Introduction. Cerebrovascular reactivity (CVR) response to arterial gas tensions can offer insight into the compliance of blood vessels [1] and may be useful for experimentally simulating conditions of hemodynamic compromise in patients with carotid artery disease. Specifically, these patients may exhibit abnormalities in several vascular characteristics in response to reduced cerebral perfusio...

purpose: hypercapnia increases minute ventilation (v’e) with little effect on heart rate (hr), whereas hypoxia may increase hr without affecting v’e. however, the effects of hypercapnia and hypoxia on both heart rate variability (hrv) and the clustering of heart beats during spontaneous breathing (respiratory sinus arrhythmia – rsa), are not clear. methods: in this study, 10 human volunteers br...

The non-invasive Xe inhalation method was modified to measure regional cerebral blood flow (rCBF) of both hemispheres and brain stem-cerebellar (BSC) regions in baboons to serve as a model for clarifying and validating human studies. Measurements were made in the alert, unanesthetized state at rest and during activation with spontaneous respiration in a primate chair or during sedation or anest...

We hypothesized that reductions in arterial PCO2 (PaCO2) below the apnea threshold play a key role in the pathogenesis of idiopathic central sleep apnea syndrome (ICSAS). If so, we reasoned that raising PaCO2 would abolish apneas in these patients. Accordingly, patients with ICSAS were studied overnight on four occasions during which the fraction of end-tidal CO2 and transcutaneous PCO2 were me...

BACKGROUND Periodic breathing (PB) during sleep and exercise in heart failure (HF) is related to respiratory acid-base status, CO2 chemosensitivity, and temporal dynamics of CO2 and O2 sensing. We studied inhaled CO2 and acetazolamide to alter these factors and reduce PB. METHODS AND RESULTS We measured expired and arterial gases and PB amplitude and duration in 20 HF patients during exercise...

Heat-related decreases in cerebral perfusion are partly the result of ventilatory-related reductions in arterial CO2 tension. Cerebral perfusion likely contributes to an individual's tolerance to a challenge like lower body negative pressure (LBNP). Thus increasing cerebral perfusion may prolong LBNP tolerance. This study tested the hypothesis that a hypercapnia-induced increase in cerebral per...

The role of phospholipase, lipoxygenase, and cyclooxygenase pathways in the mechanism of the cerebrovascular response to CO2 and H+ was investigated in newborn piglets. Responsiveness of pial arterioles, 48-206 micron diameter, to inhalation of 6% CO2 and to suffusion of acidic cerebrospinal fluid (CSF, pH = 6.84), adenosine (10(-4) M), or theophylline (10(-2) M) was studied using a closed cran...