Relationships between some oxygen and carbon dioxide indices in patients with chronic lung and cardiovascular...

A total of 281 patients were divided into groups according to their clinical diagnosis and were examined using capnography, spirometry and blood-gas analysis. The highest percentage of patients with arterial hypoxemia was found in the group with chronic bronchitis and emphysema. The same group had the highest number of patients with moderate hypoxemia and was the only group containing patients with severe hypoxemia. Alveolar hypoventilation and increased ventilation-perfusion ratio were most pronounced in patients with chronic bronchitis and emphysema. The greatest negative correlation between PaO2 and PaCO2 was found, again, in this group. We also found the greatest direct correlation between the oxygen and carbon dioxide gradients in this group. These results suggest that the relationships between the partial pressures of O2 and CO2 depend on the type of the pulmonary and cardiovascular diseases. The relationships between the partial pressures of O2 and CO2 as well as between their gradients, become stronger with the increase of the ventilation-perfusion ratio. The relationships between the expired alveolar gases are approximately the same as those of these gases in blood.