COMPARISON OF OXYGENATION SATURATION INDEX WITH OXYGENATION INDEX AND SOFA SCORE IN PREDICTING OUTCOME OF PATIENTS WITH ACUTE RESPIRATORY DISTRESS SYNDROME

Abstract

Background: Acute Respiratory Distress Syndrome (ARDS) is a severe form of hypoxemic respiratory failure with high morbidity and mortality worldwide. The Oxygenation Index (OI), calculated from arterial blood gas (ABG) data, is a well-established marker of disease severity in mechanically ventilated ARDS patients. However, its reliance on invasive arterial sampling limits utility in resource-constrained settings. The Oxygen Saturation Index (OSI), a non-invasive surrogate derived from peripheral oxygen saturation (SpO₂), FiO₂, and mean airway pressure, offers continuous bedside monitoring without arterial access. This study aimed to compare OSI with OI and the Sequential Organ Failure Assessment (SOFA) score in predicting clinical outcomes in ARDS patients admitted to a tertiary care ICU.

Methods: A hospital-based observational cross-sectional study was conducted over 18 months among 70 adult ARDS patients admitted to the ICU of Dr. D.Y. Patil Medical College, Kolhapur. Patients fulfilling the Berlin definition of ARDS were enrolled using a non-probability sampling technique. OSI, OI, and SOFA scores were serially calculated on Day 1 and Day 4 of ICU admission. Clinical outcomes including mortality and total ICU stay were recorded. Pearson correlation analysis assessed associations among study parameters.

Results: Among 70 patients, 55 (78.6%) expired and 15 (21.4%) survived. Expired patients demonstrated significantly higher OSI, OI, and SOFA scores on both Day 1 and Day 4 (p<0.001). Day 4 OSI was 8.00±3.07 in expired patients versus 2.69±1.19 in survivors. OSI exhibited an extremely strong positive correlation with OI on Day 1 (r=0.990) and Day 4 (r=0.988), and a significant positive correlation with SOFA score on Day 1 (r=0.571) and Day 4 (r=0.621), all p<0.001.

Conclusion: OSI is a reliable, non-invasive surrogate for OI and demonstrates significant prognostic value in ARDS. Serial OSI assessment, particularly by Day 4, may serve as a practical bedside tool for risk stratification and outcome prediction, with performance comparable to OI and complementary to SOFA score.