Ultrasound quantification of pleural effusion volume in supine position: comparison of three model formulae

Abstract

Background: To investigate the accuracy of three model formulae for ultrasound quantification of pleural effusion (PE) volume in patients in supine position.

Methods: A prospective study including 100 patients with thoracentesis and drainage of PE was conducted. Three model formulae (single section model, two section model and multi-section model) were used to calculate the PE volume. The correlation and consistency analyses between calculated volumes derived from three models and actual PE volume were performed.

Results: PE volumes calculated by three models all showed significant linear correlations with actual PE volume in supine position (all p < 0.001). The reliability of multi-section model in predicting PE volume was significantly higher than that of single section model and slightly higher than that of two section model. When compared with actual drainage volume, the intra-class correlation coefficients (ICCs) of single section model, two section model and multi-section model were 0.72, 0.97 and 0.99, respectively. Significant consistency between calculated PE volumes by using two section model and multi-section model existed for full PE volume range (ICC 0.98).

Conclusion: Based on the convenience and accuracy of ultrasound quantification of PE volume, two section model is recommended for pleural effusion assessment in routine clinic, though different model formulae can be selected according to clinical needs.

Keywords: Pleural effusion; Quantification; Ultrasound; Volume.

Fig. 1

Illustration of ultrasound quantifications of pleural effusion volume. Patients were in supine position with a transducer placed at midaxillary line and perpendicular to chest wall. The maximum transverse distance between the lateral chest wall and the lung surface was recorded as Sep (mm) (a & b). The distance between upper point and bottom of the anechoic area in longitudinal section was recorded as maximum suprainferior length L (cm) (c & d). The anechoic area of each intercostal space was recorded as A (cm2) (e & f)

Fig. 2

Flowchart of patient enrollment

Fig. 3

Regression analyses revealed significant linear correlations between actual drainage volume and calculated pleural effusion volumes derived from three model formulae

Fig. 4

Bland-Altman scatterplot analyses revealed that most of the points of the three models fell within the 95% CI, indicating that the calculated volumes of the three models were consistent with actual pleural effusion volume

Fig. 5

Linear regression and Bland-Altman scatterplot analyses showed significant correlation and consistency between calculated pleural effusion volumes by using two section model and multi-section model, both when actual volume > 800 ml (a & b) as well as when analyzing all patients together (c & d)