Background: In patients who have malignant pleural effusion, it is difficult to diagnose trapped lung before thoracoscopy, thoracostomy, and drainage of the effusion. Predicting the outcome of pleurodesis in patients who have malignant pleural effusion without trapped lung is also difficult.
Objective: To investigate the factors that may be useful in diagnosing trapped lung and predicting the outcome of pleurodesis.
Design: Prospective cohort study.
Setting: University medical center.
Patients: 65 patients with symptomatic malignant pleural effusion.
Intervention: A chest tube was inserted for drainage of the effusion, and pleurodesis was done using bleomycin as the sclerosant.
Measurements: The pH and glucose levels of the effusion and the elastance of the pleural space (defined as the decline in pleural fluid pressure in cm H2O after removal of 500 mL of effusion) were measured. The outcome of pleurodesis was evaluated 1 month after the chest tube was removed.
Results: Patients with an elastance of 19 cm H2O or more had a higher incidence of trapped lung (11 of 14 patients) than did those with an elastance less than 19 cm H2O (3 of 51 patients) (P < 0.001). None of the 14 patients with an elastance of 19 cm H2O or more and none of the 14 patients with a trapped lung had successful pleurodesis. Forty-two of 43 patients with an elastance less than 19 cm H2O who did not have a trapped lung had successful pleurodesis. Elastance seemed to be the best predictor for trapped lung and outcome of pleurodesis, although outcome was also correlated with pH and glucose levels of the effusion. Low-dose bleomycin (30 mg) is as effective as the usual dose of bleomycin (60 mg) for pleurodesis.
Conclusion: In patients with symptomatic malignant pleural effusion, measurement of the elastance of the pleural space is a simple and effective method for the diagnosis of trapped lung and prediction of the outcome of chemical pleurodesis with bleomycin.