ARTERJAL BLOOD GASES



The arterial partial pressures of oxygen and car­bon dioxide (Pao2 and Paco2) and pH as well as parameters derived from these values such as the alveolar-arterial 02 difference (A-a Do2) and ven­ous admixture (Qs/Qt) are the most commonly evaluated parameters of lung function . When measured while breathing room air and 100 percent 02, they can often diagnose the mechanism of abnormal pulmonary gas exchange . Measurement of these parameters requires arterial puncture, which is uncomforta­ble for the patient and occasionally difficult or dangerous to perform. When multiple samples are required over a relatively short period of time, an indwelling arterial catheter may be useful.