This in turn causes enlargement of the liver and peripheral edema, the entire sequence being termed cor-pulmonale . In summary, respiratory failure may be associated with a wide variety of clinical manifestations. However, none is specific for respiratory failure, and very significant respiratory failure may be present without dramatic signs or symptoms. This again emphasizes the importance of measuring PaO 2 and PaCO 2 in all patients in whom respiratory failure can be suspected, indeed in all patients who are seriously ill. The cause of respiratory failure is usually evident after a careful history is taken and the patient examined.
Many diseases can cause respiratory failure.
It is important, however, that certain laboratory tests be performed in all patients with respiratory failure. Results of ABG analysis not only define and classify respiratory failure but also give other valuable information. The levels of arterial pH and bicarbonate give clues to the duration of a given disturbance of PaCO 2 . 7.35, CO 2 retention has been present for weeks. If a patient with CO 2 retention has a normal has a normal alveolar-arterial PO 2 difference, then that patient has normal lungs and the cause of the respiratory failure is pure hypoventilation.