Active clinical trials for "Hypercapnia"

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.

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 purpose of this study is to determine how intraocular pressure responds to changes in the levels of carbon dioxide or oxygen that a healthy individual inspires.

Obstructive sleep apnea (OSA) and Obesity-Hypoventilation Syndrome (OHS) are common conditions in obesity, which may influence the prognosis in patients undergoing surgery. There is a need for simple screening tools to identify such patients at high risk. The current multicenter observational study aims to investigate occurrence of OSA and OHS in obese individuals undergoing elective abdominal surgery and further address its impact on perioperative and postoperative complications.

There is currently no good description of patients surviving an episode of acute hypercapnic respiratory failure in the ICU. For instance, the prevalence of OSA and sleep hypoventilation in a stable clinical condition is not known in this population. This prospective cohort describes the clinical profile, predictors of readmission (followed over a year), and the prevalence of sleep-related breathing disorders (polysomnography in a stable clinical condition 3 months after ICU discharge) in patients treated for an episode of acute hypercapnic respiratory failure in the ICU.

Noninvasive ventilation (NIV) can provide ventilatory support in selected patients with acute respiratory failure, for instance due to acute exacerbation of COPD and acute heart failure. Advantages of noninvasive ventilation compared to invasive mechanical ventilation include absence of complications associated with endotracheal intubation, lower risk of pneumonia, lower level or even absence of sedation and the ability of the patient to verbally communicate. However, in approximately 30% of patients NIV fails and endotracheal intubation is needed to provide optimal ventilatory support. Surprisingly, very few studies have investigated why patients fail on NIV. Clinical observations indicated that agitation, delirium and most importantly asynchrony between patient and ventilator play a role in unsuccessful support with NIV. The upper airways are bypassed during endotracheal intubation. However, with NIV the upper airways may play a role in the efficiency of ventilatory support. In normal breathing the upper airways actively dilate before initiation of inspiratory flow. This is a highly appropriate response as it prevents narrowing of the upper airways during inspiration, which would result in elevated inspiratory resistance. Experiments in newborn lambs have shown that NIV has profound effects on physiology of the upper airways. Positive pressure during inspiration results in constriction of upper airway muscles in the early phase of inspiration. This results in elevated upper airway resistance with lower tidal volume delivered to the lungs. Subsequent studies revealed that reflexes that mediate this response originate in vagal afferences located in the lower airways. From an evolutionary point of view this might be an appropriate response, as high pressure delivered to the lungs may induce barotraumas. However, these responses may negatively affect the efficiency of ventilatory support delivered during NIV. The understanding of upper airway constriction and dilation during NIV is rudimentary. This study aims at determining the effect of NIV on regulation of upper airway patency in patients with COPD.

We made a fortuitous observation of periodic breathing in a healthy subject coming to our outpatient mountain medicine consultation at Avicenne hospital in Bobigny (France). During this consultation, subjects perform a hypoxia exercise test, which allows a good prediction of their risk factors for severe high altitude illnesses. Surprisingly, breath-by-breath recording of the ventilation signal showed a periodic breathing pattern, which increased when the subject started to exercise in hypoxic conditions and was maintained during normoxic exercise. Therefore, our objective was to confirm this observation in a retrospective study led in 82 subjects who passed this test. We tested the hypothesis that subjects with a brisk ventilatory response to hypoxia might show a more pronounced periodic pattern of ventilation, due to a higher gain of the chemoreceptor feedback loop. Then, our objective is to investigate the mechanisms involved in the periodic pattern in healthy subjects, as a function of exercise intensity, altitude intensity, role of peripheral and central chemoreceptors to O2 and CO2. Finally, we want to investigate the possible role of this ventilatory instability in patients with obstructive or central apneas.

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.

High pressure NIV is a pressure limited ventilation, stating IPAP pressure at 20 cmH2O and gradually increasing pressure up to 30 cmH2O according to patient tolerance.

Assessment of health-related quality of life in COPD patients with severe chronic respiratory failure requires appropriate and highly specific measurement tools. We attempt to validate the Chinese version of the Severe Respiratory Insufficiency Questionnaire (SRI)