Read a hemoglobin dissociation curve


From Seeley, Stephens & Tate, 2003. Human Anatomy and Physiology. McGraw-Hill. Reprinted with permission.


Using the oxygen dissociation curve above, fill in the % saturation for blood for each of the following values of pO2.


pO2 (mm Hg)

% saturation

mL O2/100 mL blood














For the tissues, what matters is not the % saturation, but how many mL of O2 the blood is carrying.In a healthy person, the blood can carry 20 mL O2 per 100 mL of blood if it is fully saturated with O2. This is the Oxygen Capacity of the blood.


How many mL of O2 would 100 mL of blood carry if it were only 50% saturated?


20 mL O2/100 mL blood x _50_%=_______ mL O2/100 mL blood



Now fill in the third column in the table above to show how much O2 the blood will be carrying at each pO2, assuming this is a healthy person with an oxygen capacity of 20 mL O2/100 mL blood..


If the person were sick with anemia, a decrease in the number of RBCs, their blood would not be able to hold as many mL O2.Fill in the table below to show how much O2 would be in the blood of a person who had such bad anemia that their oxygen capacity is only 15 mL O2/100 mL blood.


pO2 (mm Hg)

% saturation

mL O2/100 mL blood for normal person

mL O2/100 mL blood for anemic person



















Now letís look at how much O2 the blood releases to tissues as it passes through them.What percent of the oxygen the hemoglobin is carrying will be released to the tissues as blood goes from the lungs at pO2 = 90 mmHg to the tissues at pO2 = 70 mm Hg? If this is a healthy person whose 100% saturated blood carries 20 mL O2/100 mL blood, how many mL of O2 would 100 mL of this blood drop off?






This blood is being pumped through a muscle that is exercising. The arterial pO2 of the blood entering the muscle is 90 mm Hg, and the pO2 of the blood leaving the muscle is 65 mm Hg. The muscle weighs 3600 gm, and it demands 8 x 10 -3 mL O2/ gm muscle minute. How much blood will this person have to pump through the muscle every minute for it to get enough oxygen?


(Hint: do this in three steps. First, draw a diagram like the one above and figure out what percent of the O2 is dropped off. Then figure out how many mL O2 are dropped off from 100 mL blood, if 100% = 20 mL O2/100 mL blood.Then figure out how many mL blood per minute the muscle would need to supply its O2 needs.)





If the pO2 of the venous blood decreases to 50 mm Hg, how much blood will the person have to pump through this muscle per minute?


You can demonstrate your understanding of these calculations by turning in a problem from the web page Oxygen dissociation problem. This problem must be done independently as specified in the contract you signed.