Accuracy of Arterial Blood Gas: Quality Improvement Study

Abstract

Background: Arterial blood gas (ABG) is indicated in almost all presenting problems in the emergency department (ED). When the clinical diagnosis does not match the ABG diagnosis, particularly in multiorgan failure, physicians level it as inaccurate. With the passage of time the role of ABG has been narrowed to the ICU as a monitor in ventilated patients. The accuracy of ABG can be tested by knowing and comparing the values of Hb% measured though ABG and CBC and by oxygen saturation measured though ABG and pulse oximetry.

Method: This was a prospective observational cohort quality improvement study and ABG vs. CBC hemoglobin and ABG vs. pulse-oximeter oxygen saturation in over 74 adult patients admitted to the ED were evaluated in a tertiary care center. Arterial blood was collected properly and ABG-Hb/ABG-SO₂ was measured at point-of-care testing with an ABG machine. Venous samples were collected at the same time and properly transported to the laboratory for CBC measurement. SpO₂ was measured at bedside through pulse oximeter. Data were entered into a specifically designed database and analyzed statistically.

Result: There was a strong positive correlation between ABG-Hb and CBC-Hb (p<0.001). The correlation between ABG-SO₂ and pulse-oxi-SpO₂ was also significant (p<0.001).

Conclusion: Both the ABG-Hb vs. CBC-Hb and ABG-SO₂ vs. pulse-oxi-SpO₂ methods can be used as tools for testing accuracy and improving the quality of ABG. Confident use of ABG in the management of severely ill patients significantly improves outcomes [3].

Keyword: ABG (arterial blood gas); ED (emergency department); CBC (complete blood count); Pulse-Oxi (pulse oximeter); PI (perfusion index).