Oxygen delivery and utilization.
Under normal circumstances, O 2 transport (TO 2 = cardiac output x arterial O 2 content) is regulated to provide sufficient O 2 to meet the demands of oxidative phosphorylation, quantified as the O 2 consumption (VO 2).  When metabolic demands increase, TO 2 is augmented and in addition, the fractional extraction of the delivered O 2 by the tissues, the O 2ER, also increases, to levels as high as 0.80 at maximum VO 2.  If TO 2 is decreased, at least in the experimental animal, VO 2 can be maintained initially by an increase in O 2ER, but eventually this mechanism is exhausted, VO 2 begins to fall, and the body invokes anaerobic means of energy generation to maintain cell integrity.  In normal man, this critical level of TO 2 (TO 2crit) has not been determined, but in experimental animals it has been found once the O 2ER exceeds 0.50.  Patients with sepsis and the adult respiratory distress syndrome have a very high mortality and usually die as a result of multiple organ failure.  They have in addition, an apparent abnormality in their ability to extract and utilize the delivered O 2.  Despite a TO 2 which is often higher than normal, patients with sepsis commonly have a lactic acidosis and when TO 2 is reduced, both groups of patients are usually unable to increase their O 2ER above the normal resting value of 0.33.(ABSTRACT TRUNCATED AT 250 WORDS)
Dantzker
D R
DR
Department of Medicine, Long Island Jewish Medical Center, New Hyde Park, NY 11042.
D000818:Animals; D002302:Cardiac Output; D016638:Critical Illness; D006801:Humans; D007239:Infections / Q000378:metabolism; D009102:Multiple Organ Failure / Q000378:metabolism; D010100:Oxygen / Q000097:blood / Q000502:physiology*; D010101:Oxygen Consumption; D012128:Respiratory Distress Syndrome / Q000378:metabolism