carbon dioxide tension

carbon dioxide tension (PCO₂),

the partial pressure of carbon dioxide, a measure of the relative concentration of the gas in air or in a fluid, such as plasma. It is expressed quantitatively in millimeters of mercury (mm Hg). Alveolar PCO₂ directly reflects pulmonary gas exchange in relation to blood flow: alveolar PCO₂ usually decreases as the respiration rate increases. Normal values for arterial and alveolar PCO₂ are between 35 and 45 mm Hg. Higher levels occur in conditions of slow blood flow and respiration. Below-normal values are caused by hyperventilation and lead to respiratory alkalosis. Also called carbon dioxide pressure. See also carbon dioxide, hypercapnia, hyperventilation, hypoventilation.

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carbon dioxide

an odorless, colorless gas, CO₂, resulting from oxidation of carbons, formed in the tissues and eliminated by the lungs; used with oxygen to stimulate respiration and in solid form (carbon dioxide snow—see below) as an escharotic, as a gas to euthanize laboratory rabbits and rodents.

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carbon dioxide anesthesia

exposure of pigs for 45 seconds in a mixture of 60 to 70% CO₂ in air is an adequate pre-slaughter anesthetic for pigs.

carbon dioxide combining power

the ability of blood plasma to combine with carbon dioxide; indicative of the alkali reserve and a measure of the acid-base balance of the blood.

carbon dioxide content

the amount of carbonic acid and bicarbonate in the blood; reported in millimoles per liter.

carbon dioxide dissociation curve

a graph demonstrating the relationship between the blood content of CO₂ and the Pco₂.

carbon dioxide narcosis

respiratory acidosis.

carbon dioxide snow

solid carbon dioxide, formed by rapid evaporation of liquid carbon dioxide; it gives a temperature of about −110°F (−79°C), and is used as an escharotic in various skin diseases. Called also dry ice.

carbon dioxide tension

the partial pressure of carbon dioxide in the blood; noted as Pco₂ in blood gas analysis. See also respiration.

carbon dioxide transport

carbon dioxide passes from tissues to blood by diffusion, in the blood by solution and via reactions within plasma and erythrocytes, from blood to pulmonary alveoli by diffusion.