Chapter 1
OXYGEN KINETICS
Marjorie J. Arca, MDI. Oxygen Consumption and Delivery
In a state of equilibrium, oxygen demand equals oxygen consumption, which
is the amount of oxygen used for aerobic metabolism. Under normal aerobic
conditions, O2 delivery is 3 to 4 times what is consumed by the body and oxygen
delivery does not dictate the amount of oxygen consumed. In a critically ill patient,
delivery of oxygen must be closely considered.
Oxygen delivery is the product of cardiac output (CO) and arterial oxygen
content. During the process of metabolism, oxygen is consumed as is expressed
as volume of oxygen per minute (V0 2 ) and is equal to 100-200 cc/m^2 /min. Oxygen
delivery (DO 2 ) is equal to 500-600 cc/m^2 /min.
O 2 Delivery = CO [ (1.34 x Hgb x O 2 sat) + (0.003 x PaO 2 )].(^) An analogy for oxygen delivery is as follows: Think of oxygen as beer that
needs to be delivered from Milwaukee to Green Bay. The hemoglobin molecules
are the trucks that need to be filled (low O 2 saturation) or if there are not enough
trucks (low Hgb), then the amount of beer that gets to Green Bay is less. The
cardiac output is the foreman that decides who many trucks per hour comes out of
the beer factor’s garage.