Predictors of Dyspnea Relief Using Ultrasound Measurements of Diaphragmatic Function in Symptomatic Pleural Effusions: Multicenter Prospective Study.

Rationale: Pleural effusions commonly cause dyspnea. However, the drainage of pleural effusions does not reliably result in dyspnea relief. Objectives: To evaluate the predictive value of thoracic ultrasound and clinical parameters for dyspnea relief after thoracentesis. Methods: This prospective, multicenter observational study enrolled adult patients undergoing therapeutic thoracentesis. Predrainage ultrasound assessment included visual (shape and motion) and measurable (displacement, velocity, and thickening fraction) diaphragmatic parameters. The primary study outcome was dyspnea improvement, defined as ⩾14-mm change in visual analog scale score 15 minutes after drainage. Univariate analysis was performed to identify predictors of response. Results: Of 103 effusions drained, 83% (86/103) achieved clinically meaningful dyspnea relief. Predrainage flat or everted diaphragm appearance strongly predicted symptom improvement (odds ratio, 7.92; 95% confidence interval, 2.49-25.2; P < 0.001). Other diaphragmatic parameters (displacement, velocity, and thickening fraction) did not reliably distinguish responders from nonresponders. Responders had greater predrainage dyspnea by visual analog scale scores than nonresponders (66 vs. 38 mm; P < 0.001). Conclusions: In symptomatic pleural effusions, predrainage dyspnea severity and a flat or everted diaphragm shape predicted dyspnea relief after thoracentesis. Additional diaphragmatic measurements, including displacement, velocity, and thickening fraction, did not aid in predicting dyspnea relief after pleural drainage.