Objective: The objective of our study was to assess the correlation of ultrasound guided measurement of respiratory variation in inferior vena cava diameter (IVCD) and its collapsibility index (IVCCI) and its correlation to fluid challenge, passive leg raising (PLR) and CVP (CVP) in critically ill patients. Methods: Forty adult patients admitted in intensive care unit over a period of twelve months between 18-60 years, of age with central venous catheter in situ and were spontaneously breathing and having accessible epigastric region for ultrasonography were included in the study. A Sonosite Micromax ultrasonographic machine was used for all examinations. IVC diameter measurements were recorded in centimeters with help of ultrasonography both at end-inspiratory and endexpiratory at baseline (T0), 5 min after PLR (TPLR1), 5minute after rebound(TR1), 15mins after saline infusion (TS), 5min after passive leg raising (TPLR2), 5mins after rebound (TR2) and simultaneously corresponding CVP value was recorded at each point of time. A paired sample t-test was used to compute the p-values. Results: The total number of patients enrolled was 40 (100%). In our study, both PLR and fluid challenge has positive significant effect on CVP values. A highly significant correlation was found between inferior vena cava diameter both inspiratory and expiratory and CVP. There was a statistically significant positive correlation between eIVCD and iIVCD. Results of our study show a cut-off value for CVP as 10cmH2O with respect to IVCCI of 50%. There is a negative correlation between inferior vena cava collapsibility index and CVP value and results of correlation were not statistically significant when CVP value < 10cmH2O and after saline infusion, negative correlation between IVCCI and CVP value persisted and became statistically significant when CVP was more than 10cmH2O. Also when CVP value was < 10cmH2O, the inferior vena cava collapsibility index was >50%. After saline infusion when CVP >10cmH2Othere was decrease in collapsibility of inferior vena cava <50%. Conclusion: There is a positive correlation of IVC diameters in both phases of respiration after PLR and fluid loading. IVC diameters can be measured easily and in ICU patients can be used for fluid volume assessment. IVCCI is also easily calculated and can be used for assessment of fluid volume status and response to fluid therapy
