Oxygen Transport Flashcards

Question

• C(a-v)02

Answer 1

• The arteriovenous oxygen difference, or a-vO, diff, is the difference in the oxygen content of the blood between the arterial blood and the venous blood. It is an indication of how much oxygen is removed from the blood in capillaries as the blood circulates in the body. The a-vo, diff and cardiac output are the main factors that allow variation in the body's total oxygen consumption, and are important in usually measured in milires of otogen per 100, dit is millilitres of blood (mL/100 mL)

Answer 2

• Pulmonary shunting and venous admixture are common complications in respiratory disorders, knowledge of the degree of shunting is often desirable when developing patient care plans. • The amount of intrapulmonary shunting can be calculated by using the classic shunt equation: • QS/QT = (A-aD02) .003 ———————————— (A-aD02) .003 + C(a-v)02

Answer 3

210 more times

Answer 4

• Pulmonary shunting is defined as that portion of the cardiac output that enters the left side of the heart without exchanging gases with alveolar gases (true shunt) or as blood that does exchange gases with alveolar gases but does not obtain a PO2 that equals that of normal alveolus (shunt-like effect). • Regardless of the type of shunt the physiologic effect is the same, hypoxemia.

Answer 5

• Common Causes of Absolute Shunting • Congenital heart disease • Intrapulmonary fistula • Vascular lung tumors • Capillary shunting is commonly caused by: • Alveolar collapse or atelectasis • Alveolar fluid accumulation • Alveolar consolidation • Key Concept: True shunts are refractory to supplemental oxygen. Refractory means that it does not respond to increased oxygen delivery.

Answer 6

• When pulmonary capillary perfusion is in excess of alveolar ventilation, a shunt-like effect is said to exist. • Common Causes of Relative Shunt • When pulmonary capillary perfusion is in excess of alveolar ventilation, a relative or shunt-like effect is said to exist • Hypoventilation • Ventilation/perfusion mismatches • Chronic emphysema, bronchitis, asthma • Alveolar-capillary diffusion defects • Alveolar fibrosis or alveolar edema • Key Concept: Relative or Shunt-Like effects can be corrected by supplemental oxygen

Answer 7

• The end result of pulmonary shunting is venous admixture. • Venous admixture is the mixing of shunted, non-reoxygenated blood with reoxygenated blood distal to the alveoli. • When venous admixture occurs, shunted and oxygenated blood mixes until the PO2 throughout all plasma of the newly mixed blood is in equilibrium and all the Hb molecules carry the same number of oxygen molecules.

Answer 8

• Pulmonary shunting below 10% reflects normal lung status. • A shunt between 10 and 20% is indicative of an intrapulmonary abnormality, but is seldom of clinical significance. • Pulmonary shunting between 20 and 30% denotes significant intrapulmonary disease and may be life-threatening. • Pulmonary shunting greater than 30% is a potentially life-threatening situation and aggressive support is needed.

Answer 9

• Tissue hypoxia means that the amount of oxygen available for cellular metabolism is inadequate. • There are four main types of hypoxia: • hypoxic hypoxia - circulatory hypoxia • anemic hypoxia - histotoxic hypoxia • Hypoxia leads to anaerobic mechanisms that eventually produces lactic acid and cause the blood pH to decrease.

Answer 10

• Hypoxic hypoxia or hypoxemic hypoxia refers to the condition in which the Pa02 and Ca02 are abnormally low. • This form of hypoxia is better known as hypoxemia (low oxygen concentration in the blood). • This form of hypoxia can develop from: • pulmonary shunting - low alveolar PO2 • diffusion impairment - V/Q mismatch

Answer 11

• Anemic hypoxia is when the oxygen tension in the arterial blood is normal, but the oxygen-carrying capacity of the blood is inadequate. • This form of hypoxia can develop from: • a low amount of Hb in the blood • a deficiency in the ability of Hb to carry 02 • Increased cardiac output is the main compensatory mechanism for anemic hypoxia.

Answer 12

• In circulatory hypoxia, the arterial blood that reaches the tissue cells may have a normal 02 tension and content, but the amount of of blood--and therefore the amount of 02--is not adequate to meet tissue needs. • The two main causes of circulating hypoxia are: • stagnant hypoxia • arterial-venous shunting

Answer 13

• Histotoxic hypoxia develops in any condition that impairs the ability of tissue cells to utilize oxygen. • Clinically, the Pa02 and CaO2 in the blood are normal, but the tissue cells are extremely hypoxic. • The PvO2, CvO2 and SvO2 are elevated because oxygen is not utilized. • One cause of this type of hypoxia is cyanide poisoning.