RESULTS: 38 cases were included; 24 with right and 14 with left effusion. Common etiologies included heart failure, malignancy and post-cardiac surgery. 34 patients were spontaneously breathing and 4 on mechanical ventilation. Median volume aspirated was 1310 ml (min 330, max 2500). Values of C and D in mm and H and (H+D) in cm were separately entered into linear regression in attempt to derive a predictive formula for V. Strength of association as measured by R2 in ascending order for C, D, H and (H+D) was: 0.39, 0.66, 0.73 and 0.81. The regression equation for the most 2 predictive parameters were as follows: V = H × 106.7 + 65 (95% CI for beta coefficient 83-130). V = (H+D) × 82.2 - 51 (95% CI for beta coefficient 67-97). Interestingly, when the mean coefficient for H was compared between right (119±27) and left (97±9) sides, there was statistically significant difference (p 0.01).