Carbon Dioxide

Acute ischemic stroke due to large vessel occlusion is responsible of cerebral blood flow impairment with a progressive and extensive ischemic process. Cerebral collateral circulation may preserve an ischemic penumbra that could recover providing timely reperfusion of the occluded vessel. Mechanical thrombectomy is the standard of care for anterior circulation large vessel reperfusion. Strategy to promote cerebral blood flow in collateral circulation before reperfusion is scarce and rely mainly on blood pressure maintenance. Carbon dioxide is a potent cerebral vasodilator that could enhance collateral circulation blood flow and cerebral protection before reperfusion. General anesthesia with endotracheal mechanical ventilation could be used for thrombectomy and give the opportunity to modulate and control carbon dioxide tension in the blood. This study will test the effect of moderate hypercapnia on penumbral collateral circulation before reperfusion during mechanical thrombectomy for anterior circulation acute ischemic stroke under general anesthesia.

This is an open, observational, prospective, descriptive, single-centre study including 60 patients. The study is designed to investigate if IscAlert sensor system can be used for reliable and continuous tissue carbon dioxide (pCO2)- and temperature monitoring in muscular tissue in lower extremity in patients at risk of developing acute compartment syndrome.

The goal of this clinical trial is to explore the clinical significance and value of the PRVC ventilation mode in Bariatric Surgery Patients. The main questions it aims to answer are： * Do different ventilation patterns affect intracranial pressure and partial pressure of carbon dioxide in bariatric surgery patients? * Does PRVC mode reduce intracranial pressure and partial pressure of carbon dioxide in bariatric surgery patients? * Whether intracranial pressure can be quickly measured by monitoring a patient's optic nerve sheath diameter (ONSD)？ Researchers randomized bariatric surgery patients into PC, VC, and PRVC groups for comparison, looking at breathing mechanics, PaCO2, and ICP. Participants will: * take PC mode ventilation, VC mode ventilation, and PRVC mode ventilation * monitor Respiratory mechanics, PaCO2, and ONSD

Carbon dioxide in patients on veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is eliminated via respirator as well as via the oxygenator's membrane of the ECMO machine. Consequently, monitoring of end-tidal carbon dioxide tensions is limited, which can result in marked swings towards non-physiological values. Hyper- and hypocapnia, however, can have detrimental effects on organ perfusion in a great number of patients supported with VA-ECMO. Continuous, rapidly applicable monitoring of reliable carbon dioxide measures would therefore be extremely helpful to prevent harmful deviations from the norm. The investigators therefore try to assess the accuracy and the precision of continuously measured non-invasive transcutaneous carbon dioxide partial pressures when compared with tensions determined by blood gas analysis.