Application of Compensation Rules in the Four-quadrant Graphical Tool for Arterial Blood Gas Interpretation: A Cross-sectional Study

Abstract

Introduction: Arterial Blood Gas (ABG) interpretation plays an indispensable role in emergency medicine and the care of intensive care patients, yet it remains a challenging task. Although several graphical methods exist for ABG interpretation, they are not commonly used at the bedside. The existing graphs are complicated, difficult to understand, and unable to diagnose many disorders. In previous research articles, the current author developed and published a four-quadrant graphical tool for ABG interpretation. The tool incorporates compensation rules, which are crucial for identifying changes resulting from compensations or the presence of a second primary acid-base disorder. Aim: To develop a method for applying compensation rules in a four-quadrant graphical tool to interpret ABG reports for complex acid-base disorders in clinical practice. Materials and Methods: This cross-sectional study was conducted at Shri Sathya Sai Medical College and Research Institute, Chennai, Tamil Nadu, India, from November 2022 to April 2023. A total of 232 ABG samples were utilised, and the values of pH, pCO2, HCO3, Standard HCO3, and Standard Base Excess (SBE) were recorded. These values were classified according to different acid-base disorders. Three derived ratios were calculated using the values of pCO2, bicarbonate, and standard bicarbonate, as these ratios change in various acid-base disorders and provide clues for differentiating between different acid-base disturbances. A four-quadrant graph method was constructed using the values of SBE, pCO2, and these ratios. Subsequently, compensation rules were applied to this graph method. Results: The four-quadrant method facilitated the easy identification of different acid-base disorders, and the application of compensation rules further simplified the identification of mixed or compensatory acid-base disorders. Conclusion: The application of compensation rules in this four- quadrant graphical tool for ABG interpretation distinguishes this tool as a unique method among existing approaches. This tool offers an optimal and simplified approach for interpreting ABG results for complex acid-base disturbances, making it highly suitable for clinical practice at the bedside.