Lactic acidosis: Elevated concentrations of lactate in the plasma, termed lactic acidosis, occur when there is a collapse of the circu- latory system, such as in myocardial infarction, pulmonary embolism, and uncontrolled hemorrhage, or when an individual is in shock. The failure to bring adequate amounts of oxygen to the tissues results in impaired oxidative phosphorylation and decreased ATP synthesis. To survive, the cells use anaerobic glycolysis as a backup system for generating ATP, producing lac- tic acid as the endproduct. [Note: Production of even meager amounts of ATP may be life-saving during the period required to reestablish adequate blood flow to the tissues.] The excess oxy- gen required to recover from a period when the availability of oxy- gen has been inadequate is termed the oxygen debt.