Neuronal brain activity is assumed to be reflected by blood level oxygenation levels, also known as BOLD signal, measured with fMRI. A scan of the literature points both oxygen and carbon dioxide levels effects on The roles (O2 ; hypoxia/hypoxemia, hyperoxia) (CO2 hypocapnia, hypercapnia) in neuronal signal are complex still under investigation [1,2]. Inspiration while varying O2 CO2 air have b...

Hypoventilation increases PaCO(2) (hypercapnia) and initiates the acid-base disorder known as respiratory acidosis. Hyperventilation decreases PaCO(2) (hypocapnia) and initiates the acid-base disorder known as respiratory alkalosis. The impact on acidity of these primary changes in PaCO(2) is ameliorated by secondary, directional changes in plasma bicarbonate concentration that occur in two sta...

A double blind, placebo controlled compa-rison was made of the effects of nebulised ipratropium bromide (0O05 and 0-5 mg) and salbutamol (0-25 and 2-5 mg) on lung function and the airway response to hyperventilation in eight normal subjects. Both agents at both doses caused similar baseline bronchodilatation, confirming the presence of resting bronchomotor tone. The overall mean increases as pe...

In man assuming the upright position, end-tidal P(CO(2)) (P(ETCO(2))) decreases. With the rising interest in cerebral autoregulation during posture change, which is known to be affected by P(ETCO(2)), we sought to determine the factors leading to hypocapnia during standing up from the supine position. To study the contribution of an increase in tidal volume (V(T)) and breathing frequency, a dec...

The effect of hypercapnia on coronary vascular resistance (CVR) was studied in seven open-chest dogs. Coronary blood flow was supplied to the cannulated left main coronary artery from the femoral artery by a precision pump. Coronary arterial Pco, was locally controlled with a small membrane oxygenator in the coronary perfusion circuit. Each Pco, change was made at a constant coronary flow, and ...

The intxacranial pressure was studied in nine patients with space-occupying lesions before and after addition of 4% fluroxene to a nitrous oxide-oxygen mixture at normocapnia and hypocapnia. At normocapnia (Paooa 38 mm Hg) fluroxene produced a 16 mm Hg (range 1-59 mm Hg) increase in intracranial pressure leading to a decrease in cerebral perfusion pressure, in three cases to critically low valu...

We report on an 83 yr old man with hypersomnia and central sleep apnoea (CSA). He had several possible causes for CSA, including a central nervous system lesion, hypocapnia and anatomical narrowing of the airway at the hypopharyngeal level. We postulate that reduced central respiratory drive occurring in conjunction with upper airway narrowing may have led to central apnoeas. These in turn coul...

STUDY OBJECTIVES Hypocapnia is an important mediator of sleep-dependent respiratory instability. Positive pressure-associated ventilatory control instability results in poor control of sleep apnea and persistent sleep fragmentation. We tested the adjunctive efficacy of low volumes of dead space (enhanced expiratory rebreathing space [EERS]) using a non-vented mask to minimize sleep hypocapnia. ...