Abstract

Arterial blood gas analysis has contributed immeasurably to the care of the critically ill by instantaneously providing information regarding ventilation, oxygenation, and acid-base balance. Hypoxia always is due to either ventilation/perfusion imbalanc shunting, hypoventilation, or disorders which increase the distance between the alveoli and pulmonary capillaries. Hypercarbia caused by excessive physiologic dead space or poor respiratory effort. Acid-base imbalance is a dynamic process and arterial blood gas analysis almost always reflects both a primary and a compensatory process. Though extremely sophisticated measurements and calculations may be carried out, most critically ill patients can be managed by sound clinical judgment and an understanding of the meanings of PaO2, PaCO2, pH, and base calculation