Development of a new method to measure pleural effusion volume by ultrasound in critically ill patients / 中华超声影像学杂志

ABSTRACT

Objective To develop a new method to measure pleural effusion volume by ultrasound in critically ill patients. Methods Forty-six critically ill patients admitted to emergency ICU were involved.The height of effusion (H),area of effusion at the middle section (S), thickness of effusion at middle-back line (T1) and posterior axillary line (T2) were measured by ultrasound in supine position at the end of expiration. The measured volume of pleural effusion (Vc) was calculated by H×S,and the actual volume of drainage (V) within 2 hours was also recorded. The correlation of actual volume of pleural effusion (V)with effusion height (H) ,thickness (T1, T2), area (S) and the calculated volume (Vc) were analyzed to decide the most accurate index and method. Results There was much better correlation between actual volume of effusion and S, (H & S), Vc, than these between V and T1 ,T2, H in all patients and subgroup, Vc had good correlation with V and very close to V(the average difference was 56 ml) when the actual volume was less than 500 ml,there was no difference[(417 ± 94)ml vs (402±95)ml, t = 1.095, P = 0. 285]. Both Logistic regression analysis and receiver operating characteristic (ROC) curve showed S was the most reliable index to predict the actual volume to exceed 500 ml,400 ml,and 300 ml when compared with H,S,T1 and T2. The corresponding threshold was 30.3 cm2 , 28.3 cm2 and 23. 1 cm2 , with the sensitivity and specificity of 0. 77 and 0. 88,0.72 and 1.0,0.95 and 1.0, respectively. Conclusions This new method based on measuring the area of effusion by ultrasound is more efficient and reliable than those traditional ones to measure the volume of pleural effusion. It's clinically valuable and easy to perform, and deserves broad application.