PURPOSE: Identification of abnormal lung expansion by measurment of pleural elastance is useful in evaluating patients with malignant effusion, suspected trapped lung, and post-thoracentesis pneumothorax. We sought to identify chest radiographic findings that would predict abnormal pleural elastance.
METHODS: In a blinded fashion, we reviewed and scored the radiographs of patients who had pleural manometry as well as pre and post-thoracentesis radiographs. Effusions were scored on a scale of 1-4 and the presence or absence of ipsilateral mediastinal shift (IMS), ipsilateral volume loss (IVS), and ipsilateral loculation (IL) was noted. Using Yates corrected chi square analysis, z-score, and confidence intervals, correlation between these radiographic findings and the presence or absence of abnormal pleural elastance was calculated. Sensitivity, specificity, positive and negative predictive values were calculated for each radiographic finding with abnormal pleural elastance. We attempted to create a linear regression model to predict pleural elastance based on the above radiographic signs.
RESULTS: The number (out of 172 cases) with the radiographic findings follow for pre and post-thoracentesis films: IMS(6,10),IVS (21,36), IL(50,18). There was no significant association of any radiographic finding with the presence of abnormal pleural elastance(Chi square P-values were 0.64,0.20, 0.69 for pre and 0.89, 0.67, 0.41 for post thoracentesis radiographs for IMS, IVL, and IL. PPV was 0.5, 0.48, 0.38 and 0.3, 0.38, 0.44 for pre and post radiographs. NPV was 0.68, 0.69, 0.66 and 0.66, 0.68, 0.68 for pre and post radiographs. Further, a linear regression model could not be created given the lack of association between radiographic findings and pleural elastance.
CONCLUSION: Neither pre nor post-thoracentesis radiographs can be used reliably to predict pleural elastance.
CLINICAL IMPLICATIONS: When an understanding of lung expandability is necessary in evaluation of patients with malignant effusion for possible pleurodesis, patients suspected of having trapped lung, or patients with post-thoracentesis pneumothoraces, pre and post-thoracentesis chest radiography cannot reliably be used as a surrogate for pleural elastance.
DISCLOSURE: John Huggins, None.