indomethacin. Because they are given orally instead of through a vein, the second scan is delayed 2 hours to allow time for the drug to be absorbed.
The study aims to determine how historical cases of respiratory abnormalities are documented by clinicians in the electronic health records (EHR) of Memorial Hermann Healthcare System (MHHS) inpatient facilities. The knowledge gained from this study will support the design of modern data-driven surveillance approach to continuously collect, monitor and timely recognize postoperative respiratory abnormalities using electronic healthcare recorded data.
The goal of this clinical trial is to determine whether people with paralysis due to a spinal cord injury can benefit from breathing short intermittent bouts of air with low oxygen (O2) combined with slightly higher levels of carbon dioxide (CO2), interspaced by breathing room air. The technical name for this therapeutic air mixture is 'acute intermittent hypercapnic-hypoxia,' abbreviated as AIHH. Following exposure to the gas mixture, participants will receive non-invasive electrical stimulation to the spinal cord paired with specific and targeted exercise training. The main question this trial aims to answer is: Can the therapeutic application of AIHH, combined with non-invasive electrical stimulation to the spinal cord plus exercise training, increase the strength of muscles involved in breathing and hand function in people with paralysis due to a spinal cord injury? Participants will be asked to attend a minimum of five study visits, each separated by at least a week. During these visits, participants will be required to: * Answer basic questions about their health * Receive exposure to the therapeutic air mixture (AIHH) * Undergo non-invasive spinal electrical stimulation * Complete functional breathing and arm strength testing * Undergo a single blood draw * Provide a saliva sample Researchers will compare the results of individuals without a spinal cord injury to those of individuals with a spinal cord injury to determine if the effects are similar.
Investigators will measure cerebrovascular reactivity (CVR) using functional near-infrared spectroscopy (fNIRS) and magnetic resonance imaging (MRI) during the chronic phase after repetitive mild traumatic brain injury (rmTBI) as a biomarker of traumatic cerebrovascular injury (TCVI). We hypothesize that CVR will be decreased in patients with rmTBI and that these decreases will correlate with clinical outcomes. Furthermore, we predict that 5 week administration of a phosphodiesterase 5 (PDE5) inhibitor, sildenafil citrate, will augment CVR in patients with a history rmTBI.