The fetal lungs are collapsed, and blood passes from the right atrium directly into the left atrium through the foramen ovale: an open conduit between the paired atria, or through the ductus arteriosus: a shunt between the pulmonary artery and the aorta.
By Deborah Leader, RN. Updated January 21, 2016. Hypercapnia is a condition that occurs when there is too much carbon dioxide in the blood. While it is sometimes caused by things such as hypoventilation or a narcotic drug overdose, a much more common cause is COPD. If you have COPD, it's important to know the hypercapnia symptoms, as well as the treatments available.
Gas Exchange During Respiration. Why are red blood cells needed to transport gases in the blood? Oxygen and carbon dioxide will both go into solution in the plasma (the fluid part of the blood). Hemoglobin in red blood cells will bond to both oxygen and carbon dioxide. There are several reasons why red blood cells are necessary for respiration. First oxygen gas has a very low solubility in blood fluids and the circulatory system would not be able to deliver enough oxygen to tissues using dissolved oxygen alone.