Interpretation of arterial blood gases: a clinical guide for nurses

Arterial blood gas analysis has become an essential skill for all healthcare practitioners. It provides important information with regard to adequacy of ventilation, oxygen delivery to the tissues and acid-base balance. Although each patient's clinical presentation will be judged individually, situations that warrant analysis of a blood gas sample include respiratory compromise, post-cardiorespiratory arrest, evaluation of interventions such as oxygen therapy, respiratory support and as a baseline before surgery. This article reviews the different parameters that are measured by various machines, with a focus on basic measurement of arterial blood gases. These include partial pressure of carbon dioxide in arterial blood (PaCO(2)), partial pressure of oxygen in arterial blood (PaO(2)), bicarbonate levels (HC0(3)(-)) in arterial blood and base excess/deficit. The physiology of acid-base balance is reviewed and the causes and presentation of the four acid-base disturbances is described. A systematic method to aid arterial blood interpretation is identified, together with discussion regarding the importance of interpreting PaO(2) readings in relation to the amount of inspired oxygen a patient is receiving (FiO(2)), the practice of temperate correction and the relationship between standardized and actual bicarbonate readings.