The influence of sympathetic nervous activity on cerebral circulation and cerebrovascular CO2 reactivity was investigated by an ƒ¿-adrenergic blockade with phenoxybenzamine (PBZ). Cerebral oxygen and carbon dioxide tension (BrPO2, BrPCO2) and arterial blood pressure were continuously recorded before, during and after intracarotid infusion of 5 mg/kg of PBZ. The effects of 5% CO2 inhalation were...

We evaluated the hypothesis that venous congestion (increased venous volume), as reflected by venous hypertension (increased venous pressure), can arise when the right ventricle is unable to elevate the pulmonary arterial pressure sufficiently to propel the cardiac output through an anatomically inadequate or inappropriately constricted pulmonary vasculature. Changes in venous pressure were eva...

The present study examined how cardiovascular and salivary cortisol responses varied in response to an acute challenge in medical students under exam stress versus those not under exam stress. One hundred and twenty-nine medical students were randomly assigned to undertake a CO2 inhalation test either prior to an examination period (exam group) or during a regular academic period (non-exam grou...

Breathing high concentrations of carbon dioxide (CO2) can trigger panic and anxiety in humans. CO2 inhalation has been hypothesized to activate neural systems similar to those underlying fear learning, especially those involving the amygdala. Amygdala activity is also upregulated by stress. Recently, however, a separate pathway has been proposed for interoceptive panic and anxiety signals, as p...

An investigation was conducted to determine whether intermittent exposure to 3% CO2 results in a saturation of the body with carbon dioxide and whether a compensation of the respiratory acidosis is induced by carbon dioxide inhalation. One healthy male subject was exposed for six days, 15 hours daily, to a CO2 concentration rising from 0 3% at normal oxygen concentrations of 20 21% O2. Average ...

Carbon dioxide (CO2) inhalation lowers brain pH and induces anxiety, fear, and panic responses in humans. In mice, CO2 produces freezing and avoidance behavior that has been suggested to depend on the amygdala. However, a recent study in humans with bilateral amygdala lesions revealed that CO2 can trigger fear and panic even in the absence of amygdalae, suggesting the importance of extra-amygda...

PURPOSE To develop a new system for safely supplying carbon dioxide (CO2) to open-angle glaucoma patients. METHODS The orbital hemodynamics of 7 glaucoma patients were determined by color Doppler imaging under baseline conditions and during CO2 supplementation sufficient to increase the end-tidal CO2 partial pressure by 10%. Systemic conditions, including oxygen saturation and blood pressure,...

s of papers 31 133 Venous Blood Pressure in Broilers During Acute Inhalation of 5% Carbon Dioxide, and During Unilateral Pulmonary Artery Occlusion. R. F. Wideman, Jr.*, P. Maynard, and W. G. Bottje, . We evaluated the hypothesis that venous congestion (increased venous volume) and venous hypertension (increased venous pressure), may arise when the right ventricle must elevate the pulmonary art...

The effect on ventilation of airway anaesthesia, produced by the inhalation of a 5% bupivacaine aerosol (aerodynamic mass median diameter = 4.77 micron), was studied in 12 normal subjects. The dose and distribution of the aerosol were determined from lung scans after the addition to bupivacaine of 99mTc. Bupivacaine labelled in this way was deposited primarily in the central airways. The effect...

Inhalation of concentrations greater than 30% of carbon dioxide (CO2) by volume in atmospheric air causes aversion in pigs. The objective of this study was to assess, using aversion learning techniques and behavioural studies, the aversion to three alternative gas mixtures of nitrogen (N2) and CO2: 70% N2 and 30% CO2 (70N30C), 80% N2 and 20% CO2 (80N20C) and 85% N2 and 15% CO2 (85N15C). The exp...